Positive correlation between body weight, length of human menopausal gonadotropin stimulation, and oocyte fertilization rate.

One hundred four normally cycling women were treated with fixed low-dose human menopausal gonadotropin (hMG) (2 ampules/day) in preparation for oocyte aspiration for in vitro fertilization. The response rate was related to age, weight, and the ratios weight/height2 and weight/height. The required dose of hMG was related to total body weight, but not to age or either of the weight/height ratios. In patients who required fewer than 5 days of hMG (rapid responders), a significantly higher number (P less than 0.02) of oocytes were harvested, compared with slow responders. However, a smaller percentage of the oocytes from rapid responders fertilized (P less than 0.003) and resulted in a reduced rate of embryo transfer. The difference in pregnancy rates was not statistically significant. The results of the study suggest that patients undergoing in vitro fertilization who weigh less than 55 kg may benefit from treatment with a lower dose of hMG to prolong the stimulation cycle.