A new study suggests that genetic factors may play a role in why some women tend to have children of the same sex. Researchers found that women who have already had multiple children of the same sex are more likely to have another baby of the same sex. The study also identified two genes that could increase the likelihood of having all female or all male children.
The study’s lead author, PhD student Siwen Wang from Harvard University, noticed a pattern in families where all children were boys or girls. She wondered if there was a biological reason behind this phenomenon and set out to investigate. The researchers analyzed data from over 58,000 women who had given birth to two or more children and found that families with siblings of the same sex were more common than expected by chance.
The study also found that older mothers were more likely to have children of the same sex, and that certain physiological changes associated with aging may favor one type of sperm over the other. These findings suggest that genetic factors may be at play in determining birth sex, rather than just chance. The researchers did not explore potential causes for this link further, but Wang speculated that aging-related changes in a woman’s body may tip the balance towards having more boys or girls.
The study’s results have implications for our understanding of reproductive biology and may help explain why some families seem to follow patterns of all boys or all girls.
Source: https://www.sciencefocus.com/news/boys-girls-birth