Clinical Pearls & Morning Reports

Posted by Carla Rothaus

Published July 20, 2022


What potential harms to the fetus does maternal obesity during pregnancy present?

Although the absolute risk of severe adverse maternal, fetal, and newborn outcomes is low among women with obesity, instituting healthy eating and exercising behaviors before pregnancy, ideally, or as early in pregnancy as is feasible can minimize excessive gestational weight gain and help mitigate pregnancy-related and long-term complications for women and their offspring. Read the NEJM Review Article here.

Clinical Pearls

Q: What are some of the antepartum complications associated with maternal obesity during pregnancy?

A: Women with obesity are more likely than normal-weight women to miscarry, regardless of whether conception is spontaneous or assisted. Meta-analyses have shown that women with obesity are 3 to 4 times as likely to have gestational diabetes as normal-weight women. Gestational hypertension and preeclampsia are more prevalent among women with obesity than among women of normal weight, with the estimated risk of preeclampsia doubling for every increase of 5 to 7 in the body-mass index (BMI).

Q: What potential harms to the fetus does maternal obesity during pregnancy present?

A: Maternal obesity has been found to be associated with an increased risk of a range of structural anomalies, especially congenital heart defects and neural-tube defects, with evidence of a dose–response relationship with BMI. The antepartum identification of congenital anomalies may be limited in women with obesity, since the ultrasound signal can be attenuated by predominately centrally stored fat. The risk of stillbirth is 1.3 to 2.1 times as high among women with obesity as among normal-weight women, on the basis of several meta-analyses.

Morning Report Questions

Q: In what ways are labor and delivery affected by obesity in pregnant women?

A: Heslehurst et al. found higher rates of labor induction, oxytocin augmentation, failure of labor to progress, and instrumental delivery among women with obesity as compared with normal-weight women. Also documented is a higher risk of post-term birth with increasing BMI, with an odds ratio of 1.75 (95% CI, 1.50 to 2.04) for women with a BMI of 50 or higher. Obesity alone is not an indication for cesarean delivery. Nevertheless, the association between obesity and cesarean delivery has been documented in various practice settings. The risk of cesarean delivery for women with obesity is double the risk for normal-weight women, with a dose–response relationship. Obesity alone is not an indication for labor induction, and a vaginal birth should be encouraged. Similarly, a history of bariatric surgery should not be considered an indication for cesarean delivery. 

Q: Does bariatric surgery mitigate or add to the potential complications of pregnancy in women with a history of obesity?

A: Bariatric surgery has been shown to improve fertility through ovulation restoration. In a large meta-analysis, bariatric surgery before pregnancy was associated with reduced risks of gestational diabetes, large for gestational age, hypertensive disorders, postpartum hemorrhage, and cesarean delivery, as compared with BMI-matched controls who did not undergo bariatric surgery. Conversely, bariatric surgery can be accompanied by surgical complications, micronutrient deficiencies, and endocrine and metabolic disorders, all of which need to be assessed. Adverse perinatal outcomes such as small for gestational age, preterm birth, congenital abnormalities, and perinatal mortality have also been cited, with an increased risk among women who become pregnant soon after surgery. Thus, the American College of Obstetricians and Gynecologists recommends that women wishing to conceive after bariatric surgery delay pregnancy for at least 12 to 18 months after surgery or until a stable postprocedure weight is achieved.

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