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Congenital infections are caused by pathogens transmitted from a mother to her offspring during pregnancy or delivery. These infections can cause significant fetal and neonatal morbidity and mortality. The mnemonic “TORCH” is often used to refer to common congenital infections:
T – Toxoplasma
R – Rubella
C – CMV
Congenital toxoplasmosis is caused by the parasite Toxoplasma gondii. It can be acquired when a pregnant woman consumes raw or undercooked meat, or contacts contaminated water, soil, or cat feces (generally from outdoor cats that hunt.) The classic triad of congenital toxoplasmosis is 1) chorioretinitis 2) hydrocephalus and 3) cerebral calcifications.
Symptoms often do not occur until months after birth and may include seizures, cognitive impairment, and cerebellar dysfunction (1). The retinal disease associated with congenital toxoplasmosis is progressive. Other clinical manifestations may include fever, rash, hydrocephalus or microcephaly, sensorineural hearing loss, congenital nephrosis, hematologic abnormalities, hepatosplenomegaly, various endocrinopathies, and myocarditis. Infection can lead to spontaneous abortion, prematurity, stillbirth, and perinatal death.
Congenital toxoplasmosis is more severe when acquired in early pregnancy. The incidence is highest in the Eastern Mediterranean and Africa (2). Rates are estimated at 1 per 3000-10000 live births in the United States (3) and 6.7 per 10000 live births in Europe – with 81% of all confirmed cases in the EU/EEA occurring in France (4). Spiramycin can decrease the risk of vertical transmission, but will not treat the fetus if the infection has already occurred. Infants born with this disease may benefit from pyrimethamine, sulfadiazine, and leucovorin.
To help prevent infection, pregnant women should avoid consuming raw and undercooked meat, wear gloves when gardening, and avoid changing cat litter.
Rubella, also known as “German measles,” is caused by the Rubella virus (Togaviridae family). It is most severe when acquired during the first trimester of pregnancy when the maternal infection will lead to fetal demise in 40-90% of cases (5). Congenital rubella can cause cardiac abnormalities, including patent ductus arteriosus and pulmonary artery stenosis. It can also cause ophthalmic abnormalities such as cataracts, glaucoma, retinopathy, and microphthalmia. Sensorineural deafness is common, and microcephaly, cognitive impairment, and meningoencephalitis may occur. Hepatosplenomegaly, hepatitis, hemolytic anemia, and thrombocytopenic purpura may also be observed.
The incidence of congenital rubella has plummeted in countries that employ widespread vaccination. In recent times, documented cases of rubella in the United States are virtually all imported. Cases and outbreaks continue in Europe but at a very low rate. In 2008, 48% of all cases occurred in Southeast Asia and 38% in Africa (6). There is no effective treatment for congenital rubella.
Regional comparison of Congenital Rubella Syndrome prevalence, 1999 – 2019
Congenital cytomegalovirus (CMV) is the most common congenital viral infection in the developed world. Clinical manifestations include sensorineural hearing loss, visual impairment, cerebral palsy, and cognitive difficulty. It can also cause neonatal cholestasis, pulmonary hypertension, and epilepsy. 10-20% of all hearing impairment in children is caused by congenital CMV (7).
CMV is identified in 5 to 7 per 1000 live births in the USA, Canada, Western Europe, and Australia; and 10-30 per 1000 live births in Latin America, Africa, and most Asian countries (8). Symptomatic infants may benefit from treatment with valganciclovir. It is difficult to prevent the acquisition of CMV, but some have suggested that pregnant women can decrease risk by avoiding contact with the saliva and urine of young children.
Congenital herpes simplex virus (HSV) most commonly occurs when an infant is exposed to the mother’s genital tract during delivery. Both herpes simplex-1 and herpes simplex-2 can cause congenital HSV. The risk of transmission from mother to infant depends primarily on when the maternal infection was acquired. When a mother is infected close to the time of delivery, the fetal infection rate is estimated at 25-60%. This rate drops to less than 2% when a mother is infected during the first half of pregnancy or earlier (9).
Signs of congenital HSV infection may occur between birth and six weeks of age. Disseminated disease may involve the liver, lung, central nervous system, and skin. “SEM disease” is limited to the skin, eyes, and/or mouth. Congenital HSV may cause a vesicular rash, hypothermia, lethargy, seizures, respiratory distress, hepatosplenomegaly, thrombocytopenia, hepatic dysfunction, cerebrospinal fluid pleocytosis, and sepsis. Congenital HSV is fatal in 50% of cases (10). The incidence of congenital HSV is estimated to be between 1 in 3000-20000 live births. All pregnant women should be tested for HSV, and those who are positive should receive prophylactic acyclovir or a similar drug at the time of delivery. Infected infants should be treated as well.
