Identical or fraternal twins?

[FasterMichelin]

I have to preface this by saying I have identical twins, so I have some skin in the game as they say. You may find this completely dull.

I know this doesn’t really matter for anyone other than the twins themselves, but I’m finding it crazy how many twins identify as “non-identical” (fraternal) when they’re clearly identical. There seems to be a long standing misunderstanding about what makes twins identical even amongst doctors and sonographers (who are usually the ones who have the first conversation with the parents when they ask).

The common misconception seems to be that if the babies have a placenta each, they’re not identical, but that just means the egg split early enough in the process for them to grow their own placentas.

I have worked with a set of identical twins (completely identical by sight) who had never had a DNA test and swore blind they weren’t identical because their mum had asked and the doctor confirmed they aren’t, but they clearly were. There’s a saying in the twin mum world that if 90% of people can’t tell your twins apart, there’s a very strong likelihood they’re identical. I’ve seen it a few times now where people don’t seem to wonder why no one can tell their “non-ID” twins apart.

Why does this matter? Well, it’s a huge advantage knowing your twin shares your DNA if you’re ever gravely unwell. And also it’s just interesting (to me anyway!).

I’ve attached a picture of the Olson twins - clearly identical but reports still say they aren’t. It seems so common that people accept the misinformation still.

I am a twin and we look similar but we don’t know if we are identical or fraternal. They didn’t have many scans etc 48 years ago!

I have twins & always thought that identical were when one egg splits, but fraternal are when two eggs are released.

Yes, that’s right @twinmum2007.
Sorting out whether they’re identical or fraternal at birth can sometimes be tricky though. Not with boy/girl twins obviously.

You probably already know this, but it’s possible for boy/girl twins to be identical (although incredibly rare).

It doesn’t matter though OP: one type of twin is not better than another.
Identical twins are often a result of fertility treatments (ICSI weakens the cell membrane making it more likely to divide into twins) so perhaps people don’t want to admit their child twins are identical as they prefer to keep their fertility treatments private. People can do and say what they like.

Not a twin mum (but love random medical stuff), in just going to chuck in semi identical twins here. Not fraternal trains. Not identical.

Yes, I’m often surprised by how common it seems that people don’t know DCDA (two placentas/two sacs) twins can be identical. It’s something like 30% that are.

I’m pregnant with DCDA girls and know they are non-identical because I had a specific blood test done, which has confirmed they are dizygotic and thus fraternal. Very excited to meet them in the next couple of weeks!

No, though it can happen with semi identical twins!

There have only been a couple of instances discovered as they've shared a placenta, but it's possible there are more which are either the same sex, so not so obvious, or different placentas so presumed to be fraternal.

I agree. My twins are identical. I had problems v early on and was scanned from 8 weeks. One placenta which began to disintegrate at 25 weeks. They are healthy 40 year olds. Still look identical. Share taste in clothes, humour etc but only as close as other siblings. They were always treated by us and friends and family as separate individuals-not twins.

This is an odd conversation. Identical twins come from a split egg (ie genetic information is the same) fraternal twins are when women release two eggs at the same time which are then fertised- they have different genetic information.

Not quite. Identical twins come from a split blastocyst, not an egg. But yes, fraternal twins from two eggs.

The highly unusual semi identical twins is where two sperm simultaneously fertilise an egg that splits, so both are identical in the mums side and fraternal on the dads!

They actually can though - girl twin has something called Turner Syndrome. Very rare, but possible to have identical B/G twins.

Also a mum of confirmed identical twins (MCDA). I feel the same as OP! It actually blows my mind that so many medical professionals don’t seem to know that separate placentas does not necessarily mean fraternal. In fact, with same sex DCDA (separate placenta) twins, there is a 30% chance they are identical and one fertilised egg split early enough for two placentas to develop.

It bothers because it could actually be very important, as well as interesting, to know you have a 99% DNA match.

Cousins were told they were ‘very identical’ on the scale of identicality which we found confusing.

Separately I know identical twins with different birthdays as one was born before midnight and one just after. That confuses bureaucracy.

Many siblings look very similar especially if you compare them at the same age, so its possible that fraternal twins might look like identical twins simply because they are siblings of the same age.

Even if they are genetically the same they are still two individual people with their own perspective and experiences - they might have identical genes but they are not identical people!

If ey grow in separate sacks, they are feternal. My grand mother was a faternal twin ( girl and a boy), my uncles were also likely feternal, but look very similar. Looking alike does not make a set if twins identical.

Most identical twins grow in separate amniotic sacs too.
Sharing an amniotic sac is quite rare and comes with increased risk.

How the two types are identified or mis-identified at birth is what OP is talking about though, rather than how a twin pregnancy is formed.

When 1 egg splits it's identical twins end of! I have identical twin nieces so know what I'm talking about! i also went through 3 rounds of IVF using more than 1 embryo with every possible outcome discussed.

I have a twin sister and we look very alike. Mum and dad always told us we were fraternal as there were 2 placentas. Only when I became a sonographer did I realise that that doesn’t mean you’re not identical

I’m an identical twin and I have identical twins. I know for sure that they are identical because we went through IVF and only one embryo was implanted, and we also had a placental study done after the birth. For years I volunteered with our local multiple birth organisation and we encouraged parents to get DNA tests if they thought their twins might be identical because it’s very useful to know for medical purposes. The general consensus is that if family and friends get your twins mixed up frequently, they are probably identical.

I was told by a consultant my twins would not be ID as I had 2 placenta. It was the sonographer who told me it was possible for them to be ID, depending on when the egg split.
There is absolutely no doubt mine are identical and I don't need a DNA test to confirm it. I struggle to tell them apart 25+ years later!

When 1 egg splits it's identical twins end of!

Nobody is disputing this…it’s not what the thread’s about.

I have ID twin sons now young adults. The first question I blurted out when I was told at my scan was “are they identical”, and the answer was yes, only one placenta. The second one was born with his amniotic sac intact which is supposed to be lucky!

I am shocked that in this day and age medical professionals still don’t get this right. I met a woman years ago through a twins club who insisted her clearly ID boys were non ID as they were in separate placentas.

I've got a friend who is one of triplets but actually she's one of identical twins and the third triplet doesn't look like them!

They've also got another sister who doesn't look like them either,

The two who look alike have sons and the cousins look very like each other.

Haven't there been a couple of cases as well where one twin is born prematurely but the other one isn't born until later? I'm sure it can't happen very often but I thought I saw a headline to that effect quite recently - there was something like 8 weeks between them.