Preeclampsia. A nested, case-control study of risk factors and their interactions

To study the risk factors for preeclampsia and their interactions.

We used a nested, case-control study design to analyze data collected in the Delivery Interview Program, 1977-1980, Boston Hospital for Women (now known as the Brigham and Women's Hospital), Boston. Cases (n = 386) of obstetrician-diagnosed preeclampsia were compared with randomly selected controls (n = 2,355). Using multiple logistic regression, we derived maximum likelihood estimates of adjusted odds ratios (ORs) and 95% confidence intervals (CIs).

The following risk factors were statistically significantly associated with preeclampsia: urinary tract infection (UTI) during pregnancy (OR 1.6, 95% CI 1.1-2.5), primiparity (OR 3.8, 95% CI 2.8-5.2), black race (OR 1.5, 95% CI 1.1-1.9), less than a high school education (OR 2.0, 95% CI 1.1-3.6), exposure to diethylstilbestrol in utero (OR 2.4, 95% CI 1.2-2.4), body mass index (kg/m2) > 30 (OR 2.7, 95% CI 1.6-4.4) and cigarette smoking (OR 0.6, 95% CI 0.5-0.8). When evaluating interactions between variables, we found that primiparas who had UTI during pregnancy were five times more likely (OR 5.3, 95% CI 2.9-9.7) to have preeclampsia than were primiparas who did not have UTI during pregnancy.

It is possible that the preeclampsia associated with some of the risk factors we identified could be modified by the use of prophylactic drugs or other interventions. The primipara with a UTI would be a most likely beneficiary.