Do baby girls make mum forget?

May 12, 2005, vol. 33, no. 2
By Marianne Meadahl

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Mothers who are pregnant with boys may be less plagued by forgetfulness - sometimes referred to as dumb-mum syndrome - than those who are carrying girls, according to a new study on the effects of pregnancy on cognition.

An 18-month study led by SFU psychology professor Neil Watson and PhD candidate Claire Vanston tracked 39 Vancouver area women from early pregnancy to several months after birth. They found that women who gave birth to boys consistently outperformed moms of girls in tests that specifically taxed the memory in areas of listening, computational and visualization skills.

The participating women underwent eight tests administered repeatedly during pregnancy and beyond. Three cognitively challenging tests showed a significant fetal sex effect consistently throughout the study.

Watson says evidence of a “large and enduring” fetal sex effect suggests that an unknown fetal-derived factor that differs in type or concentration between male and female fetuses may have an influence on the mother's cognition.

The findings will be published in the journal NeuroReport on May 12.

The researchers were surprised by the striking and consistent difference in the performance of the women participating in their study. “When we set out to look at the effects of pregnancy on cognition, we weren't thinking of the sex of the fetus, so we were shocked by our results,” says Watson. He notes that while the finding raises questions about the potential role of fetal hormones, it isn't clear why the disparity between mothers of girls and boys persists in the very early stages of pregnancy (as early as 10 weeks) and after birth, even after the babies were weaned from breastfeeding.

Vanston adds, “The small amount of research that has been done on maternal cognition has generated contradictory results, but our data suggest that some of this discrepancy may be due to the sex of the fetus.”

While sex steroids are known to affect cognitive functions in adults, Watson and Vanston say more study is needed to determine how the fetal sex-associated factor is responsible for affecting mothers' cognition.

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