Category: Twin FAQs

Twin Statistics

In the U.K around 33% of twins are identical

UK Twin Statistics


Twin Statistics ~ How many twins are identical and how many are non-identical?

In the UK it is thought that around 66% of twins are non-identical and 33% of twins are identical.

Identical Twins or Non-identical twins? Dizygotic or Monozygotic? What does it all mean?

When you find that you are pregnant with twins suddenly you discover that it’s not quite as simple as just having two babies. People start throwing jargon at you often with baffling results! Here is a quick guide to the different types of twins and a breakdown of some of the most commonly used twin jargon.

Mono? Di? What’s this all about?

In simple terms  ‘mono’ means one, so if you see any information starting with mono, it probably means from one where as ‘di’ means two and so if you see something with di in its name chances are it means from two. (This makes life easier as then you can apply this principle to the other twin jargon you come across, phew) We probably shouldn’t refer to twins as identical and non-identical as even identical twins have tiny differences, which often get more prominent as they get older. A more useful term for twins is monozygotic or dizygotic.

Dizygotic Twins

Those who are non-identical (or fraternal) are from two separate sperm and eggs (also called dizygotic twins) and are likely to look as similar as regular siblings. They may be the same sex or different sexes, may look similar or quite different. They might have different hair types, eye colours, hair colours, etc.

Monozygotic Twins

Identical (or monozygotic) twins however are formed from one sperm and egg which splits shortly after conception. They will be the same sex and probably look very similar to each other. Some people may struggle to tell them apart.


My same sex twins are not sharing a chorion or placenta does this mean they’re definitely non-identical?

If the split takes place very soon after conception the two embryos may implant at different places, so even if your same sex twins don’t share a placenta or chorion, this means your same sex twins could still be identical despite not sharing any membranes etc.


How can you tell if your twins are identical?

Usually you get told your twins are identical for sure if they are sharing an outer membrane (chorion) in the womb. If they have one chorion (outer membrane) they will be described as mono-chorionic. If they also share an amniotic sac they will be described as being mono-amniotic

If your twins are boy/girl twins they are definitely non-identical..

How can you tell? Go check in their nappies, do they look the same? No. Quite!

What does MC/DA or MC/MA mean?

You may have heard of twins being described as mono-chorionic/ diamniotic  (MC/DA) This means they have  one chorion or outer membrane but two amniotic sacs or mono-chorionic/monoamniotic (MC/MA) this means one chorion and one amniotic sac

You may like this article on determining zygosity