Nature protects the unborn child with amniotic fluid. The baby is vulnerable to Temperature extremes and bumping and it is very crucial in the development and safety of a fetus. A first trimester ultrasound is often done to check for many things. It can check for ectopic pregnancy or molar pregnancy. also see vaginal ultrasound. The baby needs the fluid in just the right amount. Too little ( oligohydramnios ) and the baby can't move properly, too much ( polyhydramnios ) and it could be a sign of other problems. The baby also needs the fluid for lung development, and contains cells shed from the fetus and from the placenta.
News release, Stanford University Medical Center.