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ID or frat?

post #1 of 32
Thread Starter 
This may seem silly, but how do you know if your twins are ID? Some days, they look the same but then sometimes they look totally different! And when we are out, about half the people say they look exactly the same and the other half say that they look totally different. Our doc told us that they were frat but only because they were di di and he didn't seem to know that di di can be ID. Does anyone know of any tricks to figure this out other than DNA? I think they both have the same blood type, but I also think that my boyfriend and I have the same blood type. There were two placentas in all my ultrasounds, but then only one came out! It had somehow managed to fuse but they didn't really do much, just poke around to see if there was one or two.
post #2 of 32
I don't know what to say about your situation, but I do know that Mary Kate and Ashley Olsen are fraternal twins with very similar looks. I guess they have really similar DNA or something.
post #3 of 32
Mine were in the same amniotic sac, without a dividing membrane. There's nothing else for them to be other than identical.

They have different fingerprints and heel prints, they have different hair whorl patterns, and very different personalities. I know two ID men, one gay and one straight.

I would say that DNA testing is the only way to find out. Even ID twins can be very different.
post #4 of 32
The way I understand it, if they're boy/girl they have to be fraternal (dz), if they share a sac (I think, memory's foggy . . . ) they have to be identical (mz). If neither of these things are the case, the only way to know for sure is to get a dna test.
post #5 of 32
We did a dna test, for us that was the only way to tell. I had an u/s tech tell me they were dz, but they don't know what they are talking about. I really did not think mine were mz cause they looked so different at first, but now they look sooo much alike and we did have them tested and they are mz.
post #6 of 32
Mine were di-di, too, and I wasn't sure until we got the DNA test that said that were mz. Everyone else thought they were, but I can tell them apart so well that I had my doubts. But, I have a friend with 2 year old twins who I find impossible to tell apart. Yet, she thinks they look very different. And she thinks my twins look exactly alike. Somehow, that convinced me they must be mz. We mamas just see our babies differently than the rest of the world, somehow.

If you decide to do the test, we were very pleased with www.affiliatedgenetics.com. And of course you have to let us know what happens!
post #7 of 32
I was told by my OB, who has delivered hundreds of multis, that the only way to tell for sure if they are same sex is to get the DNA test. MZs can still have separate everything in utero. Also if people outside of the family have a hard time telling them apart after a year or so, once their features are starting to get more defined, there's a good chance they are MZ.

Did anyone read that section in "Having Twins" about the semi-MZ or "near ID" theory? I thought that was very interesting. They haven't been able to prove it exists yet. Basically the egg splits into two separate identical eggs, and then those are concieved by two separate sperm. The result is very similar-looking DZ twins.
post #8 of 32
Okay, hopefully this will help.

Fraternal twins (commonly known as "non-identical twins") usually occur when two fertilized eggs are implanted in the uterine wall at the same time. The two eggs form two zygotes, and these twins are therefore also known as dizygotic as well as "biovular" twins. When two eggs are independently fertilized by two different sperm cells, fraternal twins result.

Dizygotic twins, like any other siblings, have a very small chance of having the exact same chromosome profile, but most likely have a number of different chromosomes that distinguish them. Like any other siblings, fraternal twins may look very similar, particularly given that they are the same age. However, fraternal twins may also look very different from each other. They may be a different sex or the same sex. Mixed-race twins, or twins born to parents of mixed racial origin, can vary considerably in their skin colouration and other features.

Studies show that there is a genetic basis for fraternal twinning. However, it is only the female partner that has any influence on the chances of having fraternal twins as the male cannot make her release more than one ovum. Fraternal twinning ranges from 1 or 2 per thousand births in Japan (similar to the rate of identical twins) to 14 and more per thousand in some African states.

Identical twins
Identical twins occur when a single egg is fertilized to form one zygote (monozygotic) which then divides into two separate embryos. This is not considered to be a hereditary trait, but rather an anomaly that occurs in birthing at a rate of about 1:150 births worldwide, regardless of ethnic background. The two embryos develop into fetuses sharing the same womb. When one egg is fertilized by one sperm cell, and then divides and separates, two identical cells will result. Depending on the stage at which the zygote divides, identical twins may share the same amnion (or in the same amnion and placenta/chorion), which can cause complications in pregnancy.
Monozygotic twins are genetically identical (unless there has been a mutation in development) and they are the same gender. (On extremely rare occasions, an original XXY zygote may form monozygotic boy/girl twins by dropping the Y chromosome for one twin and the extra X chromosome for the other.) Monozygotic twins generally look alike. Fine physical details such as fingerprints will differ. As they mature, identical twins often become less alike because of lifestyle choices or external influences. Genetically speaking, the children of identical twins are half-siblings rather than cousins.

