DALLAS - March 23, 2015 - Women who give birth to four or more children are more likely to have cardiovascular changes that can be early indicators of heart disease than women who have fewer children, new research by UT Southwestern Medical Center cardiologists finds.
"This study adds to a body of evidence that pregnancy, which generally occurs early in a woman's life, can provide insight into a woman's future cardiovascular risk," said Dr. Monika Sanghavi, Assistant Professor of Internal Medicine and lead author of the study.
Using data gathered for the Dallas Heart Study, researchers compared the number of live births reported by women in the study with their coronary artery calcium (CAC) levels and aortic wall thickness (AWT). High levels of coronary artery calcification and thicker aortic walls are markers of heart disease that show up before symptoms develop.
Women were divided into three groups: One or no live births, two to three live births, and four or more live births. Women who reported four or more live births had a 27 percent prevalence of a high calcium score compared with 11 percent among those with two to three live births. The trend was similar when looking at AWT measurements.
The associations were not affected by adjusting for socioeconomic status or traditional cardiovascular risk factors, suggesting that physiological changes associated with pregnancy may account for the change, Dr. Sanghavi said.
Further studies will be needed to identify the causes, but researchers said one possibility might be that women who have many pregnancies may have more visceral fat (fat around abdominal organs), which has been linked to increased heart disease risk. Another possibility could be that increased cholesterol and higher blood sugar associated with pregnancy may lead to increased risk.
"During pregnancy, a woman's abdominal size increases, she has higher levels of lipids in her blood, and higher blood sugar levels," Dr. Sanghavi said. "Each pregnancy increases this exposure."
The study also found slightly higher rates of high CAC and AWT measurements among women who had one or no children, compared with women who gave birth to two or three children, suggesting a U-shaped association between number of births and heart disease, with the lowest risk at two or three births.
"It's likely that there is a different mechanism for the increased risk at the low end," Dr. Sanghavi said. "Some of these women could have some underlying disease that prevents them from carrying births to term and increases their risk for heart disease."
"We are learning that there are numerous physiologic changes during pregnancy that have consequences for future heart health," said senior author Dr. Amit Khera, Associate Professor of Internal Medicine, who directs the Preventive Cardiology Program and holds the Dallas Heart Ball Chair in Hypertension and Heart Disease. "This study reminds us of the importance of taking a pregnancy history as part of cardiovascular disease screening."
Researchers in the Division of Cardiology of Internal Medicine and the Department of Obstetrics and Gynecology at UT Southwestern examined data reported for 1,644 women in the Dallas Heart Study, which has collected heart-related data from a sampling of Dallas County residents for more than a decade to help identify social and biological variables contributing to ethnic differences in cardiovascular health. The research appears in the European Journal of Preventive Cardiology.
Other UT Southwestern researchers involved were Dr. Colby Ayers, Faculty Associate in the Department of Clinical Sciences; Dr. David Nelson, Assistant Professor of Obstetrics and Gynecology and Dedman Family Scholar in Clinical Care; Dr. Robert Stewart, Assistant Professor of Obstetrics and Gynecology; and Dr. James de Lemos, Professor of Internal Medicine, Medical Director for the Dallas Heart Study, and holder of the Sweetheart Ball?Kern Wildenthal, M.D., Ph.D. Distinguished Chair in Cardiology. Researchers from the University of California San Francisco and Medical College of Wisconsin also were involved.
About UT Southwestern Medical Center
UT Southwestern, one of the premier academic medical centers in the nation, integrates pioneering biomedical research with exceptional clinical care and education. The institution's faculty includes many distinguished members, including six who have been awarded Nobel Prizes since 1985. Numbering approximately 2,800, the faculty is responsible for groundbreaking medical advances and is committed to translating science-driven research quickly to new clinical treatments. UT Southwestern physicians provide medical care in 40 specialties to about 92,000 hospitalized patients and oversee approximately 2.1 million outpatient visits a year.