ABSTRACT
Imaizumi6 examined the trend of twinning and triplet rates in 17 countries during the period from 1972 to 1996 using the vital statistics. Twinning and triplet rates increased in developed countries such as the four Scandinavian nations, Austria, Germany, The Netherlands, Switzerland, the UK, Canada, Australia, Israel, Japan, Singapore and Hong Kong after the 1970s6, whereas the twinning and triplet rates were lower in Japan, Singapore and Hong Kong than corresponding values for Europe, Canada and Australia6.
