[cheald]

It depends on the woman and the pregnancy. Some women do bounce back right after childbirth, but my guess is that's the exception rather than the norm. The combination of healing from childbirth (which can be minimal to significant for vaginal deliveries, and is uncompromisingly significant for C-sections), the hormonal whiplash, the sleep deprivation, and the demands a newborn places on your time will almost certainly make it exceptionally difficult - though certainly not impossible - to be productive at much of anything.

Regarding stress and exercise during gestation, there's a lot of research that shows that high stress levels during pregnancy should be avoided, and high-impact exercise is generally out. Low-impact exercise is generally fine, though your doctor will tell you to avoid it if you have a high-risk pregnancy.