Toxoplasma Serology Status and Risk of Miscarriage, A
Case-Control Study among Women with A History of
Materials and Methods
This research is a case-control study on 240 serum samples from women experiencing spon-
taneous abortion for the first time as the case group, and 240 serum samples from women who had a normal delivery
with no history of abortion as the control group. The level of anti-
Maternal acute toxoplasmosis during pregnancy is raised as one of the factors that increase the chance of spontaneous abortion. The necessary health training, especially on the parasite transmission ways to women before marriage, as well as the serological test in women before and during pregnancy is recommended. Polymerase chain reaction (PCR) and IgG avidity assays should be performed in the medical diagnostic laboratories for accurate distin- guishing of the initial infection of toxoplasmosis in the pregnant women.
Pregnancy is one of the most critical steps in women's
lives, particularly those who want to become a mother
for the first time. Abortion is a problem that any women
might experience during pregnancy, and therefore suffer
from psychological issues and medical expenses, which
make it particularly important. One of the reasons for
abortion is toxoplasmosis, which is due to an infection
In general, a human typically becomes infected by three
principal routes of transmission including drinking contaminated
water or eating contaminated food, such as the
tissue cyst in half-cooked contaminated meat or food that
is contaminated with oocysts excreted from cat feces, and
congenital transition, that means the transmission from an
infected mother to her fetus (5). Toxoplasmosis infection
might be acute or chronic with or without symptoms. The
symptoms and complications of the disease mainly occur
in the acute phase of infection. Following activation of
the host immune system, the parasite proliferation is controlled
and tissue cysts are formed in the host neuro-muscular
tissues (3, 5). Although the acquired toxoplasmosis
causes asymptomatic mild infections in people with a
healthy immune system, it can cause severe clinical signs
and even death in those with a weak or impaired immune
systems. On the other hand, in people who are suffering
from immune deficiency or are consuming immune-suppressive
drugs, the chronic infection may be reactivated,
causing severe and deadly complications such as encephalitis,
myocarditis, and pneumonia (5). Transplacental
The global estimated incidence rate of congenital toxoplasmosis is 190,100 cases annually, with an approximate incidence rate of 1.5 cases per 1000 live births [95% confidence interval (CI): 179,300-206,300] (8). The previous studies in Iran have shown that the seroprevalence rates of toxoplasmosis among childbearing age women are totally 39.9% among childbearing age women (9) and 39.3% (95% CI ¼ 33.0-45.7%) among the general population (10). Infection is more prevalent in hot and humid areas and relatively rare in cold and dry areas. The prevalence of infection is different among various ethnic groups, but the difference is more related to genetic differences, environmental health, and cooking habits (11).
One of the most popular medical concerns around the world is how to diagnose acute congenital infections in a pregnant woman that may lead to spontaneous abortion. This type of abortion is the disposal of pregnancy products before the twentieth week of gestation, without the use of medical and mechanical factors (12). Serological tests are the common diagnostic methods for congenital toxoplasmosis (13). Enzyme-linked immunosorbent assay (ELISA) test is currently the most widespread and most commonly used serological diagnosis method for toxoplasmosis (14). In recent years, efforts have been made to improve the ability to diagnose infections in pregnant women and congenital infections in the fetus and newborn. There are already a number of new methods to prove that there is great value for this purpose. For example, IgG avidity and polymerase chain reaction (PCR) applied on body fluids and tissue, as well as the western blot technique on the mother and infant serum samples, can be mentioned (15).
With regard to geographical and climatic differences in
the prevalence of toxoplasmosis, and the lack of sufficient
and precise data on the role of the parasite in abortion,
in this study, the seroprevalence of anti-
Materials and Methods
Lorestan province is the thirteenth province in Iran in terms of population and is considered as one of the most populous provinces in Iran. The city of Khorramabad is the capital of the province. Lorestan province is located in Western Iran and placed between the latitudes 32. 30´ and 48.1´ N and longitudes 55. 17´ and 61. 15´E. The long-term annual mean temperature and precipitation are 17.07°C and 580 mm, respectively. The weather of this province is variable and is classified as a region with a semi-arid climatic condition (16).
