Congenital infections affect the unborn fetus or new-born infant. They are generally caused by viruses that may be picked up by the baby at any time during the pregnancy up through the time of delivery. The viruses initially infect the mother who subsequently may pass it to the baby either directly through the placenta or at the time of delivery as the baby passes through the birth canal. Mothers generally do not feel sick with the viruses. Sometimes they have flu-like symptoms. Even if the mother is known to have a viral illness during her pregnancy, her immune system may prevent the virus from infecting the fetus or newborn infant. The more common viruses linked to congenital infections include the Cytomegalovirus (CMV), Herpes, Rubella (German measles), Parvovirus, Varicella (chickenpox), and Enteroviruses.

This can be very difficult initially. Most congenital infections in the fetus and newborn baby are totally silent and asymptomatic. However, some may be serious and cause profound damage to the body resulting in birth defects or even death. Even if the infection is silent initially, it can quietly and slowly damage the body, causing medical and developmental problems that only show up months or even years later. Diagnosis of a congenital infection can sometimes be made by the obstetrician or pediatrician based upon the mother’s symptoms, the baby’s physical findings before (by ultrasound) or after birth, as well as by blood tests on both mother and baby. Sometimes, in spite of a complicated medical workup, a congenital infection cannot be proven.

About 1.5 per 1000 women giving birth in the United States are infected with the human immunodeficiency virus. Mother-to-infant human immunodeficiency virus transmission rates in the United States are about 30% on average. Intrapartum exposure to infected maternal blood and genital secretions seems to be the most important route for perinatal human immunodeficiency virus acquisition. A first-born twin is at higher risk of infection compared with the second-born twin. Multiple human immunodeficiency virus variants exist in infected mothers, but only small subsets are transmitted to their infants. Primary maternal cytomegalovirus infection is associated with symptomatic congenital infection and significant residual neurodevelopmental abnormalities. Canciclovir has been used to treat a few infants with symptomatic congenital cytomegalovirus infections, but the benefits have been marginal. A third of asymptomatic women shedding herpes simplex virus at delivery have evidence of recent primary infections and their infants are 10 times more likely to develop neonatal herpes.

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Sophie Kate
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Microbiology: Current Research
Email: aamcr@alliedacademies.org