Vincenzo Berghella, MD

Getahun D, Fassett MJ, Jacobsen SJ, et al. Perinatal outcomes after bariatric surgery. Am J Obstet Gynecol. 2021;S0002-9378(21)00771-7. doi: 10.1016/j.ajog.2021 .06.087.

EXPERT COMMENTARY

Prepregnancy obesity continues to rise in the United States, with a prevalence of 29% among reproductive-age women in 2019, an 11% increase from 2016.¹ Pregnant patients with obesity are at increased risk for multiple adverse perinatal outcomes, including gestational diabetes and preeclampsia. Bariatric surgery is effective for weight loss and has been shown to improve comorbidities associated with obesity,² and it may have potential benefits for pregnancy outcomes, such as reducing rates of gestational diabetes and preeclampsia.^3-5 However, little was known about other outcomes as well as other potential factors before a recent study in which investigators examined perinatal outcomes after bariatric surgery.

Details of the study

Getahun and colleagues conducted a population-based, retrospective study of pregnant patients who were eligible for bariatric surgery (body mass index [BMI] ≥40 kg/m² with no comorbidities or a BMI between 35 and 40 kg/m² with obesity-related comorbidities, such as diabetes). They aimed to evaluate the association of bariatric surgery with adverse perinatal outcomes.

Results. In a large sample of pregnant patients eligible for bariatric surgery (N = 20,213), the authors found that patients who had bariatric surgery (n = 1,886) had a reduced risk of macrosomia (aOR, 0.24), preeclampsia (aOR, 0.53), gestational diabetes (aOR, 0.60), and cesarean delivery (aOR, 0.65) compared with those who did not have bariatric surgery (n = 18,327). They also found that patients who had bariatric surgery had an increased risk of small-for-gestational age neonates (aOR, 2.46) and postpartum hemorrhage (aOR, 1.79).

These results remained after adjusting for other potential confounders. The authors evaluated the outcomes based on the timing of surgery and the patients’ pregnancy (<1 year, 1-1.5 years, 1.5-2 years, >2 years). The outcomes were more favorable among the patients who had the bariatric surgery regardless of the time interval of surgery to pregnancy than those who did not have the surgery. In addition, the benefits of bariatric surgery did not differ between the 2 most common types of bariatric surgery (Roux-en-Y gastric bypass and vertical sleeve gastrectomy) performed in this study, and both had better outcomes than those who did not have the surgery. Finally, patients with chronic hypertension and pregestational diabetes who had bariatric surgery also had lower risks of adverse outcomes than those without bariatric surgery.

Study strengths and limitations

Given the study’s retrospective design, uncertainties and important confounders could not be addressed, such as why certain eligible patients had the surgery and others did not. However, with its large sample size and an appropriate comparison group, the study findings further support the perinatal benefits of bariatric surgery in obese patients. Of note, this study also had a large sample of Black and Hispanic patients, populations known to have higher rates of obesity¹ and pregnancy complications. Subgroup analyses within each racial/ethnic group revealed that those who had the surgery had lower risks of adverse perinatal outcomes than those who did not.

Patients who had the bariatric surgery had an increased risk of postpartum hemorrhage; however, there is no physiologic basis or theory to explain this finding, so further studies are needed. Lastly, although patients who had bariatric surgery had an increased risk of small-for-gestational-age babies and the study was not powered for the risk of stillbirth, the patients who had the surgery had a reduced risk of neonates admitted to the neonatal intensive care unit. More data would have been beneficial to assess if these small-for-gestational-age babies were healthy. In general, obese patients tend to have larger and unhealthy babies; thus, healthier babies, even if small for gestational age, would not be an adverse outcome.

Benefits of bariatric surgery extend to perinatal outcomes

This study reinforces current practice that includes eligible patients being counseled about the health-related benefits of bariatric surgery, which now includes more perinatal outcomes. The finding of the increased risk of small-for-gestational-age fetuses supports the practice of a screening growth ultrasound exam in patients who had bariatric surgery. ●

Getahun D, Fassett MJ, Jacobsen SJ, et al. Perinatal outcomes after bariatric surgery. Am J Obstet Gynecol. 2021;S0002-9378(21)00771-7. doi: 10.1016/j.ajog.2021 .06.087.

EXPERT COMMENTARY

Prepregnancy obesity continues to rise in the United States, with a prevalence of 29% among reproductive-age women in 2019, an 11% increase from 2016.¹ Pregnant patients with obesity are at increased risk for multiple adverse perinatal outcomes, including gestational diabetes and preeclampsia. Bariatric surgery is effective for weight loss and has been shown to improve comorbidities associated with obesity,² and it may have potential benefits for pregnancy outcomes, such as reducing rates of gestational diabetes and preeclampsia.^3-5 However, little was known about other outcomes as well as other potential factors before a recent study in which investigators examined perinatal outcomes after bariatric surgery.

Details of the study

Getahun and colleagues conducted a population-based, retrospective study of pregnant patients who were eligible for bariatric surgery (body mass index [BMI] ≥40 kg/m² with no comorbidities or a BMI between 35 and 40 kg/m² with obesity-related comorbidities, such as diabetes). They aimed to evaluate the association of bariatric surgery with adverse perinatal outcomes.

Results. In a large sample of pregnant patients eligible for bariatric surgery (N = 20,213), the authors found that patients who had bariatric surgery (n = 1,886) had a reduced risk of macrosomia (aOR, 0.24), preeclampsia (aOR, 0.53), gestational diabetes (aOR, 0.60), and cesarean delivery (aOR, 0.65) compared with those who did not have bariatric surgery (n = 18,327). They also found that patients who had bariatric surgery had an increased risk of small-for-gestational age neonates (aOR, 2.46) and postpartum hemorrhage (aOR, 1.79).

