Study type
All observational studies, including cross-sectional studies, cohort, case-control, case reports, and case series that were published in peer reviewed journals until the end of March 2020 will be reviewed. Editorials, commentaries and letter to editors will be excluded from the review. Articles in any language will be included.
Type of participants
The inclusion criteria for the studies include:
- Human studies
- Studies that include adult women over the age of 18 years old
- Women should have given birth to live child in the past 3 months
- Women should be tested positive for COVID–19
Type of exposure
The exposure in the studies will be infection with SARS-COV2 virus documented by positive COVID–19 RT-PCR (12). The sensitivity for RT-PCR in detecting COVID–19 infection was previously reported to be range between 95% and 100% (13, 14). All subjects that have at least two positive RT-PCR results for COVID–19 will be considered as COVID–19 infected. This diagnosis implies for both mothers and newborn infants.
The RT-PCR is not performed routinely for all pregnant mothers, and only those who present clinical signs and symptoms that make them suspicious to COVID–19 infection and have positive radiological findings for COVID–19 infection will be tested using RT PCR.
The RT-PCR is not performed routinely for all pregnant mothers, and only those who present clinical signs and symptoms that make them suspicious to COVID–19 infection and have positive radiological findings for COVID–19 infection will be tested using RT-PCR.
Primary objective
To assess the possibility of vertical transmission of SARS-COV2 virus through mother to child.
Secondary objective
- To assess the association between time of infection (based on gestational age) and vertical transmission of SARS-COV 2 to new born. In case sufficient case reports are present for the assessment, the relationship between gestational age at time of test positivity and vertical transmission will be analyzed.
- To assess the association between mode of delivery (normal vaginal delivery or caesarean section) and SARS_COV 2 vertical transmission.
- To assess the association between breastfeeding and SARS-COV 2 transmission
The search method used for the study
The international bibliographic databases including PubMed, Embase, and Web of Science as well as Google scholar will be searched to identify eligible studies. The search strategy will be designed based on preferred reporting items for systematic reviews and meta-analysis (PRISMA) checklist. A PRISMA-P checklist for this protocol is shown in Additional File 1. The search terms include the following keywords based on medical subject heading (MeSH) terms along with free text searching in combination with Boolean operations (AND and OR) (Table 1).
Table 1. The keyword search for the study
Keyword
|
Search terms
|
Coronavirus 2019
|
covid 19
covid 19 infection
covid 19 outbreak
covid 19 pneumonia
severe acute respiratory syndrome coronavirus 2
severe acute respiratory syndrome coronavirus infection
severe acute respiratory syndrome coronavirus sars cov
severe acute respiratory syndrome coronaviruses
severe acute respiratory syndrome sars coronavirus
|
Vertical transmission
|
vertical transmission
vertical transmission rate
vertical transmission rates
vertical transmission risk
vertical transmission risks
vertical transmission route
vertical transmission studies
vertical transmission study
vertical transmissions
vertical transovarial transmission
vertical transplacental transmission
|
The primary search will be conducted on PubMed and Embase and the search will be improved based on the search results. The final keywords and search terms will be used in the search in other databases.
Searching other resources
The World Health Organization (WHO) website (www.who.int) will be searched for the keywords. Furthermore, the reference list of the identified studies will also be checked manually for similar studies and these studies will also be included in the review.
Data collection
Study selection
The Zotero reference manager (https://www.zotero.org/) will be used to merge the identified studies and remove duplicate publications as well as screening the titles and abstracts. The identified studies will be assessed by two authors independently based on title and abstracts. The articles that meet the inclusion criteria will be selected for the review. In case of discrepancies, a third reviewer will be asked to judge whether to include or exclude the study. In the next step the full text of the studies will be reviewed by the authors.
Data extraction
All authors will contribute in data extraction from identified studies. Extracted data will be summarized in a checklist which is designed by the authors of this review. Based on this checklist, the following data will be extracted:
- General characteristics of the study (author names, title, publication date, and review date)
- Type of the study
- Sample size
- Study subject characteristics (demographic characteristics, predisposing conditions, gestational age)
- Outcome measures and analyses (diagnostic test used, number of positive samples)
- Study findings
Quality assessment of the studies
The quality of the identified studies will be assessed by two authors independently. As the studies in this review include cross-sectional studies, cohort, case-control, case reports, and case series, the quality assessment will be performed using the risk of bias assessment software by Cochrane Collaboration, review manager (revMAn).
Data analysis
Heterogeneity among studies will be assessed by DerSimonian & Laird Q test and I2 statistic which is the proportion of total variation due to between-studies heterogeneity. To calculate the pooled prevalence estimate of vertical transmission and corresponding 95% confidence intervals (CIs), we will use the Metaprop (15). a Stata-based command developed for binominal data.
To combine Risk ratio in cohort studies and odds ratio in case control studies for assessing the association of gestational age for acquiring the infected in mothers, delivery mode and breastfeeding with vertical transmission of COVID–19, we will apply random effects model in case of heterogeneity among studies. Otherwise, fixed effects model will be used. The Begg’s rank correlation and the Egger weighted regression methods will be used to statistically assess the publication bias. We will also visually assess the publication bias using funnel plot. P-value<0.05 will be considered statistically significant in all tests. Stata version 12 (Stata Corp, College Station, Texas) will be used for all statistical analyses.