IVF is a multi-step and complex process, and patients may have questions about the final stage — embryo transfer. The current best practice is Single Embryo Transfer (SET), in which a single embryo is placed into a patient’s uterus to begin a pregnancy. We talked to Dr. Charles Miller, Director of Minimally Invasive Gynecologic Surgery at the Advanced IVF Institute in Chicago, to learn more about this recommendation and how it has changed over time.
Background
When Dr. Miller first opened his IVF clinic in Naperville, Illinois in September 2001, the common practice was to transfer multiple embryos at one time. Two embryos would typically be transferred in hopes of increasing the chances of a successful pregnancy. Dr. Miller’s practice was successful, and the clinic soon earned the reputation of the “Twin Capital.” Because this was the standard at the time, patients going through treatment accepted it and sometimes even favored the practice, “embracing the idea of being ‘one and done’ in terms of family building” as put by Dr. Miller. However, sometimes multiple embryo transfers came with complications, or resulted in triplet pregnancies.
Hidden risks with multiple embryos transfers
In addition to the occasional triplet pregnancy, Dr. Miller noted that once per quarter, his patients would deliver prematurely. Most of the twin pregnancies would be delivered nearly at full term (36-38 weeks) but premature deliveries were usually due to cervical incompetence, where the cervix dilates too early. According to Dr. Miller, “the risk of delivery prior to 32 weeks was 2% for singleton pregnancies, 8% for twins, and 26% for triplets.i” Even with healthy pregnancies and births, children were left with long-term health impacts like cerebral palsy, profound developmental delays, and severe sensory and motor disabilities. Other risks associated with multiples include:
- Preterm birth
- Low birth weight
- Higher rates of Neonatal Intensive Care Unit (NICU) admission
- Maternal complications
How technology changed the game
Thanks to advancements in the embryology lab, including cryopreservation techniques and having the ability to select a genetically normal embryo, via Preimplantation Genetic Testing for Aneuploidy (PGT-A), SET is the optimal method of transfer. Dr. Miller no longer performs two-embryo transfers, only SET, and has delivery rates of over 65%.
Why is SET the recommended approach?
The values of SET extend beyond its clinical outcomes. Not only is it more cost-effective with saved NICU visits, but it also reduces the emotional strain that can come with a high-risk pregnancy. Elevated stress from pregnancy with multiples is well documented, Dr. Miller citing a study in which “22% of mothers of multiples had Parenting Stress Index scores in the severe range, compared to 5% of mothers with singleton pregnancies conceived via IVF and 9% with singleton pregnancies conceived naturally.ii” By shifting to SET, clinics and patients can experience reduced risks from multiple pregnancies and reach their family building goals more safely.
i Practice Committee of American Society for Reproductive Medicine. Multiple gestation associated with infertility therapy: an American Society for Reproductive Medicine Practice Committee opinion. Fertil Steril. 2012 Apr;97(4):825-34.
ii. Glazebrook C, et al. Parenting stress in first-time mothers of twins and triplets conceived after in vitro fertilization. Fertil Steril. 2004 Mar;81(3):505-11.