Hypertension & Preeclampsia
Evidence from Epidemiologic Studies
In 1985, Dyerberg and Bang observed the relative rarity of preeclampsia and eclampsia among Greenland Eskimos compared with Danish women. Based on these initial observations, investigators tested the hypothesis that omega-3 fatty acids might reduce the risk for preeclampsia by means of their biologic activities as inhibitors of the two series eicosanoids (TXA2) and also as antioxidants, by vasodilatation and decreasing platelet and leukocyte reactivity.[3,51] A number of observational studies that followed supported an association between increased omega-3 fatty acid concentrations in maternal erythrocytes and reduced risk for preeclampsia.[3,52,53] In the earliest of these, a 1991 case–control study, Wang measured omega-3 and omega-6 PUFA in term patients with and without preeclampsia and in nonpregnant volunteers. This study found that total plasma PUFA levels were decreased in preeclamptic women compared with normal term gravidas, and decreased levels of EPA were seen in preeclamptic women compared with normal controls. In 1995, Williams published a case–control study of maternal erythrocyte PUFA levels at delivery among 22 preeclamptic women and 40 normal controls. This study demonstrated that women with the lowest levels of omega-3 fatty acids were 7.6-times more likely to have been diagnosed with preeclampsia than normal controls, and increased omega-3:omega-6 ratios were associated with a reduced likelihood of preeclampsia. Similarly, in a recent Peruvian case–control study, 99 preeclamptic women and 100 controls were stratified into quartiles based on omega-3 fatty acid levels, using the highest quartile as the reference group. In this study, erythrocyte fatty acid levels were used because they are thought to be an accurate reflection of dietary intake over the preceding 3 months. The authors found that each successively lower quartile was associated with an increase in risk for preeclampsia (odds ratios: 1.5, 2.7 and 4.2).
However, several other observational studies using diet histories were not able to confirm an association of omega-3 fatty acid levels with preeclampsia.[48,54] In a published case–control study retrospectively utilizing food frequency questionnaires, Kesmodel found no association between maternal diet and preeclampsia risk. In a recent observational survey from Iceland, Olafsdottir et al. used prospective administration of the food frequency questionnaire at 11–15 weeks' gestation to assess the effect of cod liver oil in early pregnancy on the risk of gestational hypertension and hypertensive disorders of pregnancy. They found that moderate self-reported cod liver oil intake was protective against hypertensive disease, while low and high intake increased the risk for gestational hypertension and hypertensive disorders. Cod liver oil contains omega-3 fatty acids as well as substantial doses of vitamins A, D and E, so it is unclear whether the 'U-shaped' dose–response relationship between consumption and hypertensive disorders resulted from these vitamins or omega-3 fatty acids.
Evidence from Clinical Trials
Two recent meta-analyses have been conducted to explore the possible preventive efficacy of LC-PUFA supplementation on pregnancy-induced hypertension and preeclampsia. Among low- and high-risk women, no effect on the incidence of pregnancy-induced hypertension or preeclampsia was found.[46,47] In several of the included studies, fatty acid supplementation was not instituted until the late second or early third trimester of pregnancy, long after the pathophysiologic processes thought responsible for the clinical manifestations of preeclampsia were well underway.[56–58]
Expert Rev of Obstet Gynecol. 2010;5(1):125-138. © 2010
Cite this: Role of Omega-3 Fatty Acids in Maternal, Fetal, Infant and Child Wellbeing - Medscape - Jan 01, 2010.