Human menopausal gonadotrophin increases pregnancy rate in comparison with clomiphene citrate during replacement cycles of frozen/thawed pronucleate ova

Abstract
In a prospective randomized study, the effect of two ovulation induction regimens on implantation rate of frozen/thawed pronucleate ova was investigated. Patients received either human menopausal gonadotrophin (HMG) or clomiphene/HMG. Ovulation induction was done on an individual basis using ultrasound and plasma 17β-oestradiol concentrations. Ovulation was induced with human chorionic gonadotrophin (HCG) when the leading follicle reached a diameter of 18 mm. Pronucleate ova had been frozen using the slow-freezing method of Lassalle et al. (1985) (Fertil. Steril., 44, 645–651) and were thawed in synchrony with the age of the endometrium. Both groups of patients were comparable for age, indication for in-vitro fertilization, pre-ovulatory 17β-oestradiol concentration, number of large follicles and number and quality of embryos transferred. The only difference found was that HCG was administered 1 day earlier in the HMG group compared to the clomiphene/HMG group (P< 0.01). Using univariate analysis, the pregnancy rate was higher in patients stimulated with HMG alone compared to those stimulated with clomipheneöHMG (27 versus 15% respectively; P < 0.03), when HCG was administered later in the menstrual cycle (P < 0.01) and when more and better quality embryos were transferred (P < 0.01). Using multivariate regression analysis, the influence of the stimulation on pregnancy rate was even more pronounced (P < 0.01) when the day of HCG administration and the number and quality embryos transferred were taken into account. Therefore, we conclude that HMG alone increases pregnancy rate compared to clomiphene/HMG during replacement cycles of frozen/thawed pronucleate ova. These data suggest that HMG results in a better endometrium receptivity for embryos. This could be important not only for embryo replacement cycles but also for ovulation induction in general.

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