Table 1 Adapted Newcastle-Ottawa scale[33] for “Prosthetic heart valves in pregnancy: a systematic review and meta-analysis protocol”

Selection

1) Representativeness of the exposed cohort

 a) Population truly representative of pregnant women with prosthetic heart valves

 b) Somewhat representative of the population of pregnant women with prosthetic heart valves

 c) Selected group of users (for example, referral hospital patients)

 d) No description of the derivation of the cohort

2) Selection of the non-exposed cohort^b

 a) Drawn from the same community as the exposed cohort

 b) Drawn from a different source

 c) No description of the derivation of the non-exposed cohort

 d) Not applicable

3) Ascertainment of exposure

 a) Secure record (for example, medical records)

 b) Structured interview

 c) Written self-report

 d) No description

4) Demonstration that outcome of interest was not present at start of study^c

 a) Yes

 b) No

 c) Not applicable

Comparability

Comparability of cohorts on the basis of the design or analysis

 a) Study controls for maternal age (select the most important factor)

 b) Study controls for any additional factor (type of valve, valve location, anticoagulation regimen)

 c) Not applicable

Outcome

1) Assessment of outcome

 a) Independent blind assessment

 b) Record linkage

 c) Self-report

 d) No description

2) Was follow-up long enough for outcomes (as defined by study) to occur?

 a) Yes

 b) No

3) Adequacy of follow up of cohorts

 a) Complete follow up (all subjects accounted for and no missing data)

 b) Subjects lost to follow-up unlikely to introduce bias - small number lost - ≥ 80%

 c) Follow-up rate < 80%

 d) No statement