Bardi 2022.

Study characteristics
Patient Sampling	Study design: population‐based retrospective cohort study based on data from the European Registration of Congenital Anomalies and Twins Northern Netherlands (EUROCAT‐NNL) database Recruitment: all cases of live births, fetal deaths and terminated pregnancies with congenital anomalies in the region are registered in the database after parental consent Study start and end date: January 2010 to December 2019
Patient characteristics and setting	Setting: regional congenital anomaly registry Region(s) and country/countries from which participants were recruited: the 3 northern provinces of the Netherlands (Groningen, Friesland and Drenthe) Sample size: 139,630 (based on approximate number of births during the study period in the covered region) Study eligibility criteria: all cases of fetuses and children with congenital anomalies are registered in the database. There is no lower limit for gestational age and data are continuously updated in the register until the completed 10th year of age of the child. Only when parents actively refuse registration are cases excluded. Number of participants with the target condition: 377 Population type: unselected population Prior testing: combined test (2007 onwards); non‐invasive prenatal testing (2017 onwards)
Index tests	Type: single‐stage screening Second‐trimester scan: Timing: second trimester Ultrasound scanning protocol: not reported Cardiac screening: not reported Mode of examination: not reported Single or multiple operators: multiple Staff qualification and/or operator experience level: not reported
Target condition and reference standard(s)	Target condition(s): selected major fetal structural anomalies; anencephaly, encephalocele, spina bifida, holoprosencephaly, tricuspid/pulmonary valve atresia, hypoplastic left heart, abdominal wall and limb reduction defects, lethal skeletal dysplasia, megacystis, multiple congenital anomalies Definitions used for major and minor congenital abnormalities: EUROCAT classification system Reference standard (live birth): postnatal patient records, pregnancy outcome and delivery reports and cytogenetic laboratory investigations Reference standard (fetal or neonatal demise): cytogenetic laboratory investigations and postmortem examinations Postnatal follow‐up duration: cases are registered and updated until the completed 10th year of the child
Flow and timing	Eligible patients: 155,000 (approximate number of births during the study period in the covered region) Exclusions (study investigator): 15,269 excluded (6.6%/10,230 actively refused registration, 5039 did not meet inclusion criteria) Exclusions (review team): 101 (59 abnormal karyotype; 42 cases of selected anomalies within the larger categories of other single ventricle heart defects and conotruncal anomalies, respectively)
Comparative
Notes	Structural abnormalities detected during the first trimester of pregnancy were included as true positive test results in the 2 x 2 tables of index test 3 Funding source: the authors received no specific funding for this work
Methodological quality
Item	Authors' judgement	Risk of bias	Applicability concerns
DOMAIN 1: Patient Selection
Was a consecutive or random sample of patients enrolled?	Yes
Was a case‐control design avoided?	Yes
Did the study avoid inappropriate exclusions?	Yes
Could the selection of patients have introduced bias?		Low risk
Are there concerns that the included patients and setting do not match the review question?			Low concern
DOMAIN 2: Index Test (First‐trimester scan)
DOMAIN 2: Index Test (First + second‐trimester scan)
DOMAIN 2: Index Test (Single 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 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?	Yes
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?		Low 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