Comparison of Hadlock formula and intergrowth-21st standards for fetal growth restriction detection: A comparative study

Abstract

Introduction: Fetal growth restriction (FGR) is a critical obstetric condition associated with adverse perinatal outcomes, necessitating precise detection. This study compares the diagnostic performance of the Hadlock formula and Intergrowth- 21st (IG-21) standards for FGR identification. Methods: A retrospective comparative study was conducted at Menzel Temime Regional Hospital, Tunisia, from January 2024 to March 2025, including 350 singleton pregnancies with ultrasound data at 28-36 weeks. Estimated fetal weight (EFW) was calculated using Had- lock and IG-21 standards, with FGR defined as EFW <10th percentile. Sensitivity, specificity, predictive values, and ultrasound parameter performance were analyzed. Results: Hadlock identified 52 (14.9%) FGR cases, while IG-21 identified 44 (12.6%). Hadlock showed higher sensitivity (87.0% vs. 78.3%) but lower specificity (89.8% vs. 93.5%). Positive predictive value (PPV) was 65.0% for Hadlock and 70.5% for IG-21; negative predictive value (NPV) was 96.9% and 95.3%, respectively. Abdominal circumference (AC) <10th percentile was the most sensitive parameter for both standards (Hadlock: 82.6%, IG-21: 76.1%). Conclusion: Had- lock is more sensitive but less specific than IG-21 for FGR detection. IG-21 reduces false positives, optimizing resource allocation. Ultrasound parameters, particularly AC, enhance diagnostic accuracy. Clinicians should tailor standard selection to population characteristics.