Longitudinal and transverse uterine area measurements (LTUA) are not representative of intrauterine volume

A midline longitudinal area and the maximum transverse area of the pregnant uterus were used to compute the intrauterine volumes of 37 women in the third trimester of pregnancy. The results were compared with measurements done simultaneously using a parallel planimetric area method. The use of only two areas caused significant underestimation of total intrauterine volume, by 14-36 per cent. Because of the variable shape of the uterine cavity in pregnancy, the product of longitudinal and transverse intrauterine area measurements cannot give reliable information about intrauterine volume.