Twins & Multiples

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Can Fraternal Twins Share a Placenta?

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Up until a few years ago, it was common knowledge that only identical twins can ever share a placenta in the womb.

It’s because of the way fraternal, or non-identical twins, and identical twins are formed.

Difference Between Fraternal Twins and Identical Twins

Fraternal twins are caused by a pair of eggs being fertilised by separate sperm, when they bed themselves into the wall of the womb they each form their own placenta, with no way of sharing.

However, identical twins are caused when the same egg splits into two embryos, and if this happens late enough, it’s possible for both twins to share the same placenta.

In fact, this happens often enough that up to 70% of identical twins might end up sharing a placenta. 

But, Can Fraternal Twins Share a Placenta?

Just a few years ago, scientists discovered a pair of fraternal, or non-identical twins, that actually shared a placenta! It happened in Seattle, and was discovered by the New England Journal of medicine.

It’s worth pointing out that the chances of this happening are so small as to be vanishingly unlikely. So if you’re having fraternal twins, you can relax, because the chance of your twins sharing a placenta is so small it’s almost impossible. You’d be more likely to win the lottery and then immediately get hit by lightning.

Share a Placenta: Why Is This Important?

When babies share a placenta, it can cause problems in the pregnancy. Because the placenta is essential for providing oxygen and nutrients to your developing babies, if something goes wrong with the placenta, then it can affect the correct development of the embryo.

pregnant with twins

Your doctor will know if your babies sharing a placenta is going to be a problem, and if anything needs to be done, then he’s going to know what’s best and will give you the recommendations for what to do, so don’t worry.

But What Can Happen When Your Babies Share a Placenta?

There’s two main situations where your babies will share a placenta. These are monochorionic diamniotic twins, or mono di, where the babies share a placenta but have their own amniotic sacs, and monochorionic monoamniotic twins, or mono mono, where the babies share both their placenta and amniotic sac.

We have articles on both of these conditions that go into far more detail, but we’ll give you a quick primer below.

Mono Di Twins

Mono di twins are the most likely situation where your twins will share a placenta, and if it happens you shouldn’t worry, because most of the situations that come from mono di twins can now be dealt with.

Problems that can arise from mono di twins include:

  • Twin to twin transfusion syndrome, or TTTS. In some occurrences, this won’t be that much of an issue, but if it is then doctors can solve this issue with laser surgery.
  • TRAP sequence: This is a sad problem where one twin doesn’t develop properly, and relies on the other for all of their blood flow. Unfortunately, the dependant twin cannot survive if this happens, but the other twin is incredibly likely to go on to live a healthy, happy life.

Mono Mono Twins

Mono mono twins are much more likely to have problems than other types of twin pregnancy. However, this doesn’t mean that your twins aren’t going to be healthy, and once your doctors realise you’re having mono mono twins, it’s likely that they’re going to place you under the best care possible, to give your twin gifts the best chance possible.

Health problems that can happen because of mono mono twins are:

  • Umbilical cord entanglement. Because both babies are in the same amniotic sac, they’re free to float around in contact with each other and each other’s umbilical cord. It’s possible for one baby to become entangled in the umbilical cord of the other. This will normally rectify itself, but it’s a situation that will be carefully observed by your medical team.
  • Umbilical cord compression. This is similar to the above. One baby puts pressure on the umbilical cord of the other, restricting blood flow.
  • Twin to twin transfusion syndrome. Just like mono di twins, this is a situation that’s possible, and it’s an imbalance in blood flow between both twins.

What Can I do for my Twins that Share a Placenta?

If your doctors discover that your twins share a placenta, then you’re probably going to be referred to a specialist who is skilled in difficult pregnancies.

It’s natural to feel scared, and you might even feel slightly guilty, as if you failed your babies, or you’re somehow responsible for their situation. Remember, there’s nothing you could have done to prevent this from happening, and it doesn’t mean you’re a bad parent.

The best thing you can do is to do exactly what your doctors recommend. If your babies need anything, then you’ll be told the best thing you can do for them.

Expect more regular and detailed twin ultrasounds, and probably to spend more time than usual in hospital, making sure that everything is okay and giving you and your children to be the rest you need.

More about Twin Pregnancy

Did you have a mono mono or mono di pregnancy? Or maybe you’re one of the ultra rare cases that answer the question of can fraternal twins share a placenta? How did it make you feel? I’m sure there’s a lot of expectant mothers in your situation that would love to hear your words and stories of reassurance, so please leave a comment and also join our online community!


  1. Hello my names Tahney im from england im so glad i have found this article me and my twins are also non identical twins that shared a placenta my mum has always told us how rare it is and its nice to know that people find it so amazing

  2. I had fraternal boy twins who shared a placenta. It was huge! We didn’t even know there was only one large placenta in there until after the birth. Since I birthed at home, it was very easy to give my placenta to one of my midwives to process it into capsules and tinctures for post-partum hormonal/emotional support. She told me she picked through the placenta to find a dividing wall or something but never found one. So, instead of paying for two placental encapsulations, we only had to pay for one! Oh, and my boys were super healthy, no birth complications or anything like that, I ot was amazing having them at home! 🙂

    • Same thing with me. Two non-identical boys, own amniotic sacs but shared placenta. No IVF. Docs never told me it was rare… Neat to find out. No issues with them, but I developed hypertension when they delivered and have had to take beta blockers twice every day in the 2+ years since.

  3. I had Fraternal twin girls naturally conceived that shared one placenta and two sacs. I learned of this just recently by reading the pathology and birthing report. the birth was difficult and the babies were healthy. Now 12 years later in trying to figure out why they are the way they are it is making more sense to me about how different they are. I have one that is over 100 lbs and the other is maybe 60 lbs. I have many questions but really am not sure who to talk with…

  4. I never knew that my pregnancy was that rare. I have fraternal twin girls that shared a placenta but each had their own sac. They told me from the start that they were going to be identical. I had a whole system with color coding and ID bracelets, then they came out looking nothing alike. They’re 12 now and don’t even look related. One is 5’6’’ 200lbs pale with curly blonde hair and the other is 5’1’’ 100lbs olive skin with straight brown hair.

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