title: Birth weight discordancy in male-first and female-first pairs of unlike-sexed twins.
abstract: We studied 153 consecutive twin pairs of unlike sex. Comparison of 71 male-female pairs with 82 female-male pairs showed similar mean twin birth weight and rate of discordance. However, males were significantly heavier (p less than 0.04) compared with females in the male-first but not in the female-first combination. The rate of female discordance was significantly higher compared with male discordance in both fetal sex combinations. It is concluded that females of unlike-sexed pairs are at greater risk to be growth discordant. Fetal sex, therefore, should be included as one of several factors that produce divergent twin growth.
authors.affiliation: Department of Obstetrics and Gynecology, Kaplan Hospital, Rehovot, Israel.
authors.forename: I
authors.initials: I
authors.lastname: Blickstein
authors.forename: A
authors.initials: A
authors.lastname: Weissman
mesh_terms: D001724:Birth Weight; D036861:Delivery, Obstetric; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D012727:Sex Characteristics; D013223:Statistics as Topic; D014427:Twins