This can sometimes be dangerous if the woman begins to act on her cravings.  It could be due to some deficiencies and they should consult with their doctor. IRon and Zinc deficiencies have been linked to Pica. Cravings are not limited to only pregnancy period. Everyone experience some kind of cravings at some point in life.

Hormonal changes during pregnancy can be one of the causes of food cravings during pregnancy. Some of the cravings which the woman had before pregnancy can get amplified during pregnancy and she can go on a binge eating spree. Sometimes cravings may be for food items which she never liked before pregnancy. Why do these bizarre cravings happen? What a pregnant woman craves for is culturally related- For eg - An expectant mother in India may crave for sour mango or sour chutneys while a pregnant woman in the west may crave for chocolates and Ice creams.

A couple of explanations are - A substance called Neuropeptide is released by the hypothalamus and it is known to increase appetite. It is thought that the levels of neuropeptide usually increases during pregnancy in Mouse studies, which may explain the reason pregnant women have more appetite. Research also shows that pregnant women who tend to develop gestational diabetes tend to crave for sweets from their 6th month. There is one theory which suggests that the pregnant woman craves for a particular nutrient which is deficient in the body. For eg- the craving for pickles or sour food during pregnancy could be body’s way of getting sodium. It is thus nature’s way of obtaining the required nutrient for baby’s well being and a healthy pregnancy. Pregnancy is usually associated with abnormal smell and taste perception. This may explain the food aversions in some women.

So what do we do about these cravings?

Well, It is OK to give in to your cravings in moderation, but if you are craving for ice cream or pizza or fried samosa every day, then it may not be good for you or your baby. You may add more kilos then needed and will have to work hard after pregnancy to get rid of the extra weight. SO it is always wise to keep everything in moderation and try to substitute your craving with a healthy alternative. Eat breakfast every day, it is said that skipping breakfast makes you crave more. Exercise moderately and keep healthy.

Ref:

https://www.psychologytoday.com/blog/craving/201306/what-really-causes-pregnancy-cravings