Fetal size charts for a population from Cali, Colombia: sonographic measurements of biparietal diameter, head circumference, abdominal circumference, and femur length

Abstract

Objectives: To create reference charts for fetal sonographic biometric measurements in a population of pregnant women living in the third largest city in Colombia and compare them with charts included in ultrasound machines.

Methods: The data were obtained from women with a single pregnancy and confirmed gestational (menstrual) age between 12 and 40 weeks. All women were recruited specifically for the study, and every fetus was measured only once for biparietal diameter, head circumference, abdominal circumference, and femur length. Raw data for each fetal measurement were modeled by fitting regression models separately to estimate the mean and standard deviation as a function of gestational age. Percentile curves were constructed for each measurement by gestational age using these two regression models. We compared our mean z scores with those expected by reference equations.

Results: Measurements were obtained for 792 fetuses. A cubic polynomial model was the best-fitted regression model to describe the relationships between each fetal measurement and gestational age. The standard deviation for each measurement was estimated by simple linear regression as a function of gestational age. Comparison of our mean z scores with those by reference equations showed significant differences in some fetal measurements (P < .01).

Conclusions: We present a set of reference percentile charts, tables, and formulas for fetal biometric measurements from a Colombian population. We believe that our fetal charts could be used nationwide in Colombia; nevertheless, a national sample will contribute to their validation and promotion of the development of Colombian fetal size charts.

Keywords: abdominal circumference; biparietal diameter; femur length; fetal size chart; head circumference; obstetric sonography.