Clinical significance of routine 36-week ultrasound in detecting late fetal anomalies
Keywords:
neonatal management, fetal diagnosis, prenatal ultrasound, 36-week scan, late fetal anomalies, third trimester, late fetal anomalies, 36-week scanAbstract
Introduction: Standard prenatal care traditionally includes ultrasound screening during the first (11–14 weeks) and second (18–22 weeks) trimesters. However, growing evidence indicates that a subset of fetal structural and functional abnormalities either develops or becomes detectable only in late gestation. This has increased interest in routine third-trimester screening, specifically at 36 weeks, as an additional diagnostic window for fetal assessment. Methods: This narrative review synthesizes data from large-scale cohort studies and meta-analyses published in 2025. We evaluated the incidence and spectrum of abnormalities first detected in late pregnancy, as well as their implications for obstetric and neonatal management. Results: A routine 36-week scan identified previously undetected fetal abnormalities. The most frequently newly diagnosed conditions included: Genitourinary anomalies - hydronephrosis, duplex kidney, hydroureter; Central nervous system abnormalities - ventriculomegaly, arachnoid cyst, microcephaly; Cardiac defects - VSD, coarctation, valvular stenosis; Gastrointestinal obstruction patterns; Skeletal dysplasias - including achondroplasia. These findings had direct consequences on perinatal decision-making, influencing delivery site selection, neonatal surgical preparedness, and postnatal intervention planning. Conclusion: Routine ultrasound at 36 weeks substantially increases the detection rate of late-onset fetal abnormalities and offers clinically meaningful value alongside first- and second-trimester screening. Evidence suggests that incorporating a 36-week scan into standard prenatal care may reduce perinatal complications, improve neonatal outcomes, and enhance obstetric management - particularly in settings with adequate neonatal surgical and intensive care capacity.
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