Factors affecting pregnancy success of human in-vitro fertilization in unstimulated cycles

Successful pregnancies have recently been reported in cycles of unstimulated in-vitro fertilization (IVF) which is a simplification of the standard IVF approach utilizing ovarian stimulation. The purpose of this study was to analyse retrospectively the results of the first 3 years of unstimulated IVF cycles at our institution in order to identify factors which predispose these cycles to success or failure. All patients (n = 57) underwent serial monitoring with transvaginal ultrasound and serum oestradiol determinations. Human chorionic gonadotrophin (HCG) 10,000 IU was administered when follicles were felt to be mature and aspiration undertaken (n = 98) 34-36 h later. Among nine patients aged > or = 40 years, 13 aspirations resulted in nine embryo transfers and no pregnancies. In one completed cycle in this group, the patient, who was 42 years old had a baseline follicle stimulating hormone (FSH) concentration of 35.3 mIU/ml. The cycle progressed uneventfully and follicle aspiration yielded two oocytes and two morphologically normal embryos which, however, did not implant. In six patients < 40 years with male factor, seven aspirations yielded 18 oocytes of which 15 were inseminated and did not fertilize. One of the immature oocytes was allowed to mature in vitro and was fertilized and cryopreserved. Its transfer in a subsequent cycle yielded a live birth. Among 78 cycles in 42 patients aged < 40 years without male factor, 63 resulted in embryo transfer with 14% clinical pregnancy rates per aspiration and 17% per embryo transfer. Pregnancy was associated with higher oestradiol concentrations at the time of HCG administration and multiple embryos available for embryo transfer.(ABSTRACT TRUNCATED AT 250 WORDS)