Vanishing twin syndrome

The vanishing twin syndrome was first discovered in 1945. It occurs when a twin or twin disappears into the uterus during pregnancy after a miscarriage of the twin or twin. Fetal tissue is reabsorbed by the other twin, fetus, placenta, or mother. This gives the appearance of a "vanishing twin".

How to identify the syndrome of the vanishing twin syndrome?

Prior to the use of ultrasound, the diagnosis of death of twins or multiple twins was made by examining the placenta after delivery. Today, with early ultrasound, the presence of twins or multiple pregnancies can be detected already in the first trimester. A follow-up ultrasound may reveal the "disappearance" of the twin.

For example, a woman may have an ultrasound at 6 or 7 weeks of pregnancy. The doctor identifies two fetuses and the woman is told she has twins. When the woman returns for her next visit, a single heartbeat can be heard using Doppler.

A second ultrasound is performed and a single fetus is observed. Also, some women may have symptoms suggestive of a miscarriage, even though the ultrasound shows only one baby in the womb.

Vanishing twin syndrome is diagnosed more often after ultrasound is used in early pregnancy. Estimates show that transient vanishing twin syndrome occurs in 21-30% of multiple pregnancies.

What causes the vanishing twin syndrome?

In most cases, the cause of missing twin syndrome is unknown. The anomalies that cause twins to disappear appear early in development, not all of a sudden.

Analysis of the placenta and/or fetal tissue often reveals chromosomal abnormalities in the vanishing twin, while the surviving twin is usually healthy. Incorrect implantation of the umbilical cord can also be a cause.

What is the effect of the vanishing twin syndrome on the mother and the surviving twin?

If the loss occurs during the first trimester, neither the remaining fetus nor the mother usually shows any clinical signs or symptoms. The prognosis for the surviving twin is usually excellent, but it depends on the factors that contributed to the death of the other twin.

If a twin dies in the second or third trimester, the risk to the surviving fetus increases, including a higher rate of cerebral palsy.

When a twin dies after the fetal period of pregnancy, the water contained in the twin's tissues, amniotic fluid, and placental tissue may be reabsorbed. This results in the flattening of the deceased twin under the pressure of the surviving twin.

At birth, the deceased fetus may be identified as a fetus compressus (sufficiently compressed to be seen) or a fetus papyraceous (visibly flattened due to loss of fluid and most of the soft tissue).

What are the signs of a possible vanishing twin syndrome?

Research indicates more cases in women over 30 years of age. Symptoms usually begin early in the first trimester and include bleeding, uterine cramps, and pelvic pain.

What medical care is recommended for endangered vanishing twin syndrome?

No special medical attention is required for the uncomplicated disappearance of twins in the first trimester. Neither the surviving twin nor the mother required medical attention. If fetal death occurs in the second or third trimester, the pregnancy can be classified as high risk.

Pregnant women should see a doctor if they experience bleeding, cramping, and pelvic pain. An ultrasound should be used to determine if there are no viable fetuses left before deciding whether a caesarean section can be indicated.

In many cases, a woman may choose to wait for a natural miscarriage.