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At 29 weeks of gestation, a pregnant woman in the United States was told that her fetal ultrasound had revealed the presence of hydrocephalus. She did not recall having any symptoms or risk factors during gestation. Serological testing at the national reference laboratory for toxoplasmosis in the US (http://www.pamf.org/serology/) confirmed an acute infection likely acquired around 17 weeks of gestation. She was started on pyrimethamine/sulfadiazine, at 31 weeks. Her amniotic fluid was positive for Toxoplasma gondii DNA by polymerase chain reaction (PCR). The infant was born with hydrocephalus, brain calcifications, and chorioretinitis. In France, a screening program has been in place since 1992, and pregnant women with negative serology are tested monthly until delivery. If this pregnant woman had been followed according to this program, she would have been started on spiramycin 14 weeks earlier than in the US, her amniotic fluid would have been tested for T. gondii by PCR at 18 weeks, and she would have been started on pyrimethamine/sulfadiazine 11 to 8 weeks earlier than in the US. In the US, such a program does not exist, and infection is usually diagnosed when clinical signs are present in the fetus or at birth. Severe disease is not an uncommon situation in the US [1], but it is apparently a rare event in France (Table 1) [2]. Why is a congenital infection caused by the same parasite approached so differently in France than in the US? Below, we will discuss several factors that could account for these diverging approaches. Table 1 Differences in T. gondii genetics, epidemiology, clinical manifestations, and approach to infection detection and management during pregnancy, between France and the US. France US Parasite Genetics Type II: >95%; other types are very rare Type II: 41.5%; non-type II (including atypicals): 58.5% IgG Seroprevalence in Women of Childbearing Age 37.0% 9.1% Incidence of Acute Infection among Toxoplasma-Seronegative Pregnant Women 2.1/1,000 0.2/1,000* Incidence of Congenital Toxoplasmosis 2.9/10,000 live births 0.5/10,000 live births* Clinical Signs of Congenital Toxoplasmosis in Newborns: Absent, Mild–Moderate, and Severe 85%, 10%, and 3% 12%, 11%, and 77% Screening of Toxoplasma-Seronegative Pregnant Women Yes. Systematic screening is performed every month No. However, systematic screening is performed in some obstetric practices Diagnosis of Acute T. gondii Infection by Seroconversion Yes, because sequential samples are available Rare Diagnosis of Acute T. gondii Infection by the Use of a Single Serum Rare Yes. Only a single serum is available. Positive Toxoplasma IgM samples require confirmatory testing at reference centers such as the Palo Alto Medical Foundation Toxoplasma Serology Laboratory** Recommendation of Treatment, Amniotic Fluid for T. gondii PCR Testing, and Serial Ultrasounds for Acutely Infected Women Yes Yes Indication of Infant's Workup for Congenital Toxoplasmosis at Birth Yes, for each newborn born to a mother infected during gestation regardless of the presence of clinical signs or laboratory/radiological abnormalities Yes, for those with clinical signs and/or laboratory/radiological abnormalities suggestive of congenital infection. Seldom, for infected infants without clinical signs or laboratory/radiological abnormalities whose mothers were suspected of having or diagnosed with toxoplasmosis during gestation Postnatal Treatment of Congenitally Infected Infants Yes, for infected infants of acutely infected pregnant women (symptomatic or asymptomatic) diagnosed with congenital toxoplasmosis in utero or postnatally, regardless of the presence of clinical, laboratory, or radiological abnormalities Yes, for infants diagnosed with congenital toxoplasmosis because of the presence of clinical signs in utero or at birth. Seldom, for infected infants without clinical, laboratory, or radiological abnormalities in whom the diagnosis of congenital toxoplasmosis was made in utero or postnatally because of the presence of maternal illness, risk factors, or systematic screening by an obstetric practice Open in a separate window Ig, immunoglobulin.