Introduction

Prenatal screening to reduce the risks of congenital toxoplasmosis has always been controversial. The debate centres on two questions, first whether prenatal screening can be justified at all and second, if it can, which screening programme is the most effective.

Measures other than prenatal screening include primary prevention, for example by the provision of health information about how to avoid infection (Ho-Yen et al. 1995) and neonatal screening. The latter approach has been adopted by the Massachusetts newborn screening programme as the most cost-effective (Guerina et al. 1994) and has been evaluated in Denmark (Lebech et al. 1999).

Where prenatal screening is advocated there is controversy about which screening programme is most effective. The French approach (Thulliez 1992) involves monthly retesting of Toxoplasma gondii antibody-negative pregnant women whereas in Austria (Aspock & Pollak 1992) retesting is carried out every 3 months. The debate is hampered by inadequate information on the risks of maternal infection and mother-to-child transmission, of clinical manifestations in infected children and the efficacy of antiparasitic treatment prenatally or during infancy in preventing congenital infection or reducing the number of affected children. There have been no published reports of controlled studies of prenatal screening or treatment and the comparative studies which have been undertaken are susceptible to bias. Nevertheless, there is a widespread perception that both the birth prevalence and severity of congenital toxoplasmosis have fallen in France and Austria since prenatal screening was introduced two decades ago.