A prospective case-control study was done to determine any difference of serum calcium levels in pregnant women in third trimester and non-pregnant women. Serum calcium levels were determined in 30 normal non-gravid women and 30 women with normal pregnancies during third trimester with age range of 17-35 years. The mean serum calcium levels were found to be significantly lower in normal pregnant woman in third trimester than that of normal non-pregnant controls.