Summary
Objectives
The objectives of this study were to analyze the association between the classification of toxoplasmosis in the pregnant woman (TP) according to the classification of Lebech et al. and the incidence of congenital toxoplasmosis (CT), also taking into consideration prenatal treatment.
Methods
A clinical cohort study of 524 children followed-up until 1 year of age was conducted. Adjusted odds ratios (OR) were estimated by logistic regression.
Results
Of 519 pregnant women, 61.3% were not classified due to the incompleteness of hospital records. Among the pregnant women classified as confirmed cases of TP (n = 19), the CT risk was six times greater than in the probable/possible group. No case of CT was identified in the group of pregnant women classified as unlikely to have TP. The children with no prenatal treatment (46.2% n = 242/524) presented a risk almost three times greater of CT than the treated children (OR 2.77, 95% confidence interval (CI) 1.54–4.97; p = 0.001). Complete prenatal treatment was identified as a protecting factor for CT (OR 0.35, 95% CI 0.19–0.65; p = 0.001).
Conclusions
A lack or incomplete prenatal treatment was identified as an important risk factor for CT in this study. The proportions of non-classified mothers and children with no prenatal treatment reflect the need to improve prenatal care in Brazil.
Keywords
1. Introduction
Congenital toxoplasmosis (CT) can cause serious neurological and ocular sequelae, even among asymptomatic children. CT is a preventable and treatable infection,
1
, 2
, 3
, 4
and the identification of risk factors for transmission during pregnancy may help in the clinical management of suspected children. Well known risk factors are acute toxoplasmosis in pregnancy (TP) and the timing of occurrence (the later the appearance of the infection, the greater the chance of transmission).5
, 6
Considering that 90% of women with TP are asymptomatic, the diagnosis of TP is based on the results of serological tests.In Brazil, TP and CT screening is performed on an irregular basis, as there is limited access to laboratory tests. Although there are no guidelines from the Health Ministry, the clinical control of CT in the Federal District (FD) is guided by the Manual of gestational and congenital toxoplasmosis.
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However, even in the FD the diagnosis of TP is difficult, particularly the systematic testing of IgG and IgA, and avidity testing for IgG antibodies. Thus, the diagnosis of TP is usually based on accessible tests (IgG and IgM), the results of which are not always conclusive in relation to the occurrence of infection.Lebech et al. correlated various serological profiles to the probability of TP, classifying pregnant women as having either a confirmed or presumed (probable, possible, or unlikely) infection.
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Because this classification is possible regardless of the systematic testing for IgG and IgA and avidity testing for IgG, it was considered to be more suitable for the present study. However, studies assessing the association between the classification of TP according to Lebech et al. and the occurrence of CT were not identified in the reviewed literature. There is also controversy regarding the role of prenatal treatment in reducing vertical transmission.9
, 10
, 11
, 12
, 13
, 14
, 15
, 16
, 17
Therefore, the objective of this study was to analyze the associations between the classification of TP and the risk of CT, and prenatal treatment and the risk of CT, in a clinical cohort of children identified during 15 years and followed-up until the age of 1 year at a reference service for CT in the FD. These results may help obstetricians and pediatricians in the appropriate diagnosis and treatment of pregnant women and children who are suspected to have CT, in relation to laboratory investigations and therapeutic interventions.
2. Methods
2.1 Study population
Eligible children (n = 533) were those whose mothers were considered suspected or definite cases of TP. All of the mothers had positive IgG tests. These mothers were referred to the pediatric infectious diseases unit of the Regional Hospital of Asa Sul (PID-HRAS) by their babies’ pediatricians based on prenatal data regarding their serologic status (positive IgG). All mothers and babies referred to PID-HRAS were identified during the period from May l994 to October 2009 at the pediatric infectious diseases outpatient unit. This is the only referral service for the investigation, follow-up, and treatment of CT of the State Health Secretariat, FD. Of the 533 eligible children, nine were lost to clinical follow-up before diagnosis.
The diagnosis of CT was confirmed by the persistence of IgG antibodies up to 12 months of life. All of the children were examined at birth and underwent clinical follow-up performed by the infectious diseases specialist and ophthalmologist and laboratory testing starting within the first 3 months of life. Laboratory investigations were repeated according to the clinical criteria, and included complete specific serological tests, hemogram, radiology exams (X-ray of the skull and ultrasonogram (US) and computed axial tomography (CAT) scan of the brain), and study of the cerebrospinal fluid (CSF). Serological testing was repeated at 1, 3, 5, 8, and 12 months, or until IgG antibodies were negative.
