Pulmonary hypoplasia and deformations related to premature rupture of membranes.

In summary, fetal pulmonary development occurs in three phases. Hypoplasia results when an interruption occurs in or before the canalicular stage. Factors necessary for normal lung growth include sustained adequate amniotic fluid volume and normal fetal breathing movements. Pulmonary hypoplasia is most likely to occur with a very early rupture of membranes (less than 22 weeks) and with persistent oligohydramnios. Lack of sustained breathing movements and failure of modulation of ductal flow are strongly associated. Ultrasound measurement of fetal lung length may eventually be useful in monitoring intrauterine pulmonary development. Limb contractures resulting from prolonged oligohydramnios are examples of deformation-type defects. Their presence correlates most strongly with the length of the latent period (time from ROM to delivery) and the degree of oligohydramnios. Most contractures of this type are readily reversible. Early amnion rupture sequence, presumed to result from rupture of only the amnion in the first trimester, is associated with multiple severe fetal deformations. It usually occurs sporadically, with a minimal recurrence risk.