Fetal stomach measurements: not reproducible by the same observer.

We hypothesized that because fetal stomach filling and emptying is a dynamic process, measurements of the stomach dimensions might not be reproducible. Serial measurements 20 minutes apart were made of the stomach in 146 fetuses at 14 to 41 weeks of gestation. In 88 of these fetuses, the biparietal diameter also was measured to provide a standard for comparison. The mean percentage change between each of the paired measurements was 16.6% to 43.1% for the different stomach dimensions, compared with only 2% for the biparietal diameter (P < 0.001). We suggest that caution be excised in the diagnostic use of stomach measurements owing to their dynamically changing nature.