Signalling question ↓	Signalling question ↓	Signalling question ↓	Risk of bias ↓	Applicability ↓
Domain 1. Patient selection
Was a consecutive or random sample of patients enrolled?	Was a case‐control design avoided?	Did the study avoid inappropriate exclusions?	Could the selection of patients have introduced bias?	Are there any concerns that the included patients may not represent an unselected or low‐risk population?
“Yes” if patients were enrolled consecutively, if all eligible patients were enrolled, or if a random sample of patients were enrolled in the study. “No” if patients were selected from those eligible. “Unclear” if patient selection was not clear from the report	“Yes” if a case‐control study design was avoided. “No” if a case‐control study design was used. “Unclear” if the study design could not be determined based on the report.	“Yes” if the study avoided inappropriate exclusions (e.g. only excluding multiple pregnancies, high‐risk pregnancies, aneuploid fetuses). “No” if participants were excluded inappropriately (e.g. based on expected difficulties in visualising fetal structures). “Unclear” if appropriateness of exclusion from the study could not be derived from the report.	“Low risk” if all signalling questions were answered with “yes”. “High” or “unclear risk” if “no” or “unclear” was answered to one or more of the signalling questions.	“Low concern” if the sample of included patients represented an unselected or low‐risk population. “High concern” if the sample of women represent a selected or high‐risk population. “Unclear concern” if patient selection methods may or may not have resulted in a patient population that differs from our review question, or if insufficient information was available.
Domain 2. Index test
Were index test results interpreted without knowledge of the results of the reference standard?	If a threshold was used, was it prespecified?		Could the conduct or interpretation of the index test have introduced bias?	Are there concerns that the index test, its conduct, or its interpretation differ from the review question?
“Yes” if the ultrasound results were interpreted without knowledge of the pregnancy or postnatal outcome. “No” if the ultrasound results were interpreted with knowledge of the pregnancy or postnatal outcome. “Unclear” if this was not clear from the report.	“Yes” if criteria for a positive test were prespecified. “No” if the criteria for a positive test were not prespecified. “Unclear” if this was not clear from the report.		“Low risk” if all signalling questions were answered with “yes”. “High” or “unclear risk” if “no” or “unclear” was answered to one or more of the signalling questions.	“Low concern” if the aim of the ultrasound scan included evaluation of fetal anatomy to screen for structural anomalies. “High concern” if the primary purpose of the ultrasound scan differs from our review question. “Unclear concern” if insufficient information was available.
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?	Is the reference standard likely to correctly classify anomalies that may present after discharge from postnatal care?	Were the reference standard results interpreted without knowledge of the results of the index test?	Could the reference standard, its conduct, or interpretation have introduced bias?	Are there concerns that the target condition as defined by the reference standard does not match the review question?
“Yes” if an acceptable reference standard was used (e.g. postnatal examination, postnatal follow‐up, postmortem examination). “No” if no acceptable reference standard was used. “Unclear” if this was not clear from the report.	“Yes” if the reference standard (e.g. postnatal follow‐up) is likely to detect cases presenting after discharge from postnatal care. “No” if the reference standard is unlikely to detect cases presenting after discharge from postnatal care. “Unclear” if this was not clear from the report.	“Yes” if the diagnosis of presence or absence of structural abnormalities was made without the knowledge of the results of the ultrasound scan. “No” if the diagnosis of the presence or absence of structural abnormalities was made with knowledge of the ultrasound scan. “Unclear” if this was not clear from the report.	“Low risk” if all signalling questions were answered with “yes”. “High” or “unclear risk” if “no” or “unclear” was answered to one or more of the signalling questions.	“Low concern” if an acceptable reference standard was used and was interpreted without knowledge of the index test results. “High concern” if no reference standard was used or if the reference standard was used with knowledge of the index test results. “Unclear concern” if insufficient information was available.
Domain 4. Flow and timing
Did all live‐born infants receive a reference standard?	Did all live‐born infants receive the same reference standard?	Did all cases of fetal or perinatal loss receive the reference standard (including miscarriage, termination of pregnancy, intra‐uterine death, still birth, perinatal mortality)?	Were all patients included in the analysis?	Could the patient flow have introduced bias?
“Yes” if all live‐born infants received a reference standard. “No” if not all live‐born infants received a reference standard. “Unclear” if this was not clear from the report.	“Yes” if all live‐born infants received the same reference standard. “No” if not all live‐born infants received the same reference standard. “Unclear” if this was not clear from the report.	“Yes” if all cases of fetal or perinatal loss received the reference standard. “No” if not all cases of fetal or perinatal loss received the reference standard. “Unclear” if this was not clear from the report.	“Yes” if all patients recruited to participate in the study were included in the final analysis. “No” if not all participants were included in the final analysis. “Unclear” if this was not clear from the report.	“Low risk” if all signalling questions were answered with “yes”. “High” or “unclear risk” if “no” or “unclear” was answered to one or more of the signalling questions.