It really depends on your level of activity before and after birth and how good you're eating. Fat gained from healthy food burns off easier than fat from junk food. I always shrunk down pretty fast after each baby. The slowest part for me was for my hips to go back in. I could get down to or almost to prepregnancy weight within a few months but it usually took about six months before i could get my old jeans to go back over my hips lol.
this baby is my last.. at least for a good 6 yrs ( i may change my mind then and have another lol) but im gonna work my but off to get my pre pregnancy body back, i only had like 6 months before i got preggers again so i lost a good amount from that pregnancy and this time i havent gained hardly any so i think it can be done. ive heard walking a bunch after helps too.
If you breastfeed you'll lose the weight quick I'm also usually a size 1/2 I gained 50lbs during my pregnancy and at 3 weeks into breastfeeding I'd already lost 33 lbs