Table 1.

Summary table of the principle to distinguish the two main SARS-CoV-2 vertical transmission routes, according to the WHO definition [4].

	Maternal Infection	Evidence of in utero exposure	Viral persistence or immune response*
In utero	Yes	Yes	Yes
Intrapartum	Yes*	No	Yes

Note:

1. Maternal infection must be diagnosed according to standard WHO criteria. Maternal infection is intended to have occurred anytime during the pregnancy for in utero and in the time window from 30 days before to 2 days after the delivery, for intra partum transmission.

2. Evidence of in utero exposure is granted with several possible (virological, pathological or immunological) tests performed on placenta, amniotic fluid or cord blood. Viral persistence or immune response in the neonate is demonstrated with RT-PCR performed on several possible sites or with serology assay at different timepoints.

3. Both types of infection are classified in three level of likelihood (confirmed, possible and unlikely) according to the type of specimen and test used. The policy we suggest in the main text is compliant with this WHO guidance.

4. *For the diagnosis of in utero transmission with fetal demise, the viral persistence or immune response is replaced by the fetal tissue positivity (that might be associated with placenta or amniotic fluid positivity) obtained with RT-PCR or several possible pathology/immunology techniques.

5. More details regarding sampling, tests and their timing are freely available in the WHO definition for perinatal SARS-CoV-2 infections [4].