These results remained after adjusting for other potential confounders. The authors evaluated the outcomes based on the timing of surgery and the patients’ pregnancy (<1 year, 1-1.5 years, 1.5-2 years, >2 years). The outcomes were more favorable among the patients who had the bariatric surgery regardless of the time interval of surgery to pregnancy than those who did not have the surgery. In addition, the benefits of bariatric surgery did not differ between the 2 most common types of bariatric surgery (Roux-en-Y gastric bypass and vertical sleeve gastrectomy) performed in this study, and both had better outcomes than those who did not have the surgery. Finally, patients with chronic hypertension and pregestational diabetes who had bariatric surgery also had lower risks of adverse outcomes than those without bariatric surgery.

Study strengths and limitations

Given the study’s retrospective design, uncertainties and important confounders could not be addressed, such as why certain eligible patients had the surgery and others did not. However, with its large sample size and an appropriate comparison group, the study findings further support the perinatal benefits of bariatric surgery in obese patients. Of note, this study also had a large sample of Black and Hispanic patients, populations known to have higher rates of obesity¹ and pregnancy complications. Subgroup analyses within each racial/ethnic group revealed that those who had the surgery had lower risks of adverse perinatal outcomes than those who did not.

Patients who had the bariatric surgery had an increased risk of postpartum hemorrhage; however, there is no physiologic basis or theory to explain this finding, so further studies are needed. Lastly, although patients who had bariatric surgery had an increased risk of small-for-gestational-age babies and the study was not powered for the risk of stillbirth, the patients who had the surgery had a reduced risk of neonates admitted to the neonatal intensive care unit. More data would have been beneficial to assess if these small-for-gestational-age babies were healthy. In general, obese patients tend to have larger and unhealthy babies; thus, healthier babies, even if small for gestational age, would not be an adverse outcome.

Benefits of bariatric surgery extend to perinatal outcomes

This study reinforces current practice that includes eligible patients being counseled about the health-related benefits of bariatric surgery, which now includes more perinatal outcomes. The finding of the increased risk of small-for-gestational-age fetuses supports the practice of a screening growth ultrasound exam in patients who had bariatric surgery. ●

Getahun D, Fassett MJ, Jacobsen SJ, et al. Perinatal outcomes after bariatric surgery. Am J Obstet Gynecol. 2021;S0002-9378(21)00771-7. doi: 10.1016/j.ajog.2021 .06.087.

EXPERT COMMENTARY

Prepregnancy obesity continues to rise in the United States, with a prevalence of 29% among reproductive-age women in 2019, an 11% increase from 2016.¹ Pregnant patients with obesity are at increased risk for multiple adverse perinatal outcomes, including gestational diabetes and preeclampsia. Bariatric surgery is effective for weight loss and has been shown to improve comorbidities associated with obesity,² and it may have potential benefits for pregnancy outcomes, such as reducing rates of gestational diabetes and preeclampsia.^3-5 However, little was known about other outcomes as well as other potential factors before a recent study in which investigators examined perinatal outcomes after bariatric surgery.

Details of the study

Getahun and colleagues conducted a population-based, retrospective study of pregnant patients who were eligible for bariatric surgery (body mass index [BMI] ≥40 kg/m² with no comorbidities or a BMI between 35 and 40 kg/m² with obesity-related comorbidities, such as diabetes). They aimed to evaluate the association of bariatric surgery with adverse perinatal outcomes.

Results. In a large sample of pregnant patients eligible for bariatric surgery (N = 20,213), the authors found that patients who had bariatric surgery (n = 1,886) had a reduced risk of macrosomia (aOR, 0.24), preeclampsia (aOR, 0.53), gestational diabetes (aOR, 0.60), and cesarean delivery (aOR, 0.65) compared with those who did not have bariatric surgery (n = 18,327). They also found that patients who had bariatric surgery had an increased risk of small-for-gestational age neonates (aOR, 2.46) and postpartum hemorrhage (aOR, 1.79).

These results remained after adjusting for other potential confounders. The authors evaluated the outcomes based on the timing of surgery and the patients’ pregnancy (<1 year, 1-1.5 years, 1.5-2 years, >2 years). The outcomes were more favorable among the patients who had the bariatric surgery regardless of the time interval of surgery to pregnancy than those who did not have the surgery. In addition, the benefits of bariatric surgery did not differ between the 2 most common types of bariatric surgery (Roux-en-Y gastric bypass and vertical sleeve gastrectomy) performed in this study, and both had better outcomes than those who did not have the surgery. Finally, patients with chronic hypertension and pregestational diabetes who had bariatric surgery also had lower risks of adverse outcomes than those without bariatric surgery.

Study strengths and limitations

Given the study’s retrospective design, uncertainties and important confounders could not be addressed, such as why certain eligible patients had the surgery and others did not. However, with its large sample size and an appropriate comparison group, the study findings further support the perinatal benefits of bariatric surgery in obese patients. Of note, this study also had a large sample of Black and Hispanic patients, populations known to have higher rates of obesity¹ and pregnancy complications. Subgroup analyses within each racial/ethnic group revealed that those who had the surgery had lower risks of adverse perinatal outcomes than those who did not.

Patients who had the bariatric surgery had an increased risk of postpartum hemorrhage; however, there is no physiologic basis or theory to explain this finding, so further studies are needed. Lastly, although patients who had bariatric surgery had an increased risk of small-for-gestational-age babies and the study was not powered for the risk of stillbirth, the patients who had the surgery had a reduced risk of neonates admitted to the neonatal intensive care unit. More data would have been beneficial to assess if these small-for-gestational-age babies were healthy. In general, obese patients tend to have larger and unhealthy babies; thus, healthier babies, even if small for gestational age, would not be an adverse outcome.

