Intra- and interobserver reproducibility study of early fetal growth parameters

OBJECTIVE: To assess the intra- and interobserver reproducibility of fetal biometry measurements by transabdominal ultrasound in early pregnancy. METHODS: The study consisted of 21 singleton pregnancies with a gestational age between 9 and 14 weeks. Intraclass correlation coefficients (ICCs) and coefficients of variation (CVs) were calculated. Bland and Altman plots were computed to analyze agreement for measurements between and among observers. Limits of agreement +/- 2 SD for the differences in fetal biometry measurements in proportions of the mean of the measurements were derived. RESULTS: High intra- and interobserver ICCs were found, ranging from 0.998, crown-rump length (CRL) to 0.982, femur length (FL) and CVs ranging from 1.4% (CRL) to 5.9% (FL). Limits of agreement in the Bland and Altman plots ranged from - 2.7 to 2.3% (CRL) difference from the mean to - 13 to 23% (FL) difference. Agreement for fetal biometry increased with fetal size. CONCLUSIONS: This study demonstrated good reproducibility of most measurements of fetal biometry in early pregnancy by abdominal ultrasound. CRL and biparietal diameter (BPD) showed high reproducibility and agreement, and head circumference (HC) to a lesser extend, from 9 weeks of gestational age onwards. abdominal circumference (AC) is only reliable from circa 11 weeks onwards. FL has a poor reproducibility before 14 weeks of gestational age.