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

The relative prognosis for further assisted conception treatment(without micro-injection) after initial unexpected failure offertilization in apparently favourable couples undergoing in-vitrofertilization (IVF) treatment was assessed. After their firstcycle of treatment, 481 consecutive couples were grouped accordingto their fertilization (including cleavage) rate per oocyteinto five bands. Proportions of couples proceeding to furthercycles of treatment by IVF or gamete intra-Fallopian transfer(GIFT) and resulting fertilization and pregnancy rates werecompared. Pregnancy rates in the first cycle of treatment weresignificantly related to fertilization rate. The fertilizationrate was zero in 13 couples (3%) and only 1–24% in 18(4%). There were no significant differences between these groupsin the proportions proceeding to further treatment (31, 50%)compared with others (overall 37%, including some treated byGIFT), or in their median fertilization rates (75, 60% comparedwith 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). Amongstcouples whose initial fertilization rate was 50% there wasno fertilization in 4% of subsequent IVF cycles. We concludethat in couples with well defined favourable conditions, includingtests of sperm function for assisted conception treatment, whohave unexpected failure of fertilization, the prognosis forfurther treatment remains favourable without resort to morecomplex investigations or micro-injection methods. Such failureoccurs infrequently and generally as a random event, and shouldhave no appreciable effect on life-table calculation of cumulativepregnancy and birth rates in this group of patients.