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Can a Hidden Twin Be Detected During a Twin Ultrasound?

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Can a hidden twin be detected during a twin ultrasound? How much can you trust an ultrasound scan? While the possibility of a hidden twin is very unlikely these days, there is still a very small chance that this can happen to you.

Pretty much every pregnant woman has her doubts about expecting twins and multiples, especially during the first weeks of pregnancy. But what feeds these doubts even more is the endless stories of women who go to the hospital to give birth thinking they’re having a single pregnancy, but instead end up having two (or more) babies. What a surprise!

While the chances of this happening are minimal, it’s still worth considering that possibility, so that you can be prepared for an unexpected unfolding of the events.

 How Do You Know If You’re Pregnant with Twins?

Yes, a twin ultrasound is the more secure way of visually identifying that you’re carrying twins. In most cases if your doctor doesn’t see multiple babies on the screen then you’re unlikely to have twins of multiples. Still, there are those very few occasions when the ultrasound is not 100% accurate, but we will get to that in a little bit.

When Are Twins Usually Born

Apart from relying on an ultrasound scan, you can also be on the lookout for some of the more intense symptoms associated with a twin pregnancy. While the symptoms during a twin pregnancy and a single pregnancy are pretty much the same, these signs might be a green light for twins-on-the-go:

  • Excessive weight gain or fatigue. You are eating for two, at the end of the day
  • Severe nausea and morning sickness (hyperemesis gravidarum is more common in twin pregnancies). A proven cure that alleviates nausea and morning sickness is peppermint essential oil. We love the DoTERRA Peppermint Beadlet Essential Oil which is an insatiable blend or aromatic goodness. You can directly inhale from the bottle, put a few drops on a cotton pad or in a diffuser. Moreover, the convenient beadlets are ideal for traveling and on-the-go, because you never know when your nausea will strike in
  • Abnormally high levels of hCG (the pregnancy hormone)
  • Repeatedly measuring large for your gestational age at your prenatal exams

Lastly, there is your motherly intuition, which is entirely up to you if you want to trust or not.

twin ultrasound

Can a Twin Go Unseen in an Ultrasound?

While in most cases ultrasound scans are amazing, they are not perfect.

Ultrasound scans are used not only to detect how many babies you’re having, but also what is the gender of your baby or multiples. This is where the imperfection of ultrasounds really comes into play. We’ve all heard the stories of families thinking they’re having a boy until the minute their child is born and they welcome a girl to the family. That happens so because the 2D sonographic image of the ultrasound captures what’s going on beneath the surface and can easily mistake a vulva for a penis.

If we apply this same thinking to twin ultrasounds we are likely to give the device more room for error. The bigger your babies are the more likely they’re to be detected by a twin ultrasound, but sometimes ultrasounds are done too early in the pregnancy and one or more of the babies are not ready to show their faces in front of the camera just yet.

 Why Can a Twin Remain Hidden?

There are multiple reasons why one of the babies might be hiding and subsequently not be detected by the ultrasound.

First of all, a second fetus should be clearly visible on ultrasound after 20 weeks of pregnancy. If you’ve had your ultrasound before 20 weeks of pregnancy, there is a chance that the results might not be accurate considering how tiny the fetus is before that point. Once you enter the third trimester the accuracy of your ultrasound scan increases.

Another possibility is that your twins share the same placenta and the same amniotic sac, which increases the likelihood that one twin could be hiding behind the other during an early ultrasound. These twins are called monochorionic monoamniotic (or mo/mo twins). If, however, you are expecting dichorionic/diamniotic (di/di twins), which have separate placentas and a separate amniotic sac, your two babies will easily be detected by the twin ultrasound.

Can an Ultrasound Miss Twins

In some cases a single ultrasound might not be enough to detect a second fetus, so make sure you’re having at least a few of them throughout the 9 months of your pregnancy. When you’re 26 weeks pregnant with twins, it’s really important to have an ultrasound and monitor closely the critical development of your babies.

Of course, you shouldn’t leave out the human error factor. It is humans looking at the ultrasound scan, at the end of the day, and we are far from perfect as a species. Plus, sometimes it’s nice to let things unfold in a surprising way.

What About the Heartbeat?

Interestingly, there have been a few cases of health care providers detecting a second heartbeat before they can actually see the second fetus on an ultrasound.

However, this is extremely rare and it doesn’t always indicate that there is a hidden twin. It may simply warrant another ultrasound scan. Also, it’s really difficult to distinguish two heartbeats, because they can be in sync or your own heartbeat might be sending mixed signals.

How to Prepare for a Hidden Twin?

If you don’t entirely trust the twin ultrasound up until the last minute and have serious doubts about the number of babies that will come out of you, then it’s worth coming prepared. Especially, if you’re the type who doesn’t like surprises.

So what can you do to prepare yourself for the delivery of twins or multiples? Obviously, there is no need to overboard and buy every single baby gear in pairs. However, it’s worth it to take a few essential items with you to the hospital, such as:

  • Extra blankets to wrapped your babies up. The Upsimples Baby Swaddle Blanket is super adorable and comes in a variety of cute patterns. But most importantly, it’s extra soft, made from 70% Bamboo and 30% Cotton. The blankets come in a set of 4 and are easily machine-washable for extra ease.
  • Going home outfits for your twins: we absolutely adore the Born First – Show Off Onesies by TwinStuff, and they’re perfect for that moment of surprise. Plus, they would look awesome on your first family photo at the hospital
  • Extra babies essentials: bottles, socks and booties, blanket, diapers

when do you find out the gender of twins

Twin Ultrasound: Can be Trusted?

Ultrasound scans are a trusted tool for determining the gender and the number of babies you’re expecting, yet they’re far from perfect and we should always leave some room for error when having a twin ultrasound. The possibility of a hidden twin is quite minimal, but it still occurs. There are several reasons why the second fetus might want to shy away from the camera, such as a super early ultrasound, or the positioning of the second baby. To avoid any unwanted surprises always make sure you have a twin ultrasound after 20 weeks of pregnancy, and always come prepared.


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