Are my triplets identical or non-identical?

Understanding whether your triplets are identical or non-identical

Finding out you’re expecting triplets can feel exciting, surprising and a little overwhelming. One of the first things many parents wonder is whether their babies are identical or non-identical, and what that means for the pregnancy.

Triplets can all be non-identical (also called fraternal), all identical or a mixture of both. Identical triplets come from a single fertilised egg that has split into three. Non-identical triplets come from three separate eggs, each fertilised by a different sperm, so they have different genetic make-ups.

You might also hear about babies sharing a placenta or an amniotic sac. This matters because it can affect the risks in pregnancy and how closely you and your babies will be monitored. At your early scans your maternity team will look carefully at this and explain what they can see.

Understanding the type of triplet pregnancy you have can help you feel more informed, ask questions with confidence and make sense of the care you’re being offered.

How triplet pregnancies are classified in scans

When your dating scan, usually around 12 weeks, confirms you’re expecting triplets, the sonographer will look for how many placentas and amniotic sacs there are. This is sometimes called chorionicity (placentas) and amnionicity (sacs).

Each baby may have its own placenta and sac, or some of the babies may share. It isn’t possible for babies to share an amniotic sac without also sharing a placenta. However, one triplet can have its own placenta and sac while the other two share a placenta, or share both a placenta and a sac.

Your triplets might all be non-identical or all identical. It’s also possible to have a combination, where one baby is fraternal and the other two are identical because one fertilised egg has split into two.

Trichorionic-triamniotic (Tri/Tri)

Each baby has their own placenta and their own amniotic sac. This is when three eggs have all been fertilized by three separate sperm

Type of triplet: Non-identical (fraternal)

Occurence: Most common

Dichorionic-triamniotic (Di/Tri)

One baby has their own placenta and amniotic sac, while the other two babies share a placenta but have their own amniotic sac

Type of triplet: One non-identical baby (fraternal) and two identical babies

Occurence: Less common than tri-tri

Monochorionic-triamniotic (mo/Tri)

All three babies share a placenta but have their own amniotic sac

Type of triplet: Three identical babies

Occurence: Less common than Tri/Tri and Di/Tri and more high-risk

Monochorionic-monoamniotic (mo-Mo)

All three babies share a placenta and share the amniotic sac

Type of triplet: Three identical babies

Occurence: Very rare and high risk

In general, tri/tri pregnancies, where each baby has its own placenta and sac, are the most common and usually involve non-identical babies. Di/tri pregnancies typically involve one non-identical baby and two identical triplets. Mo/tri and mo/mo pregnancies involve three identical babies and are less common and more high risk.

The risk of complications increases when babies share a placenta or an amniotic sac. Because of this, you’ll usually be offered more frequent monitoring, and your team is likely to recommend an earlier birth as the pregnancy progresses. Find out more about complications in pregnancy through our dedicated information and support.

Family history, genetics and testing for identical triplets

Many parents ask whether triplets run in the family. Similar to twins, identical triplets are not hereditary. They happen when one fertilised egg divides, and that can occur in any pregnancy.

Fraternal triplets can be influenced by genetics on the mother’s side. If women in your family tend to release more than one egg in a cycle, you may be more likely to conceive non-identical multiples yourself.

Identical triplets remain very rare. It’s estimated that only around one in a million pregnancies result in three genetically identical babies. Fraternal triplets are more common than this, but still uncommon overall, with roughly one pregnancy in 8,000-10,000 resulting in triplets. Across the UK each year, there are around 120 recorded triplet births and a small number of higher order multiple births.

Even when your babies had separate placentas and sacs in the womb, you might still wonder whether they’re identical, especially if they look very similar. Non-identical triplets can resemble each other closely, just as any siblings can look strikingly alike or share strong family features.

If you’d like a definite answer, you can choose a zygosity test. This is done using a simple cheek swab taken from each child at home. It’s completely pain free, can be done at any age and compares your children’s DNA to show whether they’re genetically identical.

***Rafi: check with head of dev*** Twins Trust Premium Members can save 10% when ordering a zygosity test from AlphaBiolabs (LINK) or NorthGene (LINK).

Getting support throughout a triplet pregnancy

Triplet pregnancies are always considered higher risk, especially when babies share a placenta or sac. That can feel worrying, but it also means you’ll have specialist input and closer monitoring to help keep you and your babies as safe as possible.

Your team should explain how many placentas and sacs your babies have, what this means for risk and how often you’ll be seen. If you’re unsure about any terms such as tri/tri, di/tri, mo/tri or mo/mo, ask your midwife or consultant to go through them again. You’re not expected to remember everything first time, and it’s fine to write things down or bring someone with you for support.