ABSTRACT
Infertility treatment is estimated to be responsible for more than 224 000 excess multiple births between 1980 and 19971. In 2000, the latest year for which national statistics are available, 118 997 babies were born as twins and 7328 were born as triplets, quadruplets and higher orders2. In the USA, assisted reproductive technologies (ART), in vitro fertilization (IVF) and related procedures produced 11% of twin births and 45% of triplet and higher-order births3. Ovulation induction (OI) without ART is estimated to be responsible for 20% of twin births and 38% of triplet and higher-order births3 (Figure 19.1). Similar relationships are reported in Britain, where OI
exclusive of IVF and related procedures is responsible for 67% of quadruplet and higher-order births4.
