Evaluation of the INTERGROWTH-21st fetal growth standards in a single-center cohort of uncomplicated pregnancies in Poland

OBJECTIVES: To evaluate the applicability of the INTERGROWTH-21st prescriptive fetal growth standards for thirdtrimester biometry and estimated fetal weight (EFW) assessment in a Polish population. MATERIAL AND METHODS: This retrospective single-center cohort study included 594 uncomplicated singleton pregnancies with reliable firsttrimester crown rump length dating and one routine thirdtrimester ultrasound performed at a tertiary center in Poland (2014-2021). Standard biometry and EFW were obtained per international guidelines, and EFW was calculated using the INTERGROWTH-21st formula. Zscores and centiles were derived from INTERGROWTH-21st standards. EFW Zscores were grouped into < 3rd, 3rd ≤ 10th, 10th-90th, 90th-97th and > 97th centile categories; observed vs expected proportions (3%, 7%, 80%, 7%, 3%) were compared using the chisquare test. RESULTS: Mean Zscores approximated zero for all parameters (HC 0.00 ± 1.01, AC 0.00 ± 1.02, FL 0.00 ± 1.08, BPD 0.00 ± 1.01, EFW 0.00 ± 0.93); 95% confidence intervals included zero, indicating minimal bias. For EFW, proportions were 1.0%, 4.7%, 85.2%, 6.2%, and 2.9%, respectively, significantly deviating from the theoretical distribution (χ² = 14.8, df = 4). CONCLUSIONS: Third trimester fetal size in lowrisk Polish pregnancies is well described by the INTERGROWTH-21st standards regarding central tendencies. A slight underrepresentation of fetuses at the extremes suggests mild compression, warranting local audit and linking of centiles with perinatal outcomes to refine diagnostic thresholds.