Pregnant women with preeclampsia have a higher risk of delivering an infant with a congenital heart defect. An extensive study of 1.9 million mother and infant pairs by a team at the University of Montreal Hospital Research Centre (CRCHUM) has shown significant association between these diseases in mothers and newborns from early pregnancy. The study published this week in the prestigious Journal of the American Medical Association (JAMA), provides the basis for future research to better prevent and detect these diseases.
Congenital heart defects are the most common anomalies in infants, affecting every 8 births per 1,000, and are a major cause of infant illness and death, despite significant advancements in medical care. "We discovered that congenital heart defects were significantly more frequent for infants of women with preeclampsia during pregnancy," said Dr. Nathalie Auger, first author of the study, researcher at the CRCHUM, and professor at the University of Montreal's Department of Social and Preventive Medicine.
Why are some babies born with heart defects? The origin is sometimes hereditary; beyond that, however, the risk factors are mostly unknown. Researchers have considered a possible link with preeclampsia, a disorder of pregnancy characterized by high blood pressure and excess protein in the urine (proteinuria). "Pregnant women with preeclampsia and infants born with heart defects have similarities in terms of the biological factors involved in the formation of blood vessels. This coincidence in the imbalance of angiogenic factors prompted us to conduct this population-based study," said Dr. Auger.
The researchers examined the hospital records of live births for the entire province of Quebec - comprising a quarter of Canada's population - between 1989 and 2012. All women who delivered an infant after 20 weeks of pregnancy during this period were included, representing 1,942,072 neonates.
Overall, 17,296 neonates, or 8.9 per 1,000, had heart defects. Prevalence was higher for infants of women with preeclampsia than without preeclampsia (16.7 vs. 8.6 per million). The most frequent heart defects were non-critical, such as septal defects, characterized by a hole in the wall separating the ventricles or atria of the heart and causing blood flow problems. "The absolute risk of congenital heart defects is low. But there is a link between preeclampsia and heart defects in newborns. And the risk is higher when preeclampsia occurs before 34 weeks of pregnancy," noted Auger.
Preeclampsia is detectable from the 20th week of pregnancy. The disease can sometimes progress to frank eclampsia, endangering the life of the mother and child in the most serious cases. In fact, biomarkers that prevent the formation of blood vessels are present from the beginning of pregnancy in women who later develop preeclampsia. The baby's heart is formed at the beginning of intrauterine life. Heart defects usually occur between eight and ten weeks of gestation. "There is a possible common factor in the embryo and the mother that triggers both preeclampsia and heart defects very early in pregnancy," said the epidemiologist.
Currently, women diagnosed with preeclampsia are closely monitored to see if the baby is developing normally. Most infants with congenital heart defects can be saved. They are treated with medications, non-invasive procedures, or surgery. "Further research is needed before changing medical recommendations. But knowing that preeclampsia can increase the risk of congenital heart defects in the unborn child should help us better understand the pathophysiology of these diseases and ultimately improve their prevention and treatment," concluded Dr. Auger.