ABSTRACT From a prospective cohort of 344 women who seroconverted for toxoplasmosis during pregnancy, 344 amniotic fluid, 264 placenta, and 216 cord blood samples were tested for diagnosis of congenital toxoplasmosis using the same PCR assay. The sensitivity and negative predictive value of the PCR assay using amniotic fluid were 86.3% and 97.2%, respectively, and both specificity and positive predictive value were 100%. Using placenta and cord blood, sensitivities were 79.5% and 21.2%, and specificities were 92% and 100%, respectively. In addition, the calculation of pretest and posttest probabilities and the use of logistic regression allowed us to obtain curves that give a dynamic interpretation of the risk of congenital toxoplasmosis according to gestational age at maternal infection, as represented by the three sample types (amniotic fluid, placenta, and cord blood). Two examples are cited here: for a maternal infection at 25 weeks of amenorrhea, a negative result of prenatal diagnosis allowed estimation of the probability of congenital toxoplasmosis at 5% instead of an a priori (pretest) risk estimate of 33%. For an infection at 10 weeks of amenorrhea associated with a pretest congenital toxoplasmosis risk of 7%, a positive PCR result using placenta at birth yields a risk increase to 43%, while a negative result damps down the risk to 0.02%. Thus, with a molecular diagnosis performing at a high level, and in spite of the persistence of false negatives, posttest risk curves using both negative and positive results prove highly informative, allowing a better assessment of the actual risk of congenital toxoplasmosis and finally an improved decision guide to treatment.

In a cohort of 12 consecutive neonates, polymerase chain reaction (PCR) established the diagnosis of 5 of 6 cases of congenital toxoplasmosis and did so earlier than serologic methods. We validated that PCR using neonatal peripheral blood is a sensitive, rapid, and cost-effective method to affirm the diagnosis of previously undiagnosed congenital toxoplasmosis.

OBJECTIVE:To determine the effects on mother to child transmission of the timing and type of prenatal treatment, taking into account gestational age at maternal seroconversion.DESIGN:Prospective cohort study.SETTING:European centres offering prenatal screening for toxoplasmosis.POPULATION:Children born to a cohort of pregnant women with toxoplasma infection.METHODS:We determined the effects on mother to child transmission of the interval between seroconversion and start of treatment (treatment delay), and the type of treatment, taking into account gestational age at maternal seroconversion.MAIN OUTCOME MEASURE:Congenital infection status confirmed by toxoplasma IgG results at one year postnatal age.RESULTS:Of 1208 women analysed, 72% were first prescribed spiramycin, 19% pyrimethamine-sulphonamide and 9% (mostly infected during the last trimester) were untreated. The odds ratios for mother to child transmission for all women treated after a delay of four to seven weeks was 0.77 (95% CI 0.34-1.69), and after eight weeks or more was 1.33 (0.56-2.89) compared with less than four weeks. The odds ratio per week of treatment delay was 1.01 (0.93-1.08). There was no evidence that transmission risk differed in women first treated with pyrimethamine-sulphonamide versus spiramycin: odds ratio 1.10 (0.63-1.91) or in untreated versus treated women: odds ratio 0.57 (0.27-1.17).CONCLUSION:We were unable to demonstrate a beneficial effect of the timing or type of prenatal treatment on the risk of mother to child transmission but we could not exclude a clinically important effect. Randomised controlled trials are required to determine the effect of prenatal treatment on mother to child transmission.

Objective To evaluate the biological parameters obtained by cordocentesis and amniocentesis in the antenatal diagnosis of congenital toxoplasmosis.Design Nine-year retrospective study.Setting Parasitology Laboratory, Department of Obstetrics and Gynaecology and Department of Paediatrics, Centre Hospitalo-Universitaire, Montpellier, France.Participants Two hundred and eighty-six pregnant women infected with toxoplasmosis between 7 and 34 weeks of gestation.Methods Detection of abnormalities by ultrasound examination. Detection in fetal blood of Toxoplasma, of specific IgM and IgA and of nonspecific biological markers. Detection in amniotic fluid of Toxoplasma.Results Out of 286 antenatal diagnoses, 211 were negative (Ist group), 40 were positive (2nd group) and led to 8 medical abortions, and 35 were uncertain (3rd group). in the Ist and 3rd groups respectively, 7 (3.3%) and 5 (14.3%) cases of congenital toxoplasmosis were observed. Overall, 52 cases of congenital toxoplasmosis were detected: 12 were clinically apparent, 36 subclinical (of which 12 were in groups 1 and 3) and 4 were lost to follow up.Conclusion There is substantial importance in making the diagnosis of toxoplasmosis antenatally in order to limit the number of medical abortions. In our series, the most accurate predictor was the detection of the fetal antibody response (specific IgM and IgA) to Toxoplasma.

One hundred and ninety women who contracted toxoplasmosis after the seventh week of pregnancy underwent antenatal diagnosis, including ultrasound examination and biological tests. Tests included Toxoplasma isolation in fetal blood and amniotic fluid by mouse inoculation, specific IgM and IgA in fetal blood, and non-specific tests. Twenty fetuses had positive specific as well as non-specific tests for Toxoplasma infection. At birth, four of these presented with clinical congenital toxoplasmosis and 12 with subclinical forms. Antenatal diagnosis enabled the detection of 83 per cent of the infected fetuses. Under specific conditions, cordocentesis permits early diagnosis and considerably reduces the number of terminations of pregnancy.