Background: Toxoplasmosis is an infectious disease caused by the parasitic protozoan Toxoplasma gondii. It is endemic worldwide and, depending on the geographic location, 15 to 85% of the human population are asymptomatically infected. Routine diagnosis is based on serology. The parasite has emerged as a major opportunistic pathogen for immunocompromised patients, in whom it can cause life-threatening disease. Moreover, when a pregnant woman develops a primary Toxoplasma gondii infection, the parasite may be transmitted to the fetus and cause serious damnage. For these two subpopulations, a rapid and accurate diagnosis is required to initiate treatment. Serological diagnosis of active infection is unreliable because reactivation is not always accompanied by changes in antibody levels, and the presence of IgM does not necessarily indicate recent infection. Application of quantitative PCR has evolved as a sensitive, specific, and rapid method for the detection of Toxoplasma gondii DNA in amniotic fluid, blood, tissue samples, and cerebrospinal fluid.

Circulating cell-free fetal DNA in maternal serum offers an early and non-invasive method for prenatal diagnosis, but the origin of this DNA is still unknown. We report the absence of the SRY gene in maternal serum of a pregnant woman despite male genitalia at ultrasound. The karyotype was 45,X after direct trophoblast analysis and 45,X/46,Xidic(Yp) after culture and in all fetal tissues studied. Due to the absence of the SRY sequence in maternal blood and in the cytotrophoblast, we presume that free fetal DNA in this case originates from trophoblastic cells. As the case presented here is exceptional, it only has a minor impact on the accuracy of fetal sex determination by maternal serum analysis, but highlights the importance of and the necessity for the complementary ultrasonographic control.

Fetal sex prediction can be achieved using PCR targeted at the SRY gene by analysing cell-free fetal DNA in maternal serum. Unfortunately, the results reported to date show a lack of sensitivity, especially during the first trimester of pregnancy. Therefore, determination of fetal sex by maternal serum analysis could not replace karyotype analysis following chorionic villus sampling. A new highly sensitive real-time PCR was developed to detect an SRY gene sequence in maternal serum. Analysis was performed on 121 pregnant women during the first trimester of pregnancy (mean gestational age: 11.8 weeks). Among them, 51 had at least one previous male-bearing pregnancy. Results were compared with fetal sex. SRY PCR analysis of maternal serum was in complete concordance with fetal sex. Among the 121 pregnant women, 61 were bearing a male fetus and 60 a female fetus. No false-negative results were observed. Furthermore, no false-positive results occurred, even though 27 women carrying a female fetus during the current pregnancy had at least one previous male-bearing pregnancy. This study demonstrates that a reliable, non-invasive sex determination can be achieved by PCR analysis of maternal serum during the first trimester of pregnancy. This non-invasive approach for fetal sex prediction should have great implications in the management of pregnant women who are carriers of an X-linked genetic disorder. Prenatal diagnosis might thus be performed for male fetuses only, avoiding invasive procedures and the risk of the loss of female fetuses.

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Neither gB genotype nor CMV DNA load in AF correlate with the severity of CMV congenital infection and these markers are unlikely to prove useful for the management of congenital infection.

Toxoplasma reactivation is a life-threatening complication of allogeneic stem cell transplantation. A poor prognosis is probably linked to a difficult diagnosis, based on the detection of evidence of parasites in tissue. We developed a real-time PCR test using fluorescence resonance energy transfer hybridization probes to detect and quantify Toxoplasma gondii DNA in serum. This PCR test gave reproducible quantitative results over a dynamic range of from 0.75 × 106 to 0.75 parasites per PCR mixture. Serial samples from four patients with toxoplasma reactivation were evaluated. Three patients had several consecutive PCR-positive samples which corresponded to ≤0.75 parasites. These three patients became PCR negative during trimethoprim-sulfamethoxazole therapy but never developed clinically apparent toxoplasmosis. In contrast, one patient had an increasing PCR signal, from 1 to 396 parasites in 12 days, and developed cerebral symptoms. The parasite count decreased to 5 parasites in 3 days after pyrimethamine-clindamycin treatment. Real-time quantitative PCR is useful for diagnosis and follow-up of toxoplasma reactivation.

Fetal DNA is found in maternal serum even before the fetal circulation is established, which is highly suggestive that it is released, at least in part, from the trophoblast. Detection of fetal DNA in maternal serum very early in pregnancy may have clinical implications such as with the management of pregnant women carrying a fetus at risk for congenital adrenal hyperplasia.

Summary. Fetal RHD genotype determination is useful in the management of sensitized RhD-negative pregnant women. It can be ascertained early during pregnancy by chorionic villus sampling (CVS) or amniocentesis. However, these procedures are invasive, resulting both in an increased risk of fetal loss and in an increased severity of immunization due to fetomaternal haemorrhage. A reliable determination of RHD genotype by fetal DNA analysis in maternal serum during the first trimester of pregnancy is reported in this study. One hundred and six sera from RhDnegative pregnant women were obtained during the first trimester of pregnancy. These sera were tested for the presence of RHD gene using a new real-time polymerase chain reaction assay and the results compared with those obtained later in pregnancy on amniotic fluid cells and by RHD serology of the new-born. All sera from women carrying a RhD-positive fetus (n ¼ 62) gave positive results for RHD gene detection and sera from women carrying a RhDnegative fetus (n ¼ 40) were negative. The high level of accuracy of fetal RHD genotyping obtained in this study could enable this technique to be offered on a routine basis for the management of RhD-negative patients during the first trimester of pregnancy.