The living arrangements of parents at the time a baby is conceived may play a role in determining its sex, research suggests. A US study found parents who were married or living together before conception were slightly more likely to have a boy than those who were not. The study, by the US National Bureau of Economic Research, is based on data from 86,436 births. Details are published in Proceedings of The Royal Society.
Overall, the study found that 51.5% of babies born to couples living together at the time of conception were boys, compared to 49.9% among parents who were not.