The association between maternal pre-pregnancy body mass index and pregnancy outcomes of preeclampsia.

Objective: To evaluate the effects of pre-pregnancy maternal body mass index (BMI) to pregnancy outcomes in patients diagnosed as preeclampsia.

Materials And Methods: This was a retrospectively study on women who had been diagnosed as preeclampsia and delivered at Seoul National University Bundang Hospital between June 2017 and March 2020. Multifetal gestation, major fetal anomaly, and fetal death in utero were excluded. A total of 150 singleton pregnancies were included and divided into four groups according to the pre-pregnancy BMI classification: underweight (<18.5 kg/m, n = 6), normal (18.5-22.9 kg/m, n = 66), overweight (23.0-24.9 kg/m, n = 26), and obese (≥25.0 kg/m, n = 52). Pregnancy outcomes including gestational age at delivery, birthweight, and delivery modes were reviewed.

Results: The rates of preterm birth before 34 weeks of gestation were 67%, 49%, 35%, and 27% for underweight group, normal BMI group, overweight group, and obese group, respectively (p-trend = 0.006). The birthweight of newborn increased significantly as pre-pregnancy BMI increased (p-trend<0.001). The proportions of small for gestational age (SGA) were highest in underweight group and decreased as pre-pregnancy BMI increased (67%, 41%, 42%, and 10% for each group, respectively, p-trend<0.001).

Conclusion: The rates of preterm birth before 34 weeks and SGA increased as pre-pregnancy BMI decreased in patients with preeclampsia.

Implications For Practice: Women with underweight before pregnancy are at the highest risk for preterm birth and SGA, therefore they need to be monitored more intensively when diagnosed as preeclampsia.