INTRODUCTION — Toxoplasma gondii is a ubiquitous protozoan parasite that infects animals and humans. Toxoplasma infection typically is asymptomatic in immunocompetent hosts. However, serious disease can occur, most frequently in the setting of immunosuppression or congenital infection. The fetus, newborn, and young infant with congenital Toxoplasma infection are at risk of infection-associated complications, particularly retinal disease that can continue into adulthood.
The clinical features and diagnosis of congenital toxoplasmosis will be reviewed here. The treatment, outcome, and prevention of congenital toxoplasmosis are discussed separately. (See "Congenital toxoplasmosis: Treatment, outcome, and prevention".)
Toxoplasmosis in other patient populations is discussed in separate topic reviews:
●Pregnancy (see "Toxoplasmosis and pregnancy")
●Immunocompetent hosts (see "Toxoplasmosis: Acute systemic disease")
●HIV-infected patients (see "Toxoplasmosis in patients with HIV")
MICROBIOLOGY — Congenital toxoplasmosis is caused by T. gondii, an intracellular protozoan parasite. Toxoplasma has a unique biphasic life cycle, consisting of a sexual cycle that occurs exclusively in felines and an asexual cycle that can occur in other animals and humans (figure 1). Cats acquire the infection by ingesting oocysts in soil or tissue cysts from small prey. Replication occurs in the intestine of the cat, and oocysts are formed, excreted, and become infectious after 24 hours. During the primary infection, the cat can shed millions of oocysts daily for up to three weeks. Humans who come in contact with cat feces containing Toxoplasma oocysts may inadvertently ingest contaminated material, and the asexual phase of Toxoplasma replication begins. Oocysts rupture to release sporozoites that divide and become tachyzoites (picture 1), which are characteristic of the acute stage of infection. Tachyzoites spread throughout the body via the bloodstream and lymphatics. With an adequate immune response, the tachyzoites are sequestered in tissue cysts and form bradyzoites. Bradyzoites are indicative of the chronic stage of infection and can persist for the life of the individual.
EPIDEMIOLOGY — Congenital toxoplasmosis occurs throughout the world. The prevalence varies geographically according to the risk of primary Toxoplasma infection in women of childbearing age [1-4]. (See "Toxoplasmosis and pregnancy", section on 'Incidence of acute primary infection in pregnancy'.)
The highest rates of infection with T. gondii have been reported in Europe, Central America, Brazil, and Central Africa . The environment plays a key role in perpetuating the life cycle of T. gondii, and warm, humid climates are ideal. In parts of Central America, seropositivity starts around one year of age, when children begin playing in contaminated soil, and it reaches 50 to 75 percent by adolescence. In other areas, transmission occurs primarily through the ingestion of undercooked meat. In these areas, depending on eating customs, seropositivity may begin in adolescence (or sooner) and can continue throughout adulthood. In many parts of the world, the pattern is mixed.
The incidence of congenital toxoplasmosis varies considerably by region, ranging from approximately 1 per 1000 live births in some areas of Latin America to 1 per 10,000 live births in the United States [5-7]. In some European countries with high rates of seroprevalence, the incidence of congenital toxoplasmosis has declined since the 1990s and early 2000s, likely owing to aggressive screening practices and national prevention programs [1,7,8].
PATHOGENESIS — The oocyst, bradyzoite, and tachyzoite stages of T. gondii all can cause disease in humans (figure 1) . Congenital infection typically occurs via transmission of tachyzoites through the placenta after a primary maternal infection during pregnancy but rarely may occur after reactivation of disease in an immunocompromised pregnant woman [2,10].
The risk of transmission to the fetus during an acute maternal infection varies depending upon the gestational age during which maternal infection occurs . As the gestational age increases, the risk of infection in the fetus increases, but the severity of the disease decreases [3,12]. Without treatment, most fetuses infected early in pregnancy die in utero or in the neonatal period or develop severe neurologic and ophthalmologic sequelae . Those infected in the second and third trimesters typically have mild or subclinical disease at birth.
