At different times during your pregnancy, you might have sudden muscle spasms in your legs or feet. They usually occur at night. This is due to a change in the way your body processes calcium. 

What might help: 
•    Gently stretch muscles. 
•    Get mild exercise. 
•    For sudden cramps, flex your foot forward. 
•    Eat calcium-rich foods. 
•    Ask your doctor about calcium supplements