To Örebro University

OBJECTIVE: To investigate whether gastric bypass before pregnancy is associated with reduced risk of preeclampsia.

DESIGN: Nationwide matched cohort study.

SETTING: Swedish national health care.

POPULATION: =2766:2766) on pre-surgery/early-pregnancy BMI, diabetes status (pre-surgery/pre-conception), maternal age, early-pregnancy smoking status, educational level, height, country of birth, delivery year and history of preeclampsia.

MAIN OUTCOME MEASURES: Preeclampsia categorised into any, preterm onset (<37+0 weeks), and term onset (≥37+0 weeks).

RESULTS: (39kg). Post-gastric bypass pregnancies had lower risk of preeclampsia compared to pre-surgery BMI-matched controls (1.7 vs. 9.7 per 100 pregnancies; hazard ratio [HR] 0.21, 95%CI 0.15-0.28) and early-pregnancy BMI-matched controls (1.9 vs. 5.0 per 100 pregnancies; HR 0.44, 95%CI 0.33-0.60). Although relative risks for preeclampsia for post-gastric bypass pregnancies vs. pre-surgery matched controls was similar, absolute risk differences were significantly greater for nulliparous (RD -13.6 per 100 pregnancies, 95%CI -16.1 to -11.2) vs. parous women (RD -4.4 per 100 pregnancies, 95%CI -5.7 to -3.1).

CONCLUSION: We found that gastric bypass was associated with lower risk of preeclampsia, with the largest absolute risk reduction among nulliparous women.