are there five kinds of twins?

Cecil's Columns/Staff Reports
1

As a regular reader of the online version (and former Chicago Reader reader) I would like to comment on a recent Straight Dope Classic from Jan 2000. The question was “are there really 5 kinds of twins” and while your answer was adequate, I really don’t think you’ve hit it exactly on the head. As a board certified OBGYN, I can confirm that your explanation of the DiDi, DiMo, and MoMo was dead on. And the dizygotic type of twin was also correct. But I do think that the description of the type of dizygotic twin, where there may be some placental fusion, is a bit of a stretch. There are certainly many cases where Twin-Twin Transfusion Syndrome (TTTS) exists and, in the majority of those cases, are life threatening to both fetuses. But this is really not a subtype if twin, but rather a dangerous version of the dizygotic twin. I would suggest you did not consider the conjoined twin, where the cleavage of the fertilized ovum occurred beyond about 12 days post fertilization and was incomplete. But in the same way as the TTTS is a slightly different trim of the same model of dizygosity, this is merely a slightly different model of the MoMo.

Regards,

Stewart Kernes, DO, FACOG

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Welcome to SDMB, kerney, and as they say, Glad To Have You With Us.

Since most of us are not psychic, it’s always a good idea to include a link to the column in question, so we are all on the same page out of the starting gate, to mix some metaphors. Cecil & Co. have several threads on twins, but perhaps this one is the one you are commenting about. If not, please set us straight.

Do twins have identical DNA?

Or this one?

3

I understand it is rare but not impossible for twins to have different fathers. Basically fraternal twins with added twist.

So surely there are more than five kinds of twins?

I won’t even get into the depths of possibilites such as different father fraternal twins who in turn are identical twins - though technically that would be quads.