Update Reference Charts: Fetal Biometry between the 15th and 20th Week of Gestation

The aim of this study was to derive reference charts between the 15th and 20th week of gestation for biparietal diameter (BPD), occipito-frontal diameter (OFD), head circumference (HC), abdominal circumference (AC) and femur length (FL) compared to commonly used curves and to evaluate the impact of maternal body mass index (BMI), ultrasound equipment, fetal gender and nicotine abuse.

In a cross-sectional study of 4,265 low-risk pregnancies, biometric data were obtained between the 15th and 20th week of gestation. The statistical analysis included descriptive data, fitting regression curves for the 5th, 50th and 95th quantile as well as multivariate quantile regression analyses.

Reference curves for BPD, OFD, HC, AC and FL showed a linear increase between the 15th and 20th week of gestation. New equations and reference charts are presented in this study. In a comparison of influence factors sex, BMI and ultrasound systems have an impact.

As a result of the study, we determined current growth curves for BPD, OFD, HC, AC and FL for both sexes as well as for males and females separately. The updated growth curves for all biometric parameters differ from the curves used commonly in the last two decades.