Vanishing twin syndrome is when a twin or multiple disappears in the uterus during pregnancy as result of miscarriage of one twin or multiple. The fetal tissue is then absorbed by the other twin, multiple, placenta or mother.
 

 

How is vanishing twin syndrome identified ?

 
Before ultrasound came into use, the  diagnosis of the death of a twin or multiple was made through the delivery of the placenta after delivery.  Early ultrasound during the first trimester  can detect twins and multiples. A follow-up ultrasound may reveal the disappearance of a  twin.

Another way of identifying this condition is that someone may be experiencing symptoms of a  miscarriage while an ultrasound reveals  a single baby in the uterus .

Vanishing twin syndrome is estimated  to occur in 21 to 30% of multifetal pregnancies.

What causes vanishing twin syndrome ?

 
Most of the causes of vanishing twin syndrome are unknown. Abnormalities that result in vanishing twin syndrome are usually present during early pregnancy rather than  sudden occurrence.

Analysis of the placenta or fetal tissue  reveals chromosomal abnormalities in the vanishing twin. The surviving twin is however usually healthy. Improper cord implantation may also be the cause.

Does vanishing twin syndrome have any effect on the mother and surviving twin ?

 
If fetal loss occurs during the first trimester, the mother and surviving twin usually shows no clinical signs. The prognosis of the surviving twin is usually excellent but also depends on the causes of the death of the other twin.

However if the twin dies in the second or third trimesters, the surviving twin is at increased risk of conditions such as cerebral palsy.

When there is fetal loss after the embryonic period of gestation,  the water within the twin’s tissues, the amniotic fluid and the placental tissue may be reabsorbed. As a result there is flattening of the deceased twin from the pressure of the surviving twin.

At delivery, the deceased twin may be identified as  fetus compressus (compressed enough to be noticed) or as fetus papyraceous (flattened remarkably through loss of fluid and most of the soft tissue).

What are the signs of a possible vanishing twin syndrome ?

 
Symptoms usually begin in the first trimester and include bleeding, uterine cramps and pelvic pain.

NOTE
 
No special medical care is need for uncomplicated vanishing twin syndrome that occurs in the first trimester. If fetal loss occurred in the second or third trimester, the pregnancy may be treated as high risk.

Pregnant women should seek immediate medical care if they experience bleeding , cramping and pelvic pain. The ultrasound should be used to check if no viable fetus remains before deciding if a D&C may be needed. The woman also has the option of waiting for a natural abortion in most cases.