March 31, 2015
2 min read

Number of births may affect atherosclerosis risk in women

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The number of live births is associated with subclinical coronary and aortic atherosclerosis in women, according to new data from the Dallas Heart Study.

Researchers observed a U-shaped curve, in which women with four or more live births and women with one or no births had increased coronary artery calcium (CAC) and aortic wall thickness compared with women with two or three live births.

“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 [CV] risk,” Monika Sanghavi, MD, assistant professor of internal medicine at the University of Texas Southwestern Medical Center, Dallas, said in a press release.

Monika Sanghavi, MD

Monika Sanghavi

Sanghavi and colleagues analyzed 1,644 women (mean age, 45 years; 55% black) from the Dallas Heart Study. All were aged 30 to 65 years and had data on live births and CAC measured by CT or aortic wall thickness measured by MRI.

The researchers adjudicated CAC as positive at more than 10 Agatston units, and aortic wall thickness as elevated if greater than the 75th percentile by age and sex.

In sequential multivariable models, they adjusted for age, race, traditional CV risk factors, BMI, income, education, hormone therapy, oral contraceptives and physical activity.

Elevated risk and many births

Compared with two or three live births, women with four or more live births had greater risk for the prevalence of elevated CAC (OR = 2.2; 95% CI, 1.28-3.65) and aortic wall thickness (OR = 1.6; 95% CI, 1.04-2.41).

Possible explanations include women with many pregnancies having more visceral fat, and increased cholesterol and blood glucose associated with pregnancy leading to increased CV risk, Sanghavi said in the release.

“During pregnancy, a woman’s abdominal size increases, she has higher levels of lipids in her blood and higher blood sugar levels,” she said. “Each pregnancy increases this exposure.”

Elevated risk and few births

Compared with two or three live births, women with one or no live births had increased CAC (OR = 1.9; 95% CI, 1.16-3.03) and increased aortic wall thickness (OR = 1.5; 95% CI, 1.05-2.09) after multivariable adjustment.

“It is likely that there is a different mechanism for the increased risk at the low end,” Sanghavi said in the release. “Some of these women could have underlying disease that prevents them from carrying births to term and increases their risk for heart disease.”

According to the researchers, study limitations include a retrospective cohort design that limits the ability to assess for causality; the possibility of other biological or socioeconomic factors not accounted for; no data on total number of pregnancies or miscarriages; no information on preeclampsia, gestational diabetes and other pregnancy complications known to increase risk for CVD; and the inclusion of women in their 30s who may give birth in the future.

“We are learning that there are numerous physiologic changes during pregnancy that have consequences for future heart health,” researcher Amit V. Khera, MD, MSc, FACC, associate professor of medicine, director of the preventive cardiology program, program director of the cardiology fellowship, and Dallas Heart Ball chair in hypertension and heart disease at University of Texas Southwestern Medical Center, said in the release. “This study reminds us of the importance of taking a pregnancy history as part of [CVD] screening.” – by Erik Swain

Disclosure: The researchers report no relevant financial disclosures.