The mothers of the eligible children were classified into five groups according to the probability of TP, using the classification of Lebech et al.,
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modified by the authors, as follows: (1) Definite: seroconversion – both samples taken after conception; positive culture from maternal blood; confirmed congenital infection in offspring. (2) Probable: seroconversion – first sample taken within 2 months before conception; significant rise of IgG titers, and presence of IgM and/or IgA; high IgG titers, presence of IgM and/or IgA and onset of lymphadenopathy during pregnancy; high IgG titers and presence of IgM and/or IgA in the second half of pregnancy. (3) Possible: stable high IgG, without IgM, in the second half of pregnancy; high IgG and the presence of IgM and/or IgA in the first half of pregnancy. (4) Unlikely: stable low IgG, with or without IgM; stable high IgG, without IgM, in early pregnancy. (5) Not classified: non-quantified IgG antibody results.The authors modified the classification of Lebech et al. by excluding the fifth group (‘not infected’) and creating a new group ‘not classified’ to prevent the exclusion of a large number of mothers. The ‘not infected’ group was defined by Lebech et al. as: seronegative (during pregnancy); maternal preconception seropositive sample; positive IgM and/or IgA without the appearance of IgG. This group was excluded by the authors because all eligible children were born from a mother suspected of TP.
Prenatal treatment aims to prevent transplacental transmission of Toxoplasma gondii and to treat fetuses that are possibly infected. The therapeutic regimens studied were: (1) spiramycin (2 tablets every 12 h) for 21 days; (2) pyrimethamine (2 tablets once a day, at the same time) associated with sulfadiazine (2 tablets every 6 h) and with folinic acid (1 tablet three times a week); (3) regimens 1 and 2 alternately every 21 days.
Other variables related to treatment that were analyzed were the trimester in which treatment was initiated and the duration of treatment. Treatment was considered continuous when given until delivery.
2.2 Study design
This historical cohort study was based on medical records of clinical and laboratory data related to pregnancy and the follow-up of the children.
2.3 Data analysis
Data analysis included descriptive and analytic stages. In the descriptive stage, the incidence of CT was studied for each group of pregnant women classified according to the classification of Lebech et al.
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Prenatal treatment data were described with the corresponding 95% confidence intervals (95% CI) based on the exact method.In the analytic stage, associations between the selected explanatory variables (classification of TP according to the classification of Lebech et al.
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and data on prenatal treatment) and CT were estimated using logistic regression models. Crude and adjusted odds ratios (OR) were estimated along with their respective 95% CI. For the statistical significance of the hypothesis tests, the accepted type 1 error was 5%. Stata software (version 10) was used for all the analyses.18
The research protocol conforms to Brazilian Resolution No. 196/96 concerning ethical aspects of research on human beings. The study was approved and authorized by the director of the Regional Hospital of Asa Sul and by the Research Ethics Committee of the State Health Secretariat, FD.
3. Results
Among 519 mothers analyzed (n = 5 mothers of twins) it was not possible to classify 318 (61.3%) of them according to the classification of Lebech et al.
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due to incomplete information about serological tests (Table 1). Nineteen (3.7%) mothers were classified as definite, 111 (21.4%) as probable, 46 (8.9%) as possible, and 25 (4.8%) as unlikely cases of TP.Table 1Classification of the probability of toxoplasmosis infection in pregnancy (TP) and prenatal treatment among mothers (n = 519) of eligible children from the pediatric infectious diseases unit of the Regional Hospital of Asa Sul, Brasilia, May 1994–October 2009
| Variables | Cases | n | % | 95% Confidence interval |
|---|---|---|---|---|
| Classification of Lebech et al. (n = 519 mothers) | ||||
| Definite | 8 | 19 | 42.1 | 19.90–64.31 |
| Probable | 12 | 111 | 10.8 | 5.03–16.59 |
| Possible | 9 | 46 | 19.6 | 8.10–31.03 |
| Unlikely | 0 | 25 | 0 | - |
| Not classified | 30 | 318 | 9.4 | 6.22–12.65 |
| Prenatal treatment (n = 524 children) | ||||
| Yes | 19 | 282 | 6.7 | 3.81–9.66 |
| No | 37 | 222 | 16.7 | 11.76–21.57 |
| Not informed | 3 | 20 | 15 | 0.00–30.65 |
| Therapeutic regimens (n = 524 children) | ||||
| Regimen 1 | 17 | 210 | 8.1 | 4.41–11.78 |
| Regimen 2 | 1 | 35 | 2.9 | 0.00–8.38 |
| Regimen 3 | 0 | 18 | 0 | - |
| No information about the regimen | 1 | 19 | 5.3 | 0.00–15.30 |
| Not treated or not informed | 40 | 242 | 16.5 | 11.85–21.21 |
| Time of treatment (n = 524 children) | ||||
| First trimester | 3 | 95 | 3.2 | 0.00–6.67 |
| Second trimester | 7 | 107 | 6.5 | 1.86–11.23 |
| Third trimester | 9 | 80 | 11.3 | 4.33–18.17 |
| Not treated or not informed | 40 | 242 | 16.5 | 11.85–21.21 |
| Duration of treatment (n = 524 children) | ||||
| Continuous | 15 | 243 | 6.2 | 3.15–9.20 |
| Interrupted | 4 | 39 | 10.3 | 0.73–19.78 |
| Not treated or not informed | 40 | 242 | 16.5 | 11.85–21.21 |
| Total | 59 | 524 | 11.3 | 7.57–14.95 |
a Regimen 1 = spiramycin; regimen 2 = pyrimethamine + sulfadiazine + folinic acid; regimen 3 = regimens 1 and 2 alternately every 21 days.
