“Where you stand depends on where you sit.” These words could not be truer for couples undergoing IVF treatments. Some of these couples will have the opportunity to transfer one embryo (single embryo transfer, or SET) or two in what becomes one of the most important decisions of their entire treatment. For many, there will be a significant temptation to have two embryos implanted. This based on a desire to maximize the chances of at least one child, or to “get two pregnancies over with” at once. However, there is one person who will be the most interested in a singleton pregnancy: the person doing the actual delivery, the obstetrician.
The vast majority of twin pregnancies via IVF conclude with healthy babies and a healthy mom. But there are legitimate increased risks. The central risk of a twin pregnancy is of preterm delivery. Nearly 60% of twins delivery before 37 weeks (term is considered to be 37 weeks), and 11 percent delivery before 32 weeks. These involve risks to the fetus such as respiratory distress, gastrointestinal infections, and even intracranial bleeds requiring longer NICU courses for the infants. There are increased risk of developmental delay even in deliveries between 32 and 36 weeks (8%, vs 4% at term) which is not an infrequent delivery period for twin pregnancies. More substantial neuro-developmental risks are present at earlier gestational ages.
Twin pregnancies also carry a two-fold increased risk of pregnancy, induced hypertension, and increased risk of growth restriction in one or both fetuses. Unfortunately, in twin pregnancies after 20 weeks, there is a 5% chance of loss for one of the twins prior to birth. It also dramatically increases the chance of the delivery occurring via cesarean section if the position of the fetuses in the uterus is not optimal at delivery.
Twin pregnancies require patients to consult with high-risk OB doctors, called maternal fetal medicine physicians. Despite vigilance on the part of the obstetrician and the MFM doctors, these risks are inherent to the twin pregnancy itself. All this being said, for a twin pregnancy that progresses to term, nearly 94% will continue to have a good outcome for both twins through infancy.
The number of embryos to implant in an IVF cycle must always be done on a case-by-case basis. There may be situations where the fertility doctor might actually advise for the transfer for more than one embryo. Ultimately, how to proceed with an IVF cycle and embryo transfer must take into consideration the clinical situation unique to each couple.
As a generalist obstetrician/gynecologist, I urge couples that may be in a situation of deciding how many embryos to transfer to carefully consider all risks. Twin pregnancies do usually progress very well, but every OB/GYN knows that singleton pregnancies will always carry a much lower complication rate. When I walk into the room to meet an IVF couple, and I see that there is one fetus, I know that this couple has the best chance for a smooth, uneventful pregnancy, and a healthy baby at the end of their long pregnancy journey.
In December, Dr. Allan Kessel participated in a radio program on WMTR 1250AM with Dr. Jamie Morris from Reproductive Medicine Associates of New Jersey (RMANJ) on the topic of Single Embryo Transfer and general obstetrical and fertility issues.
A link to the program radio program: http://answerslivenj.com/albums/pregnancy/