Toxoplasmosis and pregnancy: complete guide (symptoms, prohibited foods, prevention)

By: Dr Elie Servan-Schreiber (Gynécologue-obstétricien) — 11/03/2020

Toxoplasmosis is a parasitic infection caused by Toxoplasma gondii. According to Santé Publique France, approximately 45% of women of childbearing age are immune in France. For the remaining 55%, simple dietary precautions can prevent any risk during pregnancy. This comprehensive guide explains how screening works, which foods to avoid, and what daily habits to adopt to protect your baby.

Definition and key facts

Toxoplasmosis is an infectious disease caused by a microscopic parasite called Toxoplasma gondii. This parasite is an obligate intracellular protozoan: it needs to penetrate the cells of a living organism to develop and reproduce.

The definitive host of the toxoplasma parasite is the cat (and more broadly, felines). It is in the cat's intestine that the parasite completes the sexual phase of its reproductive cycle. Humans are accidental hosts: they can harbor the parasite, but it cannot reproduce in the same way.

In healthy adults, toxoplasmosis most often goes completely unnoticed, or presents with mild symptoms. It then confers lifelong immunity. The problem arises when a non-immune pregnant woman contracts the infection for the first time during pregnancy: the parasite can then cross the placenta and reach the fetus.

Key figures in France

• 45% of women of childbearing age are immune to toxoplasmosis (seroprevalence has been steadily declining since the 1960s, when it exceeded 80%).
• Approximately 2,500 seroconversions per year are estimated among pregnant women (Santé Publique France).
• Approximately 300 cases of congenital toxoplasmosis per year are recorded, the majority without serious sequelae thanks to screening and early treatment (Inserm data).
• France is one of the few countries in the world to require mandatory serological screening at the beginning of pregnancy, followed by monthly monitoring for non-immune women.

Symptoms of toxoplasmosis in pregnant women

This is one of the most deceptive aspects of toxoplasmosis: in 80 to 90% of cases, the infection is completely asymptomatic. The pregnant woman does not realize she has been infected. This is precisely why systematic blood screening is essential.

When symptoms do appear, they are generally mild and non-specific. They may resemble a flu-like syndrome:

• Unusual fatigue that may last several weeks
• Mild fever (often below 38.5°C / 101.3°F)
• Swollen lymph nodes (lymphadenopathy), mainly in the neck area
• Muscle pain and body aches
• Headaches

These symptoms are easily confused with a simple cold or pregnancy-related fatigue. That is why you should never rely on the absence of symptoms to conclude there is no infection. Only monthly serology (blood test) can confirm or rule out toxoplasmic seroconversion.

How do you catch toxoplasmosis?

Contamination always occurs through the oral route, meaning by ingesting the parasite. There are three main routes of transmission:

1. Raw or undercooked meat

This is the most common route of contamination in France. Livestock (beef, lamb, pork, game) can carry toxoplasma cysts in their muscles. When meat is consumed raw, rare, or undercooked, the parasite remains viable and can infect the person who ingests it.

2. Fruits and vegetables contaminated by soil

Cats excrete the parasite's eggs (called oocysts) in their feces. These oocysts can survive for months in moist soil. Rainwater carries them to water tables, farming areas, and pastures. Fruits and vegetables grown in the ground can be contaminated by these oocysts through irrigation water or direct contact with the soil.

3. Contact with soil or cat litter

Gardening with bare hands, handling contaminated soil, or contact with soiled cat litter can lead to contamination if hands are brought to the mouth or if hand hygiene is insufficient after contact.

The parasite's life cycle

To fully understand the risks, here is the complete life cycle of Toxoplasma gondii:

1. The infected cat excretes oocysts in its feces for 1 to 3 weeks after its own contamination.
2. The oocysts mature in the environment (soil, water) and become infectious within 1 to 5 days.
3. Runoff water contaminates farming areas and water used for livestock.
4. Livestock ingest the oocysts and develop cysts in their muscles (meat).
5. Humans become infected by consuming contaminated undercooked meat, unwashed contaminated fruits or vegetables, or through direct contact with soil or litter.

It is important to note that direct transmission from cats to humans is extremely rare. Simply petting a cat does not pose a risk. It is contact with its feces (litter) or with the environment contaminated by its feces that constitutes the danger.

Toxoplasmosis during pregnancy: prohibited foods

If you are not immune to toxoplasmosis, you will need to adapt your diet throughout your pregnancy. Here is a comprehensive summary table of foods to avoid, those requiring precautions, and those you can consume without worry. These recommendations are in addition to the precautions to take for listeriosis, another foodborne infection to watch for during pregnancy.

