Fetal toxoplasmosis

Fetal toxoplasmosis is an in utero infection that results from transplacental transmission and subsequent infection with the organism Toxoplasma gondii. It falls in the TORCH group of infections.

Please refer to congenital cerebral toxoplasmosis for a specific discussion on this condition. 

Epidemiology

The incidence is highly variable dependent on individual countries.

Clinical presentation

The majority of infants (~75%) are asymptomatic. For those symptomatic, the severity of symptoms is related to the trimester of pregnancy when transmission occurred ¹¹:

• first trimester: fetal death
• second trimester: retinochoroiditis, microcephaly, and intellectual disability
• third trimester: lymphadenopathy, hepatosplenomegaly, eye injuries, and brain calcifications

Pathology

Fetal transmission occurs in ~40% of cases where the primary maternal infection is acquired during pregnancy ³. Transmission of infection acquired prior to conception is uncommon and in most cases, infection is transmitted in the 3^rd trimester. In ~10% cases the infection tends to be severe.

It classically gives a triad of (affected in ~80% ³):

• hydrocephalus
• intracranial calcification
• chorioretinitis

Serological tests

• PCR test on amniotic fluid: more specific ⁷
• cordocentesis for the detection of T. gondii-specific IgM antibodies: usually detectable after 20 weeks of gestation

Radiographic features

Ultrasound

Intracranial findings that may be present sonographically include:

• fetal hydrocephalus
• fetal intracranial calcification: tends to be distributed randomly throughout the brain

There may also be the presence of microcephaly.

See: congenital cerebral toxoplasmosis

Other findings include:

• fetal intrahepatic calcification
• fetal hepatosplenomegaly
• fetal ascites

Complications

• development of fetal hydrops
• after birth late sequelae: mainly ocular and neurological

Treatment and prognosis

Treatment involves maternal therapy with medications such as spiramycin +/- sulfadiazine +/- pyrimethamine depending on gestational age and the infective status of the fetus. Prognosis is variable dependant on fetal CNS manifestations. Long term disability can occur with intellectual disability and blindness. Overall mortality can be as high as 12% ¹⁰.