Familial occurrence of preeclampsia.

We conducted a cohort study on whether preeclampsia during the pregnancy of a mother is a risk factor for preeclampsia during the pregnancy of her daughter. Data from the Medical Birth Registry were combined with data from a local registry of births from 1955 to 1990. We could identify the births of 22,768 elder daughters and 2,959 younger daughters. These daughters had also experienced at least one delivery. If the mother had preeclampsia during her pregnancy with an elder daughter, then the elder daughter had an increased risk for preeclampsia in her first pregnancy (relative risk (RR) = 1.7; 95% confidence interval (CI) = 1.3-2.2). This increased risk persisted into the elder daughter's second pregnancy (RR = 1.7; 95% CI = 1.1-2.6). The risks for the daughters were also increased to a similar level if the mother had experienced preeclampsia in any other pregnancy. Furthermore, the risks were similarly elevated if only mothers with firstborn children were included in the analyses. Hence, preeclampsia during the pregnancy of a mother was a risk factor for development of preeclampsia during the pregnancy of her daughters; however, owing to a relatively small population attributable proportion, genetic predisposition explained only a minor part of the occurrence of preeclampsia in this population.