Maternal bariatric Surgery in a Swiss matched Cohort Study: More Harm than Good?

Introduction:

Obesity is increasing worldwide amongst the population at reproductive age and is a known risk factor for reproductive health problems and adverse pregnancy outcome. Nowadays bariatric surgery is a therapeutic option for women who do not achieve weight loss through dietary modifications and exercise. This study is the first matched cohort study to compare fetal and maternal outcomes after bariatric surgery at a tertiary hospital in Switzerland.

Methods:

All women with a history of bariatric surgery who delivered at our institution between 2005 and 2018 were identified retrospectively. Data on pre-pregnancy parameters and pregnancy outcomes were extracted from our database. Propensity score matching was applied to identify a cohort of gravidae without previous bariatric surgery, but accounting for age, pre-pregnancy Body Mass Index, parity, multiples, preexisting diabetes and hypertension. Matching was performed in a 3:1 ratio. Cohorts were compared using chi-square or Mann Whitney-U test, as appropriate.

Results:

We identified 40 gravidae with previous bariatric surgery (n = 39 for gastric bypass, n = 1 for gastric banding). There were no cases of pre-pregnancy diabetes mellitus type I or II in the group of post-surgery gravidae. Compared to the matched cohort of 120 non-surgery gravidae, we did not find significant differences in gestational weight gain (10.0 kg [6.0 – 14.3] vs. 12.0 kg [7.2 – 17.0], p= 0.126) nor in prevalence of gestational diabetes (10.0% (n = 4) vs. 20.8% (n = 25), p= 0.123) or preeclampsia (5.0% (n = 2) vs. 5.8% (n = 7), p= 0.843). However, there was a significantly increased number of late spontaneous abortions (7.5% (n = 3) vs. 0%, p= 0.002) and newborns had significantly lower birth weight (35.7 percentile [19.5 – 61.0] vs. 52.7 percentile [26.3 – 77.9], p= 0.036) in post-surgery gravidae.

Conclusions:

Our findings suggest that pre-pregnancy bariatric surgery poses the fetus at risk for a lower birth weight. We assume that it is of importance to monitor these pregnancies closely for adequate fetal growth as well as to optimize the nutritional status of the women before and during pregnancy.