Institute Activities and Advances
Studies conducted in recent years by researchers at the NICHD and elsewhere have found markers in the blood of pregnant women that seem to signal the later development of preeclampsia. Identifying such substances—related to the apparent biochemical basis for preeclampsia—is an important step in developing treatments for the condition as well as better ways to identify who is at risk.
Researchers at the NICHD's Division of Intramural Population Health Research (DIPHR) found strong evidence that an imbalance of two proteins produced by the placenta is responsible for the symptoms of preeclampsia. Abnormally high levels of these proteins appear to deprive the blood vessels of substances needed to keep the lining of the blood vessels healthy. Deprived of these essential substances, the cells lining the blood vessels begin to sicken and die. As a result, blood pressure increases, and the blood vessels leach protein into the tissues and urine. Both proteins appear to contribute to the development of preeclampsia. Severe disease usually occurs in women with high levels of both measures and not in women with high levels of only one or the other. (PMID: 16957146)
Other DIPHR researchers are investigating the relationship of angiogenic factors to the pathogenesis of preeclampsia and their potential for identifying women at high risk of developing preeclampsia. Several studies are currently exploring this area of research. In addition, a recent study found that elevated blood pressure in pregnancy is linked to an increased risk for cardiovascular disease, chronic kidney disease, and diabetes later in life. (PMID: 23401113)
The NICHD's Pregnancy and Perinatology Branch (PPB) funds and oversees research grants to independent researchers throughout the U.S. and abroad to study medical management and prevention of preeclampsia. Some avenues of research related to preeclampsia include the impact of obesity on the condition, the potential role of autoimmunity, and fetal genetic contributions.
Although the exact mechanism of preeclampsia is unknown, it appears that the condition is due to poor blood flow from the uterus to the placenta. In a normal pregnancy, placental cells known as trophoblastic cells migrate to uterine blood vessels and increase their size. In preeclampsia, the trophoblastic cells fail to migrate completely towards the uterine blood vessels, resulting in less uterine blood flow to the placenta. In turn, the poorly nourished placenta releases factors into the maternal circulation that result in the systemic symptoms of the disease.
PPB-supported research has helped determine the source and role of proteins and other chemical factors that are important in establishing sufficient blood flow to the placenta. (PMID: 20948996, PMID: 18093648).
In addition, researchers in the Program in Perinatal Research and Obstetrics, in the NICHD's Division of Intramural Research, are investigating preeclampsia as part of a larger effort to prevent preterm birth. Efforts have included examining the possibility that infection contributes to preeclampsia. Researchers also are calibrating measurements of growth factors in the blood and testing the reliability of these measurements as a way of predicting when women will develop preeclampsia. Their clinical findings indicate that this approach has promise for predicting when a woman will develop preeclampsia that requires delivery before the pregnancy reaches full term. Read more about the Program’s research in the Division’s annual report.
Other Activities and Advances
The PPB created the Maternal-Fetal Medicine Units Networkin 1986 to focus on clinical questions in maternal-fetal medicine and obstetrics, particularly with respect to the continuing problem of preterm birth. Several studies affiliated with the network are investigating preeclampsia:
- The Combined Antioxidants and Preeclampsia Prediction Studies, co-funded by the National Heart, Lung, and Blood Institute, were designed to see if antioxidants (vitamins C and E) could prevent preeclampsia in women at low risk for the condition. The results showed that antioxidants neither decrease the incidence of preeclampsia nor reduce the risk of complications associated with pregnancy-related hypertension.1
- Two other studies assessed whether low-dose aspirin (60 mg) could lower the incidence of preeclampsia. One study found that low-dose aspirin did not reduce the incidence in women at high risk of the condition (those with diabetes, chronic hypertension, previous preeclampsia, or multifetal gestation).2 The other study found that low-dose aspirin marginally decreased the incidence of preeclampsia among women in their first pregnancy but increased the risk of placental abruption.3
- Roberts, J. M., Myatt, L., Spong, C. Y., Thom, E. A., Hauth, J. C., Leveno, K. J. et al; Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. (2010). Vitamins C and E to prevent complications of pregnancy-associated hypertension. New England Journal of Medicine, 362(14), 1282–1291. [top]
- Caritis, S., Sibai, B., Hauth, J., Lindheimer, M. D., Klebanoff, M., Thom, E., et al. for the National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. (1998). Low-dose aspirin to prevent preeclampsia in women at high risk. New England Journal of Medicine, 338(11), 701–705. [top]
- Sibai, B. M., Caritis, S. N., Thom, E., Klebanoff, M., McNellis, D., Rocco, L., et al. for the National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units. (1993). Prevention of preeclampsia with low-dose aspirin in healthy, nulliparous pregnant women. New England Journal of Medicine, 329(17), 1213–1218. [top]