b Continuous = treatment compliance until the end of pregnancy; Interrupted = treatment interrupted before birth.
Overall, the incidence of CT in this study was 11.3% (n = 524). The CT incidence was larger for pregnant women classified as definite cases (42.1%, 95% CI 19.90–64.31%) compared to the other groups of mothers classified as probable cases (10.8%, 95% CI 5.03–16.59%) and possible cases (19.6%, 95% CI 8.10–31.03%) of CT. For these latter two groups, the classification of Lebech et al.
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had limited discriminatory power to identify CT. In contrast, there were no CT cases among mothers classified as unlikely cases of TP.Children whose mothers were listed as definite cases of TP (n = 19) had a risk almost four times greater of having CT than those born to mothers listed as presumed cases (n = 182). In the first group, 63.2% (n = 12/19) received specific prenatal treatment during pregnancy, and in the second group, 55.5% (n = 101/182) received such treatment (data not presented).
Among children treated during the prenatal period, the probability of CT was 6.7% (95% CI 3.81–9.66%) in contrast to the group that was not treated, in which the probability rose to 16.7% (95% CI 11.76–21.57%). Thus, children who were not treated during the prenatal period showed a risk 2.8 (95% CI 1.54–4.97) times greater of been a CT case than those who were treated.
The risk of CT among untreated children and those who had no record of receiving prenatal treatment was rather similar, indicating that in this latter group, the majority of children were probably untreated during the prenatal stage (Table 1).
Among the 19 pregnant women listed as definite cases of TP, 12 were treated, six were not, and one had no information regarding treatment (data not presented). The transmission rate of CT in the group of definite cases when treated was 41.7% (n = 5/12) and when untreated was 33.3% (n = 2/6). The rates of CT transmission were even lower among probable, possible, and unlikely cases (n = 182) when untreated (17.3%, n = 14/81) or when treated prenatally (6.0%, n = 6/101) (data not presented).
The rate of CT among children whose mothers were given regimen 1 of prenatal treatment (spiramycin; n = 210) was 8.1% (95% CI 4.41–11.78%). This rate decreased to 2.9% (95% CI 0–8.38%) among children whose mothers received regimen 2 (n = 35) and to 0% among children whose mothers were given regimen 3 (n = 18). The group of 19 children whose mothers were treated prenatally with no information regarding the drugs, showed a rate of 5.3% (95% CI 0.0–15.30%) of CT (Table 1).
Among 95 children who had treatment initiation in the first trimester of pregnancy, the rate of CT was 3.2% (95% CI 0–6.67%). The rate of CT increased for those children whose mother started treatment during the other two trimesters of pregnancy: 6.5% (95% CI 1.86–11.23%) when initiated in the second trimester and 11.3% (95% CI 4.33–18.17%) when initiated in the third.
The prenatal treatment was considered continuous for the majority of children (n = 243), and the CT rate in this group was 6.2% (95% CI 3.15–9.20%). Among children whose treatment was interrupted before birth (n = 39), the CT rate increased to 10.3% (95% CI 0.73–19.78%).
The results of logistic regression for the associations of CT rate and the classification of TP (according to Lebech et al.
