Fetal pulmonary maturity in isoimmunized pregnancies.

That the lecithin/sphingomyelin (L/S) ratio correlates very closely with fetal gestational age in the uncomplicated pregnancy is well accepted. The presence of fetal or maternal disease has been found to accelerate or retard the development of fetal lung maturity in certain pregnancies. Although only a very small number of isoimmunized pregnancies has been evaluated in the obstetric literature, there is general acceptance that most isoimmunized pregnancies have delayed pulmonary maturation. Our observation has been that, in mild to moderately severe isoimmunized pregnancies, fetal lung maturation is not delayed. This study was designed to compare fetal pulmonary maturation in pregnancies affected by isoimmunization to that in a control group of unaffected but sensitized pregnancies. The results of this study suggest that pulmonary maturation in the mild to moderately affected pregnancy as measured by the L/S ratio is neither delayed nor accelerated but unchanged when comparison is made to the control group.