Table 1.
Study characteristics and quality based on the risk of bias assessment Newcastle‐Ottawa scale
| Author, country | Single vs multicenter | Design | Number of patients/pregnancies | Inclusion criteria | Risk of bias assessment (NOS)a |
||||
|---|---|---|---|---|---|---|---|---|---|
Selection 
|
Comparability 
|
Outcome 
|
Total/8 | Risk of bias: 1‐3: high 4‐6: moderate 7‐8: low | |||||
| COVID‐19 (Pregnant) | |||||||||
| National cohort study using the UK Obstetric Surveillance System (UKOSS)4 United Kingdom |
Multicenter | Prospective Cohort | 427 | COVID‐19 | |
‐ |  |
5 | Moderate |
| Ferrazzi57 Italy |
Single | Retrospective cohort | 42 | COVID‐19 | |
‐ | |
6 | Moderate |
| Breslin6 Unites States |
Single | Retrospective cohort | 43 | COVID‐19 | |
|
|
7 | Low |
| Qiancheng58 China |
Single | Retrospective cohort | 24 | COVID‐19 | |
|
|
7 | Low |
| Pierce‐Williams19 United States |
Multicenter | Retrospective cohort | 64 | COVID‐19 | |
|
|
7 | Low |
| Yan59 China |
Multicenter | Retrospective cohort | 116 | COVID‐19 | |
|
|
7 | Low |
| Collin60 Sweden |
Multicenter | Retrospective cohort | 53 | COVID‐19 | |
|
|
7 | Low |
| Ellington18 United States |
Multicenter | Retrospective cohort | 91 412 | COVID‐19 | |
‐ | |
6 | Moderate |
| Pereira61 Spain |
Single | Retrospective cohort | 60 | COVID‐19 | |
‐ | |
5 | Moderate |
| Sentilhes62 France |
Single | Retrospective cohort | 54 | COVID‐19 | |
‐ | |
5 | Moderate |
| Nayak63 India |
Single | Retrospective cohort | 977 | COVID‐19 | |
|
|
7 | Low |
| COVID‐19 coagulopathy (non‐pregnant) | |||||||||
| Tang30 China |
Single | Prospective cohort | 183 | COVID‐19 | |
‐ | |
5 | Moderate |
| Klok64 Netherlands |
Multicenter | Prospective cohort | 184 | COVID‐19 | |
‐ | |
4 | Moderate |
| Middeldorp65 Netherlands |
Single | Prospective cohort | 198 | COVID‐19 | |
|
|
6 | Moderate |
| Tang66 China |
Single | Retrospective cohort | 449 | COVID‐19 | |
|
|
4 | Moderate |
| Fogarty67 Ireland |
Single | Retrospective cohort | 83 | COVID‐19 | |
‐ | |
6 | Moderate |
| Panigada68 Italy |
Single | Prospective cohort | 24 | COVID‐19 | |
‐ | ‐ | 2 | High |
| Llitjos69 France |
Single | Retrospective cohort | 26 | COVID‐19 | |
‐ | ‐ | 2 | High |
| Cui70 China |
Single | Retrospective cohort | 81 | COVID‐19 | |
‐ | |
3 | High |
| Helms71 France |
Multicenter | Prospective cohort | 150 | COVID‐19 | |
|
|
6 | Moderate |
| Ranucci72 Italy |
Single | Retrospective cohort | 16 | COVID‐19 | |
‐ | |
3 | High |
| Poissy73 France |
Single | Retrospective cohort | 107 | COVID‐19 | |
‐ | |
3 | High |
| Spiezia74 Italy |
Single | Prospective cohort | 22 | COVID‐19 | |
|
3 | High | |
| Lodigiani75 Italy |
Single | Retrospective cohort | 388 | COVID‐19 | |
‐ | |
5 | Moderate |
| Stoneham76 United Kingdom |
Single | Retrospective cohort | 274 | COVID‐19 | |
|
|
7 | Low |
| Longchamp77 Switzerland |
Single | Retrospective cohort | 25 | COVID‐19 | |
‐ | |
4 | Moderate |
| Ren78 China |
Multicenter | Retrospectivecohort | 48 | COVID‐19 | |
‐ | |
4 | Moderate |
| Al‐Samkari79 United States |
Multicenter | Retrospective cohort | 400 | COVID‐19 | |
‐ | |
4 | Moderate |
| Hippensteel80 United States |
Single | Retrospective cohort | 106 | COVID‐19 | |
‐ | |
4 | Moderate |
| Fraissé81 France |
Single | Retrospective cohort | 92 | COVID‐19 | |
‐ | |
4 | Moderate |
| Santoliquido82 Italy |
Single | Retrospective cohort | 84 | COVID‐19 | |
‐ | |
4 | Moderate |
| Rieder83 Germany |
Single | Prospective cohort | 190 | COVID‐19 | |
|
|
7 | Low |
| Pavoni84 Italy |
Single | Retrospective cohort | 40 | COVID‐19 | |
‐ | |
6 | Moderate |
| Nougier85 France |
Single | Retrospective cohort | 78 | COVID‐19 | |
|
|
7 | Low |
| COVID‐19 coagulopathy (pregnant) | |||||||||
| Vlachodimitropoulou8 Canada |
Single | Case report | 2 | |
|
|
|
6 | Moderate |
| Martinelli27 Italy |
Single | Case report | 1 | |
|
|
|
4 | Moderate |
| Mohammadi29 Iran |
Single | Case report | 1` | |
|
|
|
4 | Moderate |
| Ahmed28 United Kingdom |
Single | Case Report | 1 | |
|
|
|
6 | Moderate |
Abbreviation:
NOS, Newcastle Ottawa scale.
a
The number of stars is the standard assessment method used in this scale. The maximum number of stars a study could be awarded was 8 and studies receiving more than 6, 4–6, and <4 stars were considered to be at low, intermediate, and high risk of bias, respectively.