However, pregnant women are more likely to become infected with listeria, and it sometimes causes miscarriage, stillbirth, or infections in the baby after birth.

http://www.patient.co.uk/health/planning-to-become-pregnant

Food which may have high levels of listeria. This germ (bacterium) does not usually cause problems in people who are not pregnant. However, pregnant women are more likely to become infected with listeria, and it sometimes causes miscarriage, stillbirth, or infections in the baby after birth.