Ovarian stimulation can increase the risk of multiple pregnancy. Multiple pregnancy occurs when more than one fetus develops in the uterus. Multiple pregnancy carries the increased risk of complications both for the fetus and the mother, such as, for example: miscarriage, pre-eclampsia (increased blood pressure during pregnancy and other accompanying symptoms), preterm delivery. Multiple pregnancy is often associated with emotional or financial problems.
The patients with increased risk of multiple pregnancy are often women under 37 years of age who undergo the IVF procedure for the first time and those who have more than two embryos of good quality.
In the case of younger women (under 35 years of age), and in particular women who meet three of the above named criteria, transfer of no more than one embryo is recommended in order to limit the risk of multiple pregnancy.
In the case of all other patients aged up to 40, the transfer of two embryos is recommended, and in patients aged over 40, the transfer of 3 embryos can be considered.
The number of embryos transferred to the uterus impacts both the rate of achieved pregnancies and the rate of multiple pregnancies. A number of fetuses higher than the number of transferred embryos obtained in the result of IVF procedure is not a success; however, it must also be kept in mind that not always the number of transferred embryos will correspond to the number of developing fetuses.
Therefore, it is extremely important to decide what number of embryos is to be transferred before the ET procedure.
According to the recommendations published in Fertility Sterility Vol.92. No. 5 in November 2009, developed on the basis of data gathered by ASRM and SART “Guidelines on number of embryos transferred”, it can be assumed that the number of embryos transferred should depend not only on the mother’s age and the stage of embryo development but also on medical circumstances, i.e. whether: it is the first IVF program, embryos are morphologically of good quality, the sufficient number of good quality, freezable embryos was obtained, previous IVF procedures were completed successfully.
The decision concerning the number of embryos transferred should always be informed and taken by patients together with the doctor and always after thorough consideration, but definitely before the procedure of embryo transfer.
Recommended number of embryos transferred
(Source: “Guidelines on number of embryos transferred” Fertility Sterility Vol.92. No. 5, November 2009)
| Woman’s age | <35 | 35-37 | 38-40 | 41-42 | |
|---|---|---|---|---|---|
| Stage of embryonic development | Medical circumstances | ||||
| Embryo on day 2 to 3 after fertilization |
Favorable circumstances | 1-2 | 2 | 3 | 5 |
| Embryo on day 2 to 3 after fertilization |
Other cases | 2 | 3 | 4 | 5 |
| Blastocyst (embryo on day 5 or 6 after fertilization) |
Favorable circumstances | 1 | 2 | 2 | 3 |
| Blastocyst (embryo on day 5 or 6 after fertilization) |
Other cases | 2 | 2 | 3 | 3 |
In many cases, after the embryos have been transferred to the uterus in the number set in the consent form, there will be remaining embryos which, based on the decision of the patient and her partner, can be frozen and then stored for the purpose of their later thawing and use by the patient and her partner for the procedure of frozen embryo transfer (FET). The transfer of previously frozen embryos, carried out at a later date, does not require the complex stimulation of ovulation.