Have children of same sex and you are now planning for another child of opposite sex? What are the likely chances, probably not that high, according to a study that investigated the maternal and genetic factors that influence the sex of offspring.
A study published Friday in the journal Science Advances challenged assumptions that birth sex is random. In its finding the study reveals that families with three boys have a 61% chance of having a male child as the next sibling. While for families with three girls the chances of having a girl child next is as high as 58%.
This finding busts the believe that for each pregnancy, there is an equal chance of having either a boy or a girl. Over 58,000 women with two or more singleton births from 1956 to 2015 were analysed in the research that came to this conclusion.
Researchers also pointed to the mother’s age and genetics on giving birth. Women who started having kids after the age of 28 had higher chances of giving birth to children of same sex.
“We don’t know why these genes would be associated with sex at birth, but they are, and that opens up new questions,” said Jorge Chavarro, the senior author of the study and a professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health to The Washington Post.
Two genes associated with giving birth to only boys or only girls were also identified during the study. However, one limitation that the study had is it did not have any data on fathers.
Researchers concluded that more research was needed in this direction and said, “Until then, families desiring offspring of more than one sex who have already had two or three children of the same sex should be aware that when trying for their next one, they are probably doing a coin toss with a two-headed coin.”