The study shows that women who became first-time mothers in their teens were “significantly more likely” than older mums to have greater risks for heart and blood vessel disease.
Researchers found that women who had a baby before the age of 20 scored significantly higher on the Framingham Risk Score – a measure used to estimate the 10-year cardiovascular risk.
In comparison, women who had their first child in their twenties or later had lower average risk scores.
The lowest cardiovascular risk was among women who had never given birth.
Study lead author Doctor Catherine Pirkle, an assistant professor in the Office of Public Health Studies at the University of Hawaii, said: “Adolescent mothers may need to be more careful about lifestyle factors that increase the risk of cardiovascular disease, including maintaining a healthy body weight and sufficient physical activity.
“Clinicians may need to pay more careful attention to women’s reproductive characteristics, and more intensive screening of cardiovascular-disease risk may be required of women reporting early childbirths.”
While previous studies found that women who had several pregnancies had higher cardiovascular risks, here, among women who had children, the number of lifetimes births did not affect cardiovascular risk.
Dr Pirkle said that women who had never given birth may have miscarried or terminated pregnancies, but would have experienced dramatically lower average levels of pregnancy-related complications.
Therefore, they would have no, or much shorter durations, of pregnancy-related stress on the body, which may explain the lower average risk scores in that group.
The researchers obtained information about age at first birth for 1,047 women participating in the International Mobility in Ageing Study in 2012.
Study participants were between the ages of 65 and 74 and were from Canada, Albania, Colombia and Brazil.
Using the Framingham Risk Score, the researchers connected age at first birth to risk for cardiovascular disease.
Dr Pirkle said the findings, published in the Journal of the American Heart Association, must be confirmed because the study relied on self-reports of childbirth history which could be affected by memory loss – even though the participants were screened for dementia.
She said that many young mothers from the poorer countries may not have survived to the ages of 64 to 75 represented in the study, limiting the strength of the findings.
Dr Piekle added: “If adolescent childbirth increases the risk of cardiovascular disease risk, then our findings reinforce the need to assure that girls and adolescents have sufficient sexual education and access to contraception to avoid adolescent childbearing in the first place.
“If the association is mediated by lower educational attainment, poorer health behaviours and other factors caused by young motherhood, then our findings also suggest a need to provide more support to young mothers.”