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What is a decidual cast?

Dr. Betty Acker

Medically reviewed by Dr. Betty Acker, MD on May 18, 2020

At Nurx we take care of so many women that when something rare happens it hardly surprises us any more. When patients experience terrible cramping with their periods and then see a weird clump of “something” come out on their pad or when removing a tampon, we know what it is. This phenomenon is due to a decidual cast.  

Every month the hormonal changes in your body cause the lining of the uterus to build up and then to slough off. Your period is the lining of the uterus coming out in little bits and pieces. This happens when you use birth control pills too, but the lining is usually thinner and there is less to come out of you. Well, sometimes, instead of the lining coming out in little bits, it comes out all at once. It is shaped like the inside cavity of your uterus, kind of triangular, wide on the top and narrow at the bottom. It is usually pinkish-reddish or fleshy colored. The consistency is kind of fleshy, like a rubber band or chicken skin. 

Passing it is pretty uncomfortable and the cramps can really get your attention. When it passes, the cramping usually stops. 

The first time this happens, it can be alarming, but passing a cast has no health implications and means nothing in terms of your future fertility.  It is just one of those rare things that can happen. 

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