Using Renal Length for Accurate Estimation of Gestational Age

Abstract

BACKGROUNDAccurate measurement of gestational age is important for obstetric management. Ultrasound estimation of gestational age is the standard practice. Several biometric parameters can be used to calculate gestational age, commonest being biparietal diameter (BPD), abdominal circumference (AC) and femoral length (FL). In the present study, an additional parameter, the fetal renal length (KL), is taken as a biometric variable and the correlation between gestational age and renal length are calculated. AIMS-To find out the correlation between gestational age and kidney length, biparietal diameter, femoral length and abdominal circumference in the third trimester. To find out regression equations for these variables with gestational age and thus to predict gestational age. MATERIALS AND METHODSThe study was done as a cross sectional study. This study was conducted among 100 low risk antenatal women, who attended the antenatal clinics of the Department of Obstetrics and Gynaecology, Government Medical College, Thiruvananthapuram. Statistical Analysis-The data collected in the study concerning biometry and gestational age is represented in graph form called scatter diagram. Depending on the alignment of the data, the correlation between the two is visualized. Then curve fitting is done using regression analysis and regression equation for calculating the dependent variable from independent variable is found out using linear regression analysis. The coefficient of correlation (R) and coefficient of determination (R 2 ) is then found out. The better the correlation the closer these coefficients will be to one. Root mean square deviation shows how accurate is the estimate. RESULTSThe average gestational age of the study population was 35.6 ± 2.81. When comparing the correlation, it was found that kidney length had the highest correlation followed by femoral length. Regression equations for calculating gestational age from the various biometrics were calculated. Correlation was greatest when combination of KL, BPD, AC, FL and AC was used. RMSD was least with KL. The prediction interval width was least for KL. CONCLUSIONKidney length can be used along with the usual biometric variables like BPD, AC and FL with better accuracy for predicting gestational age.