What is Vanishing Twin Syndrome? (and Why We Don’t Call it That)

What is Vanishing Twin Syndrome? (and Why We Don’t Call it That)

Vanishing twin syndrome (VTS) is a type of miscarriage you can experience when you’re pregnant with multiples (twins, triplets, or more).

While you begin your pregnancy with multiple embryos in your uterus, at some point (often in the first trimester) one of the embryos stops developing as it should.

Sadly, the baby dies, and its tissue is reabsorbed into the surviving baby (or babies) or your own body.

It seems to have disappeared – hence the name vanishing twin syndrome.

But here’s the thing. Your baby hasn’t just “vanished”.

Your baby has died, and you deserve to have that loss acknowledged.

You deserve a chance to grieve if you need to.

That’s why, as part of our #RenamingRevolution, we’ve given vanishing twin syndrome another name. We call a vanished twin a miscarried multiple (MM).

Let’s talk more about this kind of pregnancy loss.

In this article: 📝

  • How common is vanishing twin syndrome (a miscarried multiple)?
  • What happens to the vanishing twin (MM)?
  • What causes vanishing twin syndrome (a miscarried multiple)?
  • How to know if you had a vanishing twin (MM)?
  • What are the complications of vanishing twins?

How common is vanishing twin syndrome (a miscarried multiple)?

We don’t know exactly because it’s thought that many losses of this kind happen very early in pregnancy.

That is, before the 12-week ultrasound scan has a chance to spot multiple embryos in your uterus.

So it’s possible you’ve experienced this without being aware of it.

But with more women having first-trimester ultrasounds now, more cases of miscarried multiples are being reported.

It’s thought that around 36% of twin pregnancies and over 50% of higher multiples may be affected.

For couples doing IVF, MM is diagnosed in up to 33% of pregnancies involving multiples.

What happens to the vanishing twin (MM)?

Although science is still trying to figure this one out, there are three main theories:

  1. Resorption: Here, the MM is resorbed into your body. Studies have shown that this can happen as early as week 7 and as late as week 12. Resorption does not affect your pregnancy
  2. Blighted ovum: Or what we’ve renamed early pregnancy without an embryo. This is when the MM co-exists with the normal pregnancy and can result in vaginal bleeding within the first trimester (in which the embryonic sac is expelled).
  3. Fetus papyraceous: Although this is very rare, it’s when the MM is compressed against the viable fetus. Here, the viable twin has been found to be affected, and in rare cases, the pregnancy can be affected.

What causes vanishing twin syndrome (a miscarried multiple)?

Sometimes, frustratingly, the cause just isn’t known.

But, in many cases, it’s likely to have the same cause as most early miscarriages: something called “chromosomal abnormalities”.

It means that as your baby’s cells have been multiplying, as their body grows, something has gone wrong with their DNA (basically, their genetic blueprint).

At this point, they stop developing, and sadly, they die.

It’s then that the tissue that makes up their body and gestational sac (the membrane that holds your baby as they grow) is reabsorbed, and they seem to “vanish”.

While this is happening, your surviving baby (or babies) continue growing and developing as normal.

How to know if you had a vanishing twin (MM)?

You might not experience any symptoms at all from miscarrying a multiple, especially if it happens very early in your pregnancy.

But some vanishing twin symptoms you could have are:

  • Vaginal bleeding
  • Abdominal cramps
  • Abnormal hCG levels. (This is the hormone that’s tested to detect a pregnancy. If your doctor does a blood test and finds your hCG levels aren’t as high as they should be, that could be a sign that one of your babies has stopped developing.)

If you’re concerned about any symptoms, give your doctor a call.

A miscarried multiple is most likely to be picked up on if you have an early ultrasound scan (before the typical 12-week scan).

What does vanishing twin syndrome (MM) look like on ultrasound

The sonographer will see that there are two (or more) gestational sacs, and you’ll be told that you’re expecting twins or multiples.

But when you go back for your next scan, the sonographer might see one fewer gestational sac and be unable to detect the expected number of heartbeats.

Though it might take a further scan to confirm, it’s around this time that you’ll find out that you’ve lost one of your babies.

This can be a painful experience with some complex emotions.

Perhaps grief for your lost baby combined with relief that you still have your remaining baby (or babies).

Just give yourself time to feel what you feel.

What are the complications of vanishing twins?

You don’t usually need any medical treatment when you miscarry a multiple in the first trimester.

And one ray of light is that the prognosis of the viable twin surviving is usually excellent.

However, this does depend upon the factors that caused the death of the MM.

It’s possible to miscarry a multiple (have a “vanishing twin”) after the first trimester, too.

Note: this is different from losing a multiple much later in pregnancy when the fetus is too highly developed to be reabsorbed.

If the twin dies in the second or third trimester, this can increase associated risks to the surviving fetus – including a higher rate of cerebral palsy

In this case, your doctor might want to keep a closer eye on you for the rest of your pregnancy because there’s a small increased risk of preterm birth, lower birth weight, hemorrhage, birth defects, and infection.

We hope that you’ll be able to honor the memory of your lost baby – not as a “vanishing twin” but as a baby who died.

Maybe one day you’ll want to talk to your surviving baby, or babies, about their sibling, too.

In the meantime, give yourself the space you need to reflect, and be gentle with yourself.

The Peanut community is here when you’re ready. ❤️


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