Pilalis 2012.

Study characteristics
Patient Sampling	Study design: retrospective observational study Recruitment: hospital records of pregnant women who attended the study centre for prenatal care were reviewed Study start and end date: not reported
Patient characteristics and setting	Setting: private maternity hospital (Leto Maternity Hospital) Region(s) and country/countries from which participants were recruited: Athens, Greece Sample size: 3889 Study eligibility criteria: pregnant women with a viable singleton pregnancy who completed the two‐step ultrasound screening protocol, who delivered at the study centre and with a known pregnancy outcome were included Number of participants with the target condition: 48 Population type: unselected Prior testing: nuchal translucency measurement at the time of the first‐trimester scan
Index tests	Type: two‐stage screening First‐trimester scan: Timing (weeks and days gestation): 11 to 14 weeks’ gestation Ultrasound scanning protocol: detailed Cardiac screening: not routinely examined Mode of examination: primary transabdominal, transvaginal if necessary Single or multiple operators: multiple Staff qualification and/or operator experience level: certified by the Fetal Medicine Foundation, with more than 2 years of experience Second‐trimester scan: Timing: 20 to 24 weeks’ gestation Ultrasound scanning protocol: detailed Cardiac screening: extended Mode of examination: not reported Single or multiple operators: multiple Staff qualification and/or operator experience level: certified by the Fetal Medicine Foundation, with more than 2 years of experience
Target condition and reference standard(s)	Target condition(s): major fetal structural anomalies Definitions used for major and minor congenital abnormalities: major anomalies were defined as requiring medical and/or surgical treatment or causing mental handicap Reference standard (live birth): all neonates were examined by a paediatrician. Pregnancy outcomes were obtained from hospital records and contact with obstetricians. Reference standard (fetal or neonatal demise): not reported Postnatal follow‐up duration: until neonatal examination (up to 48 hours after birth)
Flow and timing	Eligible patients: 3902 Exclusions (study investigator): none reported Exclusions (review team): 13 (1 soft marker for chromosomal abnormalities, 10 abnormal karyotype, 1 anomaly considered not detectable by prenatal ultrasound, 1 non‐structural anomaly)
Comparative
Notes	Funding source: the authors reported no conflicts of interest. The funding source for this work was not specified.
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Unclear
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	No
Could the selection of patients have introduced bias?		High risk
Are there concerns that the included patients and setting do not match the review question?			Unclear
DOMAIN 2: Index Test (First‐trimester scan)
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
Could the conduct or interpretation of the index test have introduced bias?		Low risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			High
DOMAIN 2: Index Test (First + second‐trimester scan)
Were the index test results interpreted without knowledge of the results of the reference standard?	Yes
If a threshold was used, was it pre‐specified?	Yes
Could the conduct or interpretation of the index test have introduced bias?		Low risk
Are there concerns that the index test, its conduct, or interpretation differ from the review question?			Low concern
DOMAIN 2: Index Test (Single second‐trimester scan)
DOMAIN 3: Reference Standard
Is the reference standard likely to correctly classify anomalies that are externally visible, present with clinically relevant symptoms shortly after birth, or that are considered to be lethal/incompatible with life?	Yes
Is the reference standard likely to correctly classify anomalies that may present after discharge from postnatal care?	No
Were the reference standard results interpreted without knowledge of the results of the index test?	No
Could the reference standard, its conduct, or its interpretation have introduced bias?		High risk
Are there concerns that the target condition as defined by the reference standard does not match the question?			Low concern
DOMAIN 4: Flow and Timing
Did all live‐born infants receive a reference standard?	Yes
Did all live‐born infants receive the same reference standard?	No
Did all cases of fetal or perinatal loss receive the reference standard (including termination of pregnancy, intra‐uterine death, stillbirth, perinatal mortality)?	Unclear
Were all patients included in the analysis?	Yes
Could the patient flow have introduced bias?		Unclear risk