In addition to the timing of fetal infection, genotypic differences and virulence of T. gondii strains, parasite burden, and maternal/fetal immune factors and host responses may also have an impact on the severity of disease in congenital toxoplasmosis [2,14-16]. (See "Toxoplasmosis and pregnancy", section on 'Incidence of acute primary infection in pregnancy'.)
CLINICAL FEATURES — Congenital toxoplasmosis has a broad spectrum of nonspecific clinical manifestations. Most newborns with congenital toxoplasmosis are asymptomatic.
Fetal infection — The clinical features of fetal Toxoplasma infection are discussed separately. (See "Toxoplasmosis and pregnancy", section on 'Fetal infection'.)
Types of postnatal presentations — There are four types of clinical presentations :
●Severe neonatal disease (picture 2)
●Mild to moderate disease that is clinically apparent within the first few months of life (see 'Clinically apparent disease' below)
●Subclinical infection (see 'Subclinical infection' below)
●Late sequelae of undiagnosed infection that become clinically apparent later in infancy, childhood, or adolescence (see 'Late manifestations' below)
Clinically apparent disease — Only approximately 10 to 30 percent of infants with congenital toxoplasmosis have clinically apparent signs and symptoms at birth or in early infancy [5,10,17-19]. Severe symptomatic infection usually results from primary maternal infection during the first trimester.
The clinical findings are multiple and nonspecific; they may be localized to the central nervous system (CNS) or eye or they may be generalized (picture 2) [20-22]. The so-called classic triad of congenital toxoplasmosis consists of chorioretinitis, hydrocephalus, and intracranial calcifications. However, the classic triad occurs in <10 percent of cases .
Among symptomatic neonates, common clinical findings include [4,21,22]:
●Chorioretinitis (85 to 92 percent) (picture 3)
●Intracranial calcifications (50 to 85 percent) (image 1)
●Hydrocephalus (30 to 68 percent)
●Abnormal cerebrospinal fluid (CSF; 63 percent)
●Jaundice (40 to 60 percent)
●Thrombocytopenia (40 percent)
●Anemia (20 to 50 percent)
●Fever (40 percent)
●Hepatosplenomegaly (30 to 40 percent)
●Lymphadenopathy (30 percent)
●Pneumonitis (27 percent)
●Rash (25 percent)
●Seizures (20 to 40 percent)
●Microphthalmia (20 percent)
●Microcephaly (15 percent)
Subclinical infection — Approximately 70 to 90 percent of newborns with congenital Toxoplasma infection have no manifestations on routine physical examination [5,10,17-19]. Additional evaluation, including examination of CSF, ophthalmologic examination, and neuroimaging, is recommended when there is a high index of suspicion for congenital infection [5,19,24]. (See 'Evaluation' below.)
Abnormalities that may be identified include:
●Retinal lesions, often consisting of unilateral macular retinal scars (picture 3)
●Small, focal cerebral calcifications (image 1)
●Elevated CSF protein (typically mild to moderately elevated, though can be >1 g/dL) and/or mononuclear CSF pleocytosis
In one study of 52 infants with congenital toxoplasmosis identified through a newborn screening program, 96 percent had normal newborn examinations . However, more detailed examination and testing revealed CNS and/or eye abnormalities in 40 percent. (See 'Evaluation' below.)
Late manifestations — Newborns with mild or subclinical congenital Toxoplasma disease at birth remain at significant risk for long-term sequelae, particularly if they do not receive extended anti-Toxoplasma therapy [25,26].
The typical lesion is a focal necrotizing retinitis (picture 3) . Associated findings may include microphthalmia, strabismus, cataract, and nystagmus. Complications of Toxoplasma chorioretinitis include vision loss, retinal detachment, and neovascularization of the retina and optic nerve. Other sequelae include cataracts, glaucoma, and changes in the iris.
