Abstract and Introduction
Transfer of multiple embryos for IVF was an early and important advance to improve procedure effectiveness. Along with the increase in live birth rate, this advance resulted in a three-decade long battle to counteract high rates of multiple delivery that have accompanied multiple embryo transfer. This review chronicles the history of the struggle in the USA to reduce the number of embryos transferred and the multiple births that resulted from this practice while continuing to strive for high live birth delivery rates in young as well as older patients. The positive and negative influences of law, professional guidelines, inadequate medical insurance and patient preference are discussed. Recent reporting strategies and technical advances in embryo selection that can help us achieve single embryo transfer are reviewed.
In 1985, while setting up the IVF program, the author visited a program in a nearby state and watched the transfer of 12 embryos to the uterus of a woman attempting to achieve pregnancy. Transfer of all fertilized embryos was required of that program at that time. The program had been told that they could not discard any embryos and since embryo freezing was not yet available to them, the program was mandated to transfer all. Multiple pregnancy occurred but success rates were so low, under 5% per cycle, that few resulted in either a live birth or multiple delivery. Transfer of 12 embryos is no longer standard at assisted reproductive technology (ART) programs. However, reaching a balance between the number to transfer that will achieve a live birth and the number beyond which multiple pregnancy occurs has remained an intractable problem to which simple solutions have not been found.
The balance of live birth delivery versus multiple birth in ART has been a moving target. Both live birth rate and multiple delivery are strongly affected by the number of embryos transferred. However, number transferred does not tell the whole story. Live birth is also a function of factors including a program's ability to grow embryos in culture, patient age and diagnosis, and parameters of treatment that can differ for every patient. Guidelines on the number of embryos to transfer, based as they are on data that is several years old when they are published, can recommend too little too late. Live birth rates have risen rapidly and consistently in ART and as these rise so does multiple birth rate. Guidelines can often not keep pace. Complicating this is the insurance situation in the USA that all to often fails to cover ART, putting pressure on patients and providers to transfer more and achieve live birth in fewer cycles of treatment.
This review will explore the changes in both effectiveness and multiple birth rate over the more than 30 years of our experience of ART. It will also explore many of the conflicting forces that have kept the risk of multiple births a continuing problem for this field.
Expert Rev of Obstet Gynecol. 2013;8(4):357-368. © 2013 Expert Reviews Ltd.