What is the cause of Vanishing Twin Syndrome?

Many women who conceive naturally may not even be aware that at one point, very early in their pregnancy, they were carrying twins! Now if you conceived via IVF and were monitored regularly after your transfer then you would be very aware if one, two or more sacs were seen and just what the condition of each might be...is there a fetal pole? a heart beat? empty? However, what can happen is that during one ultra sound a twin pregnancy is pronounced and by the next there is only one heartbeat on the monitor. This devastating news to those in love with the idea of having twins is referred to as the Vanishing Twin Syndrome.

I have posted some more "technical" information below. I would like to share with you the fact that I had a Vanishing Triplet! My very first surrogacy, and second IVF attempt, we had transferred 3 embryos. After receiving the very high beta number we scheduled our first US at 7 weeks. We were in for a shock! Having thought that it could only be twins...as we not all 3 embryos were the best, we saw 3 sacs on the monitor! And 2 of those had health heart beats. The third, however, seemed smaller. Perhaps a late implanter? Maybe...but now we had to schedule a 2nd US to see what that 3rd sac would do as my IP's had no intention of raising triplets. We had agreed, you see, on selective reduction for anything over twins.

When I returned, on my own the next time, it was obvious that the 3rd sac was already starting to dissipate and the two other sacs (both girls we came to find out later) were healthy and growing at a normal rate!

If we had conceived naturally, there most likely would never have been a Beta test, there might have been no ultra sounds until the 20th week...where we would have seen twin girls, healthy and strong....we would have never been aware of that third sac.

Sharon
www.InfertilityAnswers.net

What is the cause of Vanishing Twin Syndrome?
Vanishing twin syndrome was first recognized in 1945. Vanishing twin syndrome is when one of a set of twin/multiple fetuses disappears in the uterus during pregnancy. This is the result of a miscarriage of one twin/multiple. The fetal tissue is absorbed by the other twin/multiple, placenta or the mother. This gives the appearance of a “vanishing twin”.

How is Vanishing Twin Syndrome identified?
Before the use of ultrasound, the diagnosis of the death of a member of a multiple pregnancy was made through an examination of the placenta after delivery. Today, with the availability of early ultrasounds, the presence of twins or multiple fetuses can be detected during the first trimester. A follow-up ultrasound may reveal the “disappearance” of a twin.

For example, a woman may have an ultrasound at 6 or 7 weeks gestation. The doctor identifies two fetuses and the woman is told she is having twins. When the woman returns for her next visit, only one heartbeat can be heard with Doppler. A second ultrasound is conducted and only one fetus is observed.

Sometimes a woman may have symptoms that would indicate a miscarriage, yet, with an ultrasound, a single baby is found in her uterus.

Vanishing twin syndrome has been diagnosed more frequently since the use of ultrasonography in early pregnancy. A conservative estimate of frequency is that vanishing twin syndrome occurs in 21-30% of multi fetal pregnancies. Research from a European series of pregnancies associated with assisted reproductive technology (ART) show that 10-15% of singleton births were initially twin gestations.

First trimester: Morbidity when vanishing twin syndrome occurs during the first trimester is limited. The mother is most likely to develop mild vaginal bleeding and cramping. If the event occurs later in the first trimester, morbidity may be similar to that of the second and third trimesters.
Second and third trimesters: Maternal complications include premature labor, infection from a retained fetus, severe puerperal hemorrhage, consumptive coagulopathy, and obstruction of labor by a low-lying fetus papyraceus causing dystocia and leading to a cesarean delivery.
The diagnosis of vanishing twin in a pregnancy significantly increases both preterm (<37 gestational weeks) and very preterm (<32 gestational weeks) births.