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modified by the authors), and CT rate and prenatal treatment, are given in Table 2.Table 2Estimates of the association between congenital toxoplasmosis and selected variables (based on logistic regression analysis) among children seen at the pediatric infectious diseases unit of the Regional Hospital of Asa Sul, Brasilia, May 1994–October 2009
| Variable | Unadjusted regression model | Adjusted regression model | |||||
|---|---|---|---|---|---|---|---|
| Crude OR | 95% CI | p-Value | Adjusted OR | 95% CI | p-Value | Overall p-Value | |
| Category of infection | 0.002 | ||||||
| Definite | 6.65 | 2.47–17.91 | <0.001 | 9.59 | 3.41–26.94 | <0.001 | |
| Probable | 1.08 | 0.53–2.20 | 0.841 | 1.51 | 0.73–3.17 | 0.267 | |
| Possible | 2.22 | 0.97–5.08 | 0.058 | 1.97 | 0.85–4.56 | 1.112 | |
| Unlikely/not classified (ref.) | |||||||
| Prenatal treatment | 0.002 | ||||||
| Yes (ref.) | |||||||
| No | 2.77 | 1.54–4.97 | 0.001 | 3.01 | 1.61–5.64 | 0.001 | |
| No information | 2.44 | 0.66–9.08 | 0.182 | 2.68 | 0.68–10.56 | 0.159 | |
| Type of treatment | 0.005 | ||||||
| Regimen 1 (ref.) | |||||||
| Regimen 2 or 3 | 0.22 | 0.03–1.68 | 0.144 | 0.19 | 0.02–1.51 | 0.115 | |
| No information about the regimen | 0.63 | 0.08–5.02 | 0.663 | 0.43 | 0.05–3.76 | 0.444 | |
| No treatment (+20 children with no treatment information) | 2.25 | 1.23–4.10 | 0.008 | 2.36 | 1.24–4.46 | 0.008 | |
| Time of treatment | 0.004 | ||||||
| First trimester (ref.) | |||||||
| Second trimester | 2.15 | 0.54–8.55 | 0.279 | 2.13 | 0.52–8.67 | 0.291 | |
| Third trimester | 3.89 | 1.02–14.89 | 0.048 | 3.34 | 0.85–13.17 | 0.085 | |
| No treatment/no information | 6.07 | 1.83–20.14 | 0.003 | 6.24 | 1.83–21.22 | 0.003 | |
| Duration of treatment | 0.001 | ||||||
| Continuous | 0.35 | 0.19–0.65 | 0.001 | 0.33 | 0.17–0.64 | 0.001 | |
| Other (ref.) | |||||||
OR, odds ratios; 95% CI, 95% confidence intervals.
a Variables adjusted for classification of Lebech et al.
Initially, the analysis of the association between the classification of TP and CT indicated that among definite cases of TP the rate of CT was six times greater (OR 6.65, 95% CI 2.47–17.91; p < 0.001) than among unlikely or not classified cases of TP. The probability of CT among probable (OR 1.08, 95% CI 0.53–2.20; p = 0.84) and possible (OR 2.22, 95% CI 0.97–5.08; p = 0.058) cases of TP were similar to the reference group (unlikely or not classified cases of TP). A similar result was obtained when results were adjusted for prenatal treatment, except for the enhancement of the magnitude of association between definite cases of TP and CT: the rate of CT was 9.6 times greater among definite cases of TP than in unlikely or non-classified cases of TP (reference group).
In the univariate analysis, the lack of prenatal treatment was statistically associated with the CT rate, which remained even after controlling for classification of TP. Children who did not receive prenatal treatment had a three times greater chance of CT (OR 3.01, 95% CI 1.61–5.64; p = 0.001) than children who were treated prenatally. The treatment regimen did not appear to have any influence on the CT rate (regimen 2 or 3 vs. regimen 1: OR 0.19; p = 0.115).
When the association between the time of prenatal treatment initiation and CT (adjusting by classification of TP) was analyzed, an increasing trend in the CT rate was observed. When compared to children treated since the first trimester, the chance of CT in the group that was treated since the second trimester was two times greater (OR 2.13, 95% CI 0.52–8.67; p = 0.291), and since the third trimester it was three times greater (OR 3.34, 95% CI 0.85–13.17; p = 0.085). Children who were not treated during the prenatal period had a six times greater chance (OR 6.24, 95% CI 1.83–21.22; p = 0.003) of CT compared to those who were treated since the first trimester, even after adjusting by classification of TP. It is worth mentioning that, overall, this gradient resulted in a statistically significant association (p = 0.004), yet only the category of the untreated children presented a significant p-value (p = 0.008).
Treatment compliance until the end of pregnancy (continuous treatment), was identified as a protective factor: children with continuous treatment presented only 33% (OR 0.33, 95% CI 0.17–0.64; p = 0.001) of the chance of confirmation of CT compared to those children who did not receive prenatal treatment or for whom treatment was interrupted before birth.
