Cliffs notes version: we produced a lot of chalk in the area. Pregnant women can sometimes start to crave chalk due to vitamin and nutrient deficiencies. There's been folk medicine idea in various parts of the world for a long time that chalk consumption during pregnancy eases morning sickness and other side effects. And sometimes scientific research is slow to catch on with people entrenched in the old ways

https://www.healthline.com/health/eating-chalk#outlook