Nomogram for fetal limb bones in Chinese ethnicity

Objective: To construct fetal limb bone nomograms in the Chinese ethnic population. 

Methods: This was a prospective cross-sectional study on singleton pregnancies between 12 and 37 weeks of gestation. Femur, tibia, fibula, humerus, ulna, radius, and foot length were measured in a standardized manner by one of the three sonographers. Each fetus’s measurements were only included once and those who developed maternal or fetal complications were excluded. Fractional polynomial regression model was used to obtain the 3rd, 10th, 50th, 90th, and 97th centiles for each of the limb measurement. Z-score for the 50th centile of each fetal limb measurement was then compared with published nomograms derived from other populations. 

Results: Of the 843 scans performed, 775 were included in analysis after excluding conditions such as pre-eclampsia, chromosomal abnormalities, single umbilical artery and skeletal dysplasia. Comparison with other populations showed that Chinese had shorter fetal limb bone lengths than the Caucasian and Afro-Caribbean populations. 

Conclusion: This study established nomograms for all the fetal limb bones in the Chinese ethnic population, which showed lengths comparatively shorter than Caucasian and Afro-Caribbean nomograms. This would reduce the false alarm of short fetal limb bone lengths and its consequent anxiety and intervention.