A major study suggests that pregnancy raises cardiovascular risk across all maternal ages, with older patients facing more events mainly because of higher baseline risk rather than age-driven pregnancy-specific mechanisms.
Study: Maternal age and pregnancy-related cardiovascular complications. Image Credit: Agatha Jennifer / Shutterstock
Older maternal age may not independently intensify pregnancy-specific cardiovascular complications during pregnancy; rather, pregnancy appears to uniformly amplify women’s baseline cardiovascular risk, as reported by a new study published in the journal Nature Communications.
Maternal Age and Cardiovascular Risk Background
Pregnancy-related cardiovascular complications are major risk factors for maternal death. Approximately 20 to 30% of maternal deaths occur due to these complications worldwide. In the general population, the risk of cardiovascular events increases with advancing age. Several studies have also suggested that women who become pregnant after age 35 are at higher risk of adverse pregnancy outcomes. However, it remains unclear whether maternal age increases the pregnancy-specific risk of pregnancy-related cardiovascular complications.
The majority of previous studies have focused on pregnancy-specific risk without distinguishing it from maternal baseline cardiovascular risk. This is why it remains unclear whether aging particularly increases pregnancy-specific cardiovascular risk or whether older women simply have higher baseline cardiovascular risk.
To address this gap in the literature, Weill Cornell Medicine researchers analyzed publicly available, deidentified claims data on labor- and delivery-related hospitalizations across eleven U.S. states during 2016 to 2021.
They compared each patient’s risk of having a major adverse cardiovascular event during the defined pregnancy/postpartum risk window with the risk of having such an event during an equivalent nonpregnant control period.
Pregnancy Cardiovascular Event Findings
The researchers identified 2,710,983 patients with a first-recorded pregnancy, of whom 12,059 experienced a major adverse cardiovascular event during pregnancy or the postpartum period, compared to 1,685 during the equivalent control period one year later.
The most commonly experienced adverse cardiovascular events were venous thromboembolism, cardiomyopathy, and heart failure. Among patients who had a major adverse cardiovascular event, 240 died, representing almost 50% of all maternal deaths in the study population. Among survivors, almost 10% needed care at a rehabilitation or nursing facility or needed home healthcare.
Overall, the pregnancy and postpartum periods were associated with a 7-fold higher risk of major adverse cardiovascular events compared with the control period. However, this risk induction, relative to patients’ baseline cardiovascular risks, did not vary with maternal age.
The absolute risk of induction, however, remained stable at approximately 3 excess cardiovascular events per 1,000 pregnancies until the age of 31 years, after which it increased steadily and reached 10 excess events per 1,000 pregnancies by the age of 44 years. These findings indicate that older patients experienced more cardiovascular events during pregnancy largely because of their higher baseline cardiovascular risk, and not because older age appeared to intensify pregnancy-specific cardiovascular mechanisms.
The observed association between maternal age and cardiovascular risk remained similar across subgroups defined by race and ethnicity, insurance type, household income, region, and comorbidities.
Baseline Cardiovascular Health Implications
The study reveals that maternal age does not significantly influence the relative pregnancy-associated increase in adverse cardiovascular events during pregnancy. Rather, pregnancy appears to amplify patients’ nonpregnant baseline cardiovascular risk.
In other words, the study suggests that baseline cardiovascular health may matter more than age alone: an older, healthy woman with low cardiovascular risk at baseline may not necessarily face a higher pregnancy-specific relative risk than a younger woman with higher cardiovascular risk factors.
Notably, the researchers noticed a risk induction as high as 20 excess cardiovascular events per 1,000 pregnancies by the age of 45 years in patients with one or more comorbidities, the most common of which were hypertension and asthma. This finding demands further investigation into why asthma was over-represented among patients with pregnancy-associated cardiovascular complications.
In the study population, Black women exhibited a higher risk of experiencing cardiovascular events than White women; however, the pregnancy-associated relative risk increase did not vary by maternal age in race-stratified analyses. This suggests that other factors, such as social determinants of health and access to risk-factor management, may explain the racial disparities observed here.
Overall, the study suggests that the risk of pregnancy-related maternal cardiovascular complications can be reduced by addressing and managing the cardiovascular health of women before pregnancy. Instead of simply assuming that young age is a protective factor against pregnancy-related cardiovascular complications, obstetricians and gynecologists should consider baseline cardiovascular risk assessment, screening, close follow-up, and optimization of modifiable risk factors in women who are planning a pregnancy.
Study Limitations and Generalizability
The study used hospital discharge diagnosis codes to identify major adverse cardiovascular events, which may have resulted in misclassification. Furthermore, the study lacked information on medications, particularly aspirin, which is commonly used to prevent pre-eclampsia in high-risk patients during pregnancy. These medications may have a modulating effect on cardiovascular risks.
The study included patients from different U.S. states, which may restrict the generalizability of observed associations to the global population. However, since the study population represents 25% of the U.S. population, these findings are generalizable to other countries and healthcare systems with broadly similar characteristics.
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