Multiple pregnancies: risk factors and prognostic variables during induction of ovulation with human menopausal gonadotrophins.

Multiple pregnancies still constitute a major and relatively frequent complication of induction of ovulation by human menopausal gonadotrophins (HMG) despite the increasing sophistication of monitoring techniques. In order to define specific variables which may be associated with multiple pregnancies, we have compared 51 multiple pregnancy cycles to 51 consecutive control singleton pregnancy cycles, following HMG induction of ovulation. The aetiology and classification of anovulation, duration of infertility, total amount of HMG utilized per cycle and the duration of stimulation were not associated with an increase in the rate of multiple pregnancy. Basal serum oestradiol levels and its periovulatory pattern were remarkably similar in the singleton and multiple pregnancy groups. The mean age of the multiple pregnancy group (29.4 +/- 4.4 years) was significantly lower than the mean age of the singleton pregnancy group (31.6 +/- 5.3 years) (P less than 0.05). In the multiple pregnancy group, there were significantly more cycles with intermediate sized (15-17 mm). (P less than 0.002), small sized (12-14 mm). (P less than 0.02) and immature follicles (less than 12 mm) (P less than 0.03), at the time of human chorionic gonadotrophin (HCG) administration, as compared with the singleton pregnancy group. Furthermore, a direct linear correlation was observed between the number of intermediate sized follicles and number of implanted embryos. The presence of intermediate sized follicles at the time of HCG administration after HMG induction of follicular maturation is predictive of, and independently associated with, a higher incidence of multiple pregnancy.