In-vitro fertilization technology is one of the most exciting medical advances in this century. This fertility procedure has made it possible for many couples to conceive healthy infants. Although this procedure is quite successful in achieving pregnancy in many women, it does carry the risk of multiple-births. This is a serious concern because multiple-birth infants are predisposed to many health problems including pre-term delivery, low birth weight, congenital malformations, and infant death. In addition, the mothers who carry multiple-infants are also at risk for many health conditions and complications (e.g., high blood pressure, diabetes, etc.). A major medical and ethical dilemma is deciding on the number of embryos to transfer back into the uterus. Therefore, careful consideration must be given regarding the number of embryos to transfer when undergoing IVF. Further studies are needed in this area to minimize multiple births following IVF while maximizing pregnancy rates. A recent study published in the Journal of the American Medical Association (JAMA) investigated how the following 3 factors affected birth rates and the chance for having multiple births in women undergoing IVF:
The woman’s age
The number of embryos transferred back into the uterus during IVF
The quality of the embryos
The study, which was led by Dr. Schieve at the Center for Disease Control and Prevention (CDC), examined the outcomes of 35,554 IVF transfer procedures initiated in the US in 1996. The women who underwent these procedures were between 20 and 44 years of age and received fresh, nondonor IVF. Cryopreserved (frozen) embryos were not used for the cycles examined in this study, although some women had additional embryos cryopreserved for future use.
The study, which was led by Dr. Schieve at the Center for Disease Control and Prevention (CDC), examined the outcomes of 35,554 IVF transfer procedures initiated in the US in 1996. The women who underwent these procedures were between 20 and 44 years of age and received fresh, nondonor IVF. Cryopreserved (frozen) embryos were not used for the cycles examined in this study, although some women had additional embryos cryopreserved for future use.
The researchers found that overall, women in their 20’s and lower 30’s (30-34) had the highest birth rate when 2 embryos were transferred and extra embryos were cryopreserved. Women age 35 and over achieved higher birth rates if more than 3 embryos were transferred, however the birth rates were still lower compared to women under age 35. Cryopreservation of extra embryos did not affect birth rates in women over age 35.The rate of multiple-births was dependent on the age of the woman and the number of embryos transferred. When 3 embryos were transferred, the multiple-birth rate was 46% for women age 20-29. The rate decreased to 39% for women age 40-44 when 7 or more embryos were transferred. Therefore, younger women were at a greater risk for multiple births compared to older women, even though the number of embryos transferred may have been lower.These findings suggest that for younger women, the number of embryos transferred can be limited without compromising birth rates, and while minimizing the risk of multiple births.Drs. Lipshultz and Adamson of the American Society of Reproductive Medicine (ASRM) and the Society for Assisted Reproductive Technology (SART) responded to the results of this study with an editorial. The physicians stated that the findings of this study will likely cause changes in current ASRM guidelines regarding embryo transfer. Specifically, special consideration will be given regarding number of embryos transferred in certain types of patients. We can look forward to implementation of these study findings in future ASRM guidelines.
Reference
Schieve LA, Peterson HB, Meikle SF, et al. Live-birth rates and multiple-birth risk using invitro fertilization. JAMA 1999;282(19):1832-8.
Lipshultz L, Adamson D. Multiple-birth risk associated with in vitro fertilization: Revised guidelines. JAMA 1999; 282(19):1813-4.
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