Fetal cystic malformations of the posterior fossa in the first trimester of pregnancy.

Diagnosis of abnormalities of the posterior fossa, such as Dandy-Walker malformation, can be assessed during the first trimester of pregnancy by ultrasonography. We report on 5 cases of posterior fossa abnormalities, 4 Dandy-Walker malformations and 1 Dandy-Walker variant, diagnosed during the first trimester of pregnancy by ultrasound examination. All cases were confirmed later during the pregnancy by further ultrasound examinations or by postmortem examination when parents elected for termination of pregnancy. Two of our Dandy-Walker malformation cases were siblings from consanguineous parents and had a Meckel syndrome variant associated with the posterior fossa malformation, multicystic kidneys and hepatic fibrosis. We believe first trimester diagnosis of Dandy-Walker complex is possible, but needs to be confirmed later during the pregnancy and should prompt a detailed survey for other abnormalities.