Your chance to have a boy or girl may not be 50/50

You can assume that a woman’s chance of having a his or daughter is 50/50, similar to a corner throw, but it seems that someone or the other can be more likely to have children of onely a sex.

“From personal experience I am friends [and] Family members who have only girls or boys in their family, “says Siwen Wang at Harvard University.” This raises the question of the purely chance, or is there an underlying biology that can explain this phenomenon? “

The relationship between boys and girls at birth is about 50:50 at a population level, mainly because men’s semen is about as likely to contain an X or a Y chromosome that determines a child’s gender.

But Wang and her colleagues were strange if women can also play a role. To learn more, the data collected from more than 58,000 mothers in the United States who had previously signed up for two separate studies of birth control and mothers’ health. Of this women, 61 percent had two children, 30 per day. Hundreds had three children, 8 percent had four children and the remaining women had five or more.

The researchers compared gender of women’s children with eight material features: height, body mass index, race, hair color, blood type, chronotype (time of day when they are most aware), age at first menstruation and their age when they have to 48 years.

The team found that the women that we older older Thhan 28, when they first gave birth, had a 43 percent chance of later having children of a gender compared to a 34 percent among those younger than 23 when they were first.

“We found that older old age at first birth was attached to [a higher chance] Of only having girls or boys, ”says Wang. None of the other traits we have linked to the sexes of women’s children.

While it is unclear why maternal age can have this effect, it can come down to biological change with the body that varies between women, war says. For example, previous studies suggest that the first phase of the menstrual cycle is getting shorter with age, which can favor boys’ birth, while a decrease in vaginal pH with age can support the survival of sperm containing X chromosomes, leading to a greater chance of having a girl.

But the results could also be explained by behavioral factors, says Joshua Wilde at the University of Oxford. It is possible that older women are more likely to plan the size of their families, he says. This may mean that even if they wanted two children of different genders, they may decide to stop after having two boys or two girls, while a younger woman may be more likely to pursue a child of the other sex with less concern for the family.

Further studies are needed to shave HOWI behavior, environmental and biological factors affecting the baby’s gender, says Wilde.