In-vitro fertilization: influence of women's age on pregnancy rates.

An analysis of the influence of women's age on the results of in-vitro fertilization was performed, using 5590 attempts collected during the year 1986. Increasing age was found to be related to decreased success rates from 19.8% per attempt below the age of 25 years, to 9% per attempt at 40 years or more. A cut-off point was found between the ages of 36 and 37 years, using a mathematical model. The decrease was related to a reduction in oocyte production (4.3 +/- 2.8 at 25 years or less and 3.3 +/- 2.1 at 40 years or more, P less than 0.001), and to a reduced implantation rate, whatever the number of transferred embryos. These findings were not due to spouse's age, rank of attempt, infertility diagnosis or oocyte stimulation regimen, since the effect of age remained significant when a logistical model including these confounders was applied. Finally, a woman's age must be considered as a prognostic factor when IVF is proposed to infertile couples.