Ectopic twin gestation discordant for anencephaly. A case report

A 30-year-old white woman thought to have a 12-week intrauterine pregnancy developed a large cul-de-sac mass, which proved to be an ectopic, monoamnionic twin pregnancy (males) discordant for anencephaly. While twin pregnancies discordant for neural tube defects are well known, the extrauterine location made this case remarkable.