The incidence of new-onset retinal lesions in untreated children approaches 90 percent, and the risk extends into adulthood [21,25,28-31]. New lesions occur with the highest frequency in late childhood and adolescence. Infants and young children may show no overt signs of new-onset chorioretinitis . (See 'Evaluation' below.)
Treated patients may have episodic recurrences of chorioretinitis. (See "Congenital toxoplasmosis: Treatment, outcome, and prevention", section on 'Prognosis'.)
Other late manifestations — Other late manifestations of congenital toxoplasmosis include [25,26]:
●Motor and cerebellar dysfunction
●Sensorineural hearing loss
●Growth retardation and other endocrine abnormalities, such as precocious puberty (secondary to hypothalamopituitary dysfunction) [32-34]
Indications for testing — Timely diagnosis of congenital toxoplasmosis infections facilitates early initiation of therapy. Diagnosis may be suspected based upon maternal serology, newborn screening, or clinical manifestations. The diagnosis generally relies upon a combination of clinical and laboratory findings.
Congenital toxoplasmosis infection should be suspected in :
●Infants born to women who have evidence of primary T. gondii infection during gestation (see "Toxoplasmosis and pregnancy", section on 'Indications for maternal diagnostic testing')
●Infants born to women who are immunosuppressed and have serologic evidence of past infection with T. gondii (see "Toxoplasmosis and pregnancy", section on 'Prenatal diagnosis')
●Infants who have compatible clinical findings (eg, intracranial calcifications, chorioretinitis, otherwise unexplained mononuclear cerebrospinal fluid [CSF] pleocytosis or elevated CSF protein) (see 'Clinical features' above)
●Infants who have a positive screening test for Toxoplasma immunoglobulin M (IgM), in regions where such serologic screening is performed (see 'Newborn screening' below)
Given the potential difficulty in interpreting serologic tests in newborn infants, all infants with possible congenital toxoplasmosis should undergo additional clinical, laboratory, and imaging evaluation for evidence of infection.
●Review of the maternal history and serology (if available)
●Complete physical examination, including detailed neurologic examination
●T. gondii serology (see 'Serology' below)
●Ophthalmologic examination (see 'Eye examination' below)
●Lumbar puncture (see 'Lumbar puncture' below)
●Neuroimaging (see 'Neuroimaging' below)
●Testing for cytomegalovirus and other congenital infections as appropriate based upon maternal exposure (see 'Additional testing' below)
Evaluation and diagnosis of toxoplasmosis in the pregnant woman and the prenatal diagnosis in the fetus are discussed separately. (See "Toxoplasmosis and pregnancy", section on 'Prenatal diagnosis' and "Toxoplasmosis and pregnancy", section on 'Indications for maternal diagnostic testing'.)
Lumbar puncture — Lumbar puncture is performed to obtain CSF for protein, glucose, and cell count. CNS involvement may manifest with elevated CSF protein (sometimes >1 g/dL) or mononuclear CSF pleocytosis. In addition, in cases with strong clinical suspicion, CSF T. gondii polymerase chain reaction (PCR) should be performed. Detection of T. gondii in the CSF confirms the diagnosis. (See 'Tests to detect Toxoplasma' below.)
Neuroimaging — Neuroimaging is performed to assess focal brain lesions or hydrocephalus. Computed tomography (CT) is generally the preferred modality for neuroimaging because it has a high sensitivity for detection of calcifications and it readily detects other structural abnormalities (eg, ventriculomegaly and hydrocephalus). Head ultrasonography can detect ventriculomegaly and hydrocephalus but does not detect calcification well. Ultrasonography has been used in regions where the rate of symptomatic congenital toxoplasmosis is very low compared with the United States (ie, mainly in Europe) . Magnetic resonance imaging (MRI) is a reasonable option for initial evaluation because it obviates the risk of radiation associated with CT; however, MRI has the disadvantage of longer test duration and often requires sedation.
