Prenatal diagnosis of the rarest conjoint twin "diprosopus tetrophthalmus" during anomaly scan: A case report.

Twin pregnancy is considered high-risk pregnancy because of its various effects on maternal and fetal physiology. Twin pregnancy can be dizygotic or monozygotic, the latter being less common. Depending upon the period of separation of an embryo, monozygotic twins can share amniotic cavity and placenta with the monochorionic monoamniotic form being the least common type. Diprosopus tetrophthalmus is the rarest form of monozygotic monochorionic and monoamniotic conjoint twin, where there are 2 faces on 1 head with various degrees of duplication of facial and cranial structure. The exact etiology of diprosopus is still unknown however; there are many local environmental and oxidative theories for this anomaly. The incidence of diprosopus is 1 in 180,000 to 15 million births. Here we present a case of 20-year-old female who came for routine anomaly scan of her pregnancy in our hospital which showed the presence of diprosopus tetrophthalmus. Couples agreed to terminate pregnancy after proper counseling from treating physician. Ultrasonography images of anomaly scans as well as post-abortion images of the fetus are discussed in this case report.