Prohibited foods (avoid completely)

• Raw or rare meat: steak tartare, beef carpaccio, rare or blue steak
• Raw cured meats: dry sausage, raw ham (Parma ham, Serrano, Bayonne), bresaola, coppa, uncooked chorizo
• Uncooked smoked meat: dried beef, uncooked smoked duck breast
• Unpasteurized raw milk and raw milk cheeses (combined risk of toxoplasmosis and listeriosis)
• Foie gras semi-cooked or raw (sterilized canned foie gras is permitted)
• Game (venison, wild boar, deer): particularly at risk as these animals live in direct contact with the environment

Foods requiring precautions

• Fresh fruits and vegetables: must be thoroughly washed with clean water, or even with white vinegar. This particularly applies to foods in contact with soil: lettuce, tomatoes, strawberries, radishes, fresh herbs (parsley, chives, basil)
• Raw vegetables at restaurants: prefer cooked vegetables when you cannot control the washing process
• Fresh aromatic herbs: wash them as carefully as vegetables
• Berries and red fruits grown close to the ground: wash thoroughly before consuming

Note that fruits whose skin is not eaten (banana, orange, watermelon, melon) do not require special precautions regarding toxoplasmosis, since the consumed part has not been in contact with soil.

Permitted foods (no restrictions)

• Well-cooked meat: cooking to a core temperature above 67°C (153°F) destroys the parasite. A well-done steak, a thoroughly cooked roast, or braised meat are perfectly safe
• Pasteurized products: pasteurized milk, yogurts, pasteurized cheeses
• Canned and sterilized jarred foods: the heat treatment of canned goods eliminates the parasite
• Frozen products: freezing at -18°C (0°F) for at least 3 days kills toxoplasma cysts. However, note that the refrigerator alone is not sufficient
• Cooked cured meats: cooked ham, mortadella, cooked frankfurters
• Cooked fish and seafood: no risk of toxoplasmosis (but beware of listeriosis risk for smoked fish)
• Eggs: no risk of toxoplasmosis regardless of cooking method

Practical tip: if in doubt about how well meat is cooked, use a kitchen thermometer. The core temperature must exceed 67°C (153°F) to ensure the parasite is destroyed. Home freezing at -18°C (0°F) for at least 3 days is also effective for meats you wish to store.

Toxoplasmosis serology (blood test)

Toxoplasmosis screening is part of the mandatory first prenatal check-up tests in France. It is prescribed at the first pregnancy consultation, usually during the first trimester. It is a simple blood test that looks for two types of antibodies:

• IgG (Immunoglobulin G): memory antibodies. Their presence indicates that you have already been in contact with the toxoplasma parasite and that you are immune.
• IgM (Immunoglobulin M): recent infection antibodies. Their presence may indicate an ongoing or recent infection.

How to interpret the results?

• IgG positive + IgM negative: you have long-standing immunity. Good news — you are protected and no further monitoring is needed for toxoplasmosis.
• IgG negative + IgM negative: you are not immune. A serological check will be performed every month until delivery to detect any seroconversion as early as possible.
• IgG positive + IgM positive: an ambiguous situation requiring additional tests (IgG avidity test) to determine whether the infection is recent or old.
• IgG negative + IgM positive: rare, suggests a very recent infection. A follow-up test at 2-3 weeks is needed to confirm.

The term seroconversion refers to the change from a negative serological status (not immune) to positive (immune), meaning an infection has occurred. It is this seroconversion occurring during pregnancy that concerns doctors.

Immune or not immune: what to do?

If you are immune

Good news: long-standing immunity to toxoplasmosis (IgG positive, IgM negative) protects both you and your baby. In practical terms, this means:

• No monthly blood test for toxoplasmosis
• Fewer dietary restrictions related to this specific parasite
• You can consume raw cured meats, dry sausage, and carpaccio without risk of toxoplasmosis

However, please note: immunity to toxoplasmosis does not protect against listeriosis. Precautions regarding raw milk cheeses, deli meats sold at the counter, and refrigerated products remain valid. Rare meat is still not recommended due to the risk of listeria.

If you are not immune

Don't panic: the majority of non-immune women carry their pregnancy to term without any problems, provided they follow preventive measures. Your monitoring will include:

• A monthly blood test for toxoplasmosis serology, until delivery
• Strict dietary precautions (see the prohibited foods section above)
• Enhanced hygiene measures (see the prevention section below)

Monthly screening is your best ally: it allows for the detection of any infection very quickly and the initiation of treatment before the parasite reaches the fetus.

Seroconversion during pregnancy

Toxoplasmic seroconversion during pregnancy means that you were infected by the parasite while you were not immune. This is a situation taken very seriously, but it is important to know that seroconversion does not automatically mean the fetus is affected. The passage of the parasite through the placenta is not systematic, and it strongly depends on the stage of pregnancy.