4. Discussion
The children born to mothers listed as definite cases of TP (according to the criteria of Lebech et al.,
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modified by the authors) had a greater chance of CT compared to the group of children born to mothers listed as unlikely or not classified cases of TP. In addition, less chance of CT was observed among children who received specific continuous prenatal treatment and for whom this was initiated during the first trimester of pregnancy (in contrast to reference groups).The overall CT rate in the study population was 11.3%. Most studies on CT refer to the incidence observed in the general population of live-birth babies, regardless of their mothers’ serology status. As expected, the CT incidence in such settings is much lower than that observed in our study,
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, 20
, 21
, 22
in which all mothers had been referred to our service because they were considered suspected of TP.Among women listed as definite cases, the CT rate was 42.1%. Similar rates have been described by the Argentine Consensus on Congenital Toxoplasmosis
23
and by Lebech et al.,8
who estimated 40% for the overall CT rate.In contrast to the definite cases of TP, transmission rates of CT were considered less significant in the groups of women listed as probable (10.8%) and possible (19.6%) cases. There were no cases among women listed as unlikely to have infection in pregnancy. Mombrò et al., while studying mothers in Turin, Italy using the Lebech criteria,
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described the rate of transmission as being 4.1% among possible and unlikely TP cases.24
Once again, these small discrepancies can be attributed to rates of TP, which vary according to geographic regions and the immune status of the study population.In the present study, the classification of Lebech et al.
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was used not only for its biological plausibility, but also for its easy application. Still, 61.3% of mothers (n = 318/519) could not be classified with regard to the probability of infection, due to incompleteness of records for serological test results. These findings indicate that health staff should be made aware of the prenatal guidelines, in order to improve compliance with the requisition and registration of serological testing. In addition, the health sector must improve universal access to complementary examinations to facilitate relevant diagnostic testing during pregnancy.Congenital transmission occurs only among women who have acquired T. gondii during pregnancy (definite case), except in very unusual situations. However, a large absolute number of CT cases occurred among women listed as probable (n = 12), possible (n = 9), and non-classified (n = 30) cases of TP. These findings demonstrate difficulties in the diagnosis of acute TP and the loss of opportunities for prenatal treatment. In addition, it was demonstrated that among mothers who were considered unlikely cases of TP (n = 25 mothers), no cases of CT were actually confirmed. Still, 11 children born to this group of mothers went through laboratory investigations and treatment right after birth, which were probably unnecessary. These results raise the hypothesis of uncertainty in the clinic management of presumed CT cases based, sometimes, on unreliable classifications of maternal toxoplasmosis.
In Brazil, the local and state guidelines for the clinical management of a child born to a mother considered to be a case of acute TP is based on positivity of IgM at any time during pregnancy.
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However, there are no national guidelines concerning CT. Moreover, there are no national or local guidelines for children born to mothers listed as probable, possible, or unlikely cases of TP, as proposed by Lebech et al.8
The lack of clinical guidelines leads to individual medical decisions, based on different interpretations of the probabilities of TP, which could result in delayed or unnecessary diagnosis and treatment. To aid decision-making on the clinical management of CT, the classification of Lebech et al.,8
as modified by the authors, considers different serologic profiles and not only the positivity of IgM; these may be useful in the clinical management of children suspected of CT in developing countries where prenatal screening may be unreliable.As expected, in this study, the ‘definite’ category used for the maternal classification of TP was strongly predictive of CT: children born to this group of mothers were 9.6 times more likely to be a case of CT than those born to mothers listed as unlikely cases or who were not listed. However, the predictive values of CT considering the other three categories in the classification of Lebech et al.
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were not relevant. In future studies, other classifications should be equally assessed for their predictive capability of the probability of CT.4.1 Prenatal treatment
A little over half of pregnant women were treated during the prenatal period. However, prenatal treatment was identified in this study as a protective factor for the occurrence of CT, especially when started early on during pregnancy and continued up until delivery. Children whose mothers were not given treatment were three times more likely to be diagnosed with CT than those who did, even adjusting for the classification of probability of TP.
There are many reasons to explain why some of these children did not receive prenatal treatment (n = 222) in our setting: (1) the drugs were not available in the public health sector; (2) the doctor considered that treatment was not indicated, especially in the absence of a definitive diagnosis of TP; (3) the mother did not comply with the treatment, even though it was prescribed by the doctor, for several reasons including side effects.
The protective effect of prenatal treatment in preventing and/or reducing the transmission of CT is controversial in the literature worldwide. A multicenter European study showed no statistical significance for prenatal treatment and the prevention of the transmission of CT in a multivariate analysis adjusted for the time the infection occurred and the timing of the prenatal treatment.
