Mother Nature and science are a bit more complicated than that. For many patients who have a good prognosis for success: people using egg donors , people who are young with good egg quality, people who have PGS normal embryos embryos that have normal chromosomes by Preimplantation Genetic Screening etc. I get this question every day. Below is a typical email from one of my patients and my answer below. Hope you are having a good weekend.
I believe my nurse reached out to you. With that said I would like to give myself the best opportunity for a successful pregnancy. Would you consider transferring 2 embryos? Although most twins do well, twin pregnancies are very high risk for both the mom and baby with much higher miscarriage, birth defect and neonatal death rates than singleton pregnancies.
This is the reason that ASRM guidelines recommend only transferring one embryo at a time when you use egg donation or are transferring embryos that are normal by PGS. It is much safer and more effective. Transferring two embryos at a time is essentially wasting an embryo and putting you at risk. This would be medically irresponsible and against ASRM guidelines.
So we only put in one donor embryo at a time. It also brings up a common dilemma. Should you consider a single or double embryo transfer? The answer requires us to consider several factors. A critical statistic in IVF is the implantation rate.
The implantation rate is the proportion of transferred embryos that implant in the uterine lining. These embryos must then continue to develop until we can detect a fetal heartbeat. Implantation rate is therefore the ratio of fetal hearts to transferred embryos. In IVF, implantation rates once were highly dependent on the age of the female who provided the eggs, as egg quality declines rapidly with age.
The implantation rates can increase by genetically screening the embryos before transfer. Additionally, it can help to transfer the embryos into a uterine environment that has not been subjected to ovarian stimulation, such as with frozen embryos, egg donation cycles or gestational carrier cycles.
Single embryo transfer can be successful for women over their mid-thirties. One key factor in success rates is egg quality. As women age, the quality of their eggs decreases. Harvesting eggs before a woman is 35 and freezing them for future use can preserve egg quality. Women older than 35 who use eggs that were harvested when they were younger often experience the same success rate with single embryo transfer as women who are under This means older women can have a single embryo transferred and save the rest of their embryos for when they are ready to have another child.
This allows them to transfer a single embryo without increasing their risk of a multiple birth. Multiple embryo transfer is most beneficial to women who are over 35 and did not have their eggs frozen when they were younger. In such cases, multiple embryo transfer can be more successful than single embryo transfer. Older women typically face a lower success rate with IVF overall and their likelihood of a multiple birth is also lower.
Another thing many patients consider a benefit with multiple embryo transfer is the increased chances of multiple births. Although there are risks to the mother and babies, for many couples who have struggled to become pregnant the idea of having not only one but two or more children would be a dream come true.
Your single embryo would need to spontaneously divide in the womb to create identical twins or triplets. There are many health risks associated with multiples, including premature birth and low birth weight.
Babies born preterm have a greater chance of medical and neurological problems.
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