As, according to the testimony of Tradition and of the Church Liturgy (cf.
Feast of the Innocents), young children can also receive blood-Baptism,
blood-Baptism operates not merely ex opere operantis as does Baptism of
desire, but since it is an objective confession of Faith it operates also
quasi ex opere operato. It confers the grace of justification, and when
proper dispositions are present, also the remission of all venial sins and
temporal punishments. St. Augustine says: " It is an affront to a martyr
to pray for him; we should rather recommend ourselves to his prayers "
(Sermo 159 I.) Baptism by blood does not confer the baptismal character.
Cf. S. th. III 66, 11 and 12.
excerpt from:
https://www.ewtn.com/library/DOCTRINE/BAPTISM.TXT