Study Supports Recommendations To Avoid Pregnancy For At Least 12 Months After Bariatric Surgery

A new study supports recommendations to avoid pregnancy for 12 months after bariatric surgery due to an association with adverse outcomes in pregnancy, including an elevated risk of preterm birth. These findings were presented at the virtual European Congress on Obesity, held May 10-13.

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More than half of all female patients who undergo bariatric surgery are of reproductive age, and the resulting weight loss improves fertility, as well as reducing the risk of gestational diabetes and hypertensive disorders during pregnancy. In addition, it lowers the chance of the baby having a high birth weight, which is associated with an increased risk of complications for both mother and child, according to the study.

The current recommendations for women undergoing bariatric surgery are to avoid pregnancy for 12 to 24 months after the operation to avoid problems caused by ongoing active weight loss and an increased risk of malnutrition due to a markedly reduced calorie intake. This most likely occurs within the first 12 months after surgery and can decrease the nutritional supply to the growing fetus, potentially affecting its development and resulting in a reduced birth weight and greater likelihood of preterm birth.

"Previous studies found no associations between the time from surgery to conception and adverse pregnancy or neonatal outcomes,” the study authors said in the press release. “In fact, most studies confirm that the risk of these outcomes is not increased during the first 12 months after bariatric surgery compared to later pregnancies."

The objective of the study was to evaluate pregnancy and birth outcomes by surgery-to-conception interval and by adherence to the recommendations for gestational weight gain of the National Academy of Medicine. Births were categorized based on surgery-to-conception interval and gestational weight gain, with the primary outcome variables gestational age at delivery, preterm birth, birth weight, and weight-for-age percentile.

The authors defined preterm birth as having a gestation period of less than 37 weeks, whereas gestation periods of less than 32 weeks were classified as very preterm based on the definition used by the World Health Organization. The relationship between the weight of an infant at birth relative to its gestational age was compared against birth weight charts and adjusted for sex. Those within the top 10% were classified as being large-for-gestational-age (LGA), with the bottom 10% classified as small-for-gestational age (SGA).

The study authors performed a retrospective analysis of 196 single pregnancies in mothers who had previously undergone bariatric surgery using the Roux-en-Y gastric bypass, sleeve gastrectomy, or one anastomosis gastric bypass methods. These pregnancies were assigned to 1 of 3 groups based on time interval from surgery to conception: early group (less than 12 months), the middle group (12-24 months), and the late group (more than 24 months). Further, gestational weight gain was classified as inadequate, adequate, or excessive according to National Academy of Medicine recommendations.

In the study cohort, 23.5% of the women had conceived within 12 months of their operation. Pregnancies classified as early were associated with a lower gestational age at delivery, lower gestational weight gain, and lower neonatal birth weight than those classified as being in the middle and late groups, according to the study.

"Although the difference of 200 g in neonatal birth weight is probably not clinically relevant, the lower gestational age in the 'early' group might be alarming as we also found a trend towards more preterm births in this group,” the study authors said in the press release.

The team also found an association between “inadequate” gestational weight gain, lower gestational age at delivery, and lower neonatal birth weight compared to pregnancies in the “adequate” weight gain group. Inadequate gestational weight gain was also associated with a higher rate of preterm births than pregnancies with adequate gestational weight gain.

"Our findings support the recommendation to avoid pregnancy for 12 months after bariatric surgery. We should encourage women who wish to conceive after bariatric surgery to avoid pregnancy until their weight has stabilized to minimize the risk of inadequate gestational weight gain,” the study authors said in the press release. “In order to break the vicious cycle of obesity and its health consequences, it is important that future research and clinical care focus on the prevention of babies being born small for gestational age after bariatric surgery."

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