Twin pregnancies are fairly rare occurrences—multiples occur in only about 3 out of every 100 births—but within twin pregnancies, a phenomenon known as Vanishing Twin Syndrome is fairly common.
Vanishing Twin Syndrome is when one embryo or fetus dies or is reabsorbed (hence: the "vanishing"). This can occur in twin pregnancies and with multiples. In fact, it is more common with multiples.
According to StatPearls, Vanishing Twin Syndrome (VTS) occurs in as many as half of pregnancies with three or more gestational sacs, in 36 percent of twin pregnancies and in 20 percent to 30 percent of pregnancies that have been achieved with assistive reproduction.
As you can imagine, dealing with Vanishing Twin Syndrome can be an incredibly challenging situation to navigate for a parent or parents-to-be. On one hand, they may be grieving a loss, and on the other, cherishing the continuing pregnancy.
It's a tragedy that deserves to be talked about and understood.