A congenital infection is an infection present in a baby at birth, acquired from the mother during pregnancy or delivery. These infections occur when pathogens, such as viruses, bacteria, or parasites, are transmitted from an infected mother to her developing fetus or newborn. Unlike infections acquired after birth, congenital infections can have unique implications due to the vulnerability of the developing systems.
How Infections Reach the Fetus
Infections can reach a fetus through several pathways, primarily vertical transmission from the mother. The most common route for congenital infections is transplacental, also known as in utero transmission. This occurs when pathogens circulating in the mother’s bloodstream cross the placenta.
Infections can also be acquired by the baby as it passes through the birth canal during delivery, a process known as perinatal transmission. This direct contact allows pathogens present in the mother’s birth canal to infect the baby. The timing of maternal infection during pregnancy can influence the severity of the outcome, with infections acquired earlier in gestation often leading to more serious effects.
Key Infectious Agents
A common grouping of pathogens responsible for congenital infections is often referred to by the acronym TORCH. This acronym traditionally stands for Toxoplasmosis, Other (including Syphilis, Varicella-Zoster, Parvovirus B19, and Zika), Rubella, Cytomegalovirus, and Herpes Simplex Virus.
Toxoplasmosis is caused by the parasite Toxoplasma gondii, which can be acquired by the mother through consuming undercooked meat or contact with contaminated cat feces. The parasite can cross the placenta and infect the fetus. Rubella, also known as German measles, is a viral infection that spreads through respiratory droplets. The rubella virus can be transmitted transplacentally, potentially causing significant developmental issues.
Cytomegalovirus (CMV) is a common virus related to the herpes family, and it is the most frequent congenital viral infection worldwide. CMV can be transmitted transplacentally, and while many infected newborns show no symptoms at birth, the virus can still cause long-term problems. Herpes Simplex Virus (HSV) can be transmitted to the infant during passage through an infected maternal genital tract during birth. Syphilis, caused by the bacterium Treponema pallidum, can pass from an infected mother to her baby during pregnancy, leading to congenital syphilis if untreated.
The “Other” category in TORCH has expanded to include agents like Varicella-Zoster Virus (VZV), which causes chickenpox, and Parvovirus B19. VZV can lead to congenital varicella syndrome. Parvovirus B19 can also cross the placenta and cause fetal infection. Zika virus, transmitted primarily by mosquitoes, can cause congenital Zika syndrome if infection occurs during pregnancy.
Effects on Newborns
The effects of congenital infections on newborns can vary widely, ranging from asymptomatic presentations to severe, life-threatening conditions. The outcome depends on several factors, including the specific pathogen involved, the timing of the infection during pregnancy, and the overall health of the mother and fetus. Many newborns with congenital infections may initially show no symptoms, but some can develop clinical manifestations later in infancy or childhood.
Severe cases can result in significant birth defects and long-term developmental issues. Congenital CMV is a leading non-hereditary cause of sensorineural hearing loss, which can be present at birth or develop later. Rubella infection during pregnancy can lead to congenital rubella syndrome, characterized by deafness, cataracts, heart defects, and neurological problems. Congenital syphilis, if untreated, can cause problems such as blindness, deafness, bone deformities, and developmental delays.
Zika virus infection during pregnancy can result in microcephaly, a condition where a baby’s head is smaller than expected, along with other brain abnormalities, vision, and hearing problems. The spectrum of effects also includes low birth weight, jaundice, enlarged liver and spleen, skin rashes, and seizures.
Identifying and Preventing Congenital Infections
Identifying congenital infections often involves maternal screening during pregnancy and testing of the newborn. Maternal screening can include blood tests to detect antibodies against specific pathogens, which may indicate a recent or past infection. Fetal imaging, such as ultrasound, can also reveal certain abnormalities that might suggest an infection. After birth, newborn testing typically involves blood tests, urine tests, or examination of cerebrospinal fluid to confirm the presence of an infection.
Prevention strategies for congenital infections are crucial and encompass several key approaches. Vaccination is a highly effective method for preventing certain infections, such as rubella, which is part of the routine MMR vaccine. Women of childbearing age are encouraged to be vaccinated against rubella before pregnancy. Good hygiene practices are also important, including frequent handwashing, especially after changing diapers or contact with young children who may shed viruses like CMV.
Avoiding exposure to certain environments or sick individuals is another preventive measure. For example, to prevent toxoplasmosis, pregnant individuals are advised to avoid undercooked meat and contact with cat feces. Early screening during pregnancy allows for timely detection and, in some cases, intervention to reduce the risk of transmission or to manage potential complications. These proactive measures are important in safeguarding fetal and newborn health.