Types of Twins

Before we found out that Sarah was having twins we only thought that there were 2 types of twins, identical and fraternal.  Well it turns out there are 3 types.  There are two characteristics that are used to judge the type of twins 1. how many placentas and 2. how many amnionic sacs.

Types of Twins

Di-Di twins - this means that the babies have their own separate amnionic sacs and placentas.  These twins came from 2 separate eggs and will always be fraternal twins.  These types of twins are commonly hereditary or "helped" by fertility drugs. (Don't worry Lisa, our twins aren't Hereditary!) This is the safest type of twins to have

Mono-Di twins - these twins share 1 placenta but have separate amnionic sacs.   This type of twin is from 1 egg splitting very early in the fertilization process. This type of twins has it's risks but is relatively safe.

Mono-Mono twins - this type of twins share both 1 placenta and 1 amnionic sac.  That means that their umbilical cords can easily wrap around each other or get tangled causing problems.  These twins are always identical and come from one egg splitting slightly later in the fertilization process.  Because everything is shared these are the highest risk type of twins.

It all sounds kind of confusing so this diagram we found kind of helps explain it:

Here's a link to the report that the diagram is from: http://jdm.sagepub.com/cgi/reprint/22/1/59.pdf

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