Systematic Review and Meta-Analysis: The clinical value of color ultrasound screening for fetal cardiovascular abnormalities during the second trimester

Congenital heart abnormalities are the most common structural abnormalities associated with fetal cardiovascular development. An abnormal fetal cardiovascular function affects fetal health. The rate of congenital heart abnormalities is approximately 0.8% in fetuses, which reduces the population birth quality. The embryo begins to form a cardiovascular system at approximately 3 weeks of pregnancy but is not able to circulate blood independently. The internal structure of the fetal heart does not completely develop until 7 to 8 weeks of pregnancy. The exposure of pregnant women to external adverse stimulation during fetal cardiovascular system development at 7 to 8 weeks of pregnancy may hinder its proper development. In severe cases, the fetus is delivered with congenital heart disease, which severely affects the fetal quality of life in the later years. The causes of fetal cardiovascular abnormalities include heredity factors, fetal factors, and the maternal environment. Older women infected with viruses, or those who have congenital diseases, are more likely to give birth to newborns with fetal cardiovascular abnormalities. Furthermore, abnormalities in fetal chromosomes and amniotic fluid, and developmental delay in utero can also lead to cardiovascular abnormalities. After the birth of a newborn, its symptoms are not obvious and will delay detection time, resulting in increased difficulty in treatment. Due to insufficient development of the fetal cardiovascular system in early pregnancy, there may be some deviation in the detection results of fetal heart disease by ultrasound examination. In the second trimester of pregnancy, fetal orientation and fetal heart development are relatively stable, so it may be the best time to explore fetal heart development. Color Doppler is the use of autocorrelation technology for Doppler signal processing, and the blood flow signal obtained by autocorrelation technology is color-coded and then superimposed on a 2-dimensional image in real time, leading to the formation of a color Doppler blood flow image. It offers several advantages, including minimal trauma, no radiation exposure, quick and convenient operation, and widespread utilization in clinical practice. It can be used for examination of the brain, liver, spleen, stomach, kidney, breast and uterus, along with screening for vascular diseases, especially cardiovascular diseases. Color Doppler can be conveniently and accurately applied in the screening of fetal heart malformations during pregnancy, which can clearly diagnose and reduce the birth rate of newborns with congenital heart disease. Color Doppler can be used to assess the intrauterine placenta, umbilical cord, and amniotic fluid status of pregnant women. Furthermore, it can clearly show the general structure of the fetus in utero and the 4 chambers of the heart. It aids in clear visualization of the cardiac vein, artery abnormality, ventricular outflow tract, blood vessels, and other conditions, leading to an improved detection rate. This is of great significance for high-quality fertility. Color Doppler has been widely used in prenatal fetal screening for cardiovascular abnormalities in China because of its convenience, low trauma, and lack of radiation. Several studies have evaluated the clinical compliance rate of color Doppler in screening for fetal cardiovascular abnormalities during pregnancy. However, these studies were conducted with small sample sizes and were not representative of the general Chinese population. In addition, there have been few meta-analyses on the diagnostic accuracy of color Doppler in the diagnosis of fetal cardiovascular abnormalities during the second trimester in the Chinese population. Therefore, the purpose of this study was to use a meta-analysis to comprehensively evaluate these studies and the types of cardiovascular abnormalities in the Chinese population.

