Recommendations by the Institute of Medicine (IOM) on gestational weight gain (GWG) for women with histories of bariatric surgery have yet to be studied.

To describe GWG in women with histories of bariatric surgery and to investigate the relationship between GWG and maternal and neonatal outcomes.

A bicentric retrospective study on the medical charts of pregnant women with histories of bariatric surgery who delivered between 2003 and 2017 in two level III maternity units. In accordance with IOM guidelines, GWG was classified as insufficient, adapted, or excessive.

At least 337 pregnancies from 264 patients were included in this study. Of these pregnancies, 154 (45.7%) occurred after gastric banding, 135 (40.1%) after Roux-en-Y gastric bypass, and 48 (14.2%) after sleeve gastrectomy. GWG was adapted in 90 of the pregnancies (26.7%), insufficient in 11 of the pregnancies (35%), and excessive in 129 of pregnancies (38.3%). Gestational age at birth was significantly lower when GWG was insufficient (37.7 ± 4.2 weeks vs. 38.8 ± 2.9 weeks for adequate GWG and 39.4 ± 1.8 weeks for excessive GWG). When compared to normal GWG, insufficient GWG was indicated to be a risk factor for preterm labor (adjusted OR, 3.05, 95% CI 1.30–7.17). When compared to excessive GWG, insufficient GWG increased the rates of small for gestational age (SGA) newborns (OR, 1.96, 95% CI 1.04–3.68), preterm labor (OR, 4.13, 95% CI 1.84–9.24), and preterm delivery (OR, 6.40, 95% CI 2.41–17.0).

In our study, adequate GWG was associated with better obstetrical outcomes, resulting in the conclusion that IOM recommendations applied to pregnant women who had undergone bariatric surgery. Our findings suggest that the large proportion of women with insufficient GWG may account for increased rates of SGA and preterm birth.