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The authors, however, identified some important differences between the groups being compared in the descriptive phase of this study: a 39% transmission rate was reported among mothers who were given prenatal treatment and a 72% transmission rate was reported among untreated mothers (p > 0.05).10
In another study, Wallon et al.
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carried out a systematic review that included nine studies involving women listed as definite or presumed cases of TP, to assess the effect of prenatal treatment on CT rates. Five of these studies showed that treatment was effective in reducing the occurrence of CT while four others did not. Unlike the present study, however, the authors did not consider the regimen of drugs or the duration of treatment in the analysis. No clinical trial (randomized or not) considering prenatal treatment was identified in that review. The authors concluded that it remains unclear whether prenatal treatment actually does reduce the congenital transmission of T. gondii.In this study, the transmission rate of CT among definite cases of TP was 41.7% (n = 5/12) when treatment was given during the prenatal period, in contrast to a transmission rate of 33.3% (n = 2/6) when it was not. Studies were conducted in Lyon, France on a group of 564 pregnant women who were infected with T. gondii during pregnancy and who were treated,
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as well as in Saint Etienne26
with a similar group of 79 pregnant women. Comparable to our results (41.7%), the authors showed transmission rates of 29% and 35%, respectively. In Europe, a multicenter study in five toxoplasmosis reference centers (in France, Belgium, Norway, and Finland), investigated 144 pregnant women with the same characteristics (pregnant, infected with T. gondii, and treated prenatally), and described a transmission rate of 39%.10
The small differences between the results related to CT rates in infected pregnant women treated prenatally in the present study and those reported in the literature may be related to the period of time in which the acute infection occurred, the initiation of treatment, and regional variations.Regardless of the lack of definitive evidence on the impact of prenatal treatment on CT rates in the reviewed literature, some local guidelines
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and nationwide programs23
, 27
state that definite cases of TP must be treated during pregnancy. On the other hand, there are no recommendations regarding the treatment of presumed cases of TP. As mentioned earlier, it is imperative to conduct randomized and controlled clinical trials to assess the effect of prenatal treatment on CT transmission rates, which may generate high-quality evidence to help in clinical decision-making.4.2 Drug regimens
The three prenatal treatment regimens analyzed by the authors are the ones most commonly recommended in consensus documents and guidelines drawn up by groups studying toxoplasmosis in different countries, such as: EMSCOT (European Multicenter Study on Congenital Toxoplasmosis),
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the SYROCOT (Systematic Review on Congenital Toxoplasmosis) study group,17
the Royal Institute of Public Health in the UK,16
the US Centers for Disease Control and Prevention (CDC) National Center for Infectious Diseases,27
the Argentine Congress of Congenital Toxoplasmosis,23
and, in Brazil, from the Brazilian Network of Toxoplasmosis and State Health Secretariat Paraná29
and the State Health Secretariat, FD.7
Furthermore, future publications from the Program of Toxoplasmosis of the Ministry of Health in Brazil will include guidelines on specific drug regimens (personal communication).Regimen 1 was the most frequently used because of global and national recommendations (mentioned above), which propose the use of spiramycin until a fetal diagnosis is confirmed. This regimen is considered to be effective in eliminating T. gondii from the placenta,
14
, 16
has good compliance since it is based on only one drug and causes fewer side-effects (in contrast to pyrimethamine which may cause bone marrow aplasia), and is of lower cost and greater availability in public health services. On the other hand, the two other drug regimens are mainly prescribed if fetal toxoplasmosis is confirmed, since spiramycin does not cross the placental barrier, which makes it ineffective for treatment of the fetus.13
, 14
, 17
, 28
, 30
In the present study, there were no significant differences in CT transmission rates when regimens 2 and 3 were compared to regimen 1. In the reviewed literature, only two French studies associated transmission rates of CT to particular drug regimens. One of them, by Gilbert et al.,
11
found no difference in the transmission rates among 544 infected pregnant women treated with spiramycin or pyrimethamine combined with sulfadiazine in relation to reducing transmission. Similarly, Kieffer et al.31
found no statistical differences comparing these different treatments (as presented in our study) to the rates of CT among the 1438 pregnant women. Again, more definite scientific evidence should be accumulated, preferably from randomized therapeutic trials, to evaluate the effectiveness of the drug regimens in the prevention of CT.4.3 Timing of treatment
The multivariate analysis confirmed a higher transmission rate of CT when treatment was started in the third trimester of pregnancy in comparison to the first trimester of pregnancy, even after adjusting for the classification of TP. In this study population, it was not possible to differentiate the time of infection during pregnancy from the timing of treatment initiation, since the time of seroconversion was not identified. Therefore, this result may confirm the well-known higher transmission of T. gondii due to high placental vascularization in the last trimester of pregnancy and/or may reflect a delay of treatment if infection occurred earlier during pregnancy. This analysis would be greatly enhanced if the information about the trimester in which infection occurred was available for association with the effect of prenatal treatment. Wallon et al.
