Giving Birth Even Once Linked to Worse Cardiovascular Health

Diana Swift

November 07, 2019

Mothers may need interventions before and after giving birth to prevent poor cardiovascular health later. According to the National Heart Lung and Blood Institute's Multi-Ethnic Study of Athersclerosis (MESA), having even one baby — but especially five or more — is associated with poorer maternal cardiovascular health (CVH) in middle and late adulthood.

Oluseye Ogunmoroti, MD, MPH, a biostatistician at the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease in Baltimore, Maryland, and colleagues published the findings of their multisite study in the December issue of the American Journal of Obstetrics and Gynecology.

Analyzing health records and survey data from a large community-based cohort of women with no cardiovascular disease (CVD) at baseline, those with a history of one to two, three to four, and five or more live births had a lower prevalence of average CVH scores compared with those who had zero live births. Furthermore, in women with five or more live births, the prevalence of optimal CVH scores was lower than in those with zero live births, and the prevalence of ideal body mass index (BMI) was lower.

These findings held after factoring in demographic variables such as age, race/ethnicity, education, income, health insurance, marital status, MESA field site, current use of hormone therapy, and menopausal status.

"Future studies should be conducted to examine the implications of our findings, including exploring the mechanisms by which multiparity contributes to poor CVH and studying whether targeted preventive interventions geared at women at the time of pregnancy can improve their CVH later in life," Ogunmoroti and colleagues explain.

During 2000 to 2002, MESA recruited 3430 women aged 45 to 84 years. All had a physical exam, gave blood samples, and completed surveys about their health habits. The cohort was 38% white, 28% African American, 23% Hispanic, and 11% Chinese American; 18% reported no births, 39% reported one or two, 19% three or four, and 13% five or more.

The researchers calculated CVH scores according to Life's simple 7, a seven-metric system from the American Heart Association that assesses smoking, physical activity, BMI, diet, blood pressure, total cholesterol, and blood glucose, and graded each participant for each risk factor on a scale of 0 to 2, with 2 indicating ideal status, 1 intermediate status, and 0 poor status.

Specific Findings

The mean CVH score was lower with higher parity (8.9, 8.7 , 8.5, and 7.8 for 0, 1 - 2, 3 - 4 and ≥ 5 live births, respectively). Average scores were significantly lower for all parity categories vs nulliparity (prevalence odds ratios [OR] were 0.64 for parity of 1 - 2, 0.65 for parity 3 - 4, and 0.64 for parity of ≥ 5). Optimal CVH scores were also less common in women with more than five live births, for an OR of 0.50.

A total of 698 women scored 11 to 14 for all seven factors and were deemed to have optimal CVH. A total of 1118 scored 9 to 10 points for an average CVD risk, and 1614 women scored 8 or fewer points in total and were considered to have inadequate heart health scores.

Average CVH scores were dose-dependent (9 for 0 births, 8.7 for 1 - 2, 8.5 for 3 - 4, and 7.8 for ≥ 5). Of the 453 women with at least five live births, 35 had optimal CVH compared with 279 who had the lowest scores.

Mothers with a parity of at least five births were more likely to be Hispanic, have higher systolic blood pressure or fasting blood glucose, report less physical activity, and have an annual income of lower than $40,000.

"The metabolic processes occurring during pregnancy such as changes in lipids, glucose, and weight may partly explain the increased burden of CVD among multiparous women later in life," the authors write.

They noted that an earlier meta-analysis including 10 cohorts totaling more than 3 million women found an increased risk of incident CVD events associated with parity vs nulliparity in a nonlinear, dose-dependent fashion.

Focus On Postpartum Wellness, Risk Factor Screening

Study coauthor Erin D. Michos, MD, MHS, director of the women's cardiovascular health program at the Ciccarone Center, said in a news release the results don't indicate that women should have fewer children but that attention needs to be focused on postpartum wellness and risk factor screening, particularly in multiparous mothers.

Nor do the findings point to a causal relationship between pregnancy and CVD. "Both biological and social factors are likely the culprits in raising heart disease risk," Michos added.

On a daily basis, mothers caring for multiple children may have less time to exercise, plan for healthy eating, and take steps to return to their pre-pregnancy weight, Michos explained. In addition, gestational weight gain can raise blood lipid levels and increase insulin resistance, raising CVD risk.

"The next steps for this research will be to design a study to determine if there is a causal relationship between higher number of live births and poorer cardiovascular health, in addition to exploring the biological mechanisms by which more live births may worsen cardiovascular health," Ogunmoroti said in the release. He and his associates say their findings further emphasize the need for CVD awareness and prevention in women.

The Multi-Ethnic Study of Atherosclerosis is supported by the National Heart, Lung, and Blood Institute and the National Center for Research Resources. Michos is supported by the Blumenthal Scholars Fund in Preventive Cardiology. The remaining authors have disclosed no relevant financial relationships.

Am J Obstet Gynecol. Published online July 5, 2019. Abstract

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