Inside a pregnant woman's uterus is an amniotic sac, which contains amniotic fluid and the growing fetus.The amniotic fluid is important for several reasons -- it helps keep the baby warm, and because his body parts are growing so fast, the fluid provides lubrication that keeps them from growing together. In some cases, fingers and toes can become webbed as a result of not enough amniotic fluid circulating in the uterus. Amniotic fluid also helps the baby's lungs develop.The amniotic fluid also lets the baby move easily so he can exercise his muscles and strengthen his bones before he's born.In addition, it acts like a liquid shock absorber for the baby by distributing any force that may push on the mother's uterus. Even sex won't hurt the baby.Amniotic fluid is 98% water and 2% salts and cells from the baby. Until the fetal kidneys started working during month four, amniotic fluid is made by the mother's body. But after month 4, the little guy started to make his contribution to the amniotic fluid by urinating into it.You heard right. It may not sound appealing to us, but the urine in the amniotic sac is completely harmless to the baby.The baby swallows amniotic fluid, which then passes through his digestive system, into his kidneys, and back out again to the amniotic sac as urine. In this way, he can practice using his digestive and urinary systems before he's even born. In fact, doctors can tell by the amount of amniotic fluid whether the baby has difficulty with his swallowing reflex.By the time he's born, he will consume up to 15 ounces of amniotic fluid a day.Reviewed ByReview Date: 09/16/2008Dan Sacks MD, FACOG, Obstetrics & Gynecology in Private Practice, West Palm Beach, FL. Review provided by VeriMed Healthcare Network.