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Pregnant post-bariatric patients have similar or greater weight gain, but no impact on birth weight

Post-bariatric women seem to have similar or greater gestational weight gain (GWG) vs women without surgery matched for early-pregnancy or pre-surgery BMI, respectively, according to researchers from Imperial College London, UK. However, they also found that that for surgical patients, GWG does not seem to be associated with birth weight (BW) or the higher prevalence of small-for-gestational-age (SGA) neonates.

The authors noted that this study was part of a larger prospective, longitudinal study investigating the impact of bariatric surgery on maternal and perinatal outcomes (Maric T et al. Maternal, neonatal insulin resistance and neonatal anthropometrics in pregnancies following bariatric surgery. Metabolism. 2019;97:25–31). In that study, women with previous bariatric surgery, and those without, were recruited in the first trimester of pregnancy and seen at five time points during pregnancy (11–14, 20–24, 28–30, 30–32, 35–37 weeks) and at delivery. The neonatal BW was measured soon after delivery and SGA and large for GA neonates were defined as delivery of a neonate with BW < 10th and > 90th percentile, respectively.

In the current study, 100 post-bariatric pregnant women were matched with 100 pregnant women with no weight loss surgery history but with similar early-pregnancy BMI. The post-bariatric group included 21 women who had undergone a gastric band procedure, 30 sleeve gastrectomy and 49 with gastric bypass.


The mean surgery to conception interval was approximately 4.5 years (55.89 (36.13) months) and only 8 women conceived within 12 months of the surgery. The mean BMI loss was 12.18 (6.32) kg/m2. The total GWG and BMI gain (12 to 36 weeks) was comparable between the groups and the number of women who had appropriate, insufficient and excessive GWG was similar between the groups and among women with different types of bariatric surgery. Post-bariatric women (especially those that had undergone a sleeve gastrectomy or a gastric bypass) delivered smaller babies and tended to have more SGA and less LGA babies, although these differences did not reach a significance in our population.

The Pearson correlation revealed that maternal age (p<0.01), ethnic group (p=0.07), total GWG (p<0.05), previous bariatric surgery (p<0.01) and gestational age at delivery (p<0.01) were significant determinants of BW, whereas maternal smoking (p=0.54), method of conception (p=0.46), parity (p=0.35), presence of diabetes (p=0.45) or hypertensive disorders (p=0.41) were not.

In the post-bariatric group as a whole, we also found no association between maternal GWG and BW (p=0.52), and this was the case even if when different types of surgery were considered separately (p=0.67, p=0.93 and p=0.61 for women with a gastric band, sleeve gastrectomy and gastric bypass, respectively). There was also no correlation between insufficient GWG and delivery of a SGA neonate in the post-bariatric group or when women with a gastric band (p =0.29), sleeve gastrectomy (p = 0.71), and gastric bypass (p = 0.75) were considered separately.

“Pregnant women with previous bariatric surgery have similar or greater GWG compared to no surgery pregnant women matched for early-pregnancy and pre-surgery BMI, respectively,” they concluded. “However, the GWG of post-bariatric women does not seem to be associated with BW or the higher prevalence of SGA neonates seen in this population. Furthermore, studies are required to investigate the determinants of BW in this high-risk group.”

The outcomes were reported in the paper, ‘Gestational Weight Gain in Pregnancies Following Bariatric Surgery’, published in Obesity Surgery.

To access this paper, please click here


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