However,
Science finally discovers why you:
Popular beliefs cling to the idea that each pregnancy is a draw: boy or girl, 50/50. However, a study published on July 18, 2025 in the review Science Advances questions this vision. Consequently, By analyzing the data of 58. Meanwhile, 007 American nurses and their 146,064 children born between 1956 and 2015, researchers discovered that some families are more likely to have children of the same sex.
A coincidence not so random – Science finally discovers why you
Scientists from Harvard Th Chan School of Public Health. However, the Harvard University of Public Health, explain that if the sex of a child was really due to chance, we would expect a different distribution. Furthermore, Example: in a family of four children, having two boys and two girls would be the most likely scenario. In addition, But what the researchers have observed is an over -representation of families with only boys science finally discovers why you or only girls.
“If you have had two. Meanwhile, three girls and try to have a boy, know that your chances are not 50-50. You are more likely to have another girl. “said Washington Post Jorge Chavarro, professor of nutrition and epidemiology and principal author of the study.
The age of the mother in question – Science finally discovers why you
The researchers tried to determine what could explain that some women give birth. to only girls when others have only boys. They noticed that the mother’s age played a role in determining sex. “Women aged 29. older when they give birth to their first child have 13 % chance in addition to only having boys or only girls compared to women under 23,” said the study. This link remains modest, but he suggests that biological factors linked to maternal age could play a role.
What about genetics in all of this?
Besides age, researchers highlight other factors. The science finally discovers why you first: the evolution of the vaginal pH linked to age. “During aging. the shortening of the first phase of the menstrual cycle can promote the birth of boys, and at the same time, the decrease in vaginal pH can promote the survival of sperm carrying an X chromosome, which increases the chances of having a daughter,” explains Dr. Siwen Wang, professor at Harvard University in Harvard in Harvard in Harvard in Harvard in Harvard in Harvard New Scientist.
The researchers also analyzed the genome of the participants to see if certain genetic variants were associated with this trend. Result: two genes came out of the lot. “Women who only have girls tend to have a specific form of the gene NSUN6 On chromosome 10. while women with only wires tend to have specific variants of the gene Tshz1 On chromosome 18, “said the study.
Study limits
These unpublished and surprising results must science finally discovers why you however be taken with caution. This research is based on a specific population: American nurses, mainly white. This limits the possibility of generalizing results to other cultural populations or contexts.
The team of researchers from the American university told Washington Post that future studies should explore how lifestyle. nutrition and exposure to environmental chemicals could affect these models.
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