Risk by trimester

• First trimester (before 16 weeks): the risk of transplacental passage is low, around 5 to 10%. However, if the parasite reaches the fetus at this early stage, the consequences can be severe (neurological and eye damage, or even miscarriage in the most severe cases).
• Second trimester: the risk of passage is intermediate, around 25 to 30%. Fetal damage is possible but generally less severe than in the first trimester.
• Third trimester (after 28 weeks): the risk of passage is high, 60 to 80%. Paradoxically, the consequences are usually less serious, often with subclinical forms (no apparent symptoms at birth), but ophthalmological monitoring of the newborn remains necessary.

Management in case of seroconversion

As soon as seroconversion is confirmed, your doctor will implement the following protocol:

1. Treatment with spiramycin (Rovamycin): this antibiotic is prescribed immediately. It reduces the risk of the parasite crossing the placenta by approximately 60%.
2. Amniocentesis: performed from 18 weeks of gestation and at least 4 weeks after the estimated date of infection. A sample of amniotic fluid is taken to look for the parasite's DNA using PCR testing.
3. If the PCR is negative (fetus not infected) : spiramycin is continued until delivery. Regular ultrasound monitoring is maintained.
4. If the PCR is positive (fetal infection confirmed) : this is then called congenital toxoplasmosis. The antibiotic therapy is changed (pyrimethamine-sulfadiazine combination, which is more potent) and ultrasound monitoring is carried out at a specialized referral center, looking for signs of fetal damage.

Uncertain seroconversion

Sometimes, serology results are not clear-cut. This is particularly the case when the first test shows both positive IgG and IgM. The question is whether this is a recent infection (during pregnancy) or a serological "scar" from an old infection.

To answer this, two tools are available:

• Previous serum: if you had a blood test before pregnancy (for another reason), the laboratory can perform a retrospective serology on the stored serum.
• IgG avidity test: this test measures the binding strength of IgG antibodies. High avidity indicates an infection dating back more than 4 months (thus before pregnancy). Low avidity suggests a recent infection.

Prevention: essential precautions

If you are not immune, here is a list of daily habits to adopt to minimize the risk of contamination. These measures are simple and effective:

In the kitchen

• Cook meat thoroughly (core temperature above 67°C / 153°F). Avoid rare or medium-rare cooking. Prefer well-done, braised, or slow-cooked meats.
• Wash fruits and vegetables thoroughly with clean water, scrubbing them under running water. Soaking in vinegar water (one tablespoon of white vinegar per liter of water) enhances the cleaning.
• Wash aromatic herbs (parsley, chives, basil) with the same care as vegetables.
• Wash your hands thoroughly after handling raw meat, fruits, or soil-covered vegetables.
• Clean surfaces and utensils that have been in contact with raw meat before preparing other foods.
• Avoid raw vegetables at restaurants when you cannot verify the washing conditions.

In the garden and outdoors

• Wear gloves when gardening or handling soil.
• Wash your hands after any contact with soil, even if you wore gloves.
• Avoid putting your hands to your mouth while gardening.

With your cat

• Have someone else change the litter (partner, family). If that is not possible, wear disposable gloves and wash your hands thoroughly afterwards.
• Change the litter daily: oocysts become infectious after 1 to 5 days. Daily cleaning therefore reduces the risk.
• Wash your hands after petting the cat.

Freezing

• Freezing at -18°C (0°F) for at least 3 days destroys toxoplasma cysts in meat. This is a useful additional precaution, but it does not replace cooking.
• Note: the refrigerator (between 0 and 4°C / 32-39°F) does not destroy the parasite.

Cats and toxoplasmosis

Rest assured immediately: it is absolutely not necessary to give up your cat during pregnancy. This misconception causes unjustified abandonments every year. Here is why the risk from cats is actually very limited:

• An indoor cat that has never been outside and is fed commercial food (kibble, canned food) has virtually no chance of carrying the toxoplasma parasite. The risk is virtually zero.
• Even a cat with outdoor access only excretes oocysts for 1 to 3 weeks during its lifetime, during its initial infection. The window of risk is therefore very short.
• Oocysts are not immediately infectious: they become so after 1 to 5 days in the environment. Daily litter cleaning eliminates this risk.
• Contamination through petting is considered extremely rare. The parasite is not transmitted through fur. The risk comes exclusively from contact with feces.

In summary: keep your cat, have someone else change its litter, and wash your hands after cuddles. These simple precautions are more than sufficient.

Our expert's opinion

Dr. Elie Servan-Schreiber, physician:

"Toxoplasmosis is one of the infections that is systematically screened for in France, and that is an excellent thing. My main advice to non-immune mothers-to-be: do not live this period in anxiety. The preventive measures are simple and monthly monitoring is very effective. In the vast majority of cases, pregnancies proceed perfectly well. Remember three reflexes: cook meat thoroughly, wash fruits and vegetables well, and delegate the cat litter cleaning. If you follow these three rules, the risk becomes extremely low. And if seroconversion does occur, current management with spiramycin and specialized follow-up achieves excellent results."