You are here
IVF Study: Three Embryos Is Too Many
Women undergoing in vitro fertilization (IVF) who receive three or more embryos have no better odds than those how received two, according to a new study published in the journal Lancet. In addition, there is a greater chance of multiple births, which create more risk for the mother and for the child(ren).
The researchers also say the decision to transfer one or two embryos should be based on prognostic indicators, such as age, and they recommend that fertility doctors seeing a new couple with infertility should move older women to IVF sooner rather than later.
The British Study
The British researchers analyzed data for all 124,000 IVF cycles in the United Kingdom between 2003 and 2007, which resulted in more than 33,500 live births. The women were ages 18 to 50 and had varying histories of infertility. They found the following:
- The live birth rate was notably lower in older women than in younger women, irrespective of the number of embryos transferred.
- The odds ratios of live birth was higher in women aged 40 years or older than in those younger than 40 years when two embryos were transferred compared with one embryo.
- The live birth rate was higher among women of all ages who had two embryos transferred than among those who received one embryo.
- Among women younger than 40, transferring three embryos was associated with a lower birth rate than transferring two embryos.
- The success rate for women older than 40 who received three embryos was the same as for those who received two embryos.
- Compared with transferring one embryo, transferring two or three embryos was associated with a higher risk of all adverse perinatal outcomes.
- The risk for severe preterm birth was particularly high among women who received three embryos.
In a statement, the authors say: "Our findings provide some support for the transfer of two embryos in women older than 40 years, because the risks of preterm and low birth weight were lower than those in younger women. In older and younger women, the transfer of two embryos was associated with greatest live birth rates. A clear implication of our study is that transfer of three embryos should no longer be supported in women of any age."
Quality of embryos is an important consideration when assessing how many to transfer. "When two vs. three embryos are considered for transfer, the quality of the embryos must be considered," says Dorothy E. Mitchell-Leef, M.D., with Reproductive Biology Associates in Atlanta. "If there are two high quality embryos available, especially in young women, a third embryo would only increase the risk of multiples and would not be advised. Many times, if there are three embryos transferred, the cumulative quality is usually low and therefore would not increase outcomes."
Single Embryo vs. More
In the United States, with advanced technology such as preimplantation genetic screening with array comparative genomic hybridization (CGH) that screens all 23 pairs of chromosomes and significantly improved freezing techniques, elective single embryo transfer is becoming more often the preferred option, according to Dr. Sills. "Now the patient who wants to do a single embryo transfer can do that knowing that the single embryo has passed the test, that it really does have the genetic competency that we feel will give them a good chance of having a healthy baby," he says.
Previous studies, such as one published in the BMJ (British Medical Journal) found that women who undergo IVF are almost five times more likely to give birth to a single healthy baby following a single embryo transfer when compared with women who choose to have two embryos transferred. In addition, the Practice Committees of the American Society for Reproductive Medicine (ASRM) and the Society for Assisted Reproductive Technology (SART) issued a report this past fall calling for an increase in the use of elective single embryo transfer (SET) in good prognosis patients undergoing IVF. The committee examined a many studies to evaluate single vs. double embryo transfers and concluded that in good prognosis patients transferring one embryo could dramatically reduce the rate of multiples while maintaining high pregnancy rates.
Factors the committee cited for determining if the patient was a good candidate for single embryo transfer included:
- patient under 35
- more than one high quality embryo available for transfer
- women in their first or second IVF treatment cycle
- women with prior successful IVF cycles
- recipients of donated eggs
Typically, the decision on how many embryos to transfer is made through careful consultation with the patient and careful evaluation of factors such as patient's age, options for genetic testing to assess quality of the embryos, laboratory success rates, whether the couple can manage it if the female partner becomes pregnant with twins, etc. "We try to consult carefully with the couple to understand outcomes based on the quality of their embryos rather than the number," explains Dr. Mitchell Leef. "We often strongly recommend only one to transfer if they are young and have excellent quality embryos in their respective cohort to prevent multiples."