Effect of maternal age and number of in vitro fertilization procedures on pregnancy outcome

Five hundred twelve patients underwent 1,101 oocyte retrievals for in vitro fertilization (IVF) from July 1, 1985 to June 30, 1988. Eighty-four percent of all oocyte retrievals went on to transfer. The mean number of oocyte retrievals was 2.2 per patient, and the mean number of embryo transfers (ET) was 1.8 per patient. The pregnancy rate was 23% per retrieval, 27% per ET, and 49% per patient. There were 77 (31%) spontaneous abortions and five (2%) ectopic pregnancies. Linear regression analysis of the effect of women's age on the ongoing pregnancy rate per ET showed a highly significant negative linear correlation between age and ongoing pregnancy rate (P < 0.005). Ongoing pregnancy rate per ET for patients younger than 30 years of age was 26%, as compared with 9% for patients aged 37 years (P < 0.01). Patients aged 40 years or greater had a 50% miscarriage rate, compared with 29% in patients under the age of 40 (P > 0.05). The clinical pregnancy rate per ET for patients undergoing one to seven attempts was 25%, 29%, 28%, 33%, 35%, 30%, and two out of five, respectively. We conclude that women's age has a negative effect on IVF success that is more pronounced after the age of 36, and the pregnancy rate per ET is similar for at least seven attempts.