In contrast to the rather strong evidence for increased
severity
of
certain
infections
among
pregnant
women,
the
evidence
regarding
initial
susceptibility
is
weaker.
The
evidence
for
increased
susceptibility
during
pregnancy
is
most
credible
for
infections
with
organisms
such
as
P.
f
al c i par um
and Listeria monocytogenes, both of which have
tropism for the placenta; evidence is more limited
for
human
immunodeficiency
virus
type
1
infection
(Table
1).