Analysis of SARS-CoV-2 vertical transmission during pregnancy

Abstract

The impact of SARS-CoV-2 infection during gestation remains unclear. Here, we analyse the viral genome on maternal and newborns nasopharyngeal swabs, vaginal swabs, maternal and umbilical cord plasma, placenta and umbilical cord biopsies, amniotic fluids and milk from 31 mothers with SARS-CoV-2 infection. In addition, we also test specific anti-SARS-CoV-2 antibodies and expression of genes involved in inflammatory responses in placentas, and in maternal and umbilical cord plasma. We detect SARS-CoV-2 genome in one umbilical cord blood and in two at-term placentas, in one vaginal mucosa and in one milk specimen. Furthermore, we report the presence of specific anti-SARS-CoV-2 IgM and IgG antibodies in one umbilical cord blood and in one milk specimen. Finally, in the three documented cases of vertical transmission, SARS-CoV-2 infection was accompanied by a strong inflammatory response. Together, these data support the hypothesis that in utero SARS-CoV-2 vertical transmission, while low, is possible. These results might help defining proper obstetric management of COVID-19 pregnant women, or putative indications for mode and timing of delivery.

Fig. 1. mRNA expression of proinflammatory genes is altered in the placentas from SARS-CoV-2-positive subjects.

An 84-gene real-time PCR array was performed on placenta biopsies from subject nos. 31, 25 and 17. The results are shown as a ratio of each SARS-CoV-2-positive subject compared to a SARS-CoV-2-negative subject (CTR−). Gene expression (nfold) is shown as a colour scale from light to dark blue. Only targets showing at least >2-fold modulation are shown in the table.

Fig. 2. Secretion of proinflammatory proteins is altered in the plasma from SARS-CoV-2 -positive subjects.

A 27 cytokine/chemokine multiplex array was performed on a maternal and b umbilical plasma from subject nos. 31, 25 and 17. As reference, a SARS-CoV-2-negative plasma is shown (CTR−) (n = 4 independent analysed plasma). Protein concentration is shown as pg/ml.