Benefits of bariatric surgery extend to perinatal outcomes

This study reinforces current practice that includes eligible patients being counseled about the health-related benefits of bariatric surgery, which now includes more perinatal outcomes. The finding of the increased risk of small-for-gestational-age fetuses supports the practice of a screening growth ultrasound exam in patients who had bariatric surgery. ●

Gestational diabetes mellitus (GDM) generally is defined as any degree of glucose intolerance with onset or first recognition during pregnancy.^1-14 The best approach and exact criteria to use for GDM screening and diagnosis are under worldwide debate. In TABLE 1 we present just some of the many differing suggestions by varying organizations.^{2,7-9,11,12,15-17} The American College of Obstetricians and Gynecologists, for instance, suggests a Two Step approach to diagnosis.¹⁵ We will make the argument in this article, however, that diagnosis should be defined universally as an abnormal result with the One Step 75-g glucose testing, as adopted by the World Health Organization, International Federation of Gynecology and Obstetrics, and others. Approximately 8% of all pregnancies are complicated by GDM by the One Step test in the United States.^18-22 The prevalence may range from 1% to 14% of all pregnancies, depending on the population studied and the diagnostic tests employed.^1,19

Diagnostic options

Different methods for screening and diagnosis of GDM have been proposed by international societies; there is controversy regarding the diagnosis of GDM by either the One Step or the Two Step approach.⁶

The One Step approach includes an oral glucose tolerance test with a 75-g glucose load with measurement of plasma glucose concentration at fasting state and 1 hour and 2 hours post–glucose administration. A positive result for the One Step approach is defined as at least 1 measurement higher than 92, 180, or 153 mg/dL at fasting, 1 hour, or 2 hours, respectively.

The Two Step approach includes a nonfasting oral 50-g glucose load, with a glucose blood measurement 1 hour later. A positive screening, defined often as a blood glucose value higher than 135 mg/dL (range, 130 to 140 mg/dL), is followed by a diagnostic test with a 100-g glucose load with measurements at fasting and 1, 2, and 3 hours post–glucose administration. A positive diagnostic test is defined as 2 measurements higher than the target value.

Why we support the One Step test

There are several reasons to prefer the One Step approach for the diagnosis of GDM, compared with the Two Step approach.

Women testing negative for GDM with Two Step still experience complications pregnancy. Women who test positive for GDM with the One Step test, but negative with the Two Step test, despite having therefore a milder degree of glucose intolerance, do have a higher risk of experiencing several complications.²³ For the mother, these complications include gestational hypertension, preeclampsia, and cesarean delivery. The baby also can experience problems at birth (TABLE 2).²³ Therefore, women who test positive for GDM with the One Step test deserve to be diagnosed with and treated for the condition, as not only are they at risk for these complications but also treatment of the GDM decreases the incidence of these complications.^18,19

Continue to: US guidelines should be reconsidered...

US guidelines should be reconsidered

The One Step, 75-g, 2-hour oral glucose tolerance test is universally used to diagnose diabetes mellitus outside of pregnancy. Given our many noted reasons (TABLE 3), we recommend universal screening of GDM by using the One Step approach. It is time, indeed, for the United States to reconsider its guidelines for screening for GDM.

Gestational diabetes mellitus (GDM) generally is defined as any degree of glucose intolerance with onset or first recognition during pregnancy.^1-14 The best approach and exact criteria to use for GDM screening and diagnosis are under worldwide debate. In TABLE 1 we present just some of the many differing suggestions by varying organizations.^{2,7-9,11,12,15-17} The American College of Obstetricians and Gynecologists, for instance, suggests a Two Step approach to diagnosis.¹⁵ We will make the argument in this article, however, that diagnosis should be defined universally as an abnormal result with the One Step 75-g glucose testing, as adopted by the World Health Organization, International Federation of Gynecology and Obstetrics, and others. Approximately 8% of all pregnancies are complicated by GDM by the One Step test in the United States.^18-22 The prevalence may range from 1% to 14% of all pregnancies, depending on the population studied and the diagnostic tests employed.^1,19

Diagnostic options

Different methods for screening and diagnosis of GDM have been proposed by international societies; there is controversy regarding the diagnosis of GDM by either the One Step or the Two Step approach.⁶

The One Step approach includes an oral glucose tolerance test with a 75-g glucose load with measurement of plasma glucose concentration at fasting state and 1 hour and 2 hours post–glucose administration. A positive result for the One Step approach is defined as at least 1 measurement higher than 92, 180, or 153 mg/dL at fasting, 1 hour, or 2 hours, respectively.

The Two Step approach includes a nonfasting oral 50-g glucose load, with a glucose blood measurement 1 hour later. A positive screening, defined often as a blood glucose value higher than 135 mg/dL (range, 130 to 140 mg/dL), is followed by a diagnostic test with a 100-g glucose load with measurements at fasting and 1, 2, and 3 hours post–glucose administration. A positive diagnostic test is defined as 2 measurements higher than the target value.

Why we support the One Step test

There are several reasons to prefer the One Step approach for the diagnosis of GDM, compared with the Two Step approach.

Women testing negative for GDM with Two Step still experience complications pregnancy. Women who test positive for GDM with the One Step test, but negative with the Two Step test, despite having therefore a milder degree of glucose intolerance, do have a higher risk of experiencing several complications.²³ For the mother, these complications include gestational hypertension, preeclampsia, and cesarean delivery. The baby also can experience problems at birth (TABLE 2).²³ Therefore, women who test positive for GDM with the One Step test deserve to be diagnosed with and treated for the condition, as not only are they at risk for these complications but also treatment of the GDM decreases the incidence of these complications.^18,19

Continue to: US guidelines should be reconsidered...

