When is a woman most fertile?

Answer 1

A woman is most fertile around 2-3 weeks before menstruation.

During a 28 day cycle a woman would be fertile around days 7-16 - this includes ovulation around day 14, with a viable egg present for up to 48 hours, and a week prior when fertile cervical mucus is present. But of course everyone's menstrual cycles are different and so unless you use Fertility Awareness Method you don't know when you are fertile or not, thus you should always assume you could be fertile and use Birth Control if you want to avoid pregnancy.

Answer 2

2 weeks before her period