A recent Harvard study analyzing over 58,000 US nurses’ birth records discovered that families with three or more children are more inclined to have all boys or all girls. The research challenges the common belief that each pregnancy has an equal chance of having either a boy or a girl. The odds differ based on the genders of the siblings already in the family, with interesting factors like maternal age playing a part in the outcome. The study sheds light on why some families tend to have children of the same sex and opens discussions on the intricate science behind gender prediction.