Background: Evaluating the effect of restricted activity on the development of preeclampsia under experimental clinical settings has been compromised by inherent selection bias and differential misclassification. The aim of our study was to overcome such limitations by using hospitalized bedrest for preterm labor/birth-related indications as an unbiased measure of restricted activity and evaluate its effect on the development of hypertensive diseases of pregnancy.
Methods: We conducted a retrospective cohort study using data from the McGill Obstetrical and Neonatal Database on all pregnancies that took place between 1991 and 2001. We defined "exposure" as hospitalized bed rest for preterm labor/birth related indications and used unconditional logistic regression models to estimate its adjusted effect on the development of hypertensive diseases of pregnancy.
Results: Data were available on 36,140 pregnancies. 677 women were hospitalized and prescribed bedrest for either preterm contractions (71%), preterm premature rupture of membranes (18%), an incompetent cervix (8%), or other indications. Among all women, bedrest was associated with a significant reduced risk for developing preeclampsia, 0.27 (0.16-0.48). In a stratified analysis, women delivering prior to 34 weeks of gestation had an even more pronounced reduced risk for developing preeclampsia 0.12 (0.03-0.50) as well as a reduced risk for developing intrauterine growth restriction 0.38 (0.18-0.84).
Conclusion: When strictly adhered to, bedrest may be an effective measure in the prevention of preeclampsia and early intrauterine growth restriction.