The prognosis for assisted conception treatment after unexpected failure of fertilization in vitro: a comparative...

The relative prognosis for further assisted conception treatment (without micro-injection) after initial unexpected failure of fertilization in apparently favourable couples undergoing in-vitro fertilization (IVF) treatment was assessed. After their first cycle of treatment, 481 consecutive couples were grouped according to their fertilization (including cleavage) rate per oocyte into five bands. Proportions of couples proceeding to further cycles of treatment by IVF or gamete intra-Fallopian transfer (GIFT) and resulting fertilization and pregnancy rates were compared. Pregnancy rates in the first cycle of treatment were significantly related to fertilization rate. The fertilization rate was zero in 13 couples (3%) and only 1-24% in 18 (4%). There were no significant differences between these groups in the proportions proceeding to further treatment (31, 50%) compared with others (overall 37%, including some treated by GIFT), or in their median fertilization rates (75, 60% compared with 67%--IVF cycles only), pregnancy rates (20, 38% of cycles compared with 37%--IVF or GIFT) or birth rates (20, 38% of cycles compared with 31%--IVF or GIFT). Amongst couples whose initial fertilization rate was > or = 50% there was no fertilization in 4% of subsequent IVF cycles. We conclude that in couples with well defined favourable conditions, including tests of sperm function for assisted conception treatment, who have unexpected failure of fertilization, the prognosis for further treatment remains favourable without resort to more complex investigations or micro-injection methods. Such failure occurs infrequently and generally as a random event, and should have no appreciable effect on life-table calculation of cumulative pregnancy and birth rates in this group of patients.