Defining and interpreting pregnancy success rates for in vitro fertilization.

OBJECTIVES To review current practice in describing pregnancy success rates after IVF-ET, to identify issues associated with interpreting these rates, and to suggest useful methods of describing these rates in the future. DESIGN Review of literature concerning medical, epidemiologic, and statistical aspects of reporting IVF-ET pregnancy success rates. SETTING The United States. PATIENTS Infertile couples participating in IVF-ET. MAIN OUTCOME MEASURES Usefulness and accuracy of IVF-ET pregnancy reporting. RESULTS Several groups have collected information on the pregnancy success rates of IVF-ET clinics and have discussed appropriate definitions of pregnancy success. The largest of these groups in the United States is The American Fertility Society and its affiliate, the Society for Assisted Reproductive Technology. The number of live deliveries per 100 ET procedures and the number of live deliveries per 100 egg retrieval procedures are among the most commonly used definitions. CONCLUSION The most commonly used definitions are particularly useful for describing the probability that a live infant will be delivered after IVF-ET is completed. To measure the effectiveness of the IVF-ET procedures and the costs of undergoing IVF-ET, other definitions are also important. Success rates need to be stratified by patient characteristics, such as age, that affect the probability of success.