Women undergoing treatment with in vitro Fertilization face an approximately 20-fold increased risk of twins and 400-fold increased risk of high-order multiple pregnancies (triplets or more).
Multiple pregnancies and particularly the high-order multiple pregnancies are associated with a higher maternal and perinatal complication rate including miscarriages, pregnancy-induced hypertension, gestational diabetes, operative delivery, prematurity, and permanent handicap in the newborn. High order multiple pregnancies are therefore an undesirable consequence of assisted reproductive technology.
Although multifetal or selective reduction can be performed to reduce fetal number, the procedure may result in the loss of all fetuses and does not completely eliminate the risk associated with multiple pregnancies. Moreover, multifetal pregnancy reduction is not an acceptable option for some women.
In an effort to reduce the number of high-order multiple pregnancies the American Society of Reproductive Medicine has developed guidelines to assist programs and patients in determining the appropriate number of embryos to transfer. Strict limitations on the number or embryos transferred, as required by law in some countries, do not allow treatment plans to be individualized after careful consideration of each patients unique circumstances.
Therefore, these guidelines need to be modified according to individual clinical conditions and success rates in individual laboratories as well as taking into consideration the patient’s age, Embryo quality, stage of transfer, and the opportunity of Cryopreservation.
Individual programs should generate and use their own data regarding patient characteristics and the number of embryos to transfer and whether transfer should be a day-three (cleavage-stage transfer) versus five- to six-day transfer (blastocyst). A program should also continually monitor their results to adjust the number of embryos transferred in order to minimize undesirable outcomes.
Independent of age, the following characteristics have been associated with a patient who is known to have a favorable prognosis:
- First Cycle of in vitro fertilization (IVF)
- Good quality embryos
- Excess embryos of sufficient quality to warrant cryopreservation
The patients who have had previous success with in vitro fertilization should also be regarded in the favorable prognostic category.
The number of embryos transferred should be agreed upon by the physician and the patient with informed consent documents completed.
- Patients under the age of 35 who fit into the favorable prognosis group, the standard of care is to transfer no more than two embryos, these embryos either at the cleavage stage or blastocyst stage.
- Patients between 35 and 37 who have a favorable prognosis, two embryos are also recommended, particularly if extended culture is performed to the blastocyst stage. Once again, the emphasis is on the individualization and considering the individual history of the patient.
- Patients between 38 and 40 years of age who have a favorable prognosis, three cleavagestage embryos or two blastocysts should be transferred. This would be increased if a patient were in a poorer prognostic group.
- Patients greater than 40 years of age no more than five cleavage-stage embryos or three blastocyst-stage embryos should be transferred unless the patient is in a poor prognostic group once again.
Less favorable prognoses include patients who have had multiple IVF failures, poor-quality-looking embryos, and a diminishing functional ovarian reserve.
In donor cycles the age of the donor should be used to determine the appropriate number or embryos to transfer and the recommendation is two embryos either at the cleavage or blastocyst stage.
Individualization should at all times be carefully considered and each patients own unique circumstances taken into consideration.