The in vitro fertilization technique (IVF), along with artificial insemination (AI), is one of the most in-demand treatments in assisted reproduction to help a couple, or a woman, achieve pregnancy. In the past, it is true that these treatments increased the probability of having twins (both identical and non-identical). However, nowadays the advances and knowledge in this sector of reproductive medicine mean that specialists recommend the transfer of only one embryo. An advance that guarantees an excellent result of the treatment.
DOES HAVING IVF INCREASE THE PROBABILITY OF A MULTIPLE PREGNANCY?
The increased probability of a multiple or twin pregnancy with in vitro fertilization, when compared with that of a natural pregnancy, is notable. Studies of data from previous years demonstrate that the probability of having twins after IVF is greater than that for a natural pregnancy. The main reason for the significant difference can be found in the fact that during the in vitro fertilization (IVF) process, transfers of two or more embryos were performed.
These days, the transfer of a single embryo has gained popularity over the practice of transferring two embryos. Indeed, the incidence rate of twins has decreased constantly in recent years, arriving at around 10%, according to data from the SEF (Spanish Fertility Society).
HOW MANY EMBRYOS ARE TRANSFERRED IN IVF?
As stipulated in Spanish Law, in Spain it is possible to transfer up to a maximum of 3 embryos in an in vitro fertilization treatment (IVF). However, the practice of transferring 3 is not widespread and is not usually performed. The current trend is to transfer a single embryo, thereby avoiding an increase in the probability of having twins.
WHAT OTHER FACTORS INFLUENCE HAVING TWINS?
There are also other factors that can predispose women to having identical, or non-identical twins:
• Age: after the age of 35 hormonal alterations are more likely to occur, which can lead to multiple ovulation.
• Some assisted reproduction treatments: the drugs used to induce pregnancy substantially increase the chances of giving birth to twins.
• Body Mass Index (BMI): when BMI is over 30, the probability of a twin pregnancy is found to be higher.
• Genetic predisposition: if there is a family history of multiple pregnancies then the chances of a twin pregnancy increase.
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