Vertical transmission of COVID-19 rare, meta-analysis shows
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Vertical transmission of COVID-19 is possible but rare, with fewer than 2% of babies born to mothers with COVID-19 testing positive for the virus, according to a meta-analysis published in The BMJ.
“The main thing with the pandemic and SARS-CoV-2 is whenever a mother has an infection, the foremost thing that they worry about is ‘what’s going to happen to my baby?’” Shakila Thangaratinam, PhD, professor of maternal and perinatal health and co-director of the WHO Collaborating Centre for Global Women’s Health at the University of Birmingham, United Kingdom, told Healio. “This is the same question the health care professionals think about ... So, to answer that question, we want to know what proportion of those moms have the infection [and] their babies also test positive.
“The second question is, is it possible for the virus to be transferred from the mom to the baby while the baby is inside the womb, while being delivered or afterward?” said Thangaratinam, who is also lead of the maternal and reproductive health research theme at the University of Birmingham. “The last question is what happens to these babies with infection.”
Data collection
Thangaratinam and colleagues reviewed 472 studies that were available through databases between Dec. 1, 2019, and Aug. 3, 2021, with a total of 28,952 mothers and 18,237 babies.
Their analysis included 206 cohort studies of pregnant and recently pregnant women who went to a hospital for any reason, tested positive for COVID-19 and had data on their child’s SARS-CoV-2 infection status within 30 days after birth. The remaining 266 studies were case series and case reports that were used to assess whether transmission occurred in utero, intrapartum or in the early postnatal period, as well as the likelihood of transmission.
SARS-CoV-2 positivity, outcomes
Of 14,271 babies born to infected mothers, 1.8% (95% CI, 1.2%-2.5%; 140 studies) tested positive for COVID-19 using reverse transcriptase polymerase chain reaction (RT-PCR) tests.
Data on timing of exposure and type and timing of tests were available for 592 babies born to COVID-19-positive mothers, 14 of whom had confirmed mother-to-child transmission based on WHO classification. These included four live births with in utero transmission, three fetal deaths or miscarriages with in utero transmission, two intrapartum transmissions and five early postnatal exposures.
Data on outcomes were available for 800 babies who tested positive for SARS-CoV-2. Among those who were not alive at the end of follow-up, there were 20 stillbirths, 23 neonatal deaths and eight early pregnancy losses.
Maternal characteristics associated with babies testing positive for SARS-CoV-2 were severe COVID-19 (OR = 2.36; 95% CI, 1.28-4.36; 22 studies), death (OR = 14.09; 95% CI, 4.14-47.97; seven studies), admission to an ICU (OR = 3.46; 95% CI, 1.74-6.91; 19 studies) and postnatal infection (OR = 4.99; 95% CI, 1.24-20.13; 12 studies).
“The clinical implications are if mom has got severe COVID-19, then the baby is more likely to test positive, so I think we [as clinicians] need to keep a closer eye on the babies who are born to mothers with severe COVID-19 needing admission to the hospital,” Thangaratinam said.
She also advised that practices such as breastfeeding and mother-baby separation should not be changed due to COVID-19 transmission concerns.
Moving forward, Thangaratinam suggested future studies should focus on determining the proportion of babies who are infected with SARS-CoV-2 in utero, as well as producing more and higher quality data.
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