Toxoplasmosis and pregnancy

Toxoplasmosis is an infection that can affect the growing baby in pregnancy.

What is toxoplasmosis?

Toxoplasmosis is an infection caused by the parasite Toxoplasma gondii, a microscopic single-cell organism that can be found in meat, cat faeces, the soil where cats defecate and unpasteurised goats’ milk. The parasite can infect most birds and warm-blooded animals, including humans. Cats are the only animals that can have infected faeces. The organism completes its sexual cycle in the gut of members of the cat family. Following infection through eating birds, mice or other raw meat, a cat can shed infectious faeces for about 14 days. A healthy cat will not normally be a source of infection again, but sick cats may re-shed infected faeces.

How is toxoplasmosis caught?

Toxoplasmosis is caught by eating anything infected with, or contaminated by, the parasite.

This could be: 

  • raw or undercooked meat (meat showing any traces of pink or blood), and raw cured meat such as Parma ham or salami
  • unwashed vegetables and fruit 
  • cat faeces or soil contaminated with cat faeces 
  • unpasteurised goats’ milk and dairy products made from it.

Humans may become infected in any of the following ways: 

  • Eating the organism in soil or water that has been contaminated with cat faeces.
  • Eating the organism in raw or undercooked meat from infected animals (particularly sheep and pigs, but also cows and deer).
  • Drinking unpasteurised milk from infected goats.
  • Transmission of the organism across the placenta after maternal infection (mother to unborn baby).
  • Transmission of the organism from infected matter entering human body fluids; if, for example, during the process of lambing, material splashes into eyes or open cuts.
  • Transmission of the organism from transplanted organs or blood products from other humans with acute or latent toxoplasmosis or inhalation of sporulated oocysts (possible but very unusual). 

Toxoplasmosis can not be caught by stroking a cat or having a cat as a pet. The infection comes from coming into contact with the infected faeces of a cat. 

Person-to-person infection is not possible, except from mother to unborn child. Infection is followed by the replication of the parasite in the blood and the invasion of organs and tissue. The incubation period is 5–23 days.

Who is at risk of toxoplasmosis?

Anyone who eats anything infected with the organism is at risk of catching the infection. Some women may be at increased risk due to the job they do, for instance catering, working on the land or farming. Lambing is a particular risk for pregnant women.

How to avoid toxoplasmosis during pregnancy

  • Only eat meat that has been thoroughly cooked (ie, with no trace of blood or pinkness).
  • Avoid raw cured meat, such as Parma ham. 
  • Wash hands, chopping boards and utensils thoroughly after preparing raw meat. 
  • Wash all fruit and vegetables thoroughly before cooking/eating to remove all traces of soil.
  • Don’t drink unpasteurised goats’ milk or eat dairy products made from it. 
  • Wear gloves when gardening and wash hands and gloves afterwards – if you eat while gardening wash your hands first, and try to avoid gardening in areas that may have been soiled with cat faeces. 
  • Cover children’s sandpits to prevent cats using them as litter boxes.
  • Remove faeces from cat litter tray every day wearing rubber gloves (or ask someone else do this), scald trays regularly with boiling water.
  • If you are handling litter trays, wash gloves and hands thoroughly afterwards.
  • Do not handle lambing ewes and do not bring lambs into the house.
  • Cats are the only animals that can shed this parasite in their faeces. Provided precautions are taken, cats are not a particular risk to a pregnant woman. Like human adults, cats can sometimes, but not always, become sick when infected with the toxoplasmosis infection, so care of a sick cat should be left to someone else.

The effects of toxoplasmosis

Toxoplasmosis does not usually cause any symptoms and in most cases a person does not realise they have caught the infection. It can cause symptoms similar to flu or glandular fever, sometimes including swollen lymph nodes. Once a person has had the disease they are generally thought to be protected for life, unless they suffer an impairment of their immune system.

Toxoplasmosis can be dangerous to humans if their immune