US guidelines should be reconsidered

The One Step, 75-g, 2-hour oral glucose tolerance test is universally used to diagnose diabetes mellitus outside of pregnancy. Given our many noted reasons (TABLE 3), we recommend universal screening of GDM by using the One Step approach. It is time, indeed, for the United States to reconsider its guidelines for screening for GDM.

Gestational diabetes mellitus (GDM) generally is defined as any degree of glucose intolerance with onset or first recognition during pregnancy.^1-14 The best approach and exact criteria to use for GDM screening and diagnosis are under worldwide debate. In TABLE 1 we present just some of the many differing suggestions by varying organizations.^{2,7-9,11,12,15-17} The American College of Obstetricians and Gynecologists, for instance, suggests a Two Step approach to diagnosis.¹⁵ We will make the argument in this article, however, that diagnosis should be defined universally as an abnormal result with the One Step 75-g glucose testing, as adopted by the World Health Organization, International Federation of Gynecology and Obstetrics, and others. Approximately 8% of all pregnancies are complicated by GDM by the One Step test in the United States.^18-22 The prevalence may range from 1% to 14% of all pregnancies, depending on the population studied and the diagnostic tests employed.^1,19

Diagnostic options

Different methods for screening and diagnosis of GDM have been proposed by international societies; there is controversy regarding the diagnosis of GDM by either the One Step or the Two Step approach.⁶

The One Step approach includes an oral glucose tolerance test with a 75-g glucose load with measurement of plasma glucose concentration at fasting state and 1 hour and 2 hours post–glucose administration. A positive result for the One Step approach is defined as at least 1 measurement higher than 92, 180, or 153 mg/dL at fasting, 1 hour, or 2 hours, respectively.

The Two Step approach includes a nonfasting oral 50-g glucose load, with a glucose blood measurement 1 hour later. A positive screening, defined often as a blood glucose value higher than 135 mg/dL (range, 130 to 140 mg/dL), is followed by a diagnostic test with a 100-g glucose load with measurements at fasting and 1, 2, and 3 hours post–glucose administration. A positive diagnostic test is defined as 2 measurements higher than the target value.

Why we support the One Step test

There are several reasons to prefer the One Step approach for the diagnosis of GDM, compared with the Two Step approach.

Women testing negative for GDM with Two Step still experience complications pregnancy. Women who test positive for GDM with the One Step test, but negative with the Two Step test, despite having therefore a milder degree of glucose intolerance, do have a higher risk of experiencing several complications.²³ For the mother, these complications include gestational hypertension, preeclampsia, and cesarean delivery. The baby also can experience problems at birth (TABLE 2).²³ Therefore, women who test positive for GDM with the One Step test deserve to be diagnosed with and treated for the condition, as not only are they at risk for these complications but also treatment of the GDM decreases the incidence of these complications.^18,19

Continue to: US guidelines should be reconsidered...

US guidelines should be reconsidered

The One Step, 75-g, 2-hour oral glucose tolerance test is universally used to diagnose diabetes mellitus outside of pregnancy. Given our many noted reasons (TABLE 3), we recommend universal screening of GDM by using the One Step approach. It is time, indeed, for the United States to reconsider its guidelines for screening for GDM.

Images: Courtesy of Perinatal Quality Foundation

Transvaginal ultrasound (TVU) cervical length (CL) screening for prediction and prevention of spontaneous preterm birth (SPTB) is among the most transformative clinical changes in obstetrics in the last decades. TVU CL screening should now be offered to all pregnant women: hence the appellative ‘universal CL screening.’

TVU CL screening is an excellent screening test for several reasons. It screens for SPTB, which is a clinically important, well-defined disease whose prevalence and natural history is known, and has an early recognizable asymptomatic phase in CL shortening detected by TVU. TVU CL screening is a well-described technique, safe and acceptable, with a reasonable cutoff (25 mm) now identified for all populations, and results are reproducible and accurate. There are hundreds of studies proving these facts. In the last 10 years, TVU measurement of CL as a screening test has been accepted^1,2: it identifies women at risk for SPTB, and an early intervention (progesterone or cerclage depending on the clinical situation) is effective in preventing SPTB. Screening and treatment of short cervix is cost-effective and readily available as an early intervention (progesterone or cerclage depending on the clinical situation), is effective in preventing the outcome (SPTB), treating abnormal results is cost-effective, and facilities for screening are available and treatments are readily available.^3–5 It is also important to emphasize that CL screening for prevention of SPTB should be done by TVU, and not by transabdominal ultrasound.⁶It is best to review TVU CL screening by populations: singletons without prior SPTB, singletons with prior SPTB, and twins (Table).

Related Article:
Can transabdominal ultrasound exclude short cervix?

Singletons without prior SPTB

Women with no previous SPTB who are carrying a singleton pregnancy is the population in which TVU CL could have the greatest impact on decreasing SPTB, for several reasons:

1. Up to 60% to 90% of SPTB occur in this population.
2. More than 90% of these women have risk factors for SPTB.^7,8
3. Vaginal progesterone has been associated with a significant 39% decrease in PTB at <33 weeks of gestation and a significant 38% decrease in perinatal morbidity and mortality in a meta-analysis of randomized controlled trials (RCTs) including 606 women without prior PTB.^9,10
4. Cost-effectiveness studies have shown that TVU CL screening in this specific population prevents thousands of preterm births, saves or improves from death or major morbidity 350 babies’ lives annually, and saves approximately $320,000 per year in the US alone.³ These numbers may be even higher now as the TVU CL cutoff for offering vaginal progesterone has moved in many centers from ≤20 mm to ≤25 mm, including more women (from about 0.8% to about 2% to 3%, respectively¹¹) who benefit from screening.
5. Real-world implementation studies have indeed shown significant decreases in SPTB when a policy of universal TVU CL screening in this specific population is implemented.^12,13

Universal TVU CL screening recently called into question

In a recent article published in the Journal of the American Medical Association,¹⁴ TVU CL screening in this population, in particular for nulliparous women, has come under interrogation. The authors found only an 8% sensitivity of TVU CL screening for SPTB using a cutoff of ≤25 mm at 16 0/7 to 22 6/7 weeks of gestation in 9,410 nulliparous women. This result is different compared with other previous cohort studies in this area, however, and is likely related to a number of issues in the methodology.

