Comparison of Current Swiss Fetal Biometry Reference Charts with Reference Charts from 1999. Are Fetuses Getting...

Area of Science:

• Obstetrics and Gynecology
• Fetal Medicine
• Biometry

Background:

• Established fetal biometry reference ranges are crucial for monitoring fetal growth and identifying potential abnormalities.
• Previous reference charts, such as those from 1999, may not accurately reflect current fetal size due to secular trends.

Purpose of the Study:

• To establish current fetal biometry reference ranges.
• To compare new ranges with 1999 references to assess secular trends in fetal size.
• To evaluate the clinical relevance of updated fetal growth data.

Main Methods:

• A prospective, cross-sectional study involving 7863 patients was conducted between January 2008 and December 2014.
• Reference ranges for biparietal diameter (BPD), occipitofrontal diameter (OFD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were calculated.
• Z-scores and percentile comparisons were used to contrast new data with 1999 reference charts.

Main Results:

• A clinically relevant increase in mean fetal body measures (BPD, HC, AC) was observed.
• Using 1999 charts for the new dataset resulted in misclassification: only 47.8% of fetuses were correctly below the 5th percentile for AC, and 38.4% for HC.
• The 1999 charts overestimated fetuses above the 95th percentile for AC by 28.3%.

Conclusions:

• New fetal biometry charts show clinically significant differences compared to 1999 charts.
• Data indicate fetuses are increasing in size within a single generation.
• Regular updates of fetal reference charts are essential for accurate clinical assessment.