Abnormalities on neuroimaging may include [2,35]:
●Intracranial calcifications, single or multiple, scattered throughout the brain (image 1)
●Hydrocephalus (characteristically, secondary to periaqueductal involvement)
Eye examination — Chorioretinitis (picture 3) may be the only clinical manifestation of congenital toxoplasmosis. The examination should be performed by an ophthalmologist experienced in retinal examinations in newborn and young infants; typically, infants are referred to a pediatric ophthalmology clinic.
In a cohort of 48 infants with congenital toxoplasmosis who were identified through neonatal serologic screening and who had normal physical examinations, approximately 20 percent had retinal lesions or scars at birth .
Since infants and young children are not able to complain of vision changes, routine ophthalmologic follow-up is recommended. Examinations are performed every three months during the first two years, every six months for the third year, and then yearly at least until the child can reliably report vision changes  or even well into adulthood . (See "Vision screening and assessment in infants and children".)
Hearing evaluation — All newborns with suspected congenital toxoplasmosis should undergo hearing evaluation, and serial follow-up testing should be performed if infection is confirmed. Routine newborn hearing screening is performed in many regions (including the United States); however, diagnostic auditory brainstem response (ABR) testing may be preferred, especially in infants with symptomatic disease since this test is more sensitive than the automated tests used in screening protocols. Early identification of hearing impairment facilitates early intervention and improved outcomes. (See "Screening the newborn for hearing loss", section on 'Screening tests for hearing' and "Hearing loss in children: Screening and evaluation", section on 'Formal audiology'.)
Tests to detect Toxoplasma
Serology — The diagnosis of congenital toxoplasmosis infection in the newborn usually is made serologically, but the interpretation of serologic results can be complicated, and consultation with an infectious disease expert is generally warranted. (See 'Diagnosis' below.)
Initial testing — Serologic testing in the newborn includes peripheral blood for:
Toxoplasma-specific IgA is not always necessary for the diagnosis of congenital infection, but it is often useful and is routinely performed in conjunction with the IgM at some reference laboratories. Toxoplasma-specific IgE does not add any advantage to the combination of IgM and IgA determinations .
Serologic testing should generally be performed as soon as possible after birth. However, when testing is performed in the first 5 to 10 days of life, repeat testing may be necessary to exclude false positives. (See 'Repeat testing' below.)
For an accurate serologic diagnosis, testing of blood samples from both the infant and the mother is required. Immunologically normal women with acute Toxoplasma infection in pregnancy typically have positive Toxoplasma IgG and IgM antibodies. (See "Toxoplasmosis and pregnancy", section on 'Indications for maternal diagnostic testing'.)
Although commercial laboratories may offer Toxoplasma-specific antibody assays, definitive testing of infants with suspected congenital toxoplasmosis should be performed at a toxoplasmosis reference laboratory (eg, the Toxoplasmosis Serology Laboratory at the Palo Alto Medical Foundation; the World Health Organization/Food and Agriculture Organization of the United Nations [WHO/FAO] International Centre for Research and Reference on Toxoplasmosis, Staten Serum Institute, Copenhagen, Denmark; the Toxoplasma Reference Laboratory, Public Health Laboratory, Singleton Hospital, Swansea, United Kingdom). Reference laboratories perform the IgG enzyme-linked immunosorbent assay (ELISA) or dye test, the Toxoplasma IgM ELISA or immunosorbent agglutination assay (ISAGA), and the Toxoplasma IgA ELISA or ISAGA. The tests performed in reference laboratories are more sensitive for detection of T. gondii infection in neonates than are commercial assays. Negative Toxoplasma IgM from testing performed at a commercial laboratory does not exclude the diagnosis of congenital Toxoplasma infection .
Issues that complicate interpretation of serologic results in the newborn include [2,3,37,38]:
●Toxoplasma IgG in the newborn may reflect past or current infection in the mother (because IgG crosses the placenta).
●The fetal/newborn antibody response to T. gondii is variable. Depending on the timing of maternal infection, Toxoplasma-specific IgM may disappear before birth, may be demonstrated within the first few days of life, or may be delayed for months.
