Fundal height measurement. Part 3--The effect of maternal position on fundal height measurements.

The effect of maternal position on fundal height measurements was studied in 192 nonobese women between 21 and 36 weeks of gestation. Four clinicians participated in the study and each clinician obtained measurements on 48 women. Fundal height measurements were obtained in each of four positions: supine; trunk elevation; knee flexion; and trunk elevation with knee flexion. The sequence in which measurements were obtained was assigned randomly. Clinicians were blinded to the results of their measurements. Measurements obtained in the supine position were largest, and measurements obtained in the trunk elevation with knee flexion position were smallest. Repeated measures analysis of variance demonstrated that measurements obtained in the four positions were significantly different (F = 87.71, df = 3,573, P < .001). A posteriori comparisons demonstrated that measurements obtained in each position were significantly different except for measurements obtained in the trunk elevation and knee flexion positions. These findings indicate that clinicians should be consistent when they position patients to obtain fundal height measurements.