Why to transfer just one embryo in assisted reproduction treatment
According to recent data published by the National Statistics Institute of Spain this past June, the number of births in Spain fell by 6.1% in 2018. At the same time, the average number of children that women are having has dropped 0.06 points. In 2008, the average was around 1.44 children per woman, while a decade later this figure has gone down to 1.25.
In addition to this data, 32.2 years old was the average age at which a woman entered into motherhood in 2018 in Spain, up from the average 30.8 years of age a decade earlier. The statistics show that the decreased number of births (519,779 in 2008 compared to 369,302 in 2018), is accompanied by delayed motherhood.
The number of children born to mothers over the age of 40 has increased by 63.1% over the last ten years. This delay in entering into motherhood, along with a decline in males’ sperm quality, means that an increasingly higher number of couples have to reply on assisted reproduction techniques (ART) in order to conceive. These techniques have been found responsible for the increase in multiples (the likelihood of conceiving twins naturally is around 1.4%), which poses risks to the female during pregnancy as well as to the new-borns.
Reducing the incidence of multiples
One of the main goals of assisted reproduction specialists is to achieve an incidence of multiples (using ART), that resembles the incidence observed in natural pregnancies as closely as possible, without decreasing pregnancy success rates.
The Ministry of Health, Consumer Affairs and Social Welfare, with the collaboration of the Spanish Fertility Society, presented data on the activity of Spanish assisted reproduction clinics in 2016. The numbers showed that the rate of multiple pregnancies continues to decrease, both with own eggs (17%), as well as with donor eggs (20%). These percentages have fallen by 5% and 8% respectively over the last five years.
We still have a long way to go, but the way forward is increasingly clear. Improvements in systems for embryo assessment (which make it possible to transfer a single embryo), excellent embryo cryopreservation results and, little by little, increased public awareness on the risks associated with multiple pregnancies mean that we are on our way to making more single embryo transfers a reality.
The numbers at URE Centro Gutenberg
According to the data we’ve obtained at URE Centro Gutenberg, a single embryo transfer during in vitro fertilisation treatment lowers the likelihood of multiple pregnancies by 99%, and with that also reduces the risks associated with this type of pregnancy.
Pregnancy success rates at our Unit after just one cycle of egg donor IVF in 2013 were around 70%, but three out of every ten gestations were twin pregnancies (a 30% incidence of multiple pregnancies). Five years later, in 2018, the success rate is approximately 66%, but in return only 8% of the resulting pregnancies were twin gestations.
This difference is explained by the increase in the number of cases where the selective transfer of a single embryo was performed. That is why at our fertility clinic in Spain we recommend this option, because even though the success rate is slightly lower, at the same time the likelihood of a multiple pregnancy is reduced by 99%, along with the associated risks for mom and the foetus.
Additionally, in those cases for which the doctors recommend this selective technique, there are normally several good quality embryos. The embryos that are not used in the first transfer are frozen so that, in the event that a pregnancy is not achieved with one embryo, the patient can try again using the rest. This makes it possible for our patients’ cumulative success rate with fresh and frozen embryo transfers to be, in fact, greater than 88% in the first cycle of egg donation
We need to be aware that the incidence of multiple pregnancies resulting from assisted reproduction techniques in Spain is high. But this situation can and must be corrected. Therefore, at URE Centro Gutenberg we must make it clear that the selective transfer of a single embryo is highly recommended in the majority of assisted reproduction treatments.
Dr. Miguel Lara Lara
Co-director and embryologist at URE Centro Gutenberg
Do you have additional questions? Are you thinking about undergoing an assisted reproduction treatment? Contact us! At URE Centro Gutenberg we’ll answer all your questions.