Premature babies have the same BMI during adolescence as peers born at term.

According to an analysis of more than 250,000 people, by the time preterm babies reach the age of 14-19, they have, on average, the same body mass index as their term-born peers.

People born prematurely are likely to have the same body mass indexes (BMI) when they reach adolescence as people born at term.

To determine what effect the amount of time spent in the uterus has on body weight during childhood and adolescence, Johan Winter from the University of Copenhagen in Denmark and colleagues analyzed data collected from 16 studies conducted in Europe, North America and Australia.

These studies included data on the gestational age of newborns and subsequent data on their subsequent height and weight over several years. In total, more than 250,000 children born between 1985 and 2017 were included in the studies.

Winter and his colleagues took each person’s height and weight data and calculated their BMI at different ages.

“Body size is a good indicator of physical health,” Winter says. Although this is not the only measure.

The researchers found that while people born before 37 weeks of gestation, also known as preterm, were more likely to have a lower childhood BMI than people born after 37 weeks, the difference disappeared between 14 and 19 years of age.

“Our study shows that preterm people gain more weight during childhood compared to people born at term,” Winter says. It’s not clear why, he adds.

The findings don’t necessarily mean that babies born prematurely always reach a healthy body weight during adolescence, Winter says. Other factors, such as BMI and the mother’s level of education, will also play a role, he said.

The results are based on people in high-income countries. “We don’t really know what it will look like in low-income countries,” Winter says. The team did not look at the specific impact of gender or ethnicity on the results.

Nina Modi of Imperial College London says the results support several long-term studies around the world on the subject. However, recent work has shown that very preterm people are more likely to develop chronic conditions that are exacerbated by being overweight, she says.

“It’s critical to health that premature babies, their parents, and doctors know the importance of maintaining a healthy body weight,” she says.

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