What is vanishing twin syndrome: Causes, symptoms and diagnosis

Most parents experience double the joy when they find out that they are having twins or multiples. But that joy may turn to confusion, and soon grief when they find out that the twin has disappeared during a scan. The cause may be vanishing twin syndrome, and it’s worth knowing more about why it happens.

Vanishing twin syndrome is when an early scan reveals a twin pregnancy, but a later scan shows only one baby. It is the phenomenon of a twin or multiple ‘disappearing’ in the uterus during pregnancy, as a result of miscarriage. 

In this type of miscarriage, the fetal tissue is usually absorbed by the other twin, multiple, placenta, or the mother. This gives the appearance of a “vanishing twin.” How common is vanishing twin syndrome? It is fairly common, as it happens to 36 percent of twin pregnancies. 

Let us examine this condition in detail, together with its symptoms.

Vanishing twin syndrome symptoms and causes

So what causes vanishing twin syndrome? In most cases, the cause is unknown. 

Analysis of the placenta and/or fetal tissue has frequently revealed chromosomal abnormalities in the vanishing twin, while the surviving twin is usually healthy. Improper cord implantation may also be a cause.

Estimates indicate that this phenomenon occurs in 21 to 30 percent of multifoetal pregnancies.

In pregnancies achieved by in vitro fertilization (IVF), “it frequently happens that more than one amniotic sac can be seen in early pregnancy, whereas a few weeks later there is only one to be seen and the other has ‘vanished’.”

Research indicates more cases of vanishing twin syndrome in women over the age of 30. This may be due to the fact that older mothers in general have higher rates of multiple pregnancies, especially with the use of fertility treatments.

Signs of vanishing twin syndrome, if any, usually begin early in the first trimester, and include:

• Mild cramping 
• vaginal bleeding 
• Pelvic pain
• hCG (hormone) levels that rise more slowly than in normally developing twin pregnancies (as detected by blood tests)

Often, there are no symptoms and signs of vanishing twin syndrome at all. If you’re wondering how long do you bleed with vanishing twin syndrome, you should experience only light bleeding. Pregnant women should seek medical attention if they are experiencing bleeding, cramping, and pelvic pain.

It’s difficult to determine just how common is vanishing twin syndrome. This is because a lot of mothers most likely lose an embryo before their first ultrasound appointment. Because of this, only those who have a reason to get an early ultrasound are more likely to find out about it.

Furthermore, the signs are similar to the usual symptoms that appear in the first trimester of pregnancy. Because of this, it’s possible for one of the embryos to disappear without knowing it.   

Diagnosing vanishing twin syndrome

In the earlier days, before ultrasound was available, the diagnosis of the death of a twin or multiple was made through an examination of the placenta after delivery. Today, it is possible to diagnose vanishing twin syndrome with an ultrasound. 

For example, a mum-to-be may have an ultrasound at 6 or 7 weeks gestation. The doctor identifies two fetuses and tells the mother she is having twins. When she returns for her next visit though, it is possible that the doctor only hears one heartbeat, and a second ultrasound reveals the presence of only one fetus in the uterus. 

Then the diagnosis is given as vanishing twin syndrome after the heartbeat of the twin or multiple can no longer be detected.

This is why getting your check-up is important, as the ultrasound may reveal a vanishing twin diagnosis.

Your doctor may also request for assessment of your human chorionic gonadotropin (hCG) hormone levels. These are hormones that your body produces when you are pregnant. Your hCG levels may show the progress of your pregnancy. If your previous hCG level was high enough for multiple pregnancies but then show a decrease, it may be a sign of vanishing twin syndrome.

In some cases, doctors only determine the vanishing twin after delivery. Some fetal tissue from the twin that stopped growing may be visible in the placenta after delivery.

In the case of IVF, there is closer monitoring, so it is easier to detect this phenomenon. It is easier to see when something has gone wrong because doctors check and count the number of fertilized eggs implanted. 

Treatment and Risk Factors

It’s also important to know about the vanishing twin’s impact on the surviving twin. 

If you miscarry a twin during the first trimester, neither the surviving twin nor the mother would require special medical treatment. In most cases, your pregnancy will continue as it would have if you were carrying one baby, to begin with.

However, if the fetal death is in the second or third trimester, the pregnancy may be treated as high-risk, and require more testing and monitoring.  In most cases of a vanishing twin, the surviving baby is born healthy and without any congenital problems.

However, studies have shown that, if the twin dies in the second or third trimester, there are increased risks to the surviving fetus, including a higher rate of cerebral palsy. Other complications that can occur when a miscarriage happens in the later stage include premature labor, low birth weight, infection, and bleeding.

If the miscarriage occurs before eight weeks of gestation, the remaining fetus absorbs the vanishing twin, so there is no evidence of the twin at the time of delivery. Sometimes, instead, a paper-thin remnant of the twin remains, which we call a fetus papyraceous.

Prevention

You cannot prevent vanishing twin syndrome. A lot of parents who go through a miscarriage often feel guilty and worry about what they could have done to deliver more than one healthy baby. But there are genetic abnormalities that result in an embryo to halt development. And those are neither preventable nor curable.

Taking care of yourself

Do remember that in cases of vanishing twin syndrome, it is normal to experience conflicting emotions. You may feel extreme sadness for the baby you lost, and relief and happiness for the baby who survived. The vanishing twin doesn’t just have an impact on the surviving twin, but on the parents as well.

Having a support system during this challenging time will be a great help. Do share your feelings with your partner or someone you trust. If you need to, talking to a therapist or a grief professional is a good idea.

Understand that your feelings are valid. In addition, we all process loss in different ways. Give yourself extra self-care and time to heal. While it’s important to take care of your physical needs as your pregnancy progresses, you should accommodate your emotional needs as well. 

Republished with permission from theAsianparent Singapore

Here at theAsianparent Philippines, it’s important for us to give information that is correct, significant, and timely. But this doesn’t serve as an alternative for medical advice or medical treatment. theAsianparent Philippines is not responsible for those that would choose to drink medicines based on information from our website. If you have any doubts, we recommend consulting your doctor for clearer information.