Symptoms of intrauterine infection

The clinical symptoms in pregnant women correspond to those described above. If a pregnant woman is infected for the first time during pregnancy Toxoplasma tachyzoites may cross the placenta and infect the foetus. During the acute stage with parasitemia, parasites may colonize the placenta which may serve as a reservoir, supplying viable organisms to foetus, if the mother is not treated (Stray-Pedersen 1993). The infection is mostly asymptomatic (in approximately 90%) in the mother (Wong and Remington 1994). If the maternal infection is acquired 1-2 months before conception transmission might occur. The risk for transmission increases with length of gestation, with almost 100% transmission in the last month. The incidence and severity of congenital infection depend on which trimester the infection was acquired in. When contracted during the first trimester, 10-15% of the foetuses are infected and the result may be spontaneous abortion, stillbirth, or severe disease in the newborn. During the second trimester the incidence of foetal infection is 30%, and during the third trimester, 60%, (Wong and Remington 1994). About 85% of infected infants show no clinical sign of infection at birth. The clinical manifestations in infected newborns are varied. Sequale may not occur or may develop at various times. Most signs and clinical findings are non-specific, and testing

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for Toxoplasma infection should be performed on wide indications. Although infections during the first trimester result in a low number of infected infants, the damages are more severe. The classical triad of retinochoroiditis (usually bilateral), microcephaly, and intracranial calcifications is fortunately a rare finding. Other signs are strabismus, blindness, hearing loss, epilepsy, psychomotoric or mental retardation, anaemia, jaundice, rash, petechiae, encephalitis, pneumonitis, and hydrocephalus. If clinical signs are found at birth the sequalae are usually severe. Approximately 85% of sub-clinically infected newborns will subsequently develop chorioretinitis; 10-30%, hearing loss; and 20-75%, developmental delay (Wilson et al. 1980).

When the transmission occurs later in pregnancy, the frequency of chorioretinitis increases which may cause a symptomatic retinochoroiditis up til the age of 20 (Koppe et al. 1986). Ultra-sound findings combined with maternal serology have been found to be significantly related to clinical outcome (Virkola et al. 1997).

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