An estimated percentage of maternal Listeria infections that result in abortions, stillbirths, or fatal neonatal diseases is:

• A. 5-10%
• B. 15-30%
• C. 50%
• D. 0%

Answer: (B)

Maternal infection with Listeria can cross the placenta and infect the fetus, leading to miscarriage, stillbirth, or severe neonatal illness. Yet many infections in pregnant women are mild or asymptomatic and do not involve the fetus, so the fetal outcomes occur in only a portion of cases. The estimate falls in the range of about 15 to 30 percent, reflecting that a noticeable minority of maternal infections result in these serious fetal consequences while most do not. This level of risk helps explain why Listeria in pregnancy is taken seriously and why timely diagnosis and treatment are important, especially since the risk can vary with the stage of pregnancy.