I chose to explain the gap in my cover letter by saying that I took time off to raise my child but I am now ready to resume my career. Yes, it does tell them that you have a young child, but I do think it is a bit of misrepresentation to make it seem like you were at your old job for the length of your maternity leave. As well, if they check the employment dates (a lot of employers do) it will be apparent that you were not being truthful, which would hurt your chances much more than the fact that you are a mother.
You could also explain it as "personal leave" or "personal growth" or something along those lines if you don't want to mention your child. You could ask a career counsellor or HR specialist for more advice as well.
Good luck on your job search!