The rate of twin pregnancies has been increasing significantly in recent years. It is an increase primarily due to the development of IVF.
Suffice it to say that the chance of twins being born through natural conception is only 1 in 90, and if conception is done through IVF, the chance of twin pregnancy is almost 20 times higher: if two embryos are implanted, there is a 20% chance of twin pregnancy, with the twins that are born are almost always dizygotic – that is, they are not identical, since they do not share exactly the same DNA as the monozygotic.
It should be noted that in Greece the previous law allowed the implantation of many embryos, which has also contributed to the proliferation of multiple pregnancies. Now, with the new legislation, our country is allowed to implant up to two embryos when the woman is under 40 and up to three when she is older. In the future, legislation is expected to become even stricter, following the example of the Nordic countries and Denmark, where only one embryo is allowed to be implanted.
But why is there this tendency to limit multiple pregnancies and even twin pregnancies?
In the case of twin pregnancy, about half of births come prematurely, before 37 weeks of gestation. Preterm birth is the most important problem in multiple pregnancies, as premature babies are more likely to be underweight and to develop health problems, with respiratory problems being more dangerous.
If the preterm birth is very high, i.e. if the delivery is made before 28 weeks, in addition to the risk to the child’s life, there are other health issues – for example neurological – that may occur later in life affecting negatively in its quality.
For the mother, twin pregnancy makes pregnancy more difficult as it increases the likelihood of complications, such as preeclampsia, of a pressure disorder that can cause serious health problems. Another quite common complication of twin pregnancy is gestational diabetes. Women who are expecting twins need to be more careful about their diet and lifestyle and may need more visits to their gynecologist to adjust prenatal care to their needs.
For these reasons, our goal in the process of IVF should be to avoid twin pregnancies. This means we carry fewer embryos or even only one embryo. If, for example, there are two embryos, we may choose to have one embryo transferred and freeze the other to be used in the next attempt if the original embryo does not succeed. It is worth noting that in this way the cumulative pregnancy rate is higher. This is a very interesting subject that reflects contemporary perceptions of assisted reproduction, and we will discuss this in more detail in a subsequent article.