COLUMBUS, Ohio — Many couples expecting children often forego the revelation of their baby’s sex until birth so they can revel in the surprise of the life-changing moment.

New research, however, may lead more women to opt for the early announcement.

According to a recent study , a pregnant woman’s immune responses are heavily affected by the sex of the baby she is carrying – and when that baby is a girl, there is heightened inflammation that causes greater maternal discomfort — and greater exposure to disease.

Researchers at the Ohio State University Wexner Medical Center arrived at this startling conclusion after studying “immune markers” in 80 pregnant women across the course of gestation. Their findings were published in the February issue of the journal Brain, Behavior, and Immunity.

Women carrying female fetuses produced significantly higher levels of cytokines in their blood when exposed to bacteria, researchers discovered. That’s important because cytokines not only increase the level of inflammation experienced by the mother – causing achiness, fatigue and increased stress, among other symptoms — but can also reduce her immunity to contracting asthma and other illnesses during pregnancy – and may also affect the health of the fetus.

Amanda Mitchell, a postdoctoral researcher at the Wexner Medical Center who directed the study, said more research was needed to determine why a baby’s sex has such a strong influence on the maternal experience of pregnancy, which could also be related to hormonal factors.

“This research helps women and their obstetricians recognize that fetal gender is one factor that may impact how a woman’s body responds to everyday immune challenges and can lead to further research into how differences in immune function may affect how a women responds to different viruses,” she noted in a university release.

This is not the first study to suggest that girls are prone to irritating their mothers early.

Past studies have found the sex of the child affects levels of morning sickness, cravings and other painful symptoms experienced by mothers during pregnancy – with much higher effects attributed to fetuses that were female.

However, the latest study goes a step further: These reported differences in sex could have much longer-lasting effects – both on the mother and fetus.

It used to be considered an old wives tale: Boys are “easier” than girls. But a growing body of research suggests it may well be true.