[Diagnosis of monozygosity in multiple births by DNA fingerprinting]

The incidence of monozygotic twins is one in 250 pregnancies. Triplets are estimated to occur in 1 of 86(2) pregnancies. Determination of zygosity may be done by comparison of physical characteristics, blood group or tissue typing, chromosome studies, or examination of various other polymorphic protein markers. Here we describe the differentiation between monozygotic and dizygotic twins and triplets by DNA-fingerprinting. This is a fast, non-invasive and reliable (error probability 0.003%) method to determine monozygosity of twins or triplets. It is also a reliable paternity test.