Age-dependent decrease in embryo implantation rate after in vitro fertilization

Objective: To investigate the relation between the implantation rate per embry Design: Retrospective study using linear and biphasic models in a multivariate analysis. Setting: Academic tertiary care institution. Intervention(s): In vitro fertilization-ET and determination of gestational sacs at 6 to 7 weeks of pregnancy by ultrasound. Main Outcome Measure(s): Implantation rate as defined by the number of gestational sacs per embryo replaced. Result(s): Woman's age and embryo morphology were strongly related to the implantation rate; indication for IVF-ET and cycle rank number also were related significantly but less strongly. A linear model was built describing the decrease in implantation rate with age, resulting in a decrease of approximately 7%. A biphasic model was tested also and performed significantly better, resulting in a yearly decrease of > 20% after 37 years of age. Conclusion(s): The most important independent factors related to the ability of embryos to implant are female age and embryo morphology. The best way to describe the relation with female age is a biphasic model with a discontinuity at approximately 37 years of age.