The truth is that we don’t know exactly why so many people crave ice during pregnancy, but many people develop pagophagia when they become deficient in iron. And, as you may already know, iron deficiency anemia is very common in pregnancy (up to 25% of people become anemic at some point in their pregnancy).
Anemia in Pregnancy
1. During pregnancy, blood plasma (the fluid part of your blood) increases rapidly, while blood cell count (the amount of actual blood cells floating around in that fluid) rises more slowly. That means that for a period you have more blood in your body, but that blood is more “watered down” in the sense that there are less blood cells per ml of blood. This isn’t iron-deficient anemia per se, but it is a sort of functional anemia.
2. The baby needs a ton of iron, the placenta needs a ton of iron, and newly minted red blood cells need their share of iron as well. All in all, that means the body's overall iron demand skyrockets during pregnancy.
Ok But... Why Ice??
Theory number one: Ice is stimulating, which people with anemia crave because one of their most common symptoms is fatigue. There is a phenomenon called the “dive reflex,” in which blood is shunted away from your outer body and toward your brain and heart when your face is hit with cold water (this may explain the invigorating effects of a “polar bear plunge”). More water to the brain means more alertness and mental energy.
Theory number two: Because anemia can cause tenderness and inflammation in the mouth, people who are anemic may crave ice to numb out this tenderness.
Theory number three: Being anemic can cause stress, which can trigger compulsive behavior. This may be the most underdeveloped of the current theories on pagophagia in pregnancy: essentially saying that eating ice during pregnancy is a form of addiction. While it’s true that some people do develop addictive behavior around ice eating in pregnancy (such as attempting and being unable to stop, feeling anxious when they don’t have access to ice, etc), the majority of people are able to stop or cut down on ice eating when they are get their iron back up to normal levels.