●Antenatal treatment may affect the serologic profile of the infant. IgM usually is undetectable or reduced, along with reduction in IgA in infants exposed to anti-Toxoplasma therapy with pyrimethamine and sulfadiazine in utero [2,39].
●Though maternal IgM and IgA antibodies do not cross the placenta, small amounts can "leak" from the placenta, which may result in low positive IgM or IgA in an uninfected infant shortly after birth.
The approach to confirming the diagnosis is presented below. (See 'Diagnosis' below.)
Repeat testing — Repeat serologic testing can help to make the diagnosis. The approach to repeat testing depends on the clinical findings and the results of initial testing, as follows [4,10,40]:
●Asymptomatic infant, positive initial IgM and/or IgA – Repeat testing at least 10 days after birth to determine if this is a false positive. False-positive IgM and IgA titers can also occur following blood product transfusion, and testing should be repeated at least seven days after the last transfusion.
●Equivocal results on initial testing (positive IgG but not IgM or IgA) – Perform serial testing during the first year of life. IgG should fall if the infant is not infected. Transplacentally derived maternal Toxoplasma-IgG antibodies are expected to decrease by 50 percent per month after birth and usually fall to undetectable levels by 6 to 12 months of life .
●Negative initial results but strong clinical suspicion – This may reflect false-negative results due to delayed antibody production or antenatal treatment. Test the infant two to four weeks after birth and every four weeks until three months of age.
Decisions regarding treatment in equivocal cases must weigh the risks and benefits of initiating treatment without a definitive diagnosis versus waiting for confirmation of the diagnosis (which may take months). (See "Congenital toxoplasmosis: Treatment, outcome, and prevention", section on 'Antiparasitic therapy'.)
Polymerase chain reaction — Toxoplasma PCR of CSF should be performed if there is strong clinical suspicion for congenital toxoplasmosis. PCR testing can help establish the diagnosis when results of serologic testing are not definitive. It also can be useful even if the diagnosis of congenital infection seems likely based on serology and clinical evaluation. However, not all treatment programs routinely perform this testing .
PCR can also be performed on other samples, including peripheral blood, urine, vitreous fluid (ocular Toxoplasma), bronchoalveolar lavage fluid, cord blood, or placenta.
Neonatal testing should be performed only at reference laboratories (eg, the Toxoplasmosis Serology Laboratory at the Palo Alto Medical Foundation; the WHO/FAO International Centre for Research and Reference on Toxoplasmosis, Staten Serum Institute, Copenhagen, Denmark; the Toxoplasma Reference Laboratory, Public Health Laboratory, Singleton Hospital, Swansea, United Kingdom). Toxoplasma-specific PCR tests are available in some commercial laboratories; however, they may not have the same sensitivity or specificity as reference laboratories.
●Complete blood count with differential and platelet count – Anemia, thrombocytopenia, and eosinophilia are common nonspecific manifestations in symptomatic infants. (See 'Clinically apparent disease' above.)
●Liver function tests (aspartate aminotransferase, alanine aminotransferase, total and direct bilirubin) – Primarily for baseline studies before initiating treatment; both direct and cholestatic jaundice may occur in infected infants.
●Serum creatinine and urinalysis – Before initiating treatment with sulfadiazine, sulfamerazine, or sulfamethazine; dosing of these agents requires adjustment in patients with renal insufficiency.
●Evaluation for glucose-6-phosphatase dehydrogenase (G6PD) deficiency – Some agents used in the treatment of toxoplasmosis (eg, sulfadiazine, sulfamerazine, sulfamethazine) can trigger acute hemolysis in patients with underlying G6PD deficiency. Thus, infants should be tested for G6PD deficiency before initiating treatment with these agents. (See "Diagnosis and management of glucose-6-phosphate dehydrogenase (G6PD) deficiency".)
