EP14.05: Intra- and interobserver reproducibility of fetal measurements in third trimester ultrasound: does maternal weight matter?

To evaluate intra- and interobserver reproducibility of third trimester ultrasound fetal measurements in normal weight and overweight pregnant women. Fetal ultrasound measurements were performed at 35weeks0days-36weeks6days: biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). Each measurement was evaluated twice by the first observer and a third time by a second observer that was blinded to first observer's measurements. Consensus between and among observers was analysed using the Crohnbach's α reliability coefficient (RC). We also compared intra- and interobserver measurements within subgroups – women with normal weight (body mass index < 25 Kg/m2) and overweight women (body mass index ≥ 25 Kg/m2) with paired sample t-test. The Bland and Altman plots were created to determine agreement and bias between paired measurements by one observer and by two observers, respectively. We included 197 women, 133 with normal weight (68%) and 64 overweight (32%). For normal weight women, intra-observer α-RC for BPD, HC, AC and FL were: α=0.97; α=0.95; α=0.98 and α=0.96, respectively. Interobserver α-RC were: α =0.97; α =0.93; α=0.98 and α=0.95, respectively. For overweight women, intra-observer α -RC for BPD, HC, AC and FL were: α=0.97; α=0.93; α=0.98 and α=0.96, respectively. Interobserver α-RC were: α=0.97; α=0.94; α=0.98 and α=0.96, respectively. Intra- and interobserver differences for both groups were not considered statistically significant. Our results demonstrate a high intra- and interobserver reproducibility of third trimester ultrasound fetal measurements, even for overweight women.