Vanishing twin syndrome (VTS) is a miscarriage that causes a pregnancy involving twins to become a pregnancy involving one baby. It occurs when one of the embryos detected during an ultrasound stops developing. VTS can’t be treated or prevented. Getting both the clinical and emotional support you need is essential as you progress through your pregnancy.
Vanishing twin syndrome is a type of miscarriage that can occur during multiple pregnancies (births involving twins or triplets). It occurs when an embryo detected during an ultrasound can’t be found on a future ultrasound. The embryo stops developing, and its tissue gets absorbed by the mother, or gestational parent, and the surviving embryo(s).
With vanishing twin syndrome, a pregnancy involving twins or triplets becomes a pregnancy involving one less baby than was initially anticipated.
The vanishing twin’s tissue gets absorbed by the surviving embryo(s) and the parent, too. This absorption process is completely harmless.
It’s hard to know just how common vanishing twin syndrome is because many people likely lose an embryo before their first pregnancy ultrasound. As a result, people who are more likely to get an early ultrasound are more likely to learn that an embryo that was once present has disappeared.
For example, couples doing in vitro fertilization (IVF) may have an ultrasound as early as weeks six or seven of pregnancy. Approximately 7% to 36% of IVF pregnancies involving multiples are diagnosed with VTS.
Research suggests that vanishing twin syndrome is more common among pregnant people over 30.
The signs of vanishing twin syndrome are similar to symptoms common during the first trimester of pregnancy. The similarities make it so that it’s possible to miscarry one of the embryos in a pregnancy involving twins or triplets without knowing it. Symptoms include:
Contact your provider if you experience any pelvic pain or unexplained bleeding during pregnancy.
With vanishing twin syndrome, irregularities in the vanishing twin’s DNA prevent it from fully developing. These irregularities in the embryo’s genetic code can’t be controlled or prevented. Often, they’re present at conception.
Your provider may diagnose vanishing twin syndrome during a pregnancy ultrasound. If one of the embryos present on an earlier ultrasound is no longer present on a future ultrasound, your provider can make a vanishing twin syndrome diagnosis.
Your provider may assess your levels of human chorionic gonadotropin (hCG) hormone. Your body produces hCG during pregnancy. The amount of hCG in your body offers clues about how your pregnancy is progressing. An hCG level that was once high enough to support multiples but plateaued can be a sign of vanishing twin syndrome.
Ultrasound technology can reliably diagnose vanishing twin syndrome. Human error is always possible during a VTS diagnosis, but it’s unlikely.
It’s not always possible to know if you had a vanishing twin. It’s possible to be pregnant with multiples and to miscarry one or more of the embryos before your first pregnancy ultrasound. In this case, neither you nor your provider will know you were pregnant with twins or triplets.
In some cases, your provider may find fetal tissue from the vanished twin in your placenta after you’ve delivered your baby. Before ultrasound technology, fetal tissue in the placenta was the only indicator of a VTS pregnancy.
The best treatment for vanishing twin syndrome is proper management that attends to your health and the health of your surviving fetus. The care you receive will depend on when the embryo disappeared.
If the embryo disappears in the first trimester, neither you nor your surviving fetus will likely experience any complications. Your pregnancy will continue as usual.
If the embryo disappears in your second or third trimesters, your healthcare provider may monitor your pregnancy more closely. After the first trimester, pregnancies involving vanishing twin syndrome are considered high-risk. High-risk pregnancies involve a greater chance that your baby will have health problems or that you’ll have your baby early.
Your healthcare provider will consider multiple factors when assessing how high-risk your pregnancy may or may not be. Speak with your provider about how your diagnosis may affect your pregnancy and plans for delivery moving forward.
You can’t prevent vanishing twin syndrome. Many people who experience a miscarriage worry over what they could’ve done differently to deliver a healthy baby. But the genetic abnormalities that cause an embryo to stop developing aren’t curable or preventable.
If the embryo vanishes during your first trimester, you should expect a typical pregnancy without complications. After the first trimester, there is a greater likelihood of pregnancy complications that may require more frequent monitoring from your healthcare provider.
Allowing yourself the care needed to process a VTS diagnosis is important. Taking care of yourself after learning of a vanishing twin can be especially challenging. You may experience grief that feels complicated because although you’ve experienced a miscarriage, you’re still pregnant.
Reach out to your support network to help process what you’re feeling. Talking to your friends or partner can help. It’s a good idea to reach out to a therapist or grief counselor for clinical support.
Ask your provider about what to expect as your pregnancy progresses. Getting clarity about what to expect in terms of your care over the next several months can help you focus on both your physical health and your emotional well-being.
A note from Cleveland Clinic
Everyone processes the loss involved during a miscarriage differently. Make space to process whatever emotions you’re feeling, knowing that your feelings — whatever they may be — are valid. Taking care of your body to support your pregnancy is important. Your emotional needs require equal care.
Last reviewed by a Cleveland Clinic medical professional on 05/12/2022.
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