Low amniotic pressure oligohydramnios - is this the cause of pulmonary hypoplasia?

Pulmonary hypoplasia, the underdevelopment of fetal lung tissue, can cause fetal death. Within the uterus the fetus is surrounded by amniotic fluid. Although there are many factors predisposing the fetus to pulmonary hypoplasia, one theory suggests that an inadequate amount of amniotic fluid, oligohydramnios, is responsible. Pulmonary hypoplasia occurs because the uterine wall compresses the fetal chest which in turn compresses the lung tissue, inhibiting growth. This theory does not explain why tissue compression does not affect the development of other organs. Another theory explains that the pressure of the amniotic fluid, amniotic pressure, is decreased when the fluid volume is reduced; decreased amniotic pressure causes too much fluid to be lost from the fetal lungs. Pressure inside the small structures of the lungs must be greater than the amniotic pressure to promote growth and function. If that balance is upset, as in oligohydramnios, too much fluid escapes from the fetal lungs. To prevent this from happening the amniotic fluid volume must be increased by adding more fluid artificially. Amniotic fluid replacement was attempted in one pregnancy with oligohydramnios. Although the fetus died from other complications, the fetal lungs had no evidence of fetal lung hypoplasia.