Fetal Kidney Length Measurement, an Additional Visceral Parameter to Predict Gestational Age between 24 to 40 Weeks

Introduction: In order to provide adequate antenatal care, accurate gestational age assessment is critical.

Recent research suggests that, in addition to normal biometric indicators, kidney length should be considered when calculating the duration of pregnancy by ultrasonography.

Materials and Methods: A prospective cross-sectional study of 120 pregnant women was conducted in a single centre. Kidney length was assessed at two-week intervals between 24 and 40 weeks, in addition to usual biometric measures. A total of 240 renal vertical measurements were recorded, with the average of the right and left renal lengths being used to determine the final kidney length. The mean and standard deviations for each variable were determined using descriptive analysis. Pearson regression coefficients were used to find the association between gestational age and other foetal characteristics and to evaluate which regression model provides the best fit for prediction of gestational age.

Results: The length of the foetal kidneys grew longer as the pregnancy progressed (from 23.2 mm at 24 weeks to 40.1 mm at 40 weeks). The regression formula (gestational age = 2.195 + 0.942 X kidney length) demonstrated a good degree of correlation (R2 0.97, p<0.001, SE of prediction 4.7 ± 3.9), which was superior to other prediction models employing standard biometric parameters. When femur length was included in a stepwise manner to multiple regression models with several conventional factors, there was a considerable improvement in forecasting gestational age. Conclusion: The current study found that foetal kidney length is a credible indication of gestational age between 24 and 40 weeks of pregnancy, and that it may be useful in pregnancies with incorrect dates, the absence of a dating scan, and women who conceived during nursing.