Concordant occipital encephalocele in monoamniotic twins.

Anomalies occur with a greater frequency in twin gestations. Due to its multifactorial inheritance, twins are usually discordant for encephalocele. We present a case of monoamniotic twins concordant for occipital encephalocele and discordant for lung and cord anomalies. Ultrasonographic examination at 17 weeks' gestation revealed occipital encephalocele in both fetuses. The maternal serum level of alpha-fetoprotein was increased. Fetal autopsy revealed occipital encepaholocele in both twins and right pulmonary hypoplasia and one umbilical artery in one sibling. Monoamniotic twins concordant for encephalocele occur with extreme rarity. To the best of our knowledge, monoamniotic twins concordant for this neural tube defect have not been previously reported.