You’ve just had your first ultrasound and everything looks great. In fact, it looks perfect. You saw two heartbeats. Twins! You’re pretty excited, and your intended parents are over the moon. But everyone is telling you to calm down, and not get too excited about twins just yet.
The reason behind the caution is simple. The unfortunate reality is that, with the help of IVF, multiples pregnancies are becoming more and more common. This is, in part, because pregnancies are detected earlier than they would be in traditional conceptions. Unfortunately, many pregnancies that appear as twins or more at the six-week mark will appear as a single gestation by the end of the first trimester. The reason for this is most often a condition known as vanishing twin syndrome.
In medical terms, vanishing twin syndrome happens when one or more fetus(es) in a multiple-fetus gestation miscarries, while at least one other fetus continues to grow and thrive.
The carrier’s body, another fetus, or the placenta seems to absorb the tissue of the twin, causing the visual effect of a “vanishing twin.” While some carriers may experience miscarriage symptoms to signify that a twin has died, such as cramping and bleeding, most will not exhibit typical miscarriage symptoms at all. There is simply one less heartbeat at the next ultrasound.
The first thing you need to understand about vanishing twin syndrome (VTS) is that it’s no one’s fault. This is not the result of something you did or did not do and it’s not the fault of an improper medical dosage or administration. Researchers think that improper umbilical cord implantation or abnormal chromosomal composition may play a role in VTS.
According to the American Pregnancy Association, VTS isn’t uncommon in multi-fetus gestations in early gestation. In fact, they estimate that somewhere between 21-30% of multi-gestation pregnancies will result in VTS. This is not a new or increasingly common condition, it’s just one that modern science has allowed us to see more easily. In previous generations, the carrier would simply have never known that a second fetus existed, but earlier and better sonography now makes it possible to detect the second heartbeat before it has vanished.
Since most cases of vanishing twin syndrome seem to be linked to chromosomal abnormalities, this syndrome tends to impact fraternal twins much more than identical twins.
The immediate concern of most surrogates in the situation of a vanishing twin is, “What does this mean for the remaining fetus?” This ultimately seems to be linked to the gestational age at the time the first twin died. Typically, when VTS occurs within the first trimester (first 13 weeks of gestation) there are limited to no negative implications on the remaining twin or on the carrier. While highly unlikely, VTS can still occur in subsequent trimesters. In these cases, there does seem to be a link between the surviving twin and an increased risk of developing cerebral palsy.
From experience, the rate of losing a twin to VTS tends to decrease considerably after the close of the first trimester. So, while it’s exciting to get news that you have been confirmed with twins, try to remain calm and cautious over the next six weeks or so as doctors keep a close eye on all developing fetuses.