Women who have babies in their 30s give birth to “healthier” babies according to a new study.

In a study published in December’s journal Biodemography and Social Biology, researchers found that babies born to mothers in their 30s had the top cognitive scores whilst children born to mothers in their 40s were more likely to be obese, the Metro newspaper reports.

This article uses data from the Millennium Cohort Study (UK) and ordinary least squares and logistic regression models to compare cognitive and behavioral outcomes, and obesity at age 5 for first-born children by maternal age at first birth.

The findings suggest that giving birth to the first child at ages 30–39 compared to ages 23–29 is positively associated with children’s cognitive and behavioral outcomes and not associated with obesity.

“First-time mothers in their 30s are, for example, likely to be more educated, have higher income, and more likely to be in stable relationships, have healthier lifestyles, seek prenatal care earlier and have planned their pregnancies,” lead researcher Dr. Alice Goisis explains.

Although the results are unable to support the argument that this occurs because of the health risks associated with giving birth at advanced maternal ages, they suggest that there is a need to more closely investigate the potential trade-offs involved when births are delayed toward older maternal ages.