For a long time it was believed that the probability of having a boy or girl is exactly 50%, as if when a coin is thrown. But a new large -scale study at Harvard University changes the idea of this "equal chance".
Scientists have analyzed the data of more than 58,000 women who had at least two children, and found that the mother's age plays a significant role in the likelihood of birth of children of one sex at the time of birth.
" Gender at birth does not subordinate to a simple binomial distribution. We have found a significant intrauterine correlation ," the researchers explained.
The results are striking:
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43% of women who gave birth to their first child after 28 years later had all children of the same sex.
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While only 34% of women who became mothers under 23 gave birth to children only one sex.
Thus, the age of the first pregnancy directly affects whether a woman will have children of both sexes, or only boys or only girls.
Researchers also considered other features of the mother - height, BMI, hair color, blood group, chronotype, race, etc. - and concluded that none of them has a statistically significant effect on the sex of offspring.
Despite the generally accepted theory that everything solves the "random" X or Y-chromosome of the sperm, it turns out that the body of a woman can also affect the final result. How exactly - the question remains open and will be the subject of further research.
The coin is no longer working. The one who will give birth to a boy or a girl - can partially depend on what age she became the mother for the first time. This discovery challenges the idea of equal probability and opens new horizons to understand human reproductive biology.
