In Vitro Fertilization (IVF) concludes with the embryo transfer, where the fertilized egg is placed into the uterus. Determining the number of embryos to transfer is a central decision, directly influencing both the chance of pregnancy and the risk of multiple gestation. This determination is not made by a single person; it balances medical data, patient wishes, and professional standards. The goal is to maximize the possibility of a live birth while striving for a healthy singleton pregnancy. The final number results from a discussion involving the medical provider, the patient, and industry recommendations.
The Physician’s Medical Assessment and Recommendation
The reproductive endocrinologist initiates the discussion by proposing a recommendation rooted in the patient’s specific clinical data. The primary medical consideration is the patient’s age, which predicts embryo quality and pregnancy success rates. Women under 35, for example, generally have the highest success rates per embryo transferred, leading to a strong recommendation for single embryo transfer (SET) to avoid the complications of twins or triplets.
Embryo analysis provides the next layer of data. Embryos are assessed based on their developmental stage (cleavage-stage, Day 3, or blastocyst, Day 5 or 6), with blastocysts having higher implantation potential. Preimplantation Genetic Testing (PGT) is a key determinant, identifying whether an embryo is euploid (having the correct number of chromosomes).
If an embryo is confirmed as euploid, guidelines strongly recommend transferring only one, regardless of the patient’s age, due to the high probability of success and lower risk of multiple births. Other factors influencing the recommendation include the patient’s previous IVF cycle history, such as failed transfers, and any medical conditions that would make a multiple pregnancy dangerous.
The Role of Patient Autonomy and Informed Consent
While the physician provides the medical recommendation, the patient is integral to the final decision through shared decision-making and informed consent. The patient introduces personal factors, including their tolerance for the risks associated with a multiple pregnancy. Some patients may desire twins, accepting higher risks like preterm birth, preeclampsia, and low birth weight, to complete their family sooner.
Financial considerations often influence the preference for transferring more than one embryo. Since IVF is expensive and often not fully covered by insurance, some patients increase the number transferred to maximize success in a single cycle, avoiding the cost of a future cycle. The medical team must ensure the patient understands that a multiple pregnancy greatly increases the risk of complications, including a 60% chance of preterm birth for twins and elevated maternal risks like gestational diabetes and hemorrhage.
Informed consent requires the physician to counsel the patient thoroughly on the risks to both mother and babies if they choose to transfer more embryos than medically advised. If a patient proceeds with a number exceeding the clinic’s recommendation, this counseling and the patient’s justification must be documented. Ultimately, the patient has the right to accept or decline the medical advice, provided their choice remains within the established medical and ethical limits.
Governing Professional Guidelines and Limits
External professional organizations establish the maximum number of embryos that can be transferred, limiting both the physician’s recommendation and the patient’s preference. The American Society for Reproductive Medicine (ASRM) and the Society for Assisted Reproductive Technology (SART) issue guidelines to mitigate the public health risk associated with high rates of multiple births. These guidelines influence clinic policies and provide standardized limits based primarily on the patient’s age and embryo prognosis.
For women under 35 with a favorable prognosis, the guideline is to transfer a single embryo, known as Elective Single Embryo Transfer (eSET). As age increases, the recommended maximum number of embryos allowed is slightly raised to compensate for lower success rates per embryo. For instance, women between 38 and 40 with an unfavorable prognosis may be permitted to transfer up to two blastocysts or three cleavage-stage embryos.
These professional limits serve as a safeguard, ensuring clinics prioritize a singleton birth outcome, which is associated with the best health outcomes for the mother and child. While these are technically guidelines and not laws, most reputable fertility clinics adhere to them strictly. They act as the final boundary that cannot be crossed, regardless of the patient’s desire.