Late 40s is not unusual at all. Most women, at present, don’t reach menopause until after 50. However, we looked it up, during one of these threads about older mothers, and found 56 or 57 to be the oldest verifiable mother under natural conditions.
Theoretically, but fertility begins dropping at 35 and babies born to older mothers (like Sarah Palin’s baby) are more prone to birth defects.
I don’t personally think it’s a good idea to have a baby after 39.