Toxoplasmosis in pregnant women: how to detect it and protect your baby

During pregnancy, every decision regarding food, hygiene, and contact with animals can raise doubts. Future parents face endless medical advice and warnings, which are often difficult to tell apart. Among all of them, there is a silent risk that can affect the baby if precautions are not taken: toxoplasmosis in pregnant women.

Its detection through a blood test is the easiest way to confirm its presence. For this, you can rely on Ambar Lab, where we have more than 3,000 laboratory tests available, including those to detect toxoplasmosis in pregnant women. Below, we explain what toxoplasmosis is, how it is transmitted, and what can happen when it appears.

What is toxoplasmosis?

Toxoplasmosis is an infection caused by a parasite called Toxoplasma gondii. It is a protozoan widely distributed throughout the world that can infect humans and other warm-blooded animals.

In people with normal defences, the infection usually goes unnoticed or manifests with mild symptoms. However, when the infection is acquired for the first time during pregnancy, Toxoplasma gondii can cross the placenta and reach the foetus, leading to congenital toxoplasmosis.

Why toxoplasmosis in pregnant women is a concern

These are the three main reasons:

1. Primary infection during pregnancy can be transmitted to the foetus, leading to congenital toxoplasmosis.
2. The risk of transmission increases with gestational age, but the most severe forms are usually associated with infections in the first trimester of pregnancy.
3. Many mothers are asymptomatic, which makes it necessary to rely on laboratory tests to detect the infection and assess its impact.

How is it transmitted?

To understand toxoplasmosis in pregnant women, it is key to know the main routes of infection. The infection is primarily acquired through the digestive route.

Food route: meat, cured meats and water

The ingestion of Toxoplasma gondii cysts present in food is the most frequent route of transmission:

• Raw or undercooked meat (especially lamb, pork, or beef) and cured meats made with raw meat can contain cysts of the parasite if the animal was infected.
• Contaminated water can also act as a vehicle for transmission in certain areas.
• Raw vegetables and ready-to-eat salads can become contaminated if they have been in contact with soil or water containing Toxoplasma gondii oocysts. A recent European study detected genetic material of the parasite in around 4.1% of the salad bags analysed, which underlines the need for extreme hygiene of these products, especially in vulnerable groups such as pregnant women.

Contact with cats and contaminated soil

Infected cats can shed Toxoplasma gondii oocysts in their faeces for a limited period of time. These oocysts can reach:

• Litter boxes.
• Gardens, vegetable patches, or soil areas where children play.
• Contaminated surfaces and objects that are later handled with the hands.

People become infected if, after handling contaminated soil or cat faeces (or any object containing them), they bring their hands to their mouth without washing them properly.

Other transmission routes

Although they are less frequent, other described transmission mechanisms exist:

• Blood transfusions or organ transplants from infected donors.
• Congenital transmission, when a mother acquires toxoplasmosis for the first time during pregnancy and the parasite crosses the placenta.

In daily clinical practice, toxoplasmosis in pregnant women is evaluated by taking these risk factors into account and integrating the information with laboratory results.

What happens to a pregnant woman with toxoplasmosis?

Toxoplasmosis in pregnant women can occur without symptoms or with a clinical picture very similar to a mild viral infection. However, its consequences for the foetus can be significant.

Common symptoms in the mother

In most cases, the pregnant woman:

• Presents no symptoms or these are very discrete.
• May report tiredness, general malaise, low-grade fever, muscle pain, or swollen lymph nodes, especially in the neck.

These signs are often confused with other mild infections, so toxoplasmosis in pregnant women is rarely suspected based on clinical signs alone. Diagnosis is primarily based on serology and other complementary tests.

Risks to the foetus according to gestational age

When talking about toxoplasmosis in pregnant women, the main focus is the foetus:

• As pregnancy progresses, the probability of transmission to the foetus increases, but the severity of the sequelae usually decreases when the infection occurs in the late stages.
• In the first trimester, the risk of transmission is lower, but the infection can cause spontaneous abortion, foetal death, or severe malformations.
• In the second trimester, transmission is more likely, and neurological and ocular alterations may appear.
• In the third trimester, the foetus is infected more easily, but the newborn is often asymptomatic at birth, with the possibility of developing ocular or neurological complications years later.

