The importance of mid-trimester anomaly scans in a low-resource setting: a retrospective study of 7,615 mid-trimester anomaly scans at a tertiary maternity hospital in Nepal

Background Congenital anomalies are a leading cause of perinatal mortality in low- and middle-income countries. While mid-trimester anomaly scans are standard in high-income settings, their utility in Nepal remains undocumented. This study evaluates the spectrum, frequency, and clinical significance of fetal anomalies detected during routine anomaly scans at Nepal’s largest maternity hospital. Methods A retrospective cross-sectional study was conducted at Paropakar Maternity and Women’s Hospital (PMWH), analyzing all mid-trimester anomaly scans (18–24 weeks) performed between January 2021 and April 2023. Anomalies were classified as major (structurally significant) or minor/soft markers (e.g., echogenic bowel, intracardiac echogenic focus). Data were summarized using descriptive statistics, and associations were assessed using Chi-square test. Results Of 7,615 anomaly scans, 2,807 (36.9%) detected at least one anomaly. The most common findings were hydronephrosis (27.1%), echogenic bowel (21.4%), and central nervous system variants (26.1%). Only 88 (3.1%) were major anomalies, including neural tube defects (n = 8), holoprosencephaly (n = 2), omphalocele, gastroschisis, and skeletal dysplasia. Soft markers were present in 1,380 (49.2%) of all anomaly cases. Critically, 68 (81.0%) of 84 major anomalies occurred in fetuses with ≥ 1 soft marker, compared to only 16 without. This association was highly significant (χ² = 42.6, p  < 0.001; OR = 4.6, 95% CI: 2.6–8.1). Conclusions Mid-trimester anomaly scans in Nepal detect a substantial number of clinically significant fetal anomalies. The strong association between soft markers and major structural defects underscores their value as screening indicators, even in settings where advanced diagnostics are unavailable. These findings support the integration of standardized anomaly scans into routine antenatal care across similar low-resource regions.