In an in vitro fertilization (IVF) or oocyte donation treatment, transferring two embryos has some risks, as complications may occur during pregnancy. In addition, it also does not improve the success of the treatment, so transferring two embryos is not better than one.
Increased risk of pregnancy
In those cases in which two embryos are transferred, the risk of both embryos implanting and the possibility of twin pregnancy increases. But also, although it is less common, there is a greater risk that the embryos may divide and a triple, even quadruple pregnancy may occur.
Multiple pregnancy has more complications, both for the mother and for the fetuses. This type of pregnancy is associated with a higher incidence of:
- Miscarriage
- Gestational diabetes
- Hypertension in pregnancy
- Premature delivery
- Low birth weight
- Complications after delivery
Transferring two embryos can increase the risk even in cases of singleton pregnancy
When two embryos are transferred, initially, both embryos may be implanted, with only one fetus developing, so that the other is known as an “evanescent twin”.
If two or more embryos are transferred, perinatal outcomes may be worse in singleton pregnancies with an “evanescent twin”, with an increased risk of prematurity and low birth weight. In the case of transferring 2 embryos, if only one embryo implants, the perinatal risk would be normal, and the same as in single embryo transfers.