There is no specific time pregnancy craving start, you may not even have any pregnancy cravings.

Most women experience pregnancy cravings as early as five weeks pregnant and the cravings increase in the second trimester, by your third trimester your cravings may start to decrease and stop.

You may be craving fatty foods or sugary foods but remember you may need willpower to avoid over eating these types of cravings and try to replace with a more nutritional option and hope the cravings stop. 

If you find yourself craving non-food items such as such as chalk, clay, laundry starch or soap. This is a condition called pica, and it may indicate a mineral deficiency or anaemia and you should seek advice from your midwife.