Relationship of follicle numbers and estradiol levels to multiple implantation in 3,608 intrauterine insemination cycles.
OBJECTIVE: To determine the relationship of follicle numbers and estradiol (E(2)) levels to multiple implantations in human menopausal gonadotropin (hMG) and clomiphene citrate (CC) cycles. DESIGN: Fifteen-year prospective study. SETTING: Private infertility clinic. PATIENT(S): Women who underwent 3608 cycles of husband or donor intrauterine insemination (IUI). INTERVENTION(S): Ovulation induction (OI) with CC, hMG, or CC+hMG. MAIN OUTCOME MEASURE(S): Pregnancy and multiple implantations. RESULT(S): Triplet and higher-order implantations-but not twin implantations-were related to age, E(2) levels, and number of follicles > or = 12 mm and > or = 15 mm, but not number of follicles > or = 18 mm, in hMG and CC+hMG cycles. For patients less than 35 years old, three or more implantations tripled when six or more follicles were > or = 12 mm, in CC, hMG, and CC+hMG cycles, and when E(2) was > or = 1000 pg mL in hMG and CC+hMG cycles. For patients 35 or older, pregnancy rates in hMG and CC+hMG cycles doubled when six or more follicles were > or = 12 mm, or E(2) levels were >1000 pg mL, whereas 3 or more implantations were not significantly increased. CONCLUSIONS: Withholding hCG or IUI in CC, hMG, and CC+hMG cycles when six or more follicles are > or = 12 mm may reduce triplet and higher-order implantations by 67% without significantly reducing pregnancy rates for patients under 35 years of age.