Objective: To investigate the relation between the implantation rate per embryo after replacement in IVF-ET in relation to female age.
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 buy 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 biphasic model with a discontinuity at approximately 37 years of age.