SARS-CoV-2 and the role of vertical transmission from infected pregnant women to their fetuses: systematic review
Bibliographic record
Abstract
Background Vertical transmission of SARS-CoV-2 has been reported but appears uncommon. Objectives This study systematically reviewed the evidence on vertical transmission of SARS-CoV-2 from pregnant women to their neonates. Search strategy Literature searches in WHO Covid-19 Database, LitCovid, medRxiv, and Google Scholar for SARS-CoV-2 using keywords and associated synonyms, search date to 20 December 2020; no language restrictions. Selection criteria Studies of any design reporting transmission. Data collection and analysis Two reviewers independently assessed article eligibility and extracted data. Results were reported descriptively; no meta-analyses were possible. Main results 106 studies were included: 40 reviews and 66 primary studies, most conducted in hospitals. 32 case reports were assessed as high risk of bias, due to the study design; across the 34 remaining primary studies, risk of bias was low to moderate. Sixteen case reports described vertical transmission. In cohort studies and case series, 65/2391 (2.7%) neonates born to mothers with a COVID-19 diagnosis tested positive for SARS-CoV-2 within 24 hours of birth; the proportion of positive neonates ranged from 0% to 22%. Twenty studies reported no vertical transmission. Maternal symptomatology and mode of delivery were not correlated with vertical transmission. 7/25 studies of placental tissue identified SARS-CoV-2; vertical transmission was infrequent. No study reported the results of viral culture to detect SARS-CoV-2. Conclusions These findings indicate that vertical transmission is possible, but not frequent. Further high-quality studies are needed to understand vertical transmission. Funding World Health Organization: WHO registration No 2020/1077093.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".