Congenital malformations in twins: effect of chorionicity and zygosity.

We conducted this study to determine the pattern of congenital malformations in twins born in our hospital over a 9 month period (January to September 2006). Gross congenital anomalies were recorded within 6 hours of birth by detailed clinical examination in all successively delivered ≥23 weeks twin babies, whether stillborn or live-born. Radiological and autopsy examinations were carried out as and where indicated. All live twin babies stayed for 7 days in the NICU/ postnatal ward/ lyingin ward as per the unit protocols. They were examined daily and observed carefully for any fresh signs/symptoms. Zygosity was determined with the help of sex, placental chorionicity and 7 blood group phenotypes(7).