In vitro fertilization (IVF) offers a pathway to parenthood for many individuals and couples facing fertility challenges. A common question prospective parents often have centers on the number of embryos that will be transferred during the procedure. The decision regarding embryo quantity is intricate, requiring careful consideration of various medical factors and patient circumstances. This choice is highly individualized, aiming to balance the likelihood of pregnancy with the desire for a healthy outcome.
Current Practices in Embryo Transfer
While IVF historically involved transferring multiple embryos to enhance pregnancy rates, current practice leans towards single embryo transfer (SET). This shift is due to advancements in laboratory techniques and improved embryo selection, allowing better identification of viable embryos. Many clinics and professional organizations advocate for SET as the preferred approach, given its safety benefits. In some situations, two embryos might be transferred when specific criteria are met. Transferring more than two embryos is uncommon, reserved for very specific, medically indicated cases.
Modern cryopreservation techniques also contribute, as excess high-quality embryos can be frozen for future use without compromising success rates. This allows transferring fewer embryos per cycle while maintaining good chances of conception. The goal is to achieve a healthy pregnancy with reduced risks of multiple births.
Key Factors Influencing Embryo Number
The number of embryos transferred is determined by several considerations, tailored to each patient’s profile. Patient age is a primary factor; younger individuals often have higher success rates per embryo. For instance, women under 35 with good quality embryos are recommended to transfer only one. Conversely, older patients, especially those over 38 or 40, may consider transferring two or three embryos, as their success rates with a single embryo may be lower due to declining egg quality.
Embryo quality plays a significant role. Embryologists assess embryos based on factors like cell number, symmetry, fragmentation, and developmental stage (e.g., blastocyst). High-quality embryos, especially those that have undergone preimplantation genetic testing (PGT) and are chromosomally normal (euploid), often lead to a recommendation for single embryo transfer, regardless of age.
Previous IVF cycle outcomes also influence the decision. If a patient has experienced prior failed transfers, transferring more than one embryo might be discussed, weighed against potential risks. The health of the uterus, including the uterine lining and absence of abnormalities like fibroids or polyps, is also considered, as a healthy uterine environment is essential for successful implantation. Clinic policies and national guidelines from professional societies, such as the American Society for Reproductive Medicine (ASRM), also provide frameworks for these decisions.
Considering Multiple Embryo Transfer
Transferring more than one embryo increases the chance of a multiple pregnancy (e.g., twins, triplets, or higher-order multiples). While some patients may desire twins, multiple pregnancies carry heightened health risks for both mother and babies.
For the mother, complications include increased risk of preeclampsia, gestational diabetes, and preterm labor. There is also a higher likelihood of Cesarean section delivery, postpartum hemorrhage, or anemia. Babies conceived in multiple pregnancies face elevated risks of prematurity and low birth weight. Premature birth can lead to various short-term and long-term health issues for infants, including respiratory problems, developmental delays, and cerebral palsy. The need for neonatal intensive care is also higher for multiples.
Given these risks, single embryo transfer (SET) is recommended to maximize the chance of a healthy, singleton pregnancy. The aim of IVF is to help individuals achieve the birth of one healthy baby, minimizing complications for both mother and child.