Sex ratio in triplets

Since the introduction of different ovulation induction regimens the incidence of triplet pregnancies increased from a spontaneous rate of about 1:10,000 to the frequency of nearly 1:1000. Sex ratio of trigemini and male/female proportion of the three newborns within the same triplet set is the amazing issue that we attempted to elucidate in the present study. Data on 36 women with triplet pregnancies delivered in our hospital and information regarding 2717 triplet pregnancies reported by 16 relevant papers were included in this study. 36 women delivered 63 (58%) male and 45 (42%) female babies. Triplet sets of same gender comprised 33% of all trigemini. Sex ratios (male/female) for the spontaneous, menotropin and clomiphene group were 2.00, 1.57 and 0.94 respectively. Homogenous male/female set ratio was 5.0, 2.0 and 0.5 in menotropin, spontaneous and clomiphene groups respectively. As the percentage of ovulation induction triplet pregnancies increased constantly from 0% to 100%, a decline in the fraction of homogenous gender triplet sets was observed--from 73% to 23%. It may be concluded that sex ratio in triplet newborns is divergent according to different publications with most of the authors reporting a male/female ratio of less than 1.00. Ovulation induction results in a lower proportion of homogenous sex triplets sets. Superovulation by menotropins cause a higher percentage of male triplet newborns when compared to ovulation induction by clomiphene.