Investigation of the twinning rate in families with the fragile X syndrome.

Abstract

An excess of twins in families with the Martin-Bell or fra(X) syndrome was noted previously in one family study [Fryns, 1986]. We tried to confirm this observation in a second large sample of families from a different population. We calculated the number of twin births among the total number of live births of known obligate carriers found in fra(X) families ascertained in New South Wales, Australia. We only included births of known sex and excluded triplets. There were 5 male pairs, 3 female pairs and 9 unlike sex pairs of twins born among 752 live births. Thus the twining rate was 1/44 per live birth. We compared this rate to that found in two different types of individuals: 1) the rate of ..