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agreed that the protective effect of treatment becomes more evident when the infected pregnant woman is treated during the first trimester of pregnancy. Dunn et al.25
studied 603 pregnant women with toxoplasmosis confirmed in the laboratory in Lyon, France. The overall transmission rate was 29%, rising considerably during the pregnancy up to 72% in the 36th week (third trimester), even though these patients were given treatment.4.4 Duration of treatment
Among women who received treatment (n = 282), the majority (n = 243, 86.2%) maintained it until delivery; this is affected by access to medication, as well as awareness of the pregnant woman of the need to comply with treatment in order to reduce the chances of CT. Similarly, a study from the south of Brazil reported a lower degree of uninterrupted treatment (57%) for 290 pregnant women.
32
In the present study, continuous treatment (until the end of pregnancy) was a protective factor against CT (p = 0.001), probably because it prevents the transmission of T. gondii in the last trimesters of pregnancy when the placenta is more vascularized. Couto et al.
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strongly recommend that spiramycin should be given up until delivery. Once again, no studies analyzing the association of continuous treatment and the occurrence of CT were found in the reviewed literature.4.5 Limitations
The limitations of this study are directly associated with possible misclassification of the mothers, associated with the difficulty in estimating the likelihood of acute toxoplasmosis, as well as confirming seroconversion. Also, the limitations inherent to observational studies when the aim is to evaluate therapeutic effectiveness should be highlighted. Indication bias may occur when the groups being compared (for example, treated groups versus non-treated groups, and groups who were submitted to different treatment regimens) become notably different, due to medical indication. However, the proportion of treated mothers varied little in relation to the classification of TP, preventing the occurrence of such a bias. For example, definite cases (63.1%) and presumed cases (55.5%) had similar probability of being treated. This may be due to the fact that, in Brazil, the decision to give treatment and the choice in favor of therapeutic regimens is, at times, strongly influenced by the positivity of IgM antibodies in the pregnant woman and not by the classification (Lebech et al.
8
) used in this study. The adjustment of the analysis by the classification of the pregnant woman may have helped, in part, to control this distortion.4.6 Strengths
Based on the reviewed literature, both national and international, this is the first large group analytical study to clinically evaluate the association between the occurrence of CT and classifications of TP and prenatal treatment. Furthermore, the use of a relevant sample (524 children) adds precision to the results described. This study becomes even more relevant when the lack of controlled therapeutic trials in the literature related to this subject is considered. The results, especially the association between the time and duration of prenatal treatment, as well as the type, with the occurrence of CT, can greatly assist obstetricians and pediatricians in the clinical management of children suspected of toxoplasmosis in both the postnatal and prenatal phases.
5. Conclusions
The classification of Lebech et al.
8
(modified by the authors) showed a low predictive capability for describing the groups at high risk for CT in detail, except for the definite cases of TP group. This may be related to the great majority of pregnant women who could not be classified.Among definite cases of TP, there was an increased chance of CT when prenatal treatment was not given. The protective effect of the prenatal treatment was noticed especially when treatment was given during the first trimester of pregnancy and continued until delivery. However, the regimen of drugs was not associated with the rate of transmission of CT.
Our inability to list 61.3% of the pregnant women and to identify the trimester of seroconversion, as well as the absence of treatment in a large proportion of definite case of TP, reflect the need for guidelines and improvements in order to provide higher quality prenatal care, including universal access to essential laboratory investigations and qualified professionals in the clinical management of pregnant women.
Acknowledgements
We thank Francisca Lucena for help with the statistical analysis and Dalva Nagamini Mota for help with the data mining from the Health Surveillance Information System. We are also grateful to Elaine Cristina Rey Mourain for data entry.
Funding source: The study sponsor had no funding source involvement.
Conflict of interest: The authors have no competing interests to declare.
References
- Epidemiology of congenital toxoplasmosis identified by population-based newborn screening in Massachusetts.Pediatr Infect Dis J. 2001; 20: 1132-1135
- Risk factors for Toxoplasma gondii infection in women of childbearing age.Braz J Infect Dis. 2004; 8: 164-174
- Toxoplasma gondii: transmission, diagnosis and prevention.Clin Microbiol Infect. 2002; 8: 634-640
- Toxoplasmosis and mental retardation—report of case control study.Mem Inst Oswaldo Cruz. 1993; 88: 253-261
- Toxoplasma-IgM and IgG-avidity in single samples from areas with a high infection rate can determine the risk of mother-to-child transmission.Rev Inst Med Trop Sao Paulo. 2006; 48: 93-98
- Maternal serologic screening for toxoplasmosis.J Midwifery Womens Health. 2003; 48: 308-316
Manual de toxoplasmose gestacional e congênita. Brasília, FD: State Health Secretariat; 2010.