First, TVU CL screening was done in many women at too early a gestational age. The earlier the CL screening, the lower the sensitivity of the procedure. Data at 16 and 17 weeks of gestation should have been excluded, as almost all RCTs and other studies on universal TVU CL screening in this population recommended doing screening at about 18 0/7 to 23 6/7 weeks.

Second, women with TVU CL <15 mm received vaginal progesterone. This would decrease the incidence of PTB and, therefore, sensitivity.

Third, outcomes data were not available for 469 women and, compared with women analyzed, these women were at higher risk for SPTB as they were more likely to be aged 21 years or younger, black, with less than a high school education, and single, all significant risk factors for SPTB. (Not all risk factors for SPTB were reported in this study.)

Fourth, pregnancy losses before 20 weeks were excluded, and these could have been early SPTB; therefore, the sensitivity could have been decreased if women with this outcome were excluded.

Fifth, prior studies have shown that TVU CL screening in singletons without prior SPTB has a sensitivity of about 30% to 40%.^15,16 In nulliparas, the sensitivity of TVU CL ≤20 mm had been reported previously to be 20%.¹⁶ Additional data from 2012–2014 at our institution demonstrate that the incidence of CL ≤25 mm is about 2.8% in nulliparous women, with a sensitivity of 19.5% for SPTB <37 weeks. These numbers show again that 8% sensitivity was low in the JAMA study¹⁴ due the shortcomings we just highlighted. Furthermore, the reported sensitivity of TVU CL ≤25 mm for PTB <32 weeks was 24% in Esplin and colleagues’ study,¹⁴ while 60% in our data. Given that early preterm births are the most significant source of neonatal morbidity and mortality, women with a singleton gestation and no prior SPTB but with a short TVU CL are perhaps the most important subgroup to identify.

Sixth, a low sensitivity in and of itself is not reflective of a poor screening test. We have known for a long time that SPTB has many etiologies. No one screening test, and no one intervention, would independently prevent all SPTBs. In a population that accounts for more than half of PTBs and for whom no other screening test has been found to be effective, much less cost effective, it is important not to cast aside the dramatic potential clinical benefit to TVU CL screening.

Related Article:
A stepwise approach to cervical cerclage

Singletons with a prior SPTB

This is the first population in which TVU CL screening was first proven beneficial for prevention of SPTB. These women all should receive progesterone starting at 16 weeks because of the prior SPTB. In these women, TVU CL screening should be initiated at 16 weeks, and repeated every 2 weeks (weekly if TVU CL is found to be 25 mm to 29 mm) until 23 6/7 weeks. If the TVU CL is identified to be <25 mm before 24 weeks, cerclage should be recommended.^1,2,17

Twins

Twins are the most recent population in which an intervention based on TVU CL screening has been shown to be beneficial. Vaginal progesterone has been associated with a significant decrease in SPTB as well as in some neonatal outcomes in twin gestations found to have a TVU CL <25 mm in the midtrimester in a meta-analysis of RCTs.¹⁸ Based on these results, we at our institution recently have started offering TVU CL screening at the time of the anatomy scan (about 20 weeks) to twin gestations.

Related Article:
Which perioperative strategies for transvaginal cervical cerclage are backed by data?

Bottom line

In summary, universal second trimester TVU CL screening of both singletons and twin gestations should be considered seriously by obstetric practitioners to successfully decrease the grave burden of SPTB.

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Images: Courtesy of Perinatal Quality Foundation

Transvaginal ultrasound (TVU) cervical length (CL) screening for prediction and prevention of spontaneous preterm birth (SPTB) is among the most transformative clinical changes in obstetrics in the last decades. TVU CL screening should now be offered to all pregnant women: hence the appellative ‘universal CL screening.’

TVU CL screening is an excellent screening test for several reasons. It screens for SPTB, which is a clinically important, well-defined disease whose prevalence and natural history is known, and has an early recognizable asymptomatic phase in CL shortening detected by TVU. TVU CL screening is a well-described technique, safe and acceptable, with a reasonable cutoff (25 mm) now identified for all populations, and results are reproducible and accurate. There are hundreds of studies proving these facts. In the last 10 years, TVU measurement of CL as a screening test has been accepted^1,2: it identifies women at risk for SPTB, and an early intervention (progesterone or cerclage depending on the clinical situation) is effective in preventing SPTB. Screening and treatment of short cervix is cost-effective and readily available as an early intervention (progesterone or cerclage depending on the clinical situation), is effective in preventing the outcome (SPTB), treating abnormal results is cost-effective, and facilities for screening are available and treatments are readily available.^3–5 It is also important to emphasize that CL screening for prevention of SPTB should be done by TVU, and not by transabdominal ultrasound.⁶It is best to review TVU CL screening by populations: singletons without prior SPTB, singletons with prior SPTB, and twins (Table).

Related Article:
Can transabdominal ultrasound exclude short cervix?

