Published online by Cambridge University Press: 05 September 2014
Overview of congenital infections with description of the most frequent conditions
Definition
Congenital infections are infections of the fetus or neonate that occur during pregnancy, during delivery (intrapartum), or in the immediate postnatal period. The infection may be due to ascending infection from the vagina causing chorioamnionitis, maternal fever, and leukocytosis. The infection may be due to blood spread from the mother via the chorionic villi of the placenta to the fetus, or may be due to pre-existing endometritis spreading through the membranes at 20 weeks gestation when the amniotic sac fills the uterine cavity and fuses with the endometrium.
Macroscopic features
Both the fetus and the placenta contribute to the final diagnosis. Measurements of the fetus provide a baseline for detection of abnormalities that may guide the diagnosis. The foot length provides an accurate assessment of gestational age even in the macerated and hydropic fetus; the head circumference should approximate the crown–rump length [1]. A discrepancy of greater than 20 mm suggests the presence of hydrocephalus or microcephaly in a fetus with congenital infection. A babygram (X-ray of the fetus) provides information about the skeletal system, which is frequently abnormal in congenital infections (see Chapter 18). Typical features are seen in congenital syphilis (metaphysitis) and in congenital rubella (celery stalk pattern). A babygram also shows the presence of hydrops and calcification deposited in necrotic tissue. Hydrops is a characteristic feature of congenital infection due to maternal blood spread (see also Chapter 5).
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