In a few cases, low-dose aspirin therapy is prescribed during pregnancy to help prevent recurrent miscarriage or to treat other conditions. Generally, however, aspirin isn't recommended as a pain reliever during pregnancy.
Before birth, a baby receives oxygen through blood from the placenta. At birth, however, that situation changes suddenly and dramatically. When the baby is born, a natural drop in prostaglandin levels in some of the baby's blood vessels drives the baby's circulatory system to reroute blood flow to the lungs.
So what's the concern with aspirin during pregnancy? Prostaglandins are hormone-like substances. Aspirin and other nonsteroidal anti-inflammatory drugs, including ibuprofen (Advil, Motrin, others), block the production of prostaglandins. If you take aspirin during pregnancy — especially after 32 weeks — there's a risk that the baby's blood flow could be rerouted in the uterus. This could cause potentially fatal problems for the baby.
If you need to take a pain reliever during pregnancy, ask your doctor about the options. He or she may approve occasional use of acetaminophen (Tylenol, others).
source : mayoclinic.com
