The impact of maternal body mass index on the phenotype of pre-eclampsia: a prospective cohort study

Please cite this paper as: Anderson N, McCowan L, Fyfe E, Chan E, Taylor R, Stewart A, Dekker G, North R, on behalf of the SCOPE Consortium. The impact of maternal body mass index on the phenotype of pre‐eclampsia: a prospective cohort study. BJOG 2012;119:589–595. Objective We hypothesised that among nulliparous women with pre‐eclampsia, overweight or obese women would have a different phenotype of pre‐eclampsia compared with normal weight women with pre‐eclampsia. Specifically, they are more likely to develop term pre‐eclampsia and less likely to have indicators of impaired placental perfusion, e.g. abnormal uterine artery Doppler or a small‐for‐gestational‐age (SGA) infant. Design Prospective, multicentre, cohort SCOPE study (n = 3170). Setting New Zealand and Australia. Population Nulliparous women who developed pre‐eclampsia. Methods Participants were interviewed at 14–16 weeks of gestation, uterine artery Doppler studies were performed at 19–21 weeks and pregnancy outcome was tracked prospectively. Main outcome measures Rates of abnormal uterine artery Doppler indices, term/preterm birth and SGA infants were compared between normal, overweight and obese women with pre‐eclampsia. Multivariable analysis was performed to examine the association between body mass index (BMI) and term pre‐eclampsia. Results Of 178 women with pre‐eclampsia, one underweight woman was excluded and 66 (37%) were normal weight, 52 (29%) were overweight and 59 (34%) were obese. Pre‐eclampsia developed preterm in 26% of women and at term in 74% of women. There were no differences in the rates of term/preterm pre‐eclampsia, abnormal uterine artery Doppler indices or SGA infants between BMI groups (P > 0.10). No independent association between BMI and term pre‐eclampsia was found (P = 0.56). Conclusions Among women with pre‐eclampsia, those who are overweight or obese in early pregnancy are not more likely to have term pre‐eclampsia compared with women with a normal BMI. Overweight and obese women require vigilant surveillance for the development of preterm as well as term pre‐eclampsia.