In Hungary the frequency of multiple births has been decreasing. In 1920 the rate of multiple births was 23-5‰; by 1968 this rate decreased to 18.2‰, i.e., only 77% of the 1920 data. The male preponderance in twin births is lower than in single births, and in triplets actually a female excess can be observed. Furthermore, it can be observed that there are more boys than girls among the first-born of multiple births. The average birth weight of liveborn and stillborn twins, and of liveborn triplets is 2101 g, 1458 g, and 1723 g respectively. The ratio of MZ to DZ twins is about 30:70 in 1968. The frequency of DZ twin births increases with maternal age (the peak is now over 40 years) and birth order. According to the 1959, i960, and 1968 figures, both DZ and MZ twin births were significantly more frequent in mothers aged 16 or less than in mothers aged 17-19 years.
This demographic survey belonged to preparatory works connected with the setting up of the Budapest Twin Register which came into force on January 1st, 1970.