What is Vanishing Twin Syndrome?

You’ve just had your first ultrasound and everything looks great. In fact, it looks perfect. Your surrogate has just been confirmed with two heartbeats. Twins. Two babies. You’re over the moon. But everyone is telling you to calm down, and not start buying everything in duplicate just yet. What gives?

The reason behind the apprehension is simple. The unfortunate reality is that, with the help of IVF, multiples pregnancies are becoming more and more common. Unfortunately, many pregnancies that appear as twins or more at the six week mark will appear as a singleton gestation by the end of the first trimester. More often than not, the reason for this is a condition known as vanishing twin syndrome.

In medical terms, vanishing twin syndrome happens when one (or more) fetuses in a multiple fetus gestation miscarries (sometimes doctors will call it “self-abortion”) while at least one other fetus continues to grow and thrive.

First discovered and researched in 1945, the carrier’s body, other fetus, or placenta seems to absorb the tissue of the other twin, causing the visual effect of a “vanishing twin.” While some carriers may experience miscarriage symptoms to signify that a twin has died, things like cramping and bleeding, most will not exhibit typical miscarriage symptoms at all. There will simply be 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 your surrogate 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, Vanishing Twin Syndrome 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 condition, or one that is occurring more often than in previous generations, 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 that 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 on a far larger scale than it does identical twins.

The immediate concern of most intended parents 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 rates of losing a twin to VTS or other causes tends to decrease considerable around the time that singleton miscarriages begins to decrease as well; at the close of the first trimester. So, while it’s exciting to get news that your surrogate has 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.

Teo Martinez

Teo Martinez is the CEO of Growing Generations, a surrogacy and egg donation agency headquartered in Los Angeles, CA. Educated at both UCLA and Pepperdine University, and with over 15 years of experience working in assisted reproduction, Teo’s background makes him one of the most experienced and accomplished professionals in the field.