Ovodonation is the most successful treatment in assisted reproduction, frequently associated with the delay in the age of the pregnant woman. Therefore, it is frequent in women over 40 years old, an age in which women’s fertility decreases, reducing the number and quality of eggs.
In 2016, according to official data from the National Registry of Activity 2016-SEF Registry, 16,133 egg donation cycles were performed in Spain.
How many donated eggs are necessary to achieve a pregnancy?
A high number of eggs is needed to achieve a pregnancy by In Vitro Fertilization (IVF), even in the case of donor eggs. Regardless of the donor’s age, not all eggs will fertilize or form embryos.
On average, 23 eggs are needed to achieve pregnancy. But to achieve delivery this number increases to 32. The reason for this is that some pregnancies end in miscarriage.
In the case of using frozen donor eggs, it should be noted that not all eggs survive the thawing process (86.8% according to the SEF Registry). The surprising thing is that the numbers of frozen eggs used do not differ from the fresh ones (23 and 33).
At URH Garcia del Real we lower the figures even further. In 2016 we used 11.4 donor eggs to achieve a pregnancy and 14.1 to achieve a delivery. As for frozen eggs, we need 17 and 20. These numbers confirm the good quality of our clinical and laboratory work.
How many transferred embryos are needed?
The number of embryos will depend on the woman’s age, since the probability of having embryos with chromosomal abnormalities or aneuploidy increases. In the case of using donor eggs, being under 35 years of age by law, we expect to need a small number of embryos, according to the SEF Registry an average of 2.9 embryos transferred are needed to achieve a pregnancy; and 4.9 embryos transferred to achieve a delivery.
When embryos are frozen after an ovodonation cycle the probability of pregnancy with these frozen embryos will be good. In 2016, 25,773 embryos from egg donation cycles were thawed in Spain and 16.8% did not survive the thawing process. It took an average of 3.6 embryos to be transferred to achieve pregnancy and 5.6 to achieve a birth, which is one embryo more than fresh embryos.
In the same year, at URH Garcia del Real, we needed 1.7 embryos transferred fresh to achieve pregnancy and 2.3 to achieve delivery. In the case of frozen embryos, 6.5% did not survive the thawing process and we needed 1.9 embryos transferred for pregnancy and 2.6 for delivery.
The following table is a summary of the data provided: