How old does a woman have to be before she can not get pregnant?

This vary a lot from woman to woman.

Some go early into the menopause, some at age 29 even. Others do not until well into their 50's.

As a general rule we can say that when you start the menopause and totally stop having the period, the chances of getting pregnant are pretty slim.

For most woman this is after age of 45.

Age alone however does not limit/rule out having babies.

It will certainly lower the chances but a chance is always a chance.