ABSTRACT

The monozygotic (MZ) twinning rate is about 3.5-4 per 1000 births throughout the world, whereas variations exist in the dizygotic (DZ) twinning rate among races1. In one early survey, the DZ twinning rate in western Nigeria was very high with 40 per 1000 births, whereas the corresponding rates were 11 for Afro-American, 6-10 for Caucasian and 2.2-2.3 for Oriental people1.