Fundal height measurement. Part 2--Intra- and interexaminer reliability of three measurement techniques.

The intra- and interexaminer reliability of three fundal height measurement techniques (two tape measure and one caliper) was studied in a convenience sample of 60 pregnant women. The three measurements were obtained twice by two examiners. Four examiners with varying levels of clinical experience participated in the study; one examiner obtained measurements in all 60 cases and the other three examiners each obtained measurements in approximately one-third of the cases. Examiners were blinded to their own and to other examiners' measurements. The mean absolute differences between individual examiner's first and second measurements varied from 0.68 to 1.74 cm, the percentage of differences < or = 1.0 cm varied from 45% to 77.8%, and the maximal differences varied from 1.6 to 7.5 cm. The caliper technique consistently demonstrated the smallest mean absolute intraexaminer differences (0.68 to 1.39 cm) and the highest percentage of intraexaminer differences < or = 1.0 cm (55% to 77.8%). The differences between pairs of examiners' measurements were consistently greater than the differences between individual examiner's measurements: Mean absolute differences varied from 1.36 to 3.60 cm, the percentage of differences < or = 1.0 cm varied from 9.1% to 55.6%, and the maximal differences varied from 3.1 to 11.5 cm. Interexaminer differences were smallest for the tape "over-the-curve" measurements and the caliper measurements. These findings indicate that, to ensure maximal reliability, fundal height measurements should be obtained by the same clinician throughout pregnancy. Additionally, these findings indicate that calipers may be the most reliable method of obtaining fundal height measurements and that the accuracy of caliper measurements in identifying fetal growth disturbances and other pregnancy complications merits further investigation.