A systematic review was conducted according to PRISMA extension recommendations for diagnostic test accuracy reviews and the Cochrane Collaboration handbook. Studies published between 2015 and 2022 were identified by searching English-language databases (PubMed, Google Scholar, Cochrane Library, ClinicalTrials) and Chinese-language databases (CNKI, CQVIP, WANFANG, Baidu Scholar) using MeSH terms and keywords including “cardiac abnormality,” “heart anomaly,” “heart disease,” “congenital,” “Color Doppler,” “second trimester,” “China,” and “Chinese,” plus combinations. Reference lists of included studies were screened for additional eligible studies. Selection was performed independently by two reviewers based on titles/abstracts and full texts in English when available. Inclusion required human studies on Color Doppler screening for fetal cardiovascular abnormalities in China, with two-stage screening (questionnaire primary screening and physician diagnosis per conventional Chinese criteria). Exclusions were non-research articles (reviews, press releases, newsletters, forums) and studies with unclear diagnostic criteria or unconventional tools. Data extracted included first author, publication year, country, sample size (positive/negative), sensitivity, specificity, and counts of TP, FP, FN, and TN (recorded directly or derived). Types of cardiovascular abnormalities among positives were also collected. Study quality was assessed using GRADE and QUADAS-2 across patient selection, index test, reference standard, flow/timing, risk of bias, and applicability. Meta-analysis used Review Manager 5.3. Forest plots summarized estimates with 95% CIs. Random-effects models yielded pooled sensitivity, specificity, PPV, and NPV. An SROC curve was plotted and AUC calculated with classification: 90%–100% excellent, 80%–90% good, 70%–80% fair, 60%–70% poor, 50%–60% failure. Screening rates for anomaly types were computed per study and pooled via inverse-variance weighting; standard errors used sqrt(pq/n). Heterogeneity was anticipated; Cochrane Q and Higgins I2 were used to assess heterogeneity; I2 values of 75%–100% with P < .05 indicated substantial heterogeneity.

- Study selection: From 492 records, 13 full texts were assessed; 4 Chinese-language studies met inclusion criteria. - Sample: 151 fetuses with cardiovascular abnormalities confirmed after delivery and 3397 undiagnosed controls. - Diagnostic accuracy: Pooled sensitivity ranged between 0.91 and 0.96; specificity was 1.00. The SROC AUC was >90%, classified as excellent diagnostic performance. - Quality assessment: QUADAS-2 indicated overall acceptable quality; risk of bias and applicability were evaluated across six domains. - Anomaly type distribution (screening rates): atrioventricular septal defect 36% (highest), tricuspid atresia 16%, single ventricle 16%, ventricular septal defect 13%, tetralogy of Fallot 11%, single atrium 4%; differences were significant (P < .05).

Color ultrasound is advantageous in prenatal screening due to minimal trauma, convenience, and absence of radiation. Performing Color Doppler between 20 and 28 weeks aims to detect fetal cardiovascular anomalies and inform decisions regarding continuation of pregnancy, potentially reducing births affected by congenital heart disease and improving newborn outcomes. Compared with B-ultrasound, Color Doppler provides clearer, more comprehensive visualization of fetal structures, including the four-chamber view, ventricular outflow tracts, and vascular anomalies, thereby improving diagnostic rates. In this meta-analysis, the pooled SROC AUC exceeded 90%, with sensitivity 0.91–0.96 and specificity 1.00, supporting excellent diagnostic value and clinical utility in the second trimester. The fetal cardiovascular system is incompletely developed and more affected by fetal orientation in early pregnancy, limiting diagnostic accuracy; by the second trimester, cardiac structures are formed and less position-dependent, making it the optimal screening window. Prior evidence suggests lower sensitivity but very high specificity in the first trimester; the present findings indicate higher overall accuracy in the second trimester. Among structural cardiovascular abnormalities reported in the included studies, atrioventricular septal defects had the highest screening rate. Future advances, including deep learning methods for echocardiographic analysis, may further improve diagnostic precision and efficiency in prenatal cardiac assessment.

The use of color ultrasound during the second trimester is an effective diagnostic tool for detecting fetal cardiovascular abnormalities. Early application supports high-quality fertility by enabling timely diagnosis and informed pregnancy management decisions.

Only four studies met inclusion criteria for diagnostic accuracy, and post–induction or post-delivery diagnostic processes were not described in detail, potentially affecting overall estimates. The meta-analysis included only studies from the Chinese population and predominantly Chinese-language papers, limiting generalizability. Larger, high-quality, multicenter studies are needed for further validation.