DIAGNOSTIC ACCURACY OF ULTRASOUND IN MEASURING ESTIMATED FETAL WEIGHT WITHIN 48 HOURS BEFORE DELIVERY KEEPING THE BABY WEIGHT AT BIRTH AS A GOLD STANDARD

Background: Accurate estimation of fetal weight in the third trimester is vital for optimal perinatal care, particularly in identifying low birth weight (LBW) neonates and preventing related complications. Ultrasonography remains a cornerstone in antenatal assessment due to its safety and accessibility, yet the precision of its estimations compared to actual birth weight remains a subject of continued research interest. Objective: To determine the diagnostic accuracy of ultrasound in estimating fetal weight before delivery, using birth weight at delivery as the gold standard. Methods: This cross-sectional validation study was conducted over six months at the Department of Diagnostic Radiology, Khyber Teaching Hospital, Peshawar. A total of 265 pregnant women between 29 and 40 weeks of gestation were enrolled using consecutive non-probability sampling. Fetal weight was estimated using ultrasound based on standard biometric parameters. Actual birth weight was recorded within two hours of delivery. Diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using a 2x2 contingency table. Data were analyzed using SPSS v21. Results: Of the 265 participants, 92 (34.7%) had low fetal weight on ultrasound, and 96 (36.2%) neonates were confirmed to have low birth weight. The ultrasound showed a sensitivity of 80.21%, specificity of 91.12%, PPV of 83.70%, NPV of 89.02%, and an overall diagnostic accuracy of 87.17%, demonstrating strong agreement between ultrasound estimates and actual birth weight. Conclusion: Ultrasound proved to be a reliable tool for fetal weight estimation in late pregnancy, showing high diagnostic accuracy for detecting low birth weight. Its integration into routine obstetric care can enhance prenatal decision-making and neonatal outcomes. Keywords: Birth Weight, Diagnostic Accuracy, Fetal Biometry, Fetal Weight Estimation, Pregnancy Trimester Third, Sensitivity and Specificity, Ultrasonography, Weight Gain.