(CNN) — A new study says the sex of a baby is determined by chance.
Researchers studied the entire population of Sweden since 1932 which around 4.7 million births.
The Lead author says the study showed that individuals don’t have an innate tendency to have offspring of one sex or another, but instead random.
The study compared whether siblings tended to have offspring of the same sex and the statistical analysis ruled out the possibility that characteristics of the parent influence the likelihood of having boys or girls.
Researchers say they can’t rule out the possibility that extreme environmental events like famine could affect offspring sex ratios.