Fundal height measurement. Part 4--Accuracy of clinicians' identification of the uterine fundus during pregnancy.

The purpose of this study was to determine how accurately clinicians can identify the uppermost border of the uterine fundus when they obtain fundal height measurements. Clinicians were instructed to identify the uppermost border of the uterine fundus in their usual manner and make a small pen mark on the maternal abdomen at that point. Real-time ultrasonography was then used to locate the actual level of the fundus and measure the distance between the clinician's assessment and the actual level of the fundus. Measurements were obtained from 126 women. Six clinicians participated in the study, and the differences between the clinicians' errors were not statistically significant (F = 1.26; d.f. = 5,120; P = .2873). For the entire series, the mean error was -.45 cm (SD = 1.99 cm), the mean absolute error was 1.25 cm, the maximal error was 8.6 cm, the percentage of errors that exceeded 1 cm was 42.1%, and the percentage of errors that exceeded 2 cm was 20.6%. Examiner error was not associated with factors such as maternal height, prepregnancy weight, present weight, prepregnancy body mass index, parity, gestational weeks, the amount of fat on the anterior abdominal wall, or the presence of the placenta or fetal parts in the fundus. Examiner error was influenced by thickness of the uterine wall and fetal presentation. These findings indicate that clinicians make errors in identifying the uterine fundus in a significant number of cases and that the methods used by clinicians to identify the uterine fundus need to be evaluated and improved.