Diet During Pregnancy and Risk of Preeclampsia or Gestational Hypertension
Introduction
Hypertensive disorders of pregnancy, including preeclampsia (PE) and gestational hypertension (GH), are associated with substantial morbidity and mortality for both mother and child. Most established risk factors for PE or GH, including maternal age, race/ethnicity, parity, and previous hypertension or PE, are not modifiable (1). During the past two decades, a number of studies have examined whether maternal diet during pregnancy might influence risk for PE or GH.
A systematic review of randomized clinical trials demonstrated a reduction in the relative risk for the development of high blood pressure (0.58, 95% confidence interval [95% CI]: 0.22–0.97) and PE (0.35, 95% CI 0.20–0.60) with supplementation of at least 1 g/day of calcium during pregnancy (2). However, the largest trial, the Calcium for Preeclampsia Prevention trial, did not find a benefit of calcium supplementation on PE or GH (3). Observational studies have suggested potential benefits of other nutrients, including n-3 fatty acids or fish oils 4, 5, 6, magnesium (7), and antioxidant vitamins (8), and a potential risk of trans fatty acids (9), based upon either dietary intake or levels of biomarkers among women who develop PE. However, not all observational studies and randomized trials have shown any effect of these nutrients 10, 11, 12, 13, 14, 15, 16, 17. In particular, recent trials have not supported a benefit of vitamins C and E 18, 19, 20.
Both randomized trials and observational studies are valuable in studying nutrient-outcome associations. Although experimental trials can minimize confounding and demonstrate causality, observational studies can provide information about a range of nutrient intake and about nutrients derived from foods as well as from supplements. The purpose of this observational study was to examine associations of maternal intake of milk, fish, calcium, n-3 and n-6 fatty acids, trans fatty acids, magnesium, folate, and vitamins C, D, and E from both foods and supplements with development of PE or GH.
Section snippets
Population and Study Design
Study subjects were participants in Project Viva, a prospective observational cohort study of gestational diet and other behaviors, pregnancy outcomes, and offspring health. We recruited women attending their initial prenatal visit at one of eight urban and suburban obstetrical offices in a multispecialty group practice in eastern Massachusetts from 1999 to 2002. Recruitment and retention details have been summarized previously 21, 22. All mothers provided informed consent, and all procedures
Results
Among the 1718 participants in this study, 59 (3%) developed PE, and 119 developed (7%) GH. Half (49%) were nulliparous. Consistent with other studies, women with PE were more likely to be nulliparous, age < 20 or > 40 years, black, unmarried, less educated, overweight, have higher first-trimester systolic blood pressure, and have a prior history or PE or GH (Table 1). Women who developed GH were more likely to be nulliparous, white, less educated, overweight, have a higher first trimester
Discussion
In this prospective study, we found no evidence that intake of calcium, folate, or antioxidant vitamins reduced risk for PE or GH or that intake of n-6 or trans fatty acids increased risks. We observed a somewhat reduced risk for PE associated with intake of elongated n-3 fatty acids and fish. The prevalence of and risk factors for GH and PE in our population were similar to those reported in previous studies (30).
The hypothesis that fish oil might be protective against hypertensive disorders
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This project was supported by grants from the National Institutes of Health (HD 34568, HL 64925, HL 68041, HD 44807), the Robert H. Ebert Fellowship, the March of Dimes Birth Defects Foundation, and by Harvard Medical School and the Harvard Pilgrim Health Care Foundation.