The frequency of diagnosing twins during pregnancy has been increased to a rapid extent, due to the enhanced use of ultrasound tests. This has made it easier to diagnose twin pregnancies and the condition of the mother during early as well as later stages of pregnancy. However, it has also lead to the possible discovery of another phenomenon that is more frequent than earlier thought, and that is the vanishing twin syndrome or VTS.
What is Vanishing Twin Syndrome?
When one of a set of twin foetuses disappears during pregnancy from the womb and results in a pregnancy with a single fetus, it is known as the vanishing twin syndrome or VTS.
In most cases, after the identification of a twin pregnancy during the first trimester, one of the fetuses is miscarried and reabsorbed by the body, it is termed as vanishing. This phenomena of vanishing twin syndrome might happen even before the mother knows about her twin pregnancy and can happen even at later stages of pregnancy, but that is a rarely common a phenomenon.
How Common is Vanishing Twin Syndrome?
Over the past few decades, the rate of vanishing twin syndrome or VTS has grown significantly. It is seen to occur more frequently than earlier thought and can be seen to occur in 20 to 30% of pregnant women, having multiple pregnancies in the United States of America and generally in the rest of the world as well. Usually, when one of the multiple pregnancy fetuses is aborted during the first trimester of pregnancy, the aborted or miscarried fetus is absorbed by the mother’s placenta or by the other twin, giving the impression of a vanished fetus. A study has shown that about 1 in every 8 pregnancies starts as a twin pregnancy, but it is 1 in every 70 pregnancies that a twin is born.
What are the Causes of Vanishing Twin Syndrome?
The exact cause of Vanishing Twin Syndrome or VTS is not clear and there are many explanations out there that can be the possible causes of this Vanishing Twin Syndrome and these include:
- If the embryo that is formed is not viable due to some major chromosomal abnormalities and genetic deformities, Vanishing Twin Syndrome can occur.
- If there is improper cord implantation, that too can contribute to vanishing twin syndrome.
- Although Vanishing Twin Syndrome occurs in monozygotic or dizygotic twins, when the monochorionic monozygotic twins share the placenta, it could cause Vanishing Twin Syndrome.
What are the Signs & Symptoms of Vanishing Twin Syndrome?
There are generally no signs and symptoms of Vanishing Twin Syndrome. However, in some cases, the pregnant woman might experience a few symptoms of vanishing twin syndrome that are similar to those of miscarriage, and are:
- Vaginal bleeding.
- Mild cramping in the lower abdomen.
- Decrease in the HCG hormone that can be detected by blood test.
- Severe pelvic pain at times.
None of these symptoms might be pronounced or obvious, even if Vanishing Twin Syndrome or VTS occurs. This is because, the common sign of miscarriage, that is vaginal bleeding is a rare case for Vanishing Twin Syndrome as one of the twin fetuses is still alive and the mother is still pregnant. The fetus that is miscarried, in that case, is absorbed by the placenta or the other twin and there is no sign of that fetus in the womb.
Is Vanishing Twin Syndrome a Preventable Condition?
There is no guarantee for the causes of Vanishing Twin Syndrome and VTS cannot be prevented by the mother or her partner. If frequent miscarriages occur, a consultation with the genetic experts is recommended.
What are the Associated Complications of Vanishing Twin Syndrome?
When VTS or Vanishing Twin Syndrome occurs in the first trimester, it is absorbed by the placenta of the mother or the other twin. Hence, there is no sign or symptom of the miscarriage or Vanishing Twin Syndrome and the prognosis of the surviving foetus is excellent. However, if vanishing twin syndrome occurs in the second and third trimester, it can cause complications both for the mother and the surviving fetus. In such a case, the surviving fetus will have an increased risk of cerebral palsy. The surviving fetus can also suffer from the risk of intrauterine growth restriction and infection. As the mother is at a high risk of developing haemorrhage and thereby, the risk of premature delivery is also increased. In about 7% of the cases, women having VTS or vanishing twin syndrome at the second and third trimester will have the risk of premature delivery. The other twin is also at a higher risk of suffering from low birth weight.
How is Vanishing Twin Syndrome Diagnosed?
The diagnosis is very important for vanishing twin syndrome. This is because; there is no other sign or symptom of vanishing twin syndrome that could indicate the vanishing of one fetus. It is only an ultrasound that could indicate vanishing twin syndrome. During the first six or seven weeks of gestation, the mother is diagnosed through a USG and it is during this stage that the presence of the twins is diagnosed.
However, when after this stage, the woman undergoes another USG and only one fetus is seen then it means that the other fetus might have gone through a VTS. With Doppler Scan, it can be specified that only one fetus is diagnosed with heartbeat.
What is the Treatment of Vanishing Twin Syndrome?
Usually the vanishing twin syndrome or VTS occurs at a very early gestational stage and; hence, the mother does not get to know about it if she is not diagnosed with twins by undergoing a USG at six to seven weeks of gestational stage. It is only if the mother gets to know that she is carrying twins and then the VTS occurs that she will get to know of the other fetus being ‘vanished’ and that there has been a vanishing twin syndrome. However, in this condition, the surviving fetus remains unharmed and unaffected by the ‘vanished’ fetus and continues to grow and develop normally.
Hence, there is no need for a treatment procedure to take separate care of the surviving fetus. Regularly visiting the doctor may be needed to make sure that the surviving baby is not affected after the vanishing twin syndrome. If no heartbeat is found at a later stage and both of the fetuses are found to be no longer viable, then treatment consists of dilatation and curette of the uterus.
Coping with Vanishing Twin Syndrome
It is normal to feel sad about the loss of one baby, even if it is not yet born. The parents can feel mixed emotions from loss of one as well feel relieved regarding the health and survival of the other baby. Having to put a face of bravery and that there is nothing wrong with you might be exhausting. Hence, it is absolutely normal to be sad when suffering from vanishing twin syndrome. However, it is important for you to put vanishing twin syndrome behind you and enjoy a sense of relief that the other baby is healthy and take care of yourself so that your health and mental condition does not harm your surviving baby.
- Mayo Clinic. (2021). Vanishing Twin Syndrome. https://www.mayoclinic.org/diseases-conditions/vanishing-twin-syndrome/symptoms-causes/syc-20471091
- American Pregnancy Association. (2021). Vanishing Twin Syndrome. https://americanpregnancy.org/multiples/vanishing-twin-syndrome/
- Healthline. (2021). Vanishing Twin Syndrome: What You Need to Know. https://www.healthline.com/health/pregnancy/vanishing-twin-syndrome