intrauterine volume =
= 4/3 *
π * ((longitudinal diameter in cm) / 2) * ((transverse diameter in cm) / 2) * ((anteroposterior diameter in cm) / 2) =
= 0.5233 * (longitudinal diameter in cm) * (transverse diameter in cm) * (anteroposterior diameter in cm)
The volume increases during pregnancy, so the week of gestation needs to be known if the volume is to be accurately interpreted.
If the data in Figure 8, Gohari (1977) is approximated and analyzed in JMP, the following equations are derived:
mean intrauterine volume in cubic cm =
= (0.2274346 * ((weeks gestation) ^ 3)) - (15.17857 * ((weeks gestation) ^ 2)) + (451.07578 * (weeks gestation)) -3540.909
intrauterine volume 1.0 standard deviation below the mean in cubic cm =
= (0.0008094 * ((weeks gestation) ^ 3)) + (2.0417083 * ((weeks gestation) ^ 2)) + (11.073186 * (weeks gestation)) -141.2587
intrauterine volume 1.5 standard deviations below the mean in cubic cm =
= (-0.020639 * ((weeks gestation) ^ 3)) + (4.1177572 * ((weeks gestation) ^ 2)) - (69.56654 * (weeks gestation)) + 618.18182
Interpretation:
• A normal volume is between +/- 1 standard deviation of the mean.
• A borderline low volume is between 1.0-1.5 standard deviations below the mean.
• An abnormally low volume is less than 1.5 standard deviations below the mean.
