OBJECTIVE: To determine among unselected and low risk populations the accuracy with which fetal echocardiography during the second trimester detects congenital heart disease. DESIGN: A systematic review of studies that assess the accuracy of fetal echocardiography. SETTING: District General Hospital and Tertiary referral centres. POPULATION: Women during the second trimester attending for ultrasound assessment. METHODS: General bibliographic databases (e.g. MEDLINE, EMBASE) and specialist computerised databases (e.g. Cochrane Library, National Research Register), grey literature, manual searching of reference lists of primary and review articles and personal contact with experts were used to identify studies. Studies were included if fetal echocardiography among unselected or low risk pregnant women was compared against a postnatal reference standard. Data were extracted on quality, study design and characteristics, and accuracy data to construct 2 x 2 tables. Data were synthesised qualitatively, and sensitivity and specificity with 95% confidence intervals were calculated. MAIN OUTCOME MEASURE: Sensitivity and specificity. RESULTS: Five primary studies met the inclusion criteria and comprised 60,901 subjects. One study assessed the accuracy of fetal echocardiography among an unselected population and four studies among low risk populations. All eligible studies found that fetal echocardiography helped to correctly diagnose normal fetus among unselected and low risk populations. Correct diagnosis of babies for congenital heart defects was higher among the unselected population (85%) than among the low risk populations (range from 35% to 86%); however, the potential for ascertainment bias and the choice of reference standard limits the validity of this finding. The variation in sensitivity across studies was not explainable by clinical factors such as scanning regime, operator skill and equipment. CONCLUSIONS: The evidence from this review about the accuracy of fetal echocardiography does not lend support to its routine use among unselected and low risk populations during the second trimester to detect congenital heart disease.