INCIDENCE OF TOXOPLASMA-GONDII INFECTION IN 35,940 PREGNANT-WOMEN IN NORWAY AND PREGNANCY OUTCOME FOR INFECTED WOMEN

From 1992 to 1994 a screening program for detection of specific Toxopl asma gondii antibodies involving 35,940 pregnant women was conducted i n Norway. For women with serological evidence of primary T. gondii inf ection, amniocentesis and antiparasitic treatment were offered. The am niotic fluid was examined for T, gondii by PCR and mouse inoculation t o detect fetal infection. Infants of infected mothers had clinical and serological follow-up for at least 1 year to detect congenital infect ion, Of the women 10.9% were infected before the onset of pregnancy. F orty-seven women (0.17% among previously noninfected women) showed evi dence of primary infection during pregnancy. The highest incidence was detected (i) among foreign women (0.60%), (ii) in the capital city of Oslo (0.46%), and (iii) in the first trimester (0.29%). Congenital in fection was detected in II infants, giving a transmission rate of 23% overall, 13% in the first trimester, 29% in the second, and 50% in the third. During the 1-year follow-up period only one infant, born to an untreated mother, was found to be clinically affected (unilateral cho rioretinitis and loss of vision). At the beginning of pregnancy 0.6% o f the previously uninfected women were falsely identified as positive by the Platelia Toxo-IgM test, the percentage increasing to 1.3% at th e end of pregnancy. Of the women infected prior to pregnancy 6.8% had persisting specific immunoglobulin M (IgM). A positive specific-IgM re sult had a low predictive value for identifying primary T. gondii infe ction.