Pregnancy after bariatric surgery and adverse perinatal outcomes: A systematic review and meta-analysis

Abstract

Background: Women who undergo bariatric surgery prior to pregnancy are less likely to experience comorbidities associated with obesity such as gestational diabetes and hypertension. However, bariatric surgery, particularly malabsorptive procedures, can make patients susceptible to deficiencies in nutrients that are essential for healthy fetal development. The objective of this systematic review and meta-analysis is to investigate the association between pregnancy after bariatric surgery and adverse perinatal outcomes.

Methods and findings: Searches were conducted in Medline, Embase, PsycINFO, CINAHL, Scopus, and Google Scholar from inception to June 2019, supplemented by hand-searching reference lists, citations, and journals. Observational studies comparing perinatal outcomes post-bariatric surgery to pregnancies without prior bariatric surgery were included. Outcomes of interest were perinatal mortality, congenital anomalies, preterm birth, postterm birth, small and large for gestational age (SGA/LGA), and neonatal intensive care unit (NICU) admission. Pooled effect sizes were calculated using random-effects meta-analysis. Where data were available, results were subgrouped by type of bariatric surgery. We included 33 studies with 14,880 pregnancies post-bariatric surgery and 3,979,978 controls. Odds ratios (ORs) were increased after bariatric surgery (all types combined) for perinatal mortality (1.38, 95% confidence interval [CI] 1.03-1.85, p = 0.031), congenital anomalies (1.29, 95% CI 1.04-1.59, p = 0.019), preterm birth (1.57, 95% CI 1.38-1.79, p < 0.001), and NICU admission (1.41, 95% CI 1.25-1.59, p < 0.001). Postterm birth decreased after bariatric surgery (OR 0.46, 95% CI 0.35-0.60, p < 0.001). ORs for SGA increased (2.72, 95% CI 2.32-3.20, p < 0.001) and LGA decreased (0.24, 95% CI 0.14-0.41, p < 0.001) after gastric bypass but not after gastric banding. Babies born after bariatric surgery (all types combined) weighed over 200 g less than those born to mothers without prior bariatric surgery (weighted mean difference -242.42 g, 95% CI -307.43 to -177.40 g, p < 0.001). There was low heterogeneity for all outcomes (I2 < 40%) except LGA. Limitations of our study are that as a meta-analysis of existing studies, the results are limited by the quality of the included studies and available data, unmeasured confounders, and the small number of studies for some outcomes.

Conclusions: In our systematic review of observational studies, we found that bariatric surgery, especially gastric bypass, prior to pregnancy was associated with increased risk of some adverse perinatal outcomes. This suggests that women who have undergone bariatric surgery may benefit from specific preconception and pregnancy nutritional support and increased monitoring of fetal growth and development. Future studies should explore whether restrictive surgery results in better perinatal outcomes, compared to malabsorptive surgery, without compromising maternal outcomes. If so, these may be the preferred surgery for women of reproductive age.

Trial registration: PROSPERO CRD42017051537.

Fig 1. PRISMA flowchart of included studies.

BMI, body mass index.

Fig 2. Perinatal mortality and congenital anomalies after bariatric surgery meta-analysis.

Association between maternal bariatric surgery and (A) perinatal mortality (includes stillbirth) and (B) congenital anomalies. Studies are presented as Author, year. The forest plots are stratified by type of surgery. n = cases of perinatal mortality or congenital anomalies. N = total group size. *BPD only. BPD, biliopancreatic diversion; CI, confidence interval; OR, odds ratio; ppBMI, prepregnancy body mass index matched; RYGB, Roux-en-Y gastric bypass; SG, sleeve gastrectomy.

Fig 3. Preterm and postterm birth after bariatric surgery meta-analysis.

Association between maternal bariatric surgery and (A) preterm birth (<37 weeks) and (B) postterm birth (>41 or >42 weeks). Studies are presented as Author, year. The forest plots are stratified by type of surgery, with separate pooled OR (95% CI) when subgroup analysis was possible. n = cases of preterm or postterm birth. N = total group size. *LAGB and SG. ^†SG only. CI, confidence interval; LAGB, laparoscopic adjustable gastric banding; OR, odds ratio; ppBMI, prepregnancy body mass index matched; RYGB, Roux-en-Y gastric bypass; SG, sleeve gastrectomy.

Fig 4. Size for gestational age after bariatric surgery meta-analysis.

Association between maternal bariatric surgery and (A) small for gestational age (includes low birth weight < 2,500 g for three studies) and (B) large for gestational age (includes macrosomia > 4,000 g for seven studies). Studies are presented as Author, year. Results are subgrouped by type of surgery. n = cases of small or large for gestational age. N = total group size. *BPD only. ^†LAGB and SG. ^‡SG only. BPD, biliopancreatic diversion; CI, confidence interval; LAGB, laparoscopic adjustable gastric banding; OR, odds ratio; ppBMI, prepregnancy body mass index matched; RYGB, Roux-en-Y gastric bypass; SG, sleeve gastrectomy.

Fig 5. NICU admission after bariatric surgery meta-analysis.

Association between maternal bariatric surgery and NICU admission. Studies are presented as Author, year. The forest plot is stratified by type of surgery. n = cases of NICU admission. N = total group size. *SG only. CI, confidence interval; LAGB, laparoscopic adjustable gastric banding; NICU, neonatal intensive care unit; OR, odds ratio; ppBMI, prepregnancy BMI matched; RYGB, Roux-en-Y gastric bypass; SG, sleeve gastrectomy.