Risk factors for preeclampsia in nulliparous women in distinct ethnic groups: a prospective cohort study

To determine whether baseline characteristics during early pregnancy, proposed as potential risk factors for preeclampsia, show differences in prevalence and effects within distinct ethnic groups.

In a prospective cohort study of 2413 healthy nulliparous women from eight midwives' practices, we analyzed risk factors for preeclampsia (maternal age, body mass index, blood pressure at booking, smoking habit, and abortion history) in white, Mediterranean, Asian, and black women. In a univariate analysis, we estimated the relative risk of preeclampsia for the baseline variables and for ethnicity. In a multivariate analysis, we evaluated the simultaneous effect of the baseline variables in white (n = 1641) and black (n = 317) women.

Significant differences were found in the prevalence of the risk factors in different ethnic groups. In the univariate analysis, the relative risk (RR) of preeclampsia in black women was 2.4 (95% confidence interval [CI] 1.1, 5.6) compared with white women. In the multivariate analysis in white women, the adjusted RR of preeclampsia for a diastolic blood pressure at booking above 70 mmHg was 4.4 (CI 0.9, 20.8). Among black women, the adjusted RR of preeclampsia was increased for high maternal age (RR 1.2; CI 1.0, 1.4), but not for a diastolic blood pressure at booking above 70 mmHg (RR 0.8; CI 0.2, 3.9).

In studies of risk factors for preeclampsia, black women should be analyzed separately from white women.