This case-control study was performed on 240 serum samples from women with first spontaneous abortion referred to the only maternity hospital in Khorramabad city, during 2016, as the case group. The control group consisted of 240 serum samples from women who had a normal delivery and referred to the hospital for a checkup and had no history of abortion. All of the subjects in both the case and control groups had a history of at least one successful pregnancy, as those who did not have successful pregnancies were not included in the study. After obtaining the written consent from the participants in the study, a questionnaire based on age, education (Low literate, Diploma, Academic degree), occupation (Employee, Student, Housewife), place of residence (Urban, Rural), contact with cats, and consumption of raw/half-cocked meat was filled out by the participants. The blood sampling and serum isolation procedures were done under sterile conditions.
The level of anti-T. gondii IgM and IgG antibodies were
measured in serum samples using the commercial kit, de
To distinguish between the acute and chronic infections, all IgM- and IgG-positive samples of the case group were examined to evaluate IgG avidity by using the ELISA kit according to the manufacturer.s instruction (ELISA: Euro immune Kit, Germany). The test result is expressed as relative index avidity (RIA). According to the kit manual, the values less than 40% were considered as negative while the value more than 60% were considered positive and the borderline ranged between 40-60% (18).
Statistical analysis was done using the SPSS 22.0 software
(SPSS Inc., Chicago, IL, USA). The Logistic regression
and chi-square tests were used to evaluate the association
This study was approved by The Ethics Committee of Lorestan University of Medical Sciences (No. 200.93.11707). The written informed consent was obtained from all the participants before sampling.
Serology status and demographic information
The results of the
Additionally, there was no significant difference between the case and control groups in terms of the prevalence of abortion in relation to education level (P=0.645) or the place of residence (city versus rural areas) (P=0.404). Out of all participants, 75.8% (182/240) of the case group and 72.5% (58/240) of the control group were living in the city. The results also showed that most of the women who had an abortion (67.1%) were housewives, and most of the women in the control group (61.7%) were employees, indicating that there is a significant difference in the relationship between occupation status and abortion rate (P<0.001). Also, 15% (36/240) of the women in the case group and 13.8% (33/240) of the control group kept a cat at home, but there was no significant difference between the two groups with regards to living near a cat (P=0.39).
|Variable||Case group n=240||Control group n=240||P value|
|Age (Y)||27 ± 6.499||27.01 ± 6.459||0.989|
|Level of education||0.645|
|Low literate||73 (30.4)||69 (28.8)|
|Diploma||109 (45.4)||104 (43.3)|
|Academic degree||58 (242)||67 (27.9)|
|Employee||168 (70)||79 (32.9)|
|Housewife||72 (30)||161 (67.1)|
|Residence in the city||0.404|
|Urban||182 (75.8)||174 (72.5)|
|Rural||58 (24.2)||66 (27.5)|
|Contact with cats||0.696|
|Yes||36 (15)||33 (13.8)|
|No||204 (85)||207 (86.2)|
|Seropositivity rate for
|Yes||8 (3.3)||1 (0.4)|
|No||232 (96.7)||239 (99.6)|
|Seropositivity rate for
|Yes||114 (47.5)||111 (46.3)|
|No||126 (52.5)||129 (53.7)|
Data are presented as mean ± SD or n (%).
All samples, which were positive in terms of anti-Toxoplasma IgM in both groups (9 samples) and IgG in the case group (114 samples), were evaluated by IgG avidity. Seven out of 8 (87.5%) sera, which were related to the case group, had low avidity indicating acute infection, whereas all positive IgG sera (100%) and 1 positive IgM sample, which was related to the control group had high avidity indicating chronic infection.
