The consensus on the likelihood of giving birth to a boy or girl has long been that the odds are roughly equal and that all mothers have the same odds of having either a boy or a girl. This is partially because sperm have a 50–50 chance of carrying either an X or Y chromosome. Yet, many families seem to be prone to having all girls or all boys. New research shows that there might be a reason for this.
Some families may be ‘tossing a weighted coin’ when it comes to child sex
