One of the true wonders of nature and life is birth, and many a times couples have been contemplating the question that has been occupying human beings possibly since the beginning of humankind: will it be a boy or a girl? There are tests available these days, such as ultrasound, which is completely safe, and slightly risky invasive measures such as chorionic villus sampling and amniocentesis. Some of us, however, wish not to know what gender the unborn has.
A new study has found that women who started their period at a young age are more likely to give birth to a girl. For a long time a myth held that the sex of the newborn is determined by the father and it was popular to think that increased virility of the father would help producing a boy. The new study published in Human Reproduction now shows how the mother may actually influence the sex of the child (DOI: 10.1093/humrep/der107)
The study encompassed over 10,000 mothers who were asked at which age they had begun their period and that information was correlated with the sex of their baby. Women who began their period at the age of 10 gave birth to girls with a probability of 54 %, compared to 47% for women that started their period at the age of 14. A previous study had demonstrated that women who entered menarche before the age of 12 had higher levels of the female sex hormone Estradiol.
Male embryos are more vulnerable to hormone imbalances, giving the observations more support. The researchers performed a statistical analysis and found that “Women entering menarche outside the normal range, especially those with earlier menarche, may have an increased chance of producing female offspring.”
Another study also showed that men who have many brothers, are more likely to produce male offspring.
However, all these numbers are still very close to the 50 % mark, and such slight changes in percentages may  be statistically relevant, but they do not really give a great insight as to whether one of us will be expecting a boy or a girl. It is evident that many factors play a role in influencing the sex of a child and for sure there will be other population studies to follow. At the end of the day, we will always ask ourselves the question as to what gender a new unborn has? Whatever might be the individual probability, the miracle of life always holds the greatest surprises.
Monty Python summarised the miracle of life in a very humorous way. Maybe life is a miracle and carries its fascination by its mere existence?
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Video reproduced from Youtube/ MontyPython