Singletons without prior SPTB

Women with no previous SPTB who are carrying a singleton pregnancy is the population in which TVU CL could have the greatest impact on decreasing SPTB, for several reasons:

1. Up to 60% to 90% of SPTB occur in this population.
2. More than 90% of these women have risk factors for SPTB.^7,8
3. Vaginal progesterone has been associated with a significant 39% decrease in PTB at <33 weeks of gestation and a significant 38% decrease in perinatal morbidity and mortality in a meta-analysis of randomized controlled trials (RCTs) including 606 women without prior PTB.^9,10
4. Cost-effectiveness studies have shown that TVU CL screening in this specific population prevents thousands of preterm births, saves or improves from death or major morbidity 350 babies’ lives annually, and saves approximately $320,000 per year in the US alone.³ These numbers may be even higher now as the TVU CL cutoff for offering vaginal progesterone has moved in many centers from ≤20 mm to ≤25 mm, including more women (from about 0.8% to about 2% to 3%, respectively¹¹) who benefit from screening.
5. Real-world implementation studies have indeed shown significant decreases in SPTB when a policy of universal TVU CL screening in this specific population is implemented.^12,13

Universal TVU CL screening recently called into question

In a recent article published in the Journal of the American Medical Association,¹⁴ TVU CL screening in this population, in particular for nulliparous women, has come under interrogation. The authors found only an 8% sensitivity of TVU CL screening for SPTB using a cutoff of ≤25 mm at 16 0/7 to 22 6/7 weeks of gestation in 9,410 nulliparous women. This result is different compared with other previous cohort studies in this area, however, and is likely related to a number of issues in the methodology.

First, TVU CL screening was done in many women at too early a gestational age. The earlier the CL screening, the lower the sensitivity of the procedure. Data at 16 and 17 weeks of gestation should have been excluded, as almost all RCTs and other studies on universal TVU CL screening in this population recommended doing screening at about 18 0/7 to 23 6/7 weeks.

Second, women with TVU CL <15 mm received vaginal progesterone. This would decrease the incidence of PTB and, therefore, sensitivity.

Third, outcomes data were not available for 469 women and, compared with women analyzed, these women were at higher risk for SPTB as they were more likely to be aged 21 years or younger, black, with less than a high school education, and single, all significant risk factors for SPTB. (Not all risk factors for SPTB were reported in this study.)

Fourth, pregnancy losses before 20 weeks were excluded, and these could have been early SPTB; therefore, the sensitivity could have been decreased if women with this outcome were excluded.

Fifth, prior studies have shown that TVU CL screening in singletons without prior SPTB has a sensitivity of about 30% to 40%.^15,16 In nulliparas, the sensitivity of TVU CL ≤20 mm had been reported previously to be 20%.¹⁶ Additional data from 2012–2014 at our institution demonstrate that the incidence of CL ≤25 mm is about 2.8% in nulliparous women, with a sensitivity of 19.5% for SPTB <37 weeks. These numbers show again that 8% sensitivity was low in the JAMA study¹⁴ due the shortcomings we just highlighted. Furthermore, the reported sensitivity of TVU CL ≤25 mm for PTB <32 weeks was 24% in Esplin and colleagues’ study,¹⁴ while 60% in our data. Given that early preterm births are the most significant source of neonatal morbidity and mortality, women with a singleton gestation and no prior SPTB but with a short TVU CL are perhaps the most important subgroup to identify.

Sixth, a low sensitivity in and of itself is not reflective of a poor screening test. We have known for a long time that SPTB has many etiologies. No one screening test, and no one intervention, would independently prevent all SPTBs. In a population that accounts for more than half of PTBs and for whom no other screening test has been found to be effective, much less cost effective, it is important not to cast aside the dramatic potential clinical benefit to TVU CL screening.

Related Article:
A stepwise approach to cervical cerclage

Singletons with a prior SPTB

This is the first population in which TVU CL screening was first proven beneficial for prevention of SPTB. These women all should receive progesterone starting at 16 weeks because of the prior SPTB. In these women, TVU CL screening should be initiated at 16 weeks, and repeated every 2 weeks (weekly if TVU CL is found to be 25 mm to 29 mm) until 23 6/7 weeks. If the TVU CL is identified to be <25 mm before 24 weeks, cerclage should be recommended.^1,2,17

Twins

Twins are the most recent population in which an intervention based on TVU CL screening has been shown to be beneficial. Vaginal progesterone has been associated with a significant decrease in SPTB as well as in some neonatal outcomes in twin gestations found to have a TVU CL <25 mm in the midtrimester in a meta-analysis of RCTs.¹⁸ Based on these results, we at our institution recently have started offering TVU CL screening at the time of the anatomy scan (about 20 weeks) to twin gestations.

Related Article:
Which perioperative strategies for transvaginal cervical cerclage are backed by data?

Bottom line

In summary, universal second trimester TVU CL screening of both singletons and twin gestations should be considered seriously by obstetric practitioners to successfully decrease the grave burden of SPTB.

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Images: Courtesy of Perinatal Quality Foundation

Transvaginal ultrasound (TVU) cervical length (CL) screening for prediction and prevention of spontaneous preterm birth (SPTB) is among the most transformative clinical changes in obstetrics in the last decades. TVU CL screening should now be offered to all pregnant women: hence the appellative ‘universal CL screening.’

TVU CL screening is an excellent screening test for several reasons. It screens for SPTB, which is a clinically important, well-defined disease whose prevalence and natural history is known, and has an early recognizable asymptomatic phase in CL shortening detected by TVU. TVU CL screening is a well-described technique, safe and acceptable, with a reasonable cutoff (25 mm) now identified for all populations, and results are reproducible and accurate. There are hundreds of studies proving these facts. In the last 10 years, TVU measurement of CL as a screening test has been accepted^1,2: it identifies women at risk for SPTB, and an early intervention (progesterone or cerclage depending on the clinical situation) is effective in preventing SPTB. Screening and treatment of short cervix is cost-effective and readily available as an early intervention (progesterone or cerclage depending on the clinical situation), is effective in preventing the outcome (SPTB), treating abnormal results is cost-effective, and facilities for screening are available and treatments are readily available.^3–5 It is also important to emphasize that CL screening for prevention of SPTB should be done by TVU, and not by transabdominal ultrasound.⁶It is best to review TVU CL screening by populations: singletons without prior SPTB, singletons with prior SPTB, and twins (Table).

