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 greater than or equal to 12 mm and greater than or equal to 15 mm, but not number of follicles greater than or equal to 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 greater than or equal to 12 mm, in CC, hMG, and CC+hMG cycles, and when E-2 was greater than or equal to 1000 pg mL in hMG and CCS hMG cycles. For patients 35 or older, pregnancy rates in hMG and CC+hMG cycles doubled when six or more follicles were greater than or equal to 12 mm, or E-2 levels were >1000 pg mt, 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 greater than or equal to 12 mm may reduce triplet and higher-order implantations by 67% without significantly reducing pregnancy rates for patients under 35 years of age. (C) 2001 by American Society for Reproductive Medicine.