New research finds a link between preterm delivery and maternal risk of cardiovascular disease.
Preterm births occur when a baby is born earlier than 37 weeks into the pregnancy. According to the latest statistics from the Centers for Disease Control and Prevention (CDC), premature births affect approximately 1 in 10 babies in the United States.
Most of these babies are at a serious risk of developing disabilities or even dying, as the brain goes through crucial developments in the final weeks of the pregnancy. Additionally, the final weeks are crucial for the full development of vital organs, such as the lungs and liver.
Mothers who do not carry births to term may also be at risk of illness. Previous research has linked preterm births to cardiovascular risk later in life, but it has been unclear whether lifestyle factors leading up to the pregnancy, or pre-existing cardiovascular risk factors, have influenced this association.
New research, published in Circulation, the journal of the American Heart Association (AHA), investigates whether the previously documented risk of cardiovascular disease (CVD) remains after adjusting for lifestyle and CVD factors before the pregnancy.
The research was led by Dr. Janet Rich-Edwards, director of developmental epidemiology at the Connors Center for Women's Health and Gender Biology at Brigham and Women's Hospital (BWH) in Boston, MA.
CVD risk doubles for women who deliver earlier than 32 weeks
Researchers analyzed existing data on 70,182 women from the Nurses' Health Study 2 - one of the largest ongoing studies into the risk factors for major chronic diseases in women.
They analyzed the link between premature births and CVD, and adjusted for factors such as the mother's age, education, and lifestyle before the pregnancy, as well as CVD risk factors.
The study revealed that preterm delivery correlated with a 40 percent higher risk of developing CVD compared with women who gave birth at term, and the risk increased for women who had more than one preterm delivery. Women who delivered earlier than 32 weeks had double the risk of developing CVD.
The increased risk remained even when the preterm deliveries were not complicated by high blood pressure disorders during pregnancy.
According to AHA, women already have a risk of dying from CVD of 33 percent. This number rises to 36 percent for those who give birth 3 to 7 weeks before term, and rises to as high as 60 percent for mothers who deliver 8 or more weeks early.
Dr. Rich-Edwards and team hope that their research will help to identify women at a particularly high risk of CVD, and enable professionals to take appropriate preventive measures.
"Very little of the risk associated with preterm delivery was explained by traditional cardiovascular risk factors like overweight and hypertension. We need more research to understand why women who deliver preterm are at higher risk, and what we can do to help them lower it."
Dr. Janet Rich-Edwards
"Delivering a preterm infant may be an early warning signal of high risk for cardiovascular disease," adds Lauren Tanz, first author of the study and a programmer and analyst at BWH. "Since cardiovascular risk develops over a lifetime, it is not too early for these women to adopt a heart-healthy lifestyle."