Pregnancy toxoplasmosis is a parasitic disease caused by the penetration of T.gondii into the body of a pregnant woman. In most cases, this pathology is asymptomatic, less often accompanied by a flu-like symptom complex. Diagnosis includes serological examination with the determination of IgM and IgG, ultrasound examination of the fetus and amniocentesis followed by PCR of amniotic fluid. The drug treatment option depends on the infection of the fetus and may consist of macrolide antibiotics or a combination of sulfonamide and a folic acid antagonist.
Toxoplasmosis during pregnancy is an infectious disease caused by toxoplasmas, which is of great importance in obstetrics and gynecology due to the transplacental transmission pathway. According to statistics, about 15-25% of women aged 15 to 45 years are infected with T.gondii. The total incidence of congenital toxoplasmosis ranges from 1 to 10 cases per 10,000 newborns, of which 3-10% have severe developmental abnormalities. At the same time, about 55% of women who gave birth to infected children did not notice any signs of the disease. As a rule, women with immunodeficiency and living or traveling in endemic zones: France, Latin America and South Africa are at a higher risk of developing pregnancy toxoplasmosis.
The causative agent of pregnancy toxoplasmosis is Toxoplasma gondii. It is an obligate intracellular parasite ranging in size from 4 to 8 microns. Depending on the environment, toxoplasma can be in three forms: oocyst, tissue cyst and tachyzoitis. The first two are invasive for humans. Infection with cysts occurs when using infected meat products, oocytes – when in contact with the ground during gardening or eating unwashed vegetables and fruits. Toxoplasmas in the form of oocysts are able to remain viable for a long time, especially being in warm and humid conditions, which significantly increases the risk of their transmission. When parasites enter the body, they transform from invasive forms into tachyzoites, which cause the clinic of the disease and infection of the fetus against the background of pregnancy toxoplasmosis.
There are several variants of the path of human infection with T.gondii – eating raw minced meat or poorly heat-treated meat, contact with cat feces or soil containing oocysts, transplacental transmission from mother to child and transfusion of infected blood. A significant part of cases (up to 65%) of pregnancy toxoplasmosis occurs against the background of the consumption of infected food and water, passes in the form of primary infection. In contact with cats, the main danger is posed by pets who live on the street or eat raw meat.
An infected person can only be a source in the case of blood or organ donation. The risk of developing pregnancy toxoplasmosis increases significantly when visiting regions with a high prevalence of toxoplasmas: France, Latin America and southern Africa. It is generally believed that even with a single ingestion of T.gondii, a person remains infected for life, and the disease itself proceeds in a subclinical form. However, only in isolated cases, pregnancy toxoplasmosis is caused by the activation of a persistent infection.
More than 90% of cases of pregnancy toxoplasmosis are asymptomatic, in the form of a healthy carrier. The development of a pronounced clinic is more likely in pregnant women with weakened immunity – against the background of concomitant infectious or bacterial diseases, the use of GCS, the early stages of AIDS, etc. The incubation period in such cases can range from 1 to 3 weeks after the parasite enters the body. Acute pregnancy toxoplasmosis is characterized by a flu-like variant of the course: a rise in body temperature to 37.5–38 ° C, general weakness and malaise, headache, enlarged lymph nodes, less often – hepatosplenomegaly. Pregnant women rarely have toxoplasmosis chorioretinitis, even less often – conjunctivitis, keratitis or iridocyclitis. Only against the background of a pronounced deficiency of immunity, pregnancy toxoplasmosis can cause severe complications in the form of encephalitis, hepatitis, myocarditis or pneumonia.
Toxoplasmosis belongs to the group of TORCH infections, which includes infectious diseases that can have a teratogenic effect. Basically, the danger to the fetus is the primary infection of the mother, chronic pregnancy toxoplasmosis rarely causes intrauterine transmission. Infection occurs in the interval from 1 to 4 months after the penetration of tachyzoites into the placenta, the risk of infection increases with the gestation period. According to statistics, the frequency of transmission of parasites to the fetus against the background of lack of treatment for pregnancy toxoplasmosis in the third trimester is 10-12 times higher than in the first. Despite this, the earlier the infection of the fetus occurred, the worse the prognosis. When toxoplasmas enter the fetus in the first trimester, spontaneous abortions and severe developmental abnormalities may occur. Later congenital toxoplasmosis is manifested by Sabin’s tetrad: chorioretinitis, cerebral dropsy, convulsive syndrome, intracranial calcification. Severe intrauterine growth retardation and microcephaly may also be present. Their presence indicates acute pregnancy toxoplasmosis.
