I stumbled over article: Sex at birth is not always random — mum’s age and genetics can play a part. Wow, that is really interesting. ...but actually the study doesn’t look at the influence of male partners. Isn't that important??! www.nature.com/articles/d41... (with ref to the full paper)
Sex at birth is not always random — mum’s age and genetics can play a part
Families with three or more boys, for example, are more likely to have another boy than a girl as the next child.
nature.com