Forty-four years ago, the first successful in vitro fertilization-embryo transfer (IVF-ET) was a result of a single embryo transfer. The process of egg harvesting required a laparoscopic egg retrieval during a natural cycle, which in todays’ standards, would be considered highly inefficient. The reason: not every egg a woman produces will result in a pregnancy. Not every embryo created or transferred into a woman’s uterus will result in a live birth.
Over the past 2 decades, the field of reproductive endocrinology has seen a decline in multiple embryo transfer as pregnancy rates have improved substantially. The practice of multiple embryo transfer resulted in increased pregnancy complications such as preterm delivery, preeclampsia, and diabetes, to name a few. Early use of IVF was associated with a high twin live birth rate, thus the rise of Single Embryo Transfer (SET) was born out of the desire to decrease the occurrence of twins or multiples, for the sake of the mother and child’s health.
It is not only the physical risks that multiples can pose. Some studies suggest that the psychological impact of multiples on a couple’s relationship compared to singletons has shown higher rates of divorce compared to their singleton counterparts. The rate of postpartum depression also appears to be higher for mothers of multiples. The use of SET combined with preimplantation genetic screening has decreased this potential burden for patients desiring children while maximizing their chances of a healthy live birth.
How Many Eggs Are Removed For Single Embryo Transfer
IVF entails controlled ovarian stimulation, which means the egg provider would take injectable medications with the intent to produce many eggs in a given cycle. Egg retrieval is performed using a needle-guided transvaginal ultrasound aspiration procedure, also known as a vaginal oocyte retrieval, while the patient is comfortable and safe under anesthesia. But what happens with all these eggs? Some eggs are not mature, which means they cannot be fertilized, and hence they are discarded. Sperm is either placed near or into the egg, the latter via a sperm injection using a micropipette called intracytoplasmic sperm injection (ICSI) in the hopes of adequate fertilization. A fertilized egg is now an embryo, and they are kept in the lab to assess for adequate growth and possible genetic testing followed by embryo freezing. Preimplantation genetic testing for aneuploidy (PGT-A) allows for further refinement and determination, but not a guarantee of embryo viability and implantation potential. Though the test is not perfect, it gives information on the number of chromosomes the embryo contains. An euploid embryo, one suitable for transfer with good implantation potential, has 22 pairs of autosomes and 1 pair of sex chromosomes, XX for female, and XY for male. Success is a “numbers game” based on how many eggs are retrieved, number of embryos created, and whether those embryos are chromosomally normal.
For patients with single gene disorders or genetic translocations, preimplantation genetic testing for monogenic disease (PGT-M) or preimplantation genetic testing for structural rearrangement (PGT-SR) can also be performed to minimize the transmission of a genetic abnormality and pregnancy loss respectively.
Currently SET is the standard practice with IVF for all patients under the age of 40. In patients under 35, utilization of PGT-A vs transfer of an untested embryo has comparable outcomes. However, PGT-A allows for sex selection and may help patients decide what do when it comes to embryo disposition. SET, along with the genetic testing of embryos, has revolutionized IVF ET. Currently, non-invasive assessment of embryonic potential is being studied with promising results.
Here at IRMS, our success rate is around 65%-70% per transfer of a euploid embryo regardless of age. Through the ability to cryopreserve eggs and embryos and using SET, we can maximize the number of attempts at a pregnancy, one embryo at a time, and therefore increase the economies of scale of one IVF cycle. If legislation gets passed that impacts our ability to freeze embryos or in any way limits the number of embryos created per cycle, we lose all of the benefit the science of cryopreservation has yielded us.
Dr. Jessica Salas Mann is board certified in both Reproductive Endocrinology and Infertility and Obstetrics and Gynecology. She is a fellow of the American College of Obstetrics and Gynecologists, and is a Diplomat of the American Board of Obstetrics and Gynecology. Dr. Mann and her team deliver exemplary care and service to patients throughout Central and Southern New Jersey at her office in Old Bridge. She is an experienced reproductive surgeon, having served the patients of Middlesex, Monmouth and Ocean counties since 2011. Her areas of clinical interest and expertise are pregnancy loss, ovulation induction, in vitro fertilization, polycystic ovarian syndrome, and third party reproduction.