There used to be a long history of firing (or at least not promoting) women when they start having children. This was viewed as wrong, so a law was put in to sa

There used to be a long history of firing (or at least not promoting) women when they start having children. This was viewed as wrong, so a law was put in to say that you can't make job decisions based on a persons "family status", which includes how many, if any, children they have. (It may also include whether they are married or not, because getting married used to be a carrer limiting factor for women).