Maternal acute toxoplasmosis or congenital toxoplasmosis during pregnancy is one of the important factors that increase the chance of abortion. It was previously believed that the congenital toxoplasmosis is due to an initial infection that occurs during pregnancy (13), but not to the reactivation of a latent infection in pregnant women with an immune deficiency (19). In addition, some believe that latent toxoplasmosis can be reactivated to cause the congenital transmission of parasites to their fetus (20). Serological evidence suggests a high prevalence of toxoplasmosis worldwide (21), and in fact, based on several studies Iran is one of the countries with a considerable prevalence (9, 13, 22).
In this survey, we found that 8 out of 240 cases had the
With regards to other issues that may play as risk factors for abortion, our results showed that there was no significant relationship between the rate of abortion and urban or rural residence. Based on the results of this study with those of the present research, it can be concluded that health education and training classes for villagers has been effective in increasing the level of knowledge and personal care. Although there was no significant relationship between the level of education and prevalence of abortion, a significant correlation was observed between having a job and prevalence of abortion, since in the case group, 67.1% of the IgG-positive cases were housewives, and in the control group, 61.7% of the women were employees. The reason can be referred to as the lifestyle, which can affect the level of information. Furthermore, according to our results, there was no relationship between keeping a cat at home and the rate of abortion (24). In a study conducted in Egypt, the results showed that the seroprevalence of toxoplasmosis in high-risk pregnancy group was significantly more than a normal pregnancy group. Also, not consistent with our findings, in their study there was a significant difference between seropositivity and both living in a rural area, and undercooked meat consumption (25).
Due to the wide range of clinical signs of toxoplasmosis
and the chance of getting confused with other diseases, it
is necessary to use laboratory methods to confirm the clinical
diagnosis. The serological assays have different sensitivities
and specificities and are based on the affinity and
avidity of antibodies. Detection of specific IgG antibodies
is rarely a problem and has good sensitivity and specificity
in different methods (26). In contrast, isolation and detection
of IgM antibodies due to the less specificity of the
methods used, long-term half-life or false IgM antibody
resulted from other infections, leads to false-positive results,
unnecessary treatments and even a false decision to
terminate the pregnancy (27). Some IgM kits have lower
reliability and credibility, which leads to an unacceptable
increase in false-positive test results (28). For this purpose,
in 1997, the Food and Drug Administration (FDA)
advised physicians in the USA to clarify these limitations
and advised laboratory staff and physicians to make sure
of the quality of the kits prior to making decisions about
clinical management of patients (29). For this purpose,
the FDA has recommended that the positive IgMs should
be approved by IgG avidity test, which is provided to
discriminate between the old and new
In this study, IgG avidity test was used to evaluate IgM-
and IgG-positive cases. The result showed that 8 cases
of IgM-positive in the case group had low avidity, which
indicated an acute phase of infection. On the other hand, 1
case of IgM-positive in the control group had high avidity,
indicating a chronic phase of infection. Disagreement in
the results of different studies may be due to the patients’
varying health status, differences in consumption of raw
or undercooked meat, and keeping cats as pets at home
(34). In the current study, eating roast meat (locally called
Kebab) was very common, as it is a traditional food with
a high rate of consumption. As a result, this eating habit
is one of the important risk factors for
Healthcare providers in women’s hospitals should know that in the case of a pregnant woman the avidity test is not a validated and final test to be used solely for decision making, and that an equivocal IgG avidity result should not be considered in the diagnosis process.
According to the findings of this study, it is suggested
that the necessary health information, especially on the
This study was financially supported by Lorestan University of Medical Sciences, Research Center, Khorramabad, Iran (grant No. 35/93). The authors appreciate all people who provided any assistance in conduction of the present study. There is no conflict of interest in this study.
F.K., Sh.F., S.A.; Designed and supervised this study. M.J.T., B.E.; Developed an outline for the study and supervised the analysis process of the samples. F.K., A.K.R., P.H.; Wrote the original manuscript and Sh.F. revised it. S.J.S.T., M.J.T., B.E., A.K.R., P.H.; Contributed to data analysis and prepared the manuscript. All authors reviewed and approved the final version of the manuscript.