congenital toxoplasmosis

Last reviewed 01/2018

Toxoplasmosis in pregnancy:

• about five per 1000 non-immune pregnant women may acquire toxoplasma infection (1)
• risks of transmission to the baby are higher later in pregnancy, but risks of infection causing harm to the baby are greater earlier in pregnancy
• infection is usually acquired from undercooked meat, or from fruit and vegetables contaminated with cat faeces
• fetal infection can cause eye and brain damage, growth retardation, and intrauterine death
• children with subclinical infection at birth may have cognitive, motor, or visual defects that may be difficult to diagnose in early childhood (1)
  • children with subclinical infection at birth may have cognitive, motor, and visual deficits, which may go undiagnosed for many years.

Only infants of mothers acquiring primary infection during, or just before, pregnancy are at risk. The risk of transmission to the foetus is about 15% in mothers infected during the first trimester, 25% in the second trimester, and 65% in the third trimester. The severity of the foetal infection is greatest with first trimester infection.

• risk of transmission increased with gestational age at maternal seroconversion, reaching 70% to 90% when seroconversion occurred after 30 weeks' gestation
• highest risk of developing early signs of disease (including chorioretinitis and hydrocephaly) was about 10%, recorded when seroconversion occurred between 24 and 30 weeks' gestation

There should be serological and clinical follow-up for infants with congenital toxoplasmosis. Termination may be considered if infection occurs early in pregnancy.

Treatment of infection:

• it is unclear whether treating infected pregnant women with spiramycin, pyrimethamine-sulphonamides, or both reduces the risk of fetal infection (1)

Reference:

• Kravetz J.Congenital toxoplasmosis.Clin Evid (Online). 2010 Jun 28;2010.
• Lancet 1999;353: 1829-33.
• BMJ 1999; 318:1511-14.