- Classification system and case definitions of Toxoplasma gondii infection in immunocompetent pregnant women and their congenitally infected offspring.Eur J Microbiol Infect Dis. 1996; 15: 799-805
- Congenital toxoplasmosis: systematic review of evidence of efficacy of treatment in pregnancy.BMJ. 1999; 318: 1511-1514
- Treatment of toxoplasmosis during pregnancy: a multicenter study of impact of fetal transmission and children's sequelae at age 1 year.Am J Obstet Gynecol. 1999; 180: 410-415
- Effect of prenatal treatment on mother to child transmission of T. gondii: retrospective cohort study of 554 mother–child pairs in Lyon, France.Int J Epidemiol. 2001; 30: 1303-1308
- European Multicentre Study on Congenital Toxoplasmosis. Effect of timing and type of treatment on the risk of mother to child transmission of Toxoplasma gondii.BJOG. 2003; 110: 112-120
- Congenital toxoplasmosis.Am Fam Physician. 2003; 67: 2131-2138
- Diagnosis and management of toxoplasmosis.Clin Perinatol. 2005; 32: 705-726
- Risk factors for Toxoplasma gondii infection in mothers of infants with congenital toxoplasmosis: implications for prenatal management and screening.Am J Obstet Gynecol. 2005; 192: 564-571
- Congenital toxoplasmosis: priorities for further health promotion action.Public Health. 2008; 122: 335-353
The SYROCOT (Systematic Review on Congenital Toxoplasmosis) study group. Effectiveness of prenatal treatment for congenital toxoplasmosis: a meta-analysis of individual patients’ data. Lancet 2007;369:115–22.
StataCorp. Stata statistical software: release 10. College Station, TX: StataCorp LP; 2007.
- Congenital toxoplasmosis: value of antenatal screening and current prenatal treatment.Neonatal Netw. 2001; 20: 23-30
- Incidence of congenital toxoplasmosis in southern Brazil: a prospective study.Rev Inst Med Trop Sao Paulo. 2003; 45: 147-151
- Pesquisa de anticorpos para sífilis e toxoplasmose em recém-nascidos em Hospital de Ribeirão Preto, SP, Brasil.Rev Saude Publica. 1987; 21: 55-63
- Screening for Toxoplasma gondii antibodies in 2,513 consecutive parturient women and evaluation of newborn infants at risk for congenital toxoplasmosis.Scientia Medica. 2009; 19: 27-34
- Consenso Argentino de Toxoplasmose Congénita.Medicina (B Aires). 2008; 68: 75-87
- Congenital toxoplasmosis: assessment of risk to newborns in confirmed and uncertain maternal infection.Eur J Pediatr. 2003; 162: 703-706
- Mother-to-child transmission of toxoplasmosis: risk estimates for clinical counselling.Lancet. 1999; 353: 1829-1833
- A technique for dating toxoplasmosis in pregnancy and comparison with the Vidas anti-Toxoplasma IgG avidity test.Clin Microbiol Infect. 2008; 14: 242-249
- Preventing congenital toxoplasmosis.MMWR Recomm Rep. 2000; 49: 59-68
- Association between prenatal treatment and clinical manifestations of congenital toxoplasmosis in infancy: a cohort study in 13 European centres.Acta Pediatr. 2005; 94: 1721-1731
Londrina manual of gestational and congenital toxoplasmosis. Londrina, Paraná, Brazil: State Health Secretariat of Londrina; 2010.
- Infectious diseases of the fetus and newborn infant.5th ed. WB Saunders, Co., Philadelphia2006 (p. 229–31)
- [Prenatal treatment for congenital toxoplasmosis] (in French).Arch Pediatr. 2009; 16: 885-887
- Suspected acute toxoplasmosis in pregnant women.Rev Saude Publica. 2007; 41: 27-34
- Diagnóstico pré-natal e tratamento da toxoplasmosena gestação.Femina. 2003; 31: 85-90
Article info
Publication history
Published online: April 23, 2012
Accepted:
January 13,
2012
Received in revised form:
January 12,
2012
Received:
November 29,
2010
Corresponding Editor: Andy Hoepelman, Utrecht, the NetherlandsIdentification
Copyright
© 2012 Published by Elsevier Inc.
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