Primary toxoplasma infection in pregnant women

Antiparasitic treatment should be offered to every primary infected woman. The aim is to prevent foetal infection if it has not already occurred, and to treat and reduce tissue damage in an already infected foetus. In France, spiramycin has been used since the beginning of the 1970s. In a study of 542 pregnant women, Desmonts and Couvreur (1984) reported that parasites were detected less frequently in the placentas of spiramycin-treated mothers (19%) than in untreated mothers (50%). Maternal therapy reduced the placental infection from 25 to 8% in the first trimester, from 54 to 19% in the second trimester, and from 65 to 44% in the third trimester. Moreover, a significant reduction in the incidence of congenitally infected infants of the treated (23%) versus untreated (61%) mothers were noted, but the proportion of babies with clinical disease was the same in both groups. Thus, spiramycin appeared to reduce the incidence of foetal infection, but had little effect on an already infected foetus. The critics focus on the fact that the untreated mothers do not represent a real control group, but more or less historical controls.

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Later studies, primarily from France, have shown that pyrimethamine-sulfadiazine treatment in pregnancy is more effective that spiramycin in the eradication of parasites from placenta. In a retrospective study of congenitally infected infants, Couvreur et al. (1988) detected parasites in 89% of placentas of untreated women, in 75% of spiramycin-treated women, and in only 50% of women treated with pyrimethamine-sulfadiazine. Furthermore, pyrimethamine-sulfadiazine is shown to lead to a significant reduction in the number of severely affected babies and a shift to less severe and sub-clinical forms (Hohlfeld et al. 1989). In a recent multicentre European study (Foulon et al. 1999) a comparison was made between 144 seroconverting mothers, of whom 119 received prenatal treatment (mainly spiramycin) and 25 mothers who were not treated at all. For the first time the effect of gestational age at maternal infection on transmission risk was taken into account. It was shown that prenatal anti-parasitic treatment had no impact on the maternal-foetal transmission rate, but a significant beneficial effect on sequelae, especially on severe sequelae in the infected infants at 1 year of age. Early start of treatment in pregnancy resulted in the significant reduction in the number of infants with severe complications (Foulon et al. 1999). A similar non-beneficial effect on the transmission rate, but probably a clinically important effect on complications, has been reported in a French study (Gilbert et al. 2001). A combination of pyrimethamine and the long acting sulfadoxine (Fansidar) has been used in pregnancies with proven infected offspring (Maisonneuve et al. 1984; Piene and Garin 1989). All these studies conclude that treatment influences the long-term sequelae of infected infants and that Fansidar is well tolerated. These drugs can be given once a week, and thus the compliance is probably better than for daily pyrimethamine.

The present guidelines recommend that anti-parasitic treatment should be offered to every primary infected woman (Stray-Pedersen and Foulon 2000). Initially, spiramycin can be given until the status of the foetus is settled by prenatal diagnosis (Table 26.1). If the foetus is infected, pyrimethamine-sulfadiazine-folinic acid should be offered in three-week courses alternating with spiramycin. Alternative regimen is pyrimethamine-sulphadoxine (Fansidar) two tablets every week, sometimes alternating with spiramycin daily until term.

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