The diagnosis of pregnancy toxoplasmosis is based on anamnestic data, identified symptoms, results of laboratory and instrumental studies. When collecting an anamnesis by an obstetrician-gynecologist or an infectious disease specialist, all the circumstances under which infection with toxoplasmas could occur are clarified: eating raw meat, unwashed vegetables or fruits, contact with street cats, working with the ground in the garden, staying in endemic areas. Physical examination in women with pregnancy toxoplasmosis can reveal a flu-like symptom complex, but in the vast majority of cases it is uninformative.
Serological tests, ultrasound scanning and puncture of the amniotic membrane of the fetus play a leading role in the diagnosis of pregnancy toxoplasmosis. Laboratory diagnostics is often the first step and it is implemented by enzyme immunoassay (ELISA) or special test systems. The essence of this study is to determine the immunoglobulins of class M (IgM) and G (IgG). Their complete absence refutes the diagnosis of pregnancy toxoplasmosis. The presence of IgM and its increase by 4 times or more indicates primary infection of T.gondii. Further, the titer gradually continues to increase and reaches a maximum 5-20 days after the invasion. The first manifestation of IgG in the mother’s blood occurs after 7-14 days and reaches its maximum concentration in the interval from 3 to 6 months. In most cases, a high IgG level indicates a latent course of pregnancy toxoplasmosis. If positive results are obtained, the study should be repeated 3-4 times within 2-3 weeks.
Ultrasound for women with suspected pregnancy toxoplasmosis is necessary to assess the condition of the fetus. In most cases, it is not possible to identify any pronounced signs of congenital toxoplasmosis or the changes present are not enough to confirm the diagnosis. The main manifestations of fetal infection against the background of pregnancy toxoplasmosis include a general delay in intrauterine development and disorders of the structure of the central nervous system – hydro- or microcephaly, the formation of calcifications. Termination of pregnancy is recommended only if severe morphological abnormalities are detected.
Puncture of the amniotic membrane (amniocentesis) is required in cases of primary pregnancy toxoplasmosis against the background of low information content of serological diagnostics and the presence of ultrasound signs of fetal damage. The decision on the expediency of puncture of the amniotic sac is made by the treating infectious disease specialist together with neonatologists and obstetricians-gynecologists. The essence is to take amniotic fluid and determine the presence of T.gondii in it by polymerase chain reaction (PCR). The sensitivity and specificity of this procedure ranges from 90-95%. As a rule, amniocentesis in the presence of signs of pregnancy toxoplasmosis is performed no earlier than 18 obstetric weeks, which is associated with a high risk of false positive results. Also, this study is shown only 4 weeks after the alleged infection. Cordocentesis, which was previously considered the “gold standard”, is now almost not used due to the risk to the fetus, the high informativeness of amniocentesis and PCR.
Treatment is necessary only in cases of acute pregnancy toxoplasmosis, accompanied by clinical manifestations. In the absence of clinical symptoms of infection, recovery occurs independently. Depending on the lesion of the fetus, there are two directions of drug therapy for pregnancy toxoplasmosis. In the absence of signs of infection of the fetus, macrolide antibiotics (spiramycin) are used according to the results of PCR of the amniotic fluid. These agents are able to accumulate in the tissues of the placenta and prevent a vertical transmission path.
If infection of the fetus is confirmed or suspected against the background of pregnancy toxoplasmosis, pharmacotherapy should consist of a folic acid antagonist (pyrimethamine) and sulfonamide (sulfadiazine). The first one is able to suppress cell division in the bone marrow, so its purpose is always supplemented with folic acid preparations. Also, the use of the drug is contraindicated in the first trimester of pregnancy due to the potential teratogenic effect. This treatment option is aimed at reducing the severity of the disease in the child and improving the overall prognosis.
Prognosis and prevention
The prognosis for a woman with pregnancy toxoplasmosis is favorable. Almost all cases end in clinical recovery. The prognosis for the unborn child directly depends on the trimester in which the infection occurred – the penetration of parasites into the fetus in the first trimester is associated with a high risk of spontaneous abortion or severe developmental abnormalities.
Prevention of pregnancy toxoplasmosis implies the rupture of all mechanisms of transmission of infection and screening of pregnant women. The first part of preventive measures includes the use of only clean water and products that have undergone high-quality heat treatment, restriction of work with the ground and contact with cats, thorough washing of vegetables and fruits, etc. Screening of toxoplasmosis is indicated only for pregnant women with a high risk of infection and includes monthly serological monitoring.