●Quantitative serum immunoglobulins (IgG, IgM, and IgA) – These may be useful in the confirmation of congenital infection. The ratio of Toxoplasma-specific IgG to total IgG decreases in the second to third month in infants without congenital toxoplasmosis and remains stable or increases in infants with congenital toxoplasmosis .
●Testing for other congenital infections – Cytomegalovirus may have clinical manifestations similar to toxoplasmosis or may occur as a concomitant infection. We suggest routinely testing for cytomegalovirus (eg, via urine PCR or viral culture) in any symptomatic neonate. Testing for Zika virus may also be appropriate, based on maternal exposure. (See "Congenital cytomegalovirus infection: Clinical features and diagnosis", section on 'Approach to testing' and "Congenital Zika virus infection: Clinical features, evaluation, and management of the neonate", section on 'Laboratory evaluation'.)
The clinical presentation in some infants with symptomatic toxoplasmosis may overlap with other congenital infections (eg, rubella, syphilis, congenital lymphocytic choriomeningitis virus syndrome) and congenital retinal anomalies, but these usually can be distinguished from congenital toxoplasmosis through serology (mother and infant), maternal prenatal and postnatal history and routine screening tests, ophthalmologic evaluation, and CNS imaging. (See "Overview of TORCH infections".)
●Histologic and cytologic examination of available tissue samples (eg, placenta) – Observation of parasites (eg, demonstration of cysts or tachyzoites) in placenta or other tissue can help establish the diagnosis (picture 4 and picture 1).
DIAGNOSIS — Diagnosis in the newborn relies on the presence of Toxoplasma-specific IgM or IgA or molecular detection of T. gondii DNA in the cerebrospinal fluid (CSF). These tests should be performed in a reference laboratory, and interpretation should be done in conjunction with infectious disease consultation.
●Confirmed congenital Toxoplasma infection – Congenital infection is confirmed by any of the following:
•Positive IgG with positive IgM and/or IgA – A positive Toxoplasma IgM (after five days of life) and/or IgA (after 10 days of life) is considered diagnostic of congenital toxoplasmosis in infants with a positive Toxoplasma IgG and compatible maternal serology, provided false positives (eg, due to contamination with maternal blood and/or transfusion) have been excluded. Infants who have positive initial serology but lack clinical abnormalities require repeat serologic testing to confirm or exclude congenital toxoplasmosis. (See 'Repeat testing' above.)
•Positive CSF polymerase chain reaction (PCR) – In the setting of confirmed acute maternal T. gondii infection during pregnancy and/or characteristic clinical findings in the neonate, a positive Toxoplasma PCR in the CSF is diagnostic of infection.
•Increase in anti-Toxoplasma IgG titer during the first year of life or increasing IgG titer compared with the mother's – The congenitally infected infant usually can synthesize Toxoplasma IgG by the third month of life if not treated; synthesis may be delayed until six to nine months of age in treated infants .
•Positive IgG beyond 12 months of age – Persistence of anti-Toxoplasma IgG at one year of age (by which time transplacentally acquired maternal IgG should have disappeared) is considered the gold standard and is diagnostic of congenital toxoplasmosis.
●Presumed congenital Toxoplasma infection – Congenital infection is presumed in the following situation; repeat testing may establish a more definitive diagnosis:
•Infants with characteristic clinical findings, positive IgG, but negative IgM and IgA – Negative IgM and IgA titers do not exclude infection and may be due to delayed antibody production. PCR testing and repeat serologic testing can help establish the diagnosis. (See 'Polymerase chain reaction' above and 'Repeat testing' above.)
●Excluded congenital Toxoplasma infection – Congenital infection is excluded in either of the following circumstances:
•Negative IgG, IgM, and IgA.
•Negative IgM and IgA with positive IgG titer that declines over time – Congenital toxoplasmosis is excluded if, in the absence of treatment, serial serologic testing demonstrates a continuous decline in IgG titer until its disappearance in the absence of Toxoplasma-specific IgM or IgA , provided that the child is capable of synthesizing IgG (as assessed by measurement of serum quantitative immunoglobulins) .
