From nausea and headaches to food cravings, could the baby's sex play a role in how women's bodies react to pregnancy? Evidence from a study published in the journal Brain, Behavior and Immunity suggests that carrying a male or female fetus could lead to different immune responses in pregnant women.
Pregnant women carrying girls have a greater chance of experiencing nausea and fatigue, according to the results of a study from the Ohio State University Wexner Medical Center.
In fact, a mother's immune system is thought to behave in different ways depending on the sex of their baby.
Researchers followed 80 pregnant women who were monitored for levels of cytokines in the blood. Cytokines are immune markers for inflammation.
Inflammation is an immune response triggered to tackle wound healing, viruses, bacteria and chronic illness. However, excessive inflammation can be stressful for the body and can contribute to illness-related symptoms such as aches and fatigue.
The researchers also analyzed samples of the women's immune cells that were exposed to bacteria in the lab.
Their initial findings revealed that the immune cells of women carrying female fetuses produced a heightened inflammatory response when exposed to bacteria, compared to women carrying male fetuses.
This more intense inflammatory reaction in women pregnant with girls could also explain exacerbated symptoms of certain medical conditions, such as asthma.
The researchers suggest that sex hormones and other hormones in the placenta could affect inflammation levels in pregnant women, which could explain the phenomenon.
The study is published in the journal Brain, Behavior and Immunity.