Related Article:
Can transabdominal ultrasound exclude short cervix?

Singletons without prior SPTB

Women with no previous SPTB who are carrying a singleton pregnancy is the population in which TVU CL could have the greatest impact on decreasing SPTB, for several reasons:

1. Up to 60% to 90% of SPTB occur in this population.
2. More than 90% of these women have risk factors for SPTB.^7,8
3. Vaginal progesterone has been associated with a significant 39% decrease in PTB at <33 weeks of gestation and a significant 38% decrease in perinatal morbidity and mortality in a meta-analysis of randomized controlled trials (RCTs) including 606 women without prior PTB.^9,10
4. Cost-effectiveness studies have shown that TVU CL screening in this specific population prevents thousands of preterm births, saves or improves from death or major morbidity 350 babies’ lives annually, and saves approximately $320,000 per year in the US alone.³ These numbers may be even higher now as the TVU CL cutoff for offering vaginal progesterone has moved in many centers from ≤20 mm to ≤25 mm, including more women (from about 0.8% to about 2% to 3%, respectively¹¹) who benefit from screening.
5. Real-world implementation studies have indeed shown significant decreases in SPTB when a policy of universal TVU CL screening in this specific population is implemented.^12,13

Universal TVU CL screening recently called into question

In a recent article published in the Journal of the American Medical Association,¹⁴ TVU CL screening in this population, in particular for nulliparous women, has come under interrogation. The authors found only an 8% sensitivity of TVU CL screening for SPTB using a cutoff of ≤25 mm at 16 0/7 to 22 6/7 weeks of gestation in 9,410 nulliparous women. This result is different compared with other previous cohort studies in this area, however, and is likely related to a number of issues in the methodology.

First, TVU CL screening was done in many women at too early a gestational age. The earlier the CL screening, the lower the sensitivity of the procedure. Data at 16 and 17 weeks of gestation should have been excluded, as almost all RCTs and other studies on universal TVU CL screening in this population recommended doing screening at about 18 0/7 to 23 6/7 weeks.

Second, women with TVU CL <15 mm received vaginal progesterone. This would decrease the incidence of PTB and, therefore, sensitivity.

Third, outcomes data were not available for 469 women and, compared with women analyzed, these women were at higher risk for SPTB as they were more likely to be aged 21 years or younger, black, with less than a high school education, and single, all significant risk factors for SPTB. (Not all risk factors for SPTB were reported in this study.)

Fourth, pregnancy losses before 20 weeks were excluded, and these could have been early SPTB; therefore, the sensitivity could have been decreased if women with this outcome were excluded.

Fifth, prior studies have shown that TVU CL screening in singletons without prior SPTB has a sensitivity of about 30% to 40%.^15,16 In nulliparas, the sensitivity of TVU CL ≤20 mm had been reported previously to be 20%.¹⁶ Additional data from 2012–2014 at our institution demonstrate that the incidence of CL ≤25 mm is about 2.8% in nulliparous women, with a sensitivity of 19.5% for SPTB <37 weeks. These numbers show again that 8% sensitivity was low in the JAMA study¹⁴ due the shortcomings we just highlighted. Furthermore, the reported sensitivity of TVU CL ≤25 mm for PTB <32 weeks was 24% in Esplin and colleagues’ study,¹⁴ while 60% in our data. Given that early preterm births are the most significant source of neonatal morbidity and mortality, women with a singleton gestation and no prior SPTB but with a short TVU CL are perhaps the most important subgroup to identify.

Sixth, a low sensitivity in and of itself is not reflective of a poor screening test. We have known for a long time that SPTB has many etiologies. No one screening test, and no one intervention, would independently prevent all SPTBs. In a population that accounts for more than half of PTBs and for whom no other screening test has been found to be effective, much less cost effective, it is important not to cast aside the dramatic potential clinical benefit to TVU CL screening.

Related Article:
A stepwise approach to cervical cerclage

Singletons with a prior SPTB

This is the first population in which TVU CL screening was first proven beneficial for prevention of SPTB. These women all should receive progesterone starting at 16 weeks because of the prior SPTB. In these women, TVU CL screening should be initiated at 16 weeks, and repeated every 2 weeks (weekly if TVU CL is found to be 25 mm to 29 mm) until 23 6/7 weeks. If the TVU CL is identified to be <25 mm before 24 weeks, cerclage should be recommended.^1,2,17

Twins

Twins are the most recent population in which an intervention based on TVU CL screening has been shown to be beneficial. Vaginal progesterone has been associated with a significant decrease in SPTB as well as in some neonatal outcomes in twin gestations found to have a TVU CL <25 mm in the midtrimester in a meta-analysis of RCTs.¹⁸ Based on these results, we at our institution recently have started offering TVU CL screening at the time of the anatomy scan (about 20 weeks) to twin gestations.

Related Article:
Which perioperative strategies for transvaginal cervical cerclage are backed by data?

Bottom line

In summary, universal second trimester TVU CL screening of both singletons and twin gestations should be considered seriously by obstetric practitioners to successfully decrease the grave burden of SPTB.

