Fetal Heart Size: A Comparison Between the Point-to-Point Trace and Automated Ellipse Methods Between 20 and 40 Weeks' Gestation.

Objectives: To evaluate whether the global area and circumference of the heart varies between two measurement techniques: the point-to-point trace and the electronic ellipse methods.

Methods: The epicardial border of the 4-chamber view was measured in 200 fetuses between 20 and 40 weeks' gestation, from which the area and circumference using the point-to-point trace and electronic ellipse were measured. Analysis of variance, correlation, and regression analysis using fractional polynomials and 7 independent variables (head circumference, biparietal diameter, abdominal circumference, femur length, estimated fetal weight, mean ultrasound gestational age, and last menstrual period gestational age) were performed.

Results: The correlation between the mean ultrasound gestational age and last menstrual period gestational age was 0.9880 (5% confidence limit, 0.9716; 95% confidence limit, 0.9880), with an R of 0.9762. The R value for the 7 independent variables regressed against the area and circumference using the point-to-point trace and electronic ellipse methods ranged between 0.885 and 0.965. Comparison of Z scores between this study and previous publications demonstrated that there were differences and similarities, depending on whether the area or circumference was measured.

Conclusions: This study shows high R values when comparing measurements of the area and circumference against 7 independent variables, irrespective of whether the point-to-point trace or the electronic ellipse method was used to obtain the measurements. A calculator to evaluate the area and circumference is provided, using 7 independent variables from which Z scores and percentiles for individual measurements can be computed.