OBJECTIVE:

To examine the association between physical activity in early pregnancy and risk of pre-eclampsia.

DESIGN:

Prospective cohort.

SETTING:

Denmark.

POPULATION:

A total of 85,139 pregnant Danish women, recruited between 1996 and 2002.

METHODS:

The authors assessed leisure time physical activity in first trimester by a telephone interview and categorised women a priori into seven groups: 0 (reference), 1-44, 45-74, 75-149, 150-269, 270-419 and 420+ minutes/week. Pre-eclampsia diagnoses were extracted from the Danish National Patient Registry. A number of potential confounders were adjusted for by logistic regression.

MAIN OUTCOME MEASURES:

Pre-eclampsia and severe pre-eclampsia.

RESULTS:

The two highest physical activity levels were associated with increased risk of severe pre-eclampsia compared with the nonexercising group, with adjusted odds ratios of 1.65 (95% CI: 1.11-2.43) and 1.78 (95% CI: 1.07-2.95), whereas more moderate levels of physical activity (1-270 minutes/week) had no statistically significant association with risk of pre-eclampsia (total n = 85,139).

CONCLUSIONS:

We were unable to document a protective effect of leisure time physical activity against pre-eclampsia. Our data even suggest that leisure time physical activity exceeding 270 minutes/week in first trimester may increase risk of severe pre-eclampsia.