Usefulness of fetal sacral length measurement for the prediction of gestational age

Objective: To establish the usefulness of fetal sacral length measurement for the prediction of gestational age. Methods: A longitudinal and prospective study was conducted between January 2016 and December 2022 in women with low-risk singleton pregnancies, between 14 and 40 weeks of gestation, who attended prenatal consultation at the Central Hospital “Dr. Urquinaona”, Maracaibo. Biparietal diameter, abdominal circumference, femur length, and fetal sacrum length were measured during pregnancy. Results: For the final analysis, data from 215 healthy women was selected. A total of 3,033 total evaluations were performed, with the lowest number of evaluations at 38 weeks with 104 and the highest number of 139 at 22 weeks. When analyzing the correlation between sacral length and gestational age by date of last menstrual period and the rest of the ultrasound variables used, strong, positive, and significant correlations were found (p < 0.0001). The average difference between the gestational age determined by the date of the last menstrual period and that obtained by the model was +/- 0.3 weeks. The value of the coefficient of determination of the model of gestational age predicted by measurement was 0.975. When combining the four ultrasound parameters studied in the resulting model, it was 0.990. Conclusion: Measurement of fetal sacral length by ultrasonography is useful for predicting gestational age with high precision.