The likelihood of a single fertilization resulting in identical twins is a random event, not a hereditary trait, and is uniformly distributed in all populations around the world. This is in marked contrast to fraternal twinning which ranges from 1 or 2 per thousand births in Japan (similar to the rate of identical twins) to 14 and more per thousand in some African states[citation needed]. The exact cause for the splitting of a zygote or embryo is unknown.

Studies have shown that identical twins reared in different environments share similar personality traits, mannerisms, job choices, attitudes, and interests[citation needed]. These findings add to the belief that many behaviors are derived from genes.

Identical twins have identical DNA but differing environmental influences throughout their lives affect which genes are switched on or off. This is called epigenetic modification. A study of 80 pairs of human twins ranging in age from 3 to 74 showed that the youngest twins have relatively few epigenetic differences. The number of differences between identical twins increases with age. 50-year-old twins had over three times the epigenetic difference of 3-year-old twins. Twins who had spent their lives apart (such as those adopted by two different sets of parents at birth) had the greatest difference. (Fraga, et al., 2005).

Mirror twins
Some monozygotic twins are known as "mirror twins" or mirror image twins. These are identical twins with opposite features, that is, one may be right-handed and the other left-; mirrored hair curls, etc. This condition is comparatively rare in humans. It results from a late split of the fertilized egg at around 9-12 days. One mirror may have situs inversus, where some or all of the organs are on the opposite side of the body, such as the heart on the right (dextrocardia). Such conditions are usually associated with a higher incidence of other birth defects.

Polar twins
Polar twins are monozygotic but develop differently, due to different genes being activated.[1] These "half-identical twins" may occur when one sperm fertilizes the egg, while another fertilizes a polar body.
post #9 of 32
When my boys were born, I was told immediately that they were faternal twins because they had different blood types - does that constitute DNA testing - dont think so, but not sure.
post #10 of 32
Quote:
Originally Posted by MomSquared View Post
When my boys were born, I was told immediately that they were faternal twins because they had different blood types - does that constitute DNA testing - dont think so, but not sure.
Different blood types are fraternal.
post #11 of 32
Quote:
Originally Posted by Mamma Mia View Post
I don't know what to say about your situation, but I do know that Mary Kate and Ashley Olsen are fraternal twins with very similar looks. I guess they have really similar DNA or something.
In no way do I believe that those girls are fraternal! I think that they were just given misinformation at birth due to being di/di or something along those lines. Someone needs to send them a DNA kit ASAP!

A pp mentioned fingerprints. All twins - even identical twins - have different fingerprints.
post #12 of 32
Mary Kate and Ashley are mirror twins-- that's probably why they think they're fraternal. Mary Kate is left handed, and Ashley right; their hair parts naturally on opposite sides of their heads, etc. Watch one of the first year episodes of Full House, and you can see not only the differences in their hair & handedness, but the size discrepancy (much diminished over the years); they'll both be wearing the same sized sweater, for example, and on Mary Kate it comes over her hands, while on Ashley it's about 3/4" 'shorter.' The girls wore ponytails on the tops of their heads as soon as it was long enough, because the difference was *obvious* and made for a continuity nightmare, I'm sure. Even with the ponytails, you can see the difference; it's quite noticeable, especially earlier in the series. They probably think that this makes them fraternal by definition, but the fact is that you have to be identical to be a mirror image of your twin.
They look very much alike, but it's pretty easy to tell them apart once you realize that Ashley's taller and right handed.


I'm one of those obnoxious non-twin mothers who knows more than everyone else. Sorry, couldn't resist. Your twins are definately dizygotic if:

1. They have different sexes and both have a full complement of chromosomes.

2. They have different blood types.

Your twins are definately monozygotic if:

1. They shared a placenta, amniotic (inner) sack, and/or chorionic sack.

If none of those three things are true for yours, then the only way to know for sure is with a DNA test.
post #13 of 32
Not to take it off topic, but I think you can tell them apart because they look different. :
post #14 of 32
I've never been able to tell the Olsen twins apart.
post #15 of 32
While it's true that only mz twins can share a placenta, it's possible (& often happens) for the two placentas to grow so close together that it's virtually impossible to determine if it's a single placenta or two that have grown together. Therefore, in general a "shared placenta" shouldn't be used as the only proof that twins are mz.

