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CONGENITAL INFECTIONS

BACKGROUND

Congenital infections acquired in utero are a significant cause of neonatal mortality and childhood morbidity. The original concept of the TORCH acronym was to group five infections with similar presentations: toxoplasmosis, “other” (traditionally referring to syphilis), rubella, cytomegalovirus (CMV), and herpesvirus. However, recent additions have expanded the scope of this term to include infections such as human immunodeficiency virus (HIV), enteroviruses, parvovirus B19, and varicella. The incidence of TORCH infections in the United States is variable, ranging from 0.7% for CMV, the most common congenital viral infection, to ≤1 in 10,000 for rare infections such as rubella and toxoplasmosis. A high index of suspicion for congenital infection and awareness of the prominent features of the most common etiologies will help to facilitate early diagnosis and management.

Pathophysiology

Transplacental spread and invasion of the bloodstream after maternal infection is the primary route for intrauterine infection, though it is also possible for the fetus to be infected by extension from adjacent infections of the peritoneum and the genitalia during the birth process or during invasive procedures such as fetal monitoring and intrauterine transfusion.1

In order for the maternal immune system to tolerate pregnancy, the placenta serves as a protective barrier that shields the fetus from maternal humoral and cell-mediated immune activity. Without immunologic mechanisms necessary to eradicate an infecting organism, the fetus is susceptible to infection, and a state of immunologic tolerance is often established. The fetus is particularly vulnerable during the first trimester of pregnancy, when the most complex events in embryogenesis occur, including development of sensory organs such as the eyes and ears.

The outcome of fetal infection depends on several factors, including gestational age at the time of infection, organism virulence, degree of associated placental damage, and maternal disease severity.1 Primary infection is also likely to have more significant effects on the fetus than recurrent infection. Infection during the first few weeks of gestation may cause embryonal death and resorption, prior to recognition of pregnancy. Spontaneous abortion and stillbirth are among the earliest recognizable effects of fetal infection after 6 to 8 weeks of pregnancy. In infants who are live-born, effects of fetal infection may present as preterm birth, intrauterine growth restriction (IUGR), congenital anomalies, or local or systemic signs of infection. Alternatively, fetal infection may present in live-born infants as the complete absence of any clinical signs of disease, with abnormalities becoming obvious only as the child develops and fails to reach appropriate physiologic or developmental milestones.

CLINICAL PRESENTATION

Intrauterine infection with CMV, herpes simplex virus (HSV), syphilis, rubella, toxoplasmosis, and enterovirus may present in the neonatal period with signs of widely disseminated disease caused by microbial invasion and proliferation over weeks or months prior to delivery.1 In such infants it can be difficult to determine whether infection was acquired in utero, ...

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