NEWBORN SCREENING — Some European countries (eg, France, Austria, Denmark) and a few states in the United States (eg, Massachusetts, New Hampshire, Rhode Island) have implemented routine neonatal screening for toxoplasmosis to identify infants for early treatment [5,41,42]. Neonatal screening involves performance of a Toxoplasma IgM immunoassay on blood specimens routinely collected for metabolic screening. Positive screens are followed up with serologic testing of the infant and mother to confirm the diagnosis. (See 'Evaluation' above.)
DIFFERENTIAL DIAGNOSIS — Toxoplasmosis must be differentiated from other intrauterine infections (table 2) that have similar manifestations in the newborn and from other conditions that cause retinal lesions. These include :
●Rubella (see "Congenital rubella", section on 'Evaluation')
●Syphilis (see "Congenital syphilis: Clinical features and diagnosis")
●Congenital Zika virus infection (see "Congenital Zika virus infection: Clinical features, evaluation, and management of the neonate")
●Congenital herpes simplex infection (see "Neonatal herpes simplex virus infection: Clinical features and diagnosis", section on 'Intrauterine HSV')
●Congenital varicella infection (see "Varicella-zoster infection in the newborn", section on 'Congenital varicella syndrome')
●Congenital lymphocytic choriomeningitis virus syndrome  (see "Viral meningitis in children: Epidemiology, pathogenesis, and etiology", section on 'Lymphocytic choriomeningitis virus')
●Congenital hypertrophy of the retinal pigmented epithelium
Serology, ophthalmologic evaluation, and central nervous system (CNS) imaging usually can differentiate congenital toxoplasmosis from these conditions.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Toxoplasmosis" and "Society guideline links: TORCH infections".)
SUMMARY AND RECOMMENDATIONS
●Microbiology – Congenital toxoplasmosis is caused by Toxoplasma gondii, an intracellular protozoan parasite. (See 'Microbiology' above.)
●Incidence – Congenital toxoplasmosis occurs throughout the world. The incidence ranges from 1 per 1000 live births to 1 per 10,000 live births, depending upon the risk of primary Toxoplasma infection in women of childbearing age. (See 'Epidemiology' above.)
●Risk of transmission – The risk of transmission to the fetus during an acute maternal infection increases with increasing gestational age of the fetus, but the severity of infection decreases with increasing gestational age. (See 'Pathogenesis' above.)
●Clinical features – Most newborns with congenital toxoplasmosis are asymptomatic. Among those who are symptomatic, clinical findings may include chorioretinitis (picture 3), intracranial calcifications (image 1), hydrocephalus, abnormal cerebrospinal fluid (CSF) parameters, seizures, jaundice, hepatosplenomegaly (picture 2), lymphadenopathy, anemia, and thrombocytopenia. (See 'Clinical features' above.)
Late manifestations of untreated congenital toxoplasmosis may include chorioretinitis and neurologic abnormalities (motor abnormalities, intellectual disability, hearing loss), even if there are no clinical symptoms or findings at birth. (See 'Late manifestations' above.)
•Review of the maternal history and serology (if available)
•Complete physical examination, including detailed neurologic examination
•T. gondii serology (see 'Serology' above)
•Ophthalmologic examination (see 'Eye examination' above)
•Lumbar puncture (see 'Lumbar puncture' above)
•Neuroimaging (see 'Neuroimaging' above)
•Testing for cytomegalovirus and other congenital infections as appropriate based upon maternal exposure (see 'Additional testing' above)
●Diagnosis – The diagnosis of congenital toxoplasmosis usually is established based upon serologic testing, usually performed in a reference laboratory. Serial testing may be necessary to confirm or exclude the diagnosis. (See 'Tests to detect Toxoplasma' above and 'Diagnosis' above.)
ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Ruth Lynfield, MD, and Jennifer Lee, MD, MS, who contributed to an earlier version of this topic review.