Congenital syphilis occurs when the bacterium Treponema pallidum is transmitted transplacentally or via the birth canal. The rate of vertical transmission increases as the pregnancy advances and transmission is more likely when the mother is experiencing early disease (11). Congenital syphilis can sometimes be detected by the appearance of nonimmune hydrops fetalis on ultrasound examination.
Congenital syphilis may be divided into two clinical syndromes: early congenital syphilis and late congenital syphilis. The early disease manifests within the first two years of life and is characterized by rash, adenopathy, and hepatosplenomegaly. Mucous patches and condylomata lata may be seen. The eyes may be affected, and cranial nerve palsy and seizures may occur. Thrombocytopenia with petechiae and purpura are often noted. Other manifestations can include anemia, myocarditis, pancreatitis, nephrotic syndrome, and malabsorption. Osteochondritis is often seen on imaging.
Late congenital syphilis manifests after two years of age. Dental findings include “Hutchinson’s teeth” and “mulberry molars.” Interstitial keratitis and eighth cranial nerve deafness can occur. Rhagades may be seen. Bone and joint abnormalities may include frontal bossing, saddle nose deformity, protuberant mandible, short maxilla, high palatal arch, sternoclavicular joint thickening (Higouménakis sign), saber shin, and Clutton’s joints. Central nervous system involvement can include cognitive impairment, hydrocephalus, seizures, cranial nerve palsy, paralysis, and optic nerve atrophy.
Congenital infections, Syphilis in the United States, 1941 – 2019
The WHO estimates that there were approximately 661,000 total cases of congenital syphilis in 2016, resulting in over 200,000 stillbirths and neonatal deaths (12) – with most cases occurring in South America and Africa. The CDC reports that congenital syphilis is on the rise in the United States, with the number of cases in 2018 being highest since 1998 (13).
All pregnant women should be tested for syphilis at their first prenatal visit. Penicillin is the only known effective antimicrobial agent for the prevention of vertical transmission and treatment of fetal and neonatal infection.
Parvovirus B19 is estimated to infect 1-5% of pregnant women. Most infections are without consequence to the fetus, but in rare cases, serious fetal disease can arise (14). In infected fetuses, ultrasound may show nonimmune hydrops fetalis.
Congenital parvovirus B19 often causes severe anemia and may also cause thrombocytopenia. Neurological manifestations include hydrocephalus, cerebellar hemorrhage, and polymicrogyria. Cardiac complications can include Ebstein’s anomaly, ventricular septal defect, cardiomyopathy, second‐degree heart block, and myocarditis. Ocular involvement may include corneal opacification, aphakia, and microphthalmia. Gastrointestinal manifestations include meconium peritonitis, fetal liver calcifications, portal tract fibrosis, and hypoplasia of the abdominal muscles. Congenital parvovirus B19 can also cause cleft lip and palate, micrognathia, bifid scrotum, Secundum atrial septal defect, and micropenis with perineoscrotal hypospadias.
Intrauterine fetal blood transfusion can be used to treat the severe fetal anemia associated with congenital parvovirus B19 infection.
Varicella-zoster congenital infections are caused by the virus that causes chickenpox and shingles. Infection may be characterized by low birth weight, hypoplasia of the extremities, dermal scarring, focal muscular atrophy, encephalitis, cortical atrophy, chorioretinitis, and microcephaly. Neonatal varicella zoster may occur when a mother contracts varicella virus between five days before delivery – to 48 hours after delivery. Neonatal varicella has a fatality rate of up to 30% (15). Congenital Varicella-Zoster virus infection is rare since most women are immune by childbearing age – having either been infected during childhood or vaccinated. Infants born with congenital varicella zoster may improve with acyclovir.
Additional viral agents of fetal and neonatal morbidity and mortality include HIV, Hepatitis B and C, measles, enteroviruses, adenovirus, lymphocytic choriomeningitis virus, West Nile virus, Zika virus, and Chikungunya virus. Additional bacterial causes include Group B Streptococcus, Chlamydia trachomatis, Neisseria gonorrhoeae, Escherichia coli, Mycobacterium tuberculosis, and Coxiella burnetii. A parasite, Plasmodium falciparum (the causative agent of malaria) is also associated with congenital infection.
By obtaining proper prenatal and perinatal care, pregnant women can optimize their chances of preventing, detecting, and treating congenital infections.
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