Little Evidence for Vertical COVID-19 Transmission Across the Human Placental Barrier

3D Illustration of Fetus (Baby) in Womb Anatomy
Study authors quantified SARS-CoV-2 viral load in maternal and neonatal biofluids, tranplacental movement of anti-SARS-CoV-2 antibody, and incidence of fetoplacental infection.

No evidence for vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) between mother and fetus was found from a cohort study published in JAMA Network Open.

Pregnant women (N=127) who tested for coronavirus disease 2019 (COVID-19) by nasopharyngeal swab at 3 centers in Boston, Massachusetts, were recruited. Study authors obtained biopsies of lung and placenta tissues, and assessed viral load and antibody quantification. Data were compared with nonpregnant women (n=11) hospitalized with SARS-CoV-2 infection.

Pregnant women who were positive for COVID-19 (n=64) had lower gestational weight gain (P =.007), were younger (P =.02), had higher incidence of thyroid disease (P =.02), and higher BMI (P =.04). Of the women with a positive COVID-19 diagnosis, 36% were asymptomatic; they presented with either mild (34%), severe (16%), moderate (11%), or critical (3%) symptoms, and were diagnosed during the third (86%) or second (14%) trimester.

Detectable viral load was associated with disease severity (mild: 11% vs severe: 32%; P =.04), white blood cell count (P <.001), C-reactive protein concentration (P =.003), and alanine aminotransferase concentration (P =.004).

Viral load was not significantly different between pregnant and nonpregnant women (P =.31). No evidence of SARS-CoV-2 viremia were detected in umbilical cord blood from 62 mother-neonate dyads with infection and 45 mother-neonate dyads without infection.

Among pregnant mothers positive for SARS-CoV-2, 70% had anti-nucleocapsid immunoglobulin (Ig)G and 65% had anti-receptor binding domain (RBD) IgG (P <.001) antibodies. Samples from their umbilical cords detected anti-RBD IgG (62%) and anti-nucleocapsid IgG (59%) antibodies.

Compared with influenza, COVID-19 antibody transfer appeared to be reduced for anti-RBD IgG (P <.001) and anti-nucleocapsid IgG (P <.001).

Among placentas, no evidence for SARS-CoV-2 infection was observed despite maternal exposure. Maternal vascular malperfusion was observed among 36% of placentas from positive mothers and 18% from negative mothers. Stratified by disease severity, malperfusion lesions increased with SARS-CoV-2 symptom severity (odds ratio [OR], 2.09; 95% CI, 1.11-3.97; P =.02).

This study may have been limited by recruiting more women scheduled for cesarean section, as these procedures were pre-scheduled during the daytime when recruitment occurred.

This study found little evidence of vertical transmission of mother-neonate SARS-CoV-2 dyads and a low transfer rate of SARS-CoV-2 antibodies.

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.


Edlow A G, Li J Z, Collier A-R Y, et al. Assessment of Maternal and Neonatal SARS-CoV-2 Viral Load, Transplacental Antibody Transfer, and Placental Pathology in Pregnancies During the COVID-19 Pandemic. JAMA Netw Open. 2020;3(12):e2030455. doi:10.1001/jamanetworkopen.2020.30455.