Researchers at the Liverpool School of Tropical Medicine suggest that expectant mothers who smoke during pregnancy are more likely to have girls than boys.
Researchers revealed that the chance of having a male baby drops by almost half if both parents smoke during early pregnancy, also smoking raises the chances of a miscarriage.
Researchers reportedly found that substances contained in cigarettes, such as nicotine, inhibit sperm carrying male chromosomes from fertilizing eggs.
Led by Professor Bernard Brabin, the researchers studied 9,000 cases of pregnancy in Liverpool, and found that mothers who smoked during pregnancy were one-third less likely to have male children than those who did not smoke. Furthermore, if the father also smoked, and if factors such as the health and age of the mother were accounted for, the chances of having a male child reduces by almost half.
The study also reveals that even those mothers who do not smoke but are exposed to cigarettes from partners are less likely to have boys. It shows that substances contained in cigarettes, such as nicotine, inhibit sperm carrying male chromosomes from fertilising eggs.