I think it depends on each person and the babies size. I'm 30 weeks and still sleep on my stomach with little discomfort, but I also don't have a large belly or baby. I'm actually more uncomfortable lying on my sides because she moves to the side I lay on and makes it hurt.
thankz and congrats on uur lil girl...well im not for sure if i am pregnant yet all hpt i take have come up negative but i have been havin signs that i might be i havent had a normal period since april and in june i was spotting light almost nothing at all for 3 to 4 days then 2 days after that i spotted brownish with sum mucous discharge and ive been feelin sick to my stomach off and on for the past 2 weeks and when i was at walmart shoppin i felt even worse with all the different smells also my nipples were sore right now they not bad but i asked my sister she said her first pregnancy her nipples where not sore but her second one they where sore off and on i have also have had sum hart burn and i have noticed that usualy i go to the bathroom about maybe 4 to 5 times a day but not its doubled that maybe even more monday im callin to find me a doctor so i can get a blood test done i want to know if i am and if im not i want to find out whats wrong with me
This varies from woman to woman and pregnancy to pregnancy. There is no specific week that this happens.