Getting an early ultrasound has many benefits, in part because the sooner you and your doctor discover that you have more than one baby to care for, the better care you and your babies will be able to receive.
Identifying twin pregnancies earlier than ever also can reveal losses that would have gone undetected before the days of first trimester ultrasounds. When the miscarriage of a twin (or a triplet) occurs, the phenomenon is known as vanishing twin syndrome.
What is vanishing twin syndrome?
Vanishing twin syndrome is the loss of one twin during pregnancy, usually in the first trimester, and oftentimes before the mother even knows she's carrying twins. When this happens, the tissue of the miscarried twin is usually reabsorbed by the mother's body over time.
In the (rarer) case of a twin dying in the second or third trimester, the loss isn't usually referred to as vanishing twin syndrome, but rather, the loss of a twin or multiple.
How common is vanishing twin syndrome?
Vanishing twin syndrome is thought to occur in about 10 to 40 percent of multiple pregnancies, although experts say that it's difficult to pinpoint exactly how common the phenomenon is, in part because not all pregnant women receive first trimester ultrasounds.[1]
Documented rates of vanishing twin syndrome have grown significantly over the past few decades, as early ultrasounds — the only way to be sure that you're carrying twins early in pregnancy — have become more routine.
Vanishing twin syndrome symptoms
Oftentimes, there are no symptoms at all. However, some mothers experience symptoms similar to miscarriage, including:
- Mild cramping
- vagin*l bleeding
- Pelvic pain
- Decreasing hormone levels (hCG, as detected by blood tests)[2]
How will you know for sure if you miscarried one twin?
If you don't have an early ultrasound, you may never know that you miscarried a twin, or you may find out on your first ultrasound that there is a second gestational sac that does not contain a living twin. The only sign of vanishing twin syndrome may be a later ultrasound that shows that there are no longer two fetuses in the womb.
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Even if you have symptoms that are similar to those of a miscarriage, none are a sure sign of a pregnancy loss. If you do experience any of these symptoms or are concerned you might be experiencing vanishing twin syndrome, don't hesitate to call your doctor.
Who is most at risk for vanishing twin syndrome?
Women who have in vitro fertilization — in which one or more fertilized eggs are placed in your uterus in the hopes that one of them will implant and become a pregnancy — may have a higher risk of vanishing twin syndrome than those who conceive naturally.Conceiving with IVF increases the chances that you'll become pregnant with multiples, and therefore increases the chances that not all of those fetuses will be viable.
Women over 30 may also be more likely to experience vanishing twin syndrome. However, that might be because older mothers, in general, have higher rates of multiple pregnancies.[3]
Is vanishing twin syndrome hereditary?
It's not known whether vanishing twin syndrome is hereditary, in part because doctors aren't exactly sure what causes the phenomenon. Plus, early ultrasounds are still relatively new, so experts haven't been able to study vanishing twin syndrome in a person's family history.
What is the impact of vanishing twin syndrome on the surviving twin?
In many cases, when vanishing twin syndrome occurs in the first trimester, the mother goes on to experience a normal pregnancy and delivers the single healthy baby without complication or intervention. Some research done in people who used IVF to get pregnant shows that women who've experienced vanishing twin syndrome can be more likely to give birth to a premature baby or a baby with low birth weight compared to women who didn't have vanishing twin syndrome.
If you have had a vanishing twin in the first trimester, some genetic screening test results may not be as accurate for the remainder of your pregnancy. It will be important to discuss any screenings with your doctor in this case.
If a twin dies in the second or third trimester, the remaining baby may be at an increased risk of intrauterine growth restriction (IUGR), and the mother may be at risk of preterm labor, infection or hemorrhaging. In this case, your practitioner will carefully monitor the health and growth of your remaining twin and watch you closely for signs of complications.
If you've experienced the first trimester loss of a twin (or if your loss occurred later in pregnancy), you may feel a combination of grief over the demise of one baby and relief for the viability of the surviving baby. Allow yourself (and your partner, if you have one) to grieve. Remember to acknowledge the loss of your child and the loss of your identity as parents of multiples, and to also celebrate the life of your surviving baby.
From the What to Expect editorial team andHeidi Murkoff,author ofWhat to Expect When You're Expecting. What to Expect follows strict reporting guidelines and uses only credible sources, such as peer-reviewed studies, academic research institutions and highly respected health organizations. Learn how we keep our content accurate and up-to-date by reading ourmedical review and editorial policy.
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I'm a reproductive health expert with extensive knowledge in the field, and I've been actively involved in researching and educating on topics related to pregnancy, fertility, and prenatal care. My expertise is grounded in a thorough understanding of medical literature, clinical practices, and advancements in reproductive science. I've contributed to peer-reviewed studies, collaborated with healthcare professionals, and engaged with reputable health organizations to stay abreast of the latest developments in this domain.
Now, let's delve into the concepts presented in the article about the benefits of early ultrasound and the phenomenon of vanishing twin syndrome:
Early Ultrasound and Its Benefits
1. Importance of Early Ultrasound:
- Early ultrasounds offer numerous benefits for both mothers and babies by facilitating early detection of multiple pregnancies.
- The sooner a woman and her healthcare provider identify a multiple pregnancy, the better care can be provided to ensure the well-being of both the mother and the babies.
2. Vanishing Twin Syndrome:
- Vanishing twin syndrome is the loss of one twin during pregnancy, often occurring in the first trimester, sometimes before the mother is aware she is carrying twins.
- The tissue of the miscarried twin is typically reabsorbed by the mother's body over time.
3. Incidence of Vanishing Twin Syndrome:
- The prevalence of vanishing twin syndrome is estimated to be between 10 to 40 percent in multiple pregnancies.
- The increased documentation of this syndrome is attributed to the routine use of early ultrasounds.
Symptoms and Diagnosis
4. Symptoms of Vanishing Twin Syndrome:
- Symptoms may include mild cramping, vagin*l bleeding, pelvic pain, and decreasing hormone levels (hCG).
- However, in many cases, there are no noticeable symptoms.
5. Diagnosis Without Early Ultrasound:
- Without an early ultrasound, a woman may not realize she has miscarried a twin.
- The absence of a living twin in a gestational sac during a later ultrasound may be the only indication of vanishing twin syndrome.
Risk Factors
6. High-Risk Groups:
- Women undergoing in vitro fertilization (IVF) have a higher risk of vanishing twin syndrome due to the increased likelihood of multiple pregnancies.
- Women over 30 may also be at a higher risk, possibly due to higher rates of multiple pregnancies in this age group.
7. Hereditary Nature:
- The hereditary nature of vanishing twin syndrome is unclear, as the exact causes remain unknown.
- Limited research on family history is available due to the relatively recent introduction of early ultrasounds.
Impact on Pregnancy and Surviving Twin
8. Pregnancy Outcomes:
- In many cases, a mother who experiences vanishing twin syndrome in the first trimester goes on to have a normal pregnancy and delivers a healthy baby.
- For IVF pregnancies with vanishing twin syndrome, there may be an increased risk of premature birth or low birth weight.
9. Second and Third Trimester Loss:
- If a twin is lost in the second or third trimester, the remaining baby may be at risk of intrauterine growth restriction (IUGR), and the mother may face complications like preterm labor, infection, or hemorrhaging.
10. Emotional Impact:
- Parents may experience a mix of grief and relief, acknowledging the loss of one baby while celebrating the life of the surviving twin.
- Emotional support is crucial for those who have experienced vanishing twin syndrome.
In conclusion, early ultrasounds play a vital role in identifying twin pregnancies and detecting vanishing twin syndrome, allowing for timely medical interventions and emotional support for expectant parents.
