Summer Babies Healthier in the Long Run

New research finds that babies born in June, July and August showed signs of better health than others. Baby due in winter? Here's what you can do to make it better.


If you've just found out you're pregnant and calculated your due date, you'll be happy to hear that summer babies tend to be healthier as adults, according to a new report. Its authors say more sunlight during the second and third trimesters—and thus more vitamin D exposure—could be responsible for these results.

Researchers looked at how the month a baby is born affects her birth weight, age of puberty and height—factors known to impact a child's health as they grow. The team from the University of Cambridge examined data from about 450,000 men and women as part of the UK Biobank study and found that babies born in June, July and August were slightly heavier at birth and taller as adults compared to babies born in the winter. Their analysis revealed that girls born in those months started puberty later, which is another sign of good health later in life.

Vitamin D a possible link

Ken Ong, M.D., M.P.H., a pediatric endocrinologist on the research team behind the study, said that sunshine during the second trimester seemed to have the strongest effect on birth weight, alongside significant time in the sun during the third trimester, when brain development starts.

Vitamin D isn't the only factor that could be tied to improved health in summer children. They have fewer infections in the first few months of life, which benefits their health in the long run, Dr. Ong says. Janet Currie, Ph.D., a professor at Princeton University who has studied this topic, says this could be because women who are due in the winter are more likely to have their babies come to term in the height of cold and flu season.

When you're due in another season

If your baby is due in autumn, winter or spring, don't despair. Dr. Ong believes the link with vitamin D is so strong that even babies born in these chillier seasons can have the same benefits as summer-born babies, simply by supplementing with the nutrient. "[Vitamin D] is something that mothers can make sure they have enough of," he says.

What counts as enough? Pregnant women are technically supposed to get 600 IU of vitamin D a day, but a National Institutes of Health report states that up to 4,000 IU a day can be tolerated during pregnancy and lactation.