Bariatric surgery reduces pregnancy weight gain, study reveals

Pregnancy weight gain is decreased in women with a history of bariatric surgery, according to a recent study published in JAMA Network Open.

Obesity is defined as a body mass index (BMI) of 30 or greater, and rates of obesity have increased worldwide among women of reproductive age over time. Currently, bariatric surgery is the most effective obesity treatment, with associated decreased risks of gestational diabetes, preeclampsia, cesarean delivery, and large-for-gestational age birth.

While these outcomes are also associated with pregnancy weight gain, a connection has not been made between bariatric surgery and postoperative pregnancy weight gain. There is also little data on the impact of time and weight loss from bariatric surgery to conception on postoperative pregnancy weight gain.

To determine the association between bariatric surgery and postoperative pregnancy weight gain, investigators conducted a nationwide, population-based, matched cohort study. Deliveries from 2014 to 2021 registered in the Swedish Medical Birth Register and Pregnancy Register were included in the analysis.

Exclusion criteria included no valid personal identification number, multiple births, bariatric surgical procedures that aren’t gastric bypass or sleeve gastrectomy and missing gestational age. Pregnancies with missing early-pregnancy BMI or pregnancy weight gain, implausible pregnancy weight gain z score values, presurgery BMI below 30, and 31 or more days from last weight measurement to delivery were also excluded.

A history of gastric bypass or sleeve gastrectomy before conception was the primary exposure of the analysis, determined using data from the Scandinavian Obesity Surgery Registry. The surgery-to-conception interval and surgery-to-conception weight lossof participants were also reported.

Pregnancy weight gain was identified by measuring weight at delivery or weight at last antenatal visit when weight at delivery wasn’t available. Early-pregnancy BMI-specific z score charts were used to measure pregnancy weight gain z scores. Covariates included early pregnancy smoking status, mother’s country of birth, highest education level, and parity.

There were 12,776 pregnancies included in the final analysis, of which 6388 were bariatric surgery pregnancies and 6388 were controls. After a 1:1 propensity score matching,890 gastric bypass pregnancies were matched to 890 sleeve gastrectomy pregnancies.

A mean early-pregnancy BMI of 29.4 was reported in both groups, with overweight being the BMI category with the most women at 40.8%. Women in both groups were more often nonsmokers, had 10 to 12 years of education, and had a previous child.

Decreased pregnancy weight gain was observed in patients with a history of bariatric surgery compared to those with no prior bariatric surgery across all early-pregnancy BMI categories. Women with a normal or overweight early-pregnancy BMI status saw the greatest magnitude of difference. 

Similar pregnancy weight gains were observed among matched women with a history of sleeve gastrectomy vs gastric bypass. The lowest pregnancy weight gain was observed among women who conceived within 1 year of bariatric surgery, with a continuous increase in pregnancy weight gain until 2 years post-surgery observed.

Weight gain remained mostly stable from 4 to 10 years post-surgery. Surgery type and parity did not impact this association. Additionally, a positive association between surgery-to-conception weight loss and pregnancy weight gain was observed in all early-pregnancy BMI categories.

These results indicated an association between bariatric surgery and reduced pregnancy weight gain. Investigators concluded women with a clinical history of bariatric surgery and normal weight gain in early pregnancy should receive clinical attention.

Reference

Xu H, Holowko N, Näslund I, et al. Pregnancy weight gain after gastric bypass or sleeve gastrectomy. JAMA Netw Open. 2023;6(12). doi:10.1001/jamanetworkopen.2023.46228