ABSTRACT
In the first half of pregnancy, the fetal skin and the surface of the placenta and umbilical cord allows free movement of the fluid between the fetus and the amniotic cavity; however, in the second half, the fetal skin becomes waterproof and most of this movement is stopped. In late pregnancy, amniotic fluid is produced largely as fetal urine and it is absorbed by the fetal gut after swallowing. Fetal production and absorption of urine is adequate to ensure replacement of the amniotic fluid in less than a day.