Possible consequences for the newborn

Congenital toxoplasmosis can manifest in very varied ways:

• Hydrocephalus or ventriculomegaly (accumulation of fluid in the brain).
• Intracranial calcifications.
• Chorioretinitis (inflammation of the retina) with a risk of vision loss.
• Seizures.
• Psychomotor development delay.
• Jaundice, anaemia, or hepatosplenomegaly in the neonatal period.

How is toxoplasmosis diagnosed in pregnant women?

The evaluation of toxoplasmosis in pregnant women is based on laboratory tests to find out if the woman:

• Has never been in contact with the parasite.
• Has prior immunity.
• Has been recently infected, with a possible risk of transmission to the foetus.

Serology: IgG and IgM antibodies

The first step is usually the determination of IgG and IgM antibodies against Toxoplasma gondii:

• IgG negative / IgM negative: suggests that the pregnant woman has had no prior contact with the parasite and is susceptible to infection during pregnancy.
• IgG positive / IgM negative: compatible with an old infection and established immunity; in general, the risk of transmission to the foetus is very low.
• IgG positive / IgM positive: may indicate a recent infection, but interpretation requires caution, as IgM can persist for months.
• IgG negative / IgM positive: suggests a very recent infection, although false positive results must also be ruled out.

IgG avidity study

When positive IgG and IgM are detected in a pregnant woman, the IgG avidity study is a key tool to distinguish between recent and past infection. Avidity reflects how strongly the IgG antibodies bind to the antigen:

• Low avidity: points toward a recent primary infection.
• High avidity: practically rules out a primary infection in the last few weeks or months (for example, in the last 16 weeks according to the criteria of some laboratories).

PCR for Toxoplasma gondii in amniotic fluid or other samples

When foetal infection is suspected, PCR to detect Toxoplasma gondii DNA in amniotic fluid is the reference technique to confirm if the foetus is infected.

• It is usually performed after documenting a recent maternal infection and at a specific point in the pregnancy, as indicated by clinical protocols.
• A positive result indicates foetal infection and helps to adjust treatment and follow-up.

How is toxoplasmosis treated during pregnancy?

The pharmacological management of toxoplasmosis in pregnant women has two main objectives:

1. Reduce the probability of transplacental transmission.
2. Decrease the severity of congenital toxoplasmosis manifestations when the foetus is infected.

Therapeutic schemes depend on the timing of the pregnancy, whether foetal infection is confirmed or not, and the characteristics of each patient. Regarding the most commonly used drugs, they are spiramycin, when maternal infection is detected in the early stages of pregnancy and foetal infection has not yet been proven, and a combination of pyrimethamine, sulfadiazine, and folinic acid, which is usually reserved for situations where foetal infection is confirmed or strongly suspected.

Follow-up of the pregnancy and the newborn

Clinical protocols usually incorporate:

• Serial ultrasounds to assess foetal anatomy and development, as well as the presence of findings suggestive of congenital toxoplasmosis (ventriculomegaly, calcifications, hepatosplenomegaly, etc.).
• Amniocentesis with PCR for Toxoplasma gondii when indicated, to confirm or rule out foetal infection.
• Serological studies of the newborn (specific IgM/IgA, serial IgG) and, in many cases, PCR in blood, urine, CSF, or placenta, to determine if congenital toxoplasmosis exists.
• Long-term follow-up with ophthalmological and neurological checks, as some complications, such as chorioretinitis, can manifest years after birth.

Caring for pregnancy from the laboratory

Toxoplasmosis in pregnant women is a clear example of how an infection, often silent in the mother, can have an impact on the baby’s health. At Ambar Lab, we are your ally so that you can undergo the necessary tests for its detection.

We have a highly qualified professional team that offers you personalised advice, reliable results, and close follow-up so that you have all the necessary information during this important stage. Get in contact with us today to obtain more information about the toxoplasmosis screening test for pregnant women and access a fast and safe diagnosis.