Obstetric aspects of the Prader-Willi syndrome.

The Prader-Willi syndrome (PWS) is a complex, multisystem disorder. The syndrome affects the central nervous system, with a predilection for the hypothalamus. The clinical picture in PWS is very variable, and depends on the age of the affected child. Frequently, the most prominent features such as obesity, mental retardation and behavioral disorders do not become evident until the later childhood stage, which can lead to underdiagnosis or late diagnosis in early childhood. Because of the long-term implications of this syndrome, it is important to recognize its features as soon as possible so that early counseling of parents and the affected child is possible. Because PWS can also lead to complications in both pregnancy and labor, proper diagnosis in the fetus can also help optimize perinatal care in affected children. In three cases we illustrate that certain combinations of obstetric symptoms such as polyhydramnios, diminished fetal movements, malpresentation and abnormal fetal heart rhythm can help alert clinicians to the possibility of this syndrome in fetuses.