One thing I read indicated that Mary Kate & Ashley are actually . . . forgot the term, but where an egg splits & then is fertilized by two sperm (so half of their dna is identical). Now that they're older I don't think they look much alike (though I haven't paid enough attention to be able to say who is who).
post #16 of 32
I read that today too after reading this thread. That they are "false identical" twins. That's where the ovum splits before fertilization and so the mother's DNA is the same but each egg receives a different sperm. With the identicle DNA contribution from the mother, the twins share similar features.
post #17 of 32
Quote:
Originally Posted by sweetpeas View Post
One thing I read indicated that Mary Kate & Ashley are actually . . . forgot the term, but where an egg splits & then is fertilized by two sperm (so half of their dna is identical). Now that they're older I don't think they look much alike (though I haven't paid enough attention to be able to say who is who).
That is a Polar Twin. When the egg splits before being fertilized. However from what I've read that is a theory and not possible to identify through DNA. Who knows....
post #18 of 32
Quote:
Originally Posted by balawre View Post
Mine were in the same amniotic sac, without a dividing membrane.
Wow momma. Mono/Mono right? I remember the time we spent looking for my Mono/Di boys membrane and hearing about the difficulties if no membrane was found. Would you mind sharing how the pg went with this difficult circ?
post #19 of 32
Quote:
Originally Posted by eilonwy View Post

Your twins are definately monozygotic if:

1. They shared a placenta, amniotic (inner) sack, and/or chorionic sack.
The problem with a statement like that is that most people, docs included, don't describe the sacs and placenta definitively enough. Frat twins can "share" a chorion and placenta. But it's not really shared, it's two separate sets that fused.

To the OP, I think a good rule of thumb is that if you have to use color codes or positioning to know who is who in pictures, they are id. My dh's aunt does this, she totally cracks me up. She was looking at the individual school pictures her twins took and couldn't tell who's picture it was, then turned to me and said "but they have different eyeglass prescriptions, I'm sure they're fraternal" :
post #20 of 32
Quote:
Originally Posted by TripMom View Post
Wow momma. Mono/Mono right? I remember the time we spent looking for my Mono/Di boys membrane and hearing about the difficulties if no membrane was found. Would you mind sharing how the pg went with this difficult circ?
Don't want to hijack here, but I don't have a pregnancy/birth story elsewhere...

It was far different from what I'd imagined our 2nd pregnancy would be and not as bad as I thought it would turn out.

We planned a hospital (vbac) birth with a very natural-friendly OB - he was okay with water labor, pushing however I wanted, etc and then we found out we were having twins at 10W. He was still very happy with a natural birth, but added that we'd have to deliver in the OR. I think I posted around that time asking how to avoid that and looking back that was such a tiny detail!

Around 3 months, we got the final declaration of monoamniotic twins and our care was transfered to the head of MFM at our University hospital. I felt fortunate that he was a pretty "crunchy" guy, his wife delivered at our birthing center and he even encouraged triplet moms to delivery vaginally. That said, he told me there was no way around a c-section again and that the twins would be delivered sometime between 32-34 weeks. He told us at our first appointment that if we made it to viability, he would see us again. I thought at the time it was terribly rude, but then we started reading all the studies and literature.

We made it to 26W, our choice of viability, and from there out started monitoring the girls at home for two sessions per day, each lasting from 1-2 hours. We chose not to do in-patient, like most mono pregnancies, because we are so close to the hospital and I felt like I needed to be at home for my sanity and for my toddler.

At 29W, I had contractions every 4-6 minutes apart and was admitted to the hospital for a week. I was dilating and had severe cervical funneling, so we chose mag sulfate and steroids. The funneling actually improved which is supposedly quite rare, and I went home on light bedrest, natural progesterone injections, and ibuprofen as a muscle relaxant.

We chose a 32W delivery because we saw what an emergency situation would be like during the PTL scare. I didn't want to deliver under general, and we hadn't experienced any heartrate decels the entire time we'd monitored the girls. The whole pregnancy was somewhat of a game of playing the odds, so we decided to play them again.

Meagan needed CPAP for 3 days then a cannula and Morgan was on a cannula for a couple of weeks. They were out of the NICU within two weeks and home after five long weeks. They took awhile to discharge because of apnea and brady spells.

They just turned 6 months old, breastfeed like champs, and they roll over, giggle, play with toys, try to sit up, and babble like nuts. I wouldn't want to have the experience again, but it was certainly worth it to have my two sweet girls.
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