Follicular diameters in conception cycles with and without multiple pregnancy after stimulated ovulation induction

BACKGROUND: Controlled ovulation induction and intrauterine insemination (OI-IUI) is associated with multiple pregnancies, which are a cause of much concern. No reliable datasets have shown clear criteria for predicting multiple pregnancy. The aim of this study was to eliminate a number of variables by examining only conception cycles to determine ultrasound criteria posing risks of multiple pregnancy. METHODS: 112 OI-IUI conception cycles (multiple pregnancy rate 19.6%) were analysed retrospectively to identify factors that may be used to evaluate multiple pregnancy risk. Analyses of ultrasound data on the day of hCG administration allowed study of the role of primary, secondary and tertiary follicle diameters (FD). RESULTS: There were no multiple pregnancies in cases where there was a single FD $14 mm, and no higher-order pregnancies where the tertiary follicle measured < 14 mm. Follicles with an FD of 15 mm showed an 8% attributable implantation rate. CONCLUSIONS: Revision of the criteria for administration of the ovulatory dose of hCG should include the concept that follicles of 15 mm diameter may yield a pregnancy. We suggest that rigorous application of such criteria (critical FD of 16 mm combined with secondary FD evidence) will not reduce the programme pregnancy rate, but will reduce the incidence of multiple conceptions.