Diagnosis of fetal congenital anomalies in the first trimester of pregnancy

Objective: To investigate the incidence and types of fetal congenital anomalies (FCA) detected during first-trimester screening in pregnant women from various risk groups.

Materials and methods: This retrospective study included 10,044 patients who underwent first-trimester screening at 11–14 weeks of pregnancy at V.I. Kulakov NMRC for OG&P of the Ministry of Health of Russia from 2018 to 2023. Based on baseline medical history and established recommendations, patients were categorized into low- and high-risk groups for fetal pathology. The incidence and types of FCA were analyzed for each group. Pregnancy outcomes including diagnostic verification were assessed using archived electronic patient records. Ultrasound examinations were performed by expert physicians of the Ultrasound and Functional Diagnostics Department with appropriate qualifications. Statistical analysis was conducted using the generalized D'Agostino–Pearson test, Mann–Whitney U test, and Kruskal–Wallis test, with differences considered significant at p<0.05.

Results: Of the study population, 61.6% were in the low-risk group, and 38.3% were in the high-risk group. The mean age of high-risk patients was 37.6 (3.5) years, compared to 29.7 (3.2) years for low-risk patients (p<0.001). Although the median body mass index (BMI) did not differ significantly between the groups, obesity (BMI>30 kg/m²) was more common in the high-risk group (8.7%) than in the low-risk group (4.8%). Additionally, assisted reproductive technologies (ART) were used more frequently in the high-risk group (19.2%) than in the low-risk group (8.4%; p<0.01). In the low-risk group, most women were primigravidae (64.6%) and primiparae (63.2%), whereas in the high-risk group, 41.5% were primigravidae and 44% were primiparae. The overall incidence of FCA in the cohort was 4.3%, with fetal defects occurring in 1.9% of the low-risk patients and 8.1% of the high-risk patients (p<0.01). Combined fetal defects were the most common, accounting for 55% of all the detected anomalies. The most frequently isolated FCAs were congenital heart, limb anomalies, genitourinary, anterior abdominal wall, and gastrointestinal tract defects. Statistically significant differences in isolated FCA incidences were observed between the groups, specifically for facial, chest, and genitourinary pathologies in low-risk patients (p<0.05). Of the 194 isolated defects, anomalies consistently detected before 14 weeks of pregnancy accounted for 35%, those sometimes detected constituted 58.3%, and those practically not detected made up 6.7%.

Conclusion: Prenatal ultrasound diagnostics enables the detection of a significant proportion of fetal anomalies at 11–14 weeks of gestation. The higher incidence of FCA in the high-risk group than in the low-risk group supports the efficacy of risk-based stratification in prenatal screening.