Not that long ago it was common for reproductive endocrinologists to transfer three, four, sometimes even five embryos in a patient when they were going through IVF. Technology has improved so rapidly in the reproductive world that nowadays the norm in a good prognostic patient is transferring one or two embryos. The world of IVF has definitely started to focus on the single embryo transfer(SET) and having one healthy baby. The Society of Assisted Reproductive Technology (SART) stated in their most recently published IVF clinic success rate reports that, ìcycle success is measured by the live birth rate with a singleton delivery occurring after 37 weeks of gestation being the optimal outcome of IVF cycle.î Their reasoning for emphasizing singleton live births is that twin and multiple rate pregnancies have a higher risk of premature delivery and complications during the pregnancy and after delivery.
While IVF success rates have continued to increase over the years, there is still the ìmore is betterî mentality with patients when it comes to their chance of success. When given the option of putting back one or two embryos the majority of patients will choose to put back two to increase their chance of success. Are they improving their chance of success? Yes, anywhere from 30-50% but they are also increasing their chance of having multiples. According to the CDC, if a woman under 38 who is undergoing IVF for the first time, and is using her own eggs, chooses to put back two embryos she has a 16-27% likelihood of having twins depending on the day the embryo was transferred.
So why are having twins risky? According to the CDC, almost 3out of 5 twin babies are born preterm (37 weeks gestation). Twin babies are nearly six times as likely to be born preterm as single babies. About 1 out of 4 twin babies are admitted to the neonatal intensive care unit (NICU), more than five times more likely than single babies. Also, twin babies are also more likely to be stillborn, experience neonatal death, have birth defects and autism. Twin pregnancy is also risky for the mother, not just baby. Mothers are more likely to get pregnancy-related high blood pressure and gestational diabetes.
While twin pregnancies are more risky that is not to say that there are not a lot of healthy twin pregnancies that result in two healthy babies. Obviously, there are many patients who have successful outcomes with multiples. Patients should take away that physicians and organizations are trying to educate them so that they have all the info they need to make the decision that is best for them. It is great progress that we are in a place where SET is an appropriate option for most patients.