The average age of first-time mothers is increasing because more women are waiting until their 30s and 40s to start having children, and fewer women are having their first child during their teens and 20s.

The vast majority of all births are still to women under 35 (about 85 percent). However, rates for all births, not just of a first child, to women over 35 have been rising over the past 20 years, while birth rates for younger women are stable or declining, especially in developed countries.

However, waiting until one’s 30s to have children may pose health risks to both mother and child. In addition to the decline in fertility, especially after age 35, both mother and father are more likely to have pre-existing health issues than younger parents.

For the children of older parents, exposure to prenatal stressors, including hypoxia, micro‐ and macronutrient deficiency, and maternal stress, increases the risk of cardiovascular disease in adulthood.

In a recent study, researchers at the University of Alberta investigated the impact of the age a mother gives birth on the health of her offspring. Older female rats, which were equivalent to a 35-year-old human, were mated with young males.

At 4 months, their offspring's blood vessels and heart function were tested. In 4‐month‐old offspring, researchers noted impaired endothelium‐dependent relaxation in male (P<0.05), but not female, offspring born from aged dams. The antioxidant pegSOD improved relaxation only in arteries from male offspring of aged dams (delta E_max: young dam ‐1.63 ± 0.80 vs. aged dam 11.75 ± 4.23, P<0.05).

Further, endothelium‐dependent hyperpolarization relaxation was reduced in male, but not female, offspring of aged dams (P<0.05). Interestingly, there was a significant increase in nitric oxide contribution to relaxation in females born from aged dams (delta E_max: young dam ‐24.8 ± 12.1 vs. aged dam ‐68.7 ± 7.7, P<0.05), which was not observed in males.

Recovery of cardiac function following an ischemia‐reperfusion insult in male offspring born from aged dams was reduced by about 57 percent (P<0.001), an effect that was not evident in female offspring.

These data illustrate that offspring born from aged dams have an altered cardiovascular risk profile that is sex‐specific.

According to the Sandra Davidge, lead author, the research is important because it improves our understanding of the impact of giving birth at an older age on the health of offspring in later life. In future studies, the researchers will investigate whether the findings are true in humans.