Nonimmune fetal hydrops: diagnosis and obstetrical management.

As the incidence of Rh-isoimmunization has been decreasing with the availability of Rh immune globulin, the proportion of cases of fetal hydrops from nonimmune causes has increased. Evaluation of the fetus with hydrops requires an integrated approach, beginning with targeted ultrasound evaluation and potentially including maternal and fetal blood testing and other invasive testing. Because the list of conditions that may cause hydrops is long and continues to grow, it is often difficult to make a precise diagnosis; however, through a systematic approach, one may frequently narrow the etiology to a category of disorders and determine whether any interventions are available that are likely to be helpful in improving the outlook for the fetus.