Share your thoughts! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Preterm birth (PTB) remains a major cause of perinatal morbidity and mortality, and so its prediction and prevention are 2 of the most important issues in obstetrics. Cervical length (CL) measured by ultrasound has been shown to be the best predictor; several interventions (vaginal progesterone and cerclage) have been shown to be effective at reducing PTB if a short CL is identified. In fact, both the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) recommend CL being measured every 2 weeks from 16 to 23 weeks in singletons with prior spontaneous PTB (sPTB), with cerclage placed for CL less than 25 mm. Moreover, both ACOG and SMFM recommend that “universal CL screening” (CL measured in singletons without a prior sPTB) be considered as a single measurement at about 18 to 23 weeks.

Details of the study
Rhoades and colleagues present data on CL screening done by transabdominal ultrasound (TAU), as an alternative to transvaginal ultrasound (TVU). This study confirms early data:

There are several other reasons why TVU is considered the gold standard for CL screening, and instead TAU CL should be avoided as possible. All randomized controlled trials that showed benefit from interventions (vaginal progesterone, cerclage, pessary) aimed at decreasing PTB in women with short CL used TVU CL screening and never TAU CL screening. In addition, TAU CL is less accurate than TVU CL screening. On TAU, fetal parts can obscure the cervix, obesity makes it hard to visualize CL, the distance between probe and cervix is longer, manual pressure can mask CL shortening, and bladder filling can elongate CL.⁷ Cost-effectiveness studies show that TVU CL screening is more effective, and less costly, compared with TAU CL screening, even in singletons without a prior sPTB.⁸

Societies such as ACOG and SMFM all have recommended TVU CL for prediction and prevention of PTB, over TAU CL.^9,10 Importantly, a TVU CL should be done by sonographers educated and trained formally, through such programs as those made available by SMFM.¹¹

What this evidence means for practice
If CL assessment is done, TVU should be preferred, as it is the gold standard, and not TAU.
>>Vincenzo Berghella, MD

Share your thoughts on this article! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Preterm birth (PTB) remains a major cause of perinatal morbidity and mortality, and so its prediction and prevention are 2 of the most important issues in obstetrics. Cervical length (CL) measured by ultrasound has been shown to be the best predictor; several interventions (vaginal progesterone and cerclage) have been shown to be effective at reducing PTB if a short CL is identified. In fact, both the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) recommend CL being measured every 2 weeks from 16 to 23 weeks in singletons with prior spontaneous PTB (sPTB), with cerclage placed for CL less than 25 mm. Moreover, both ACOG and SMFM recommend that “universal CL screening” (CL measured in singletons without a prior sPTB) be considered as a single measurement at about 18 to 23 weeks.

Details of the study
Rhoades and colleagues present data on CL screening done by transabdominal ultrasound (TAU), as an alternative to transvaginal ultrasound (TVU). This study confirms early data:

There are several other reasons why TVU is considered the gold standard for CL screening, and instead TAU CL should be avoided as possible. All randomized controlled trials that showed benefit from interventions (vaginal progesterone, cerclage, pessary) aimed at decreasing PTB in women with short CL used TVU CL screening and never TAU CL screening. In addition, TAU CL is less accurate than TVU CL screening. On TAU, fetal parts can obscure the cervix, obesity makes it hard to visualize CL, the distance between probe and cervix is longer, manual pressure can mask CL shortening, and bladder filling can elongate CL.⁷ Cost-effectiveness studies show that TVU CL screening is more effective, and less costly, compared with TAU CL screening, even in singletons without a prior sPTB.⁸

Societies such as ACOG and SMFM all have recommended TVU CL for prediction and prevention of PTB, over TAU CL.^9,10 Importantly, a TVU CL should be done by sonographers educated and trained formally, through such programs as those made available by SMFM.¹¹

What this evidence means for practice
If CL assessment is done, TVU should be preferred, as it is the gold standard, and not TAU.
>>Vincenzo Berghella, MD

Share your thoughts on this article! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.

Preterm birth (PTB) remains a major cause of perinatal morbidity and mortality, and so its prediction and prevention are 2 of the most important issues in obstetrics. Cervical length (CL) measured by ultrasound has been shown to be the best predictor; several interventions (vaginal progesterone and cerclage) have been shown to be effective at reducing PTB if a short CL is identified. In fact, both the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine (SMFM) recommend CL being measured every 2 weeks from 16 to 23 weeks in singletons with prior spontaneous PTB (sPTB), with cerclage placed for CL less than 25 mm. Moreover, both ACOG and SMFM recommend that “universal CL screening” (CL measured in singletons without a prior sPTB) be considered as a single measurement at about 18 to 23 weeks.

Details of the study
Rhoades and colleagues present data on CL screening done by transabdominal ultrasound (TAU), as an alternative to transvaginal ultrasound (TVU). This study confirms early data:

There are several other reasons why TVU is considered the gold standard for CL screening, and instead TAU CL should be avoided as possible. All randomized controlled trials that showed benefit from interventions (vaginal progesterone, cerclage, pessary) aimed at decreasing PTB in women with short CL used TVU CL screening and never TAU CL screening. In addition, TAU CL is less accurate than TVU CL screening. On TAU, fetal parts can obscure the cervix, obesity makes it hard to visualize CL, the distance between probe and cervix is longer, manual pressure can mask CL shortening, and bladder filling can elongate CL.⁷ Cost-effectiveness studies show that TVU CL screening is more effective, and less costly, compared with TAU CL screening, even in singletons without a prior sPTB.⁸

Societies such as ACOG and SMFM all have recommended TVU CL for prediction and prevention of PTB, over TAU CL.^9,10 Importantly, a TVU CL should be done by sonographers educated and trained formally, through such programs as those made available by SMFM.¹¹

What this evidence means for practice
If CL assessment is done, TVU should be preferred, as it is the gold standard, and not TAU.
>>Vincenzo Berghella, MD

Share your thoughts on this article! Send your Letter to the Editor to [email protected]. Please include your name and the city and state in which you practice.