Toxoplasmosis and pregnancy: prevention, screening and treatment

What is toxoplasmosis and why is it monitored during pregnancy?

Toxoplasmosis is caused by a parasite, Toxoplasma gondii. In healthy adults it usually goes unnoticed or looks like a mild flu with a few swollen glands. Once infected, you are protected for life.

The risk concerns women who have never encountered the parasite and catch it for the first time during pregnancy: this is called a primary infection. The parasite can then cross the placenta and infect the foetus (congenital toxoplasmosis). That is why the blood test is part of the early pregnancy check-up described on our Giving birth in Paris page and at the first pregnancy appointment.

In France, according to the expert panel of the French College of Gynaecologists and Obstetricians (CNGOF), about 70% of pregnant women are not immune, and 0.2 to 0.25% have a primary infection during pregnancy.

How do you catch toxoplasmosis?

• by eating raw or undercooked meat containing parasite cysts;
• by swallowing parasite eggs present in soil: poorly washed vegetables, fruit or herbs, dirty hands after gardening;
• through contact with the faeces of cats that hunt or eat raw meat (litter tray, sandpit, garden).

What are the risks of toxoplasmosis for the baby at each stage of pregnancy?

The risk depends strongly on when the infection occurs. Two things change in opposite directions:

• transmission to the foetus is rare in early pregnancy and becomes common in late pregnancy;
• the severity of harm, on the contrary, is greater when infection occurs early.

These figures come from the Lyon cohort of women who were screened and treated. Across all stages, the average risk of transmission is 25 to 29%. When the foetus is infected, the baby is born alive in 95% of cases; 90% of infected children have no symptoms and 10% have a symptomatic form, which is severe in one third of these cases.

The possible effects are mainly neurological (calcifications, enlarged brain ventricles) and ocular (chorioretinitis, an inflammation of the retina that can appear years after birth). That is why an infected child is followed by a paediatrician and an ophthalmologist for several years.

How do I know if I am immune to toxoplasmosis?

A blood test (serology) looks for two types of antibody: IgG, a sign of past infection, and IgM, which points to a recent infection. In France, it is compulsory in the first trimester unless your immunity is already documented by a written result.

• IgG positive, IgM negative: you are immune. No special precautions or further tests are needed.
• IgG and IgM negative: you are not protected. The prevention measures apply and, in France, a blood test is repeated every month until birth.
• IgM positive: this may be a recent infection or antibodies that have persisted for a long time. The laboratory performs an IgG avidity test and compares with an earlier sample if you have one. A specialist opinion is sought if there is any doubt.

Keep your previous results: a blood test done before pregnancy is very helpful for dating an infection. If you are planning a pregnancy, a pre-conception blood test is useful.

How can I avoid toxoplasmosis during pregnancy if I am not immune?

Hygiene measures are simple, but the CNGOF expert panel stresses that they are often poorly followed. Yet they are the foundation of prevention.

On your plate

• Eat meat thoroughly cooked all the way through (beef, lamb, pork, horse, game, poultry): no steak tartare, carpaccio, rare or pink meat.
• Avoid raw, smoked or cured meats (Parma-style ham, saucisson, chorizo, air-dried beef).
• Wash vegetables, fruit and herbs carefully in water, especially if they have soil on them or are eaten raw. In restaurants, avoid raw salads and fresh herbs if you do not know how they were washed.
• Avoid raw goat's milk and raw oysters or shellfish.

In the kitchen

• Wash your hands with soap before cooking and after touching raw meat, vegetables with soil on them, or soil.
• Clean knives, chopping boards and worktops after preparing raw meat; if possible, use separate boards for raw and cooked food.

With cats and in the garden

• Ask someone else to change the litter tray. If that is not possible, wear gloves and change it every day.
• Avoid stroking unfamiliar or stray cats.
• Wear gloves for gardening and wash your hands afterwards.

For all dietary advice (listeriosis, fish, vitamins), see our article on nutritional needs in pregnancy.

Why is a monthly toxoplasmosis blood test done in France?

A primary infection usually causes no symptoms: only a blood test can detect it. Monthly testing of non-immune women, carried out in France since 1992, has two aims:

• to date the infection precisely, which allows the risk to the baby to be estimated;
• to start treatment as early as possible, ideally within three weeks of seroconversion.

In the Lyon cohort, introducing monthly screening was followed by a lower transmission rate and fewer symptoms in infected children at age 3. In 2020, the expert panel commissioned by the CNGOF recommended keeping this programme. A final test is usually done a few weeks after birth, to detect an infection caught at the very end of pregnancy.

What happens if I catch toxoplasmosis during pregnancy?

Seroconversion does not mean the baby will be ill. Care is organised with a multidisciplinary prenatal diagnosis centre.

• Immediate preventive treatment for the mother to limit the parasite crossing the placenta: spiramycin is used before 14 weeks; after that, the combination of pyrimethamine and sulfadiazine (with folinic acid) tends to be more effective according to the French randomised TOXOGEST trial. The choice and monitoring of treatment (blood tests for tolerance) are decided by your doctor.
• Amniocentesis: testing the amniotic fluid for the parasite by PCR is carried out some time after the infection and not before 18 weeks. It shows whether the foetus is infected.
• Frequent ultrasound scans, usually monthly, looking for signs in the brain or other abnormalities.
• At birth: tests on the newborn (cord blood, eye examination, imaging if needed) and long-term eye follow-up if the child is infected.

If the foetus is infected, treatment is adjusted. In the rare severe forms with major brain damage, a termination of pregnancy for medical reasons may be discussed with the couple, but is never imposed.

When should I go to the maternity unit urgently?

Toxoplasmosis itself does not require a visit to the emergency department. Simply tell your doctor about a fever with swollen glands or a change in your blood test result. However, as in any pregnancy, some signs mean you should go straight to your maternity unit's emergency department, open day and night (the one where you are registered: Maternité Sainte-Félicité or Clinique Sainte-Thérèse):

• vaginal bleeding, even if light;
• leaking fluid, clear or coloured, from the vagina;
• regular or painful contractions before 37 weeks;
• reduced or absent baby movements (once you usually feel them);
• a fever of 38 °C or more, shivering, burning when passing urine with back pain;
• severe headaches, visual disturbance, pain under the ribs on the right or in the pit of the stomach, sudden swelling of the face or hands;
• severe or constant abdominal pain, a fall or a blow to the abdomen;
• intense itching of the palms and soles of the feet, especially at night.

If you feel faint, have heavy bleeding or very severe pain, in France call 15 (SAMU) or 112, or your local emergency number.

Frequently asked questions

General information article: it does not replace a medical consultation. In an emergency, call 15 or 112 in France, or your local emergency number.