Update Reference Charts: Fetal Biometry between the 15th and 42nd Week of Gestation.

OBJECTIVES

This study was designed to establish new reference charts for BPD (biparietal diameter), OFD (occipitofrontal diameter), HC (head circumference), CM (cisterna magna), TCD (transverse cerebellar diameter), PCV (posterior cerebral ventricle), AC (abdominal circumference), FL (femur length), and HL (humerus length) and extend known charts to 42 weeks of gestation. These new charts were compared to studies carried out by Snijders and Nicolaides, the INTERGROWTH 21st Project, and the WHO Fetal Growth Charts.

METHODS

In this retrospective cross-sectional single-center study of 12,972 low-risk pregnancies, biometric data between the 15th and 42nd weeks of gestation were evaluated. Only one examination per pregnancy was selected for statistical analysis. Descriptive analysis for the 5th, 50th, and 95th quantile was performed for each parameter as listed above. Regression models were used to fit the mean and the SD at each gestational age.

RESULTS

Initially the reference curves for BPD, OFD, HC, AC, FL, and HL show a linear increase, which changes into a cubic increase towards the end of pregnancy. The results of this study show statistically noticeable differences from the percentile curves of the studies listed above.

CONCLUSIONS

The percentile curves in this study differ from the commonly used ones. The presented standard curves can be used as a reference in prenatal diagnostics.