FACTORS THAT AFFECT OUTCOME OF IN-VITRO FERTILIZATION TREATMENT

Background The effectiveness of in-vitro fertilisation (IVF) treatment depends both on the overall success rate in the treating clinic and o n the characteristics of the couple seeking treatment. Since 1991, the Human Fertilisation and Embryology Authority (HFEA) has been collecti ng information on all IVF cycles carried out in the UK. This database has been analysed to identify the factors that affect the outcome of t reatment. Methods All IVF treatment cycles and outcomes registered bet ween August, 1991, and April, 1994, were identified (52 507). Cycles t hat involved gamete or embryo donation, frozen embryo transfer, or mic romanipulation and unstimulated cycles were excluded. Thus, 36 961 cyc les (70% of those registered) were included in the analysis. The main outcome measure was livebirth rate per cycle started, The relation bet ween age and outcome was investigated by fitting of different fraction al polynomials of age with logistic regression models. All other facto rs were analysed by logistic regression with age included in the model . Findings The overall livebirth rate per cycle of treatment was 13.9% . The highest livebirth rates were in the age-group 25-30 years; young er women had lower rates and there was a sharp decline in older women. At all ages over 30, use of donor eggs was associated with a signific antly higher livebirth rate than use of the woman's own eggs, hut ther e was also a downward trend in success rate with age (p=0.04. After ad justment for age, there was a significant decrease in livebirth rate w ith increasing duration of infertility from 1 to 12 years (p<0.001). T he medical indication for treatment had no significant effect on the o utcome. Previous pregnancy and livebirth significantly increased treat ment success. The possibility of success decreased with each IVF treat ment cycle. Interpretation We were able to identify by logistic regres sion the factors that significantly affect the outcome of IVF treatmen t, and to measure the magnitude of that effect. These factors should b e taken into account in assessment of IVF results. After allowance for background clinic success rates, these factors can be used to predict outcome in individual cases.