Having twin pregnancies is exciting but often associated with pregnancy and delivery related complications. One such complication which involves the loss of one of the multiple gestation is vanishing twin syndrome.

In this article:

What is Vanishing Twin Syndrome?
How Common is it?
How is it Identified?
Who’s Most at Risk?
Symptoms you Should be Concerned?
What you can do?

All You Need to Know about Vanishing Twin Syndrome

What is Vanishing Twin Syndrome?

A condition seen in a multiple pregnancy in which one (or more than one in a triplet or quadruplet pregnancy) foetus happens to disappear intrauterine before birth. It is assumed that the wasted foetal tissues are taken up either by the placenta or the other twin for nutrition.

How Common is it?

As per reports, multiple gestation occurs at a frequency of 3 to 5 per 100 pregnancies. The statistics of vanishing twin syndrome say that about 20-25% of these multiple pregnancies witness the vanishing twin syndrome. The data related to pregnancies and childbirth from European countries suggests that among every 100 babies born with assisted reported techniques (ART) around 15-20 are twin gestations.

Occurring early in the first trimester, this syndrome rarely causes any complications in the mother besides subtle abdominal cramping/pain and PV bleeds (vaginal bleeding).

Vanishing twin syndrome occurring in later pregnancy may cause complications such as premature delivery, sepsis due to the retained products of conception, excessive bleeding, coagulopathies (inability of the blood to clot) and an increased risk of disseminated intravascular coagulation (creation of blood clots in the small blood cells). The foetal remnants, if low-lying in the uterine outlet may cause an obstructed labor and might require assisted surgical delivery or cesarean section.

Besides mortality of the vanishing twin, it may also affect the well-being of the other twin by causing neurological problems like cerebral palsy or skin problems like aplasia cutis (absence of skin).

This is associated with multiple pregnancies which are quite common nowadays owing to the availability of assisted reproductive techniques.

How is it Identified?

The causes of vanishing twin syndrome largely remain undescribed. It is observed that the main reasons for the demise of one of the twins are developmental malformations and chromosomal anomalies both largely genetic in nature. The other twin is usually healthy and unaffected.

Diagnosis is often made before it gets clear that the mother was having twins. An ultrasound examination confirms the diagnosis. It shows the presence of an embryonic sac with incompletely developed foetal parts or by the absence of foetal cardiac motion in one of the two foetal masses (vanishing twin syndrome ultrasound diagnosis). When multiple gestation is confirmed, a blood test for beta hCG can also help diagnose vanishing twin syndrome. Therefore, vanishing twin radiology is the only confirmatory and preferred investigation for diagnosis.

Who’s Most at Risk?

According to studies suggest that maternal age is associated with vanishing twin syndrome. Increased maternal age (more than 30-35 years) often requires assisted reproductive techniques (ART) which in turn increases the probability of multiple gestations.

The complications of this are rare for the mother and the surviving twin if it occurs early (during the first trimester of pregnancy). However, the cause of foetal mortality may have an impact on the pregnancy outcome.

If it occurs during the second or third trimester, the other foetus is at a higher risk of having developmental problems including cerebral palsy.

Death of a twin during the embryonic phase may significantly reduce the amniotic fluid and cause the placenta to shrink in size the living twin exerts pressure which causes structural changes in the dead foetal tissue. During delivery, the dead foetus may appear significantly compressed. This is called as foetus compression. It could also be notable flattened due to the reduced amniotic fluid and placental shrinkage. This is called as foetus papyraceus.

Symptoms you Should be Concerned?

Vanishing twin syndrome in early pregnancy can be totally asymptomatic for the mother. In later pregnancy, it my cause symptoms similar to those of miscarriages which include –

• Abdominal cramps
• Bleeding through the vagina
• Dull pain in the pelvic region
• Routine blood tests may show a reduced level of beta-hCG or the pregnancy hormone. It is secreted by the placenta and is usually tested to exclude conditions like vesicular mole.

These symptoms are considered as non-specific and may only suggest a possibility of vanishing twin syndrome. Consult the doctor.

What you can do?

No specific treatment is required for this. It is detected in early trimester of pregnancy, as long as the mother and living twin have stable blood flow. However, regular monitoring of the surviving foetus is advised. If the surviving twin is healthy and scans show no abnormalities, there are good chances of a normal, uneventful pregnancy with the delivery of a single, healthy baby.

In cases diagnosed later (in the second or third trimester) the plan of treatment is largely based on the duration of pregnancy, developmental profile and chorionic pattern of the living foetus. The twins can have either monochorionic (shared chorionic and amniotic sac) or dichorionic (separate chorionic and amniotic sacs). Dichorionic twin gestations with either twin vanishing are considered as safe and require no intervention. However, the death of a monochorionic twin is an indication of urgent delivery of the other twin, telling that it has attained lung maturity or crossed 32 weeks of gestation. The benefits of delivering the living baby should outweigh the risks of

perinatal complications. In cases where delivery is not possible or advisable, the living foetus should be closely monitored for any intrauterine complications.

A recent advancement in the medical care for this is cord occlusion for selective termination of the weaker twin. In case of a monochorionic twin pregnancy with an impending vanishing twin, the umbilical cord of the affected twin is surgically closed off. This deprives the nutrition and circulation and completely cuts off the weaker twin from the placental circuit but on the other hand, safeguards the other twin from an interruption in blood supply.

Conclusion

Vanishing twin syndrome is an unfortunate and inevitable complication of multiple pregnancies. Timely diagnosis and appropriate medical care can ensure the safety and well being of the mother and the surviving twin with the doctor.

References

https://www.whattoexpect.com/pregnancy/pregnancy-health/complications/vanishing-twin-syndrome.aspx

https://parenting.firstcry.com/articles/vanishing