A recent Finnish study examined how maternal smoking affected children’s mental health at ages 25 to 27. It found adult men whose mothers smoked during pregnancy had worse problem-solving skills and vocabulary than men not exposed to maternal smoking. But no negative effects were seen in the female children of mothers who smoked. [...]
Many other studies show how different sexes may respond differently to adverse exposures during pregnancy. These studies are difficult to explore in humans due to the number and range of adverse exposures one accumulates after birth. So they only offer associations between the two events, rather than evidence one caused the other. [...]
Sex differences in response to adverse exposures during pregnancy may be mediated by the placenta. The placenta connects the developing fetus to the mother’s uterus, ensuring the baby receives the nutrients it needs. It also takes care of waste, gases and hormone production. The placenta actually has the same DNA sequence as the baby, not the mother. [...]
A possible reason for these sex differences may hark back to our evolutionary past when relatively few males survived to adulthood and reproduced. Those who did tended to be the biggest and strongest and most able to compete to pass on their genes to the next generation. Females, on the other hand, were more likely to survive to adulthood because that level of competition wasn’t there, and the vast majority would reproduce.
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