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 does not appear to be common. This study aims to systematically review the evidence for vertical transmission of SARS-CoV-2. Methods This review is part of an Open Evidence Review on the transmission dynamics of SARS-CoV-2 and the role of intrauterine mother to fetus transmission. Literature searches were performed in the WHO Covid-19 Database, LitCovid, medRxiv, and Google Scholar for SARS-CoV-2 using keywords and associated synonyms, search date up to 20 December 2020, no language restrictions. Results We included 106 studies assessing vertical transmission of SARS-CoV-2 from pregnant women to their neonates: these studies comprised 40 reviews (21 fulfilled systematic review methodology, including risk of bias assessment of included studies) and 66 primary studies including 32 case reports (of up to two cases) and 34 prospective and retrospective cohort studies, prospective and retrospective case series, observational studies (including asymptomatic screening), database studies and a quality improvement project. Almost all were conducted in a hospital setting. The 32 case reports were considered to be at 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 examined vertical transmission, which was not related to maternal symptomatology. For the cohort and case series studies, the percentage of positive neonates ranged from 0% to 22% across the studies. Twenty studies reported no positive vertical transmission. Three studies that reported the highest positivity rates of 11%, 15% and 22% had specifically selected neonates with a positive test (within up to 35 days) within the study population and were therefore more selective populations. Across the cohort and case series studies there were 65/2391 (2.7%) neonates born to mothers with a diagnosis of COVID-19 tested positive for SARS-CoV-2 within 24 hours of birth. No evidence correlated maternal symptomatology to vertical transmission. Mode of delivery did not correlate with rates of vertical transmission. Of 25 studies, 7 identified SARS-CoV-2 in placental tissue; some of these did not demonstrate vertical transmission to the neonate. No study reported the results of viral culture to detect SARS-CoV-2. Conclusions The results of these studies indicate that vertical transmission is possible, but is not frequent, and factors that influence when vertical transmission occurs are unknown. Further studies using standardised methods to establish viral infection are needed to establish vertical transmission rates and to assess clinical and other conditions affecting transmission.
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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 | 0.004 |
| 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".