Types of Twins

How I Practice Video Series
Sharon Phelan, MD, FACOG

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When I talk to a woman who's just been told she's having twins, I talk to her about the routine risks of preterm labor, anemia, nutritional needs, but one of the things I find that most women don't understand are the three different types of twins that, as an obstetrician, I worry about. They only know about identical twins and non-identical twins. So I found the following analogy works well. I tell them if you have two children in a room fighting and you're wanting to break up the fight, if you can send each child to their own room and their own bed, the fighting stops. It's the same thing with twins. If you think of the bedroom as the placenta and the bed as the bag of waters, if each baby has their own placenta and own bag of waters, they tend not to get into a whole lot of trouble with each other. Now if instead with those two children, they're fighting and you have to send them to their own bed but their beds are in the same room, they will continue to fight. They'll steal from each other, they'll yell at each other and so that's similar to twins where they have the same placenta and two separate bags of water. These twins can steal from each other and sometimes this is called a twin-twin transfusion, where one child is taking more of the blood and the nourishment from the other child. The last kind of twins from our perspective is the set where you have the two children fighting, you send them to their bed and their bedroom, but unfortunately they share the same bed in the same bedroom. Their fighting is going to continue, now they're going to get tangled up in sheets and so forth. This is like the twins that have one placenta, one bag of water. Those twins continue to fight with each other, get tangled up in their cords and this type of twin is a problem in that they often don't make it to point where we can deliver them safely. This is how I explain twins to patients. This is how I practice.


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