In the early days of IVF treatment, large numbers of embryos were transferred into the uterus. The aim was to have a successful treatment process. Success simply meant getting pregnant. It was not considered how many embryos would attach to the uterus. When the first IVF baby, Louise Brown, was born in 1978, exactly 102 embryo transfer attempts before her had failed. In other words, IVF success was less than 1% in those years.

Over the years, different strategies have been tried to be developed as situations that put mother and baby at risk such as premature birth, miscarriage and other pregnancy problems due to multiple pregnancies (twins, triplets and more). As of 2017, 90% of embryo transfers in Australia, New Zealand and Scandinavian countries started to be made as “single embryo transfer”. In the United States, this rate is now 71%. But not all parts of the world are the same.In European countries, this rate is only around 38% as of 2015.

The main reasons couples want to transfer more than one embryo are as follows:

  • Female age: Especially after the age of 35, pregnancy success decreases with the decrease in egg quality. For this reason, it is tried to increase the chance of success by transferring excess embryos. In addition, expectant mothers who think that they do not have time for a second or even third child may want to close this book by having more than one baby at a time.
  • Long infertility period: The couple who want to have a child have waited long enough and are now impatient. For this reason, she wants to conceive and give birth as soon as possible and demands maximum luck.
  • Previously unsuccessful IVF attempts: The couple, who had difficulties psychologically and financially, had a very low tolerance, and therefore they want 2 or more embryos to be placed in the uterus and a successful result as soon as possible.
  • Number and quality of embryos suitable for transfer: It is generally preferred to transfer both of them, especially when there is a good quality and a medium quality embryo.
  • Financial problems: In IVF, which is an expensive treatment, a large number of embryo transfers are requested in order to be successful in the first treatment and not to spend more money.
  • Cultural status and religious beliefs:

In the past 43 years, especially with the developments in the laboratory, embryo freezing technology has been improved (in the past, slow freezing, “slow freezing” was used, now vitrification method is used), it has been possible to follow the embryos up to the blastocyst stage and to select the best embryo, so the success of IVF treatments is high. increased. With these developments, the strategies of single embryo transfer and freezing and storage of the remaining embryos for future use have also gained importance. In addition, Pre-implantation Genetic Diagnosis (PGD), which is one of the embryo selection criteria, has been successfully implemented and has contributed positively to the single embryo transfer strategy. In the old practices, the best embryo could not be followed up to the blastocyst stage, and as the freezing techniques were not good, any embryos were placed in the uterus.

In many published studies, the effect of two embryo transfers and single embryo transfer on live birth was compared, and it was shown that live birth was significantly higher after two embryo transfers. BUT, two embryo transfers increase the risk of multiple pregnancies (twins, triplets) almost 10 times. In addition, after a single embryo transfer with a negative result, after one or more transfers of cryopreserved embryos, the chance of pregnancy increases in each trial, and the success of live birth is achieved with two embryo transfers. In summary, we can say that the success of live birth obtained by transferring two embryos at once is similar to the success of live birth by transferring a single embryo more than once. The most important advantage of single embryo transfer is to minimize the risks of multiple pregnancy.

In twin pregnancies, the risk of delivery before 28 weeks increases 5 times, and the intensive care needs of babies born increase 6 times. Since they are born prematurely and cannot be fed enough, their birth weight is 850 g less on average.

We should not think of pregnancy only as a test positivity, but as a 9-month period, and we should not forget the complications caused by multiple pregnancy such as premature birth, gestational blood pressure, gestational diabetes, and an increase in the frequency of cesarean section.

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