Boy or Girl? Your Pregnant Body Will React Differently

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ByAnisa Arsenault
Associate Editor
Feb 2017
smiling pregnant woman touching her belly
Photo: Jovo Jovanovic

Carrying low? It’s a boy. Your left boob’s bigger than your right? Get ready for a girl.

While these gender-predicting theories are just myths, they’re not totally rooted in fiction. A new study suggests that a pregnant woman’s body does react differently based on the sex of the baby—but not in ways you may realize.

The Ohio State University Wexner Medical Center followed 80 women throughout their pregnancies, monitoring the levels of immune markers called cytokines in their blood and in immune cells that were exposed to bacteria in a lab. Cytokines were then analyzed based on the sex of the baby.

"While women didn’t exhibit differences in blood cytokine levels based on fetal sex, we did find that the immune cells of women carrying female fetuses produced more pro-inflammatory cytokines when exposed to bacteria,” says Amanda Mitchell, principal investigator of the study.

What does this mean? When the immune system of a woman pregnant with a girl is challenged, their bodies demonstrate a higher inflammatory response compared to women carrying boys.

Inflammation is a normal pregnancy symptom and essential to healing when it comes to your immune system, but excessive inflammation can exacerbate symptoms of medical conditions, from asthma to fatigue. While more research is needed, the Ohio State team thinks this may be why moms of girls often have more severe symptoms.

“This research helps women and their obstetricians recognize that fetal sex 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 woman responds to different viruses, infections or chronic health conditions (such as asthma), including whether these responses affect the health of the fetus,” Mitchell says.

She cautions against simply trying to boost your immune system, since “it’s problematic to have too little or too great of an immune response.”

To maintain a healthy immune system, Mitchell suggests exercising, eating leafy greens and even making time to meditate.

“Of course, it’s always important to check with your healthcare provider before making any changes to your routine or diet,” she reminds moms-to-be.

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