Can ultrasonography reliably predict the occurrence of multiple pregnancies in gonadotrophin ovulation induction?

A retrospective study of 78 patients with 106 stimulated conception cycles after successful gonadotrophin ovulation induction was made to analyze the relationship between the sizes and numbers of ovarian follicles seen on ultrasound and the eventual number of conceptions that resulted in each cycle. Fifteen cycles (14.2%) resulted in spontaneous abortions. There were 58 singleton pregnancies (54.8%), 26 sets of twins (24.5%), 6 sets of triplets (5.6%) and 1 set of quadruplets (0.9%). In 86 cycles with the last scans performed shortly before the ovulating dose of HCG, 3 or more mature follicles were found in 50 (58%). These cycles resulted in 31 (62%) singletons, 16 (32%) twin pregnancies and 3 (6%) triplet pregnancies. Pregnancies resulted even when there were no 'mature' follicles seen on scan. No statistical correlation was found between plurality of pregnancy and size or number of follicles, or oestradiol excretion on the day the ovulating dose of HCG was given, although high-order multiple pregnancies were more likely if the oestrogen excretion was more than 200 ug/24 hours (p = 0.001). The dosage of HCG correlated inversely with the occurrence of multiple pregnancies (p = 0.02). In conclusion, neither oestrogens nor ultrasonography could accurately predict multiple conceptions in gonadotrophin stimulated cycles.