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PLoS Med. 2018 Sep 26;15(9):e1002656. doi: 10.1371/journal.pmed.1002656. eCollection 2018 Sep.

Delivery outcomes in term births after bariatric surgery: Population-based matched cohort study.

Author information

Department of Medicine, Solna, Clinical Epidemiology Unit, Karolinska Institutet, Stockholm, Sweden.
Division of Obstetrics and Gynaecology, Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden.
Department of Surgery, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.



Obesity increases the risk of adverse delivery outcomes. Whether weight loss induced by bariatric surgery influences these risks remains to be determined. The objective was to investigate the risk of adverse delivery outcomes among post-surgery women compared with women without bariatric surgery history but with similar characteristics.


We identified 801,443 singleton live-born term births (≥37 gestational weeks) in the Swedish Medical Birth Register between 1 January 2006 and 31 December 2013, of which 1,929 were in women with a history of bariatric surgery and a pre-surgery weight available from the Scandinavian Obesity Surgery Registry. For each post-surgery delivery, up to 5 control deliveries were matched by maternal pre-surgery BMI (early-pregnancy BMI used for controls), age, parity, smoking, education, height, country of birth, and delivery year (N post-surgery deliveries:matched controls = 1,431:4,476). The main outcome measures were mode of delivery, induction of labor, post-term pregnancy (≥42 + 0 gestational weeks), epidural analgesia, fetal distress, labor dystocia, peripartum infection, obstetric anal sphincter injury (perineal tear grade III-IV), and postpartum hemorrhage. Among the women with a history of bariatric surgery, the mean pre-surgery BMI was 42.6 kg/m2, the median surgery-to-conception interval was 1.4 years, and the mean BMI loss between surgery and early pregnancy was 13.5 kg/m2 (38 kg). Compared to matched control women, post-surgery women were less likely to have cesarean delivery (18.2% versus 25.0%, risk ratio [RR] 0.70, 95% CI 0.60-0.80), especially emergency cesarean (6.8% versus 15.1%, RR 0.40, 95% CI 0.31-0.51). Post-surgery women also had lower risks of instrumental delivery (5.0% versus 6.5%, RR 0.73, 95% CI 0.53-0.98), induction of labor (23.4% versus 34.0%, RR 0.68, 95% CI 0.59-0.78), post-term pregnancy (4.2% versus 10.3%, RR 0.40, 95% CI 0.30-0.53), obstetric anal sphincter injury (1.5% versus 2.9%, RR 0.46, 95% CI 0.25-0.81), and postpartum hemorrhage (4.6% versus 8.0%, RR 0.58, 95% CI 0.44-0.76). Since this study was not randomized, a limitation is the possibility of selection bias, despite our efforts using careful matching.


Bariatric-surgery-induced weight loss was associated with lower risks for adverse delivery outcomes in term births.

Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: MN reports being a member of the scientific advisory board for Itrim (<$5000 (£3876; €4430)/year). IN reports fees for lectures and consulting, Baricol Bariatrics AB, Sweden. The other authors have no competing interests to state.

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