Toxoplasmosis in pregnancy

Definition

• Prenatal toxoplasmosis occurs when the mother acquires a first infection with Toxoplasma gondii during pregnancy and the parasite crosses the placenta to the unborn child.

Aetiopathogenesis

Pathogen and Transmission (Logbook 087)

• The pathogen: Toxoplasma gondii.
• Most common route of human infection: ingesting raw meat with tissue cysts.
• Second route: oocysts from cat faeces (soil, vegetables).
• Seroprevalence in Germany: approx. 1/3 to 1/2 of women are immune.
• What is dangerous: only the primary infection during pregnancy.

Aetiology and pathogenesis

• Sources of infection are tissue cysts in raw or undercooked meat and oocysts from cat faeces, for example via contaminated soil during gardening.
• If infection occurred before pregnancy, the fetus is usually protected by maternal antibodies.
• As pregnancy advances, the transmission rate rises from about 15% in the first to about 60% in the last trimester, while the severity of disease in the child decreases.

Clinical features

What to Look for in the Child

• The classic triad of congenital toxoplasmosis: chorioretinitis, hydrocephalus, calcifications.
• Findings on ultrasound may include: ventriculomegaly, calcifications, ascites.
• The most common manifestation overall: silent infection, late chorioretinitis.

Clinical features and complications

• In immunocompetent people, 80–90% do not notice the infection; otherwise a flu-like illness with fever and lymphadenitis, mainly in the head and neck region, occurs.
• Infection in the first third of pregnancy can severely damage the embryo or cause miscarriage.
• The classic triad is retinochoroiditis, hydrocephalus and intracranial calcifications; retinochoroiditis is the most frequent and may appear in initially normal children only after months or years.

Diagnosis

• High IgG avidity excludes infection within the preceding 3–4 months, whereas low avidity does not prove recent infection.
• Prenatally, PCR of amniotic fluid provides evidence of infection of the child; a positive result proves it, a negative one does not reliably exclude it.

Keep learning in the app

Further reading (selection)

1. Robert Koch Institute, RKI-Ratgeber (German): Toxoplasmose
2. DocCheck Flexikon, Toxoplasmose

Cross-references