Chemiluminescence (CMIA) assay replaced the MEIA, Toxo IgG assay in June 2009 and the Toxo IgM assay in January 2010 (Architect, Abbott, Wiesenbaden, Germany). first serology was 29.9 years (SD 5.2, range 18C42). In 37 (21%) women only the avidity increased from low to high in < 3 months. In 139 (79%) the IgG avidity remained Rabbit polyclonal to AASS below the high threshold 3 months and within this group 74 (42%) women had stable low IgG avidity during the observation period. Median gestational age at first test was 10.6 weeks (range 4.6C28.7). Fetal contamination was detected in four children, but none among children whose mother had stable low IgG avidity. The first antenatal toxoplasma serology should ideally be collected in early pregnancy and if stable values of toxoplasma IgM and low IgG-avidity are detected in a second sample after three to four weeks, the need for amniocentesis can be questioned. Introduction Primary contamination with during pregnancy may result in severe damage to the fetus if the parasites are transmitted through the placenta [1]. The risk of transmission and the severity of fetal disease depend on gestational age at the time of maternal contamination [2]. The fetus becomes infected during the period of maternal parasitemia, before the development of toxoplasma-specific antibodies [1]. Maternal antibodies safeguard the foetus, and Menaquinone-4 contamination prior to pregnancy does not affect the fetus [3]. Maternal toxoplasma contamination is usually asymptomatic; therefore, the diagnosis relies mainly on serologic assessments collected through screening programmes or random testing. The presence of toxoplasma immunoglobulin G (IgG) antibodies confirms ongoing or previous contamination, and the presence of toxoplasma immunoglobulin M (IgM) antibodies indicates a possible ongoing contamination. However, discrimination between past and recent contamination is usually challenging, as an individual can be positive for toxoplasma IgM antibodies for several months or years after primary contamination [4C6]. In recent decades, determination of toxoplasma IgG avidity has been included as a standard diagnostic tool to improve the estimation of the time of contamination acquisition [7, 8]. The IgG avidity test measures antibody binding force, which is low in the early stage after primary contamination but generally increases with time. High toxoplasma IgG avidity indicates that an contamination likely occurred at least four months earlier [8, 9]. However, several studies have shown that IgG avidity can remain low for a longer period following contamination [6, 8, 9]. This may be a normal reaction after contamination in some individuals, due to immunological changes during pregnancy or a response to Menaquinone-4 antibiotic treatment [5, 10]. Therefore, toxoplasma contamination is usually impossible to confirm during pregnancy based solely on low toxoplasma IgG avidity. The Prevention of congenital toxoplasmosis in Norway project, performed two decades ago, recommended the screening of pregnant women for toxoplasma contamination [11]. However, health authorities did not find sufficient evidence for implementing a screening programme, mainly because of uncertainty concerning the effect of antenatal treatment [12]. Nevertheless, toxoplasma testing during pregnancy has steadily increased, at least in southern Norway [13, Menaquinone-4 14]. The first antenatal visit is generally in gestational week 8 to 12, and if requested, toxoplasma serology is commonly performed during this visit. When the test is performed at the end of the first trimester, physicians often face a dilemma: the combination of IgM positivity and low IgG avidity may indicate recent contamination and warrant a recommendation for amniocentesis; however, this result does not necessarily indicate that this contamination occurred during the last three months. To better understand the possible impact of a low toxoplasma IgG avidity result in pregnancy, we re-examined the laboratory records of pregnant women who were repeatedly tested for toxoplasma antibodies and who later underwent amniocentesis, with particular focus on low toxoplasma IgG avidity persisting for three months or longer. Materials and Methods Study population In Menaquinone-4 this retrospective study, the toxoplasma antibody results of serum samples collected from 01 September 1992 until 31 December 2013 from 352 women who had undergone amniocentesis as part of their prenatal diagnosis at Oslo University Hospital due to suspected primary contamination were evaluated for inclusion. The pregnant women were mainly referred from health centres in the Southeast Health Region, which includes more than 50% of Norways pregnant population [15]. Only women with initial low toxoplasma IgG avidity and follow-up sera collected and analysed over a Menaquinone-4 period of at least three months were included. A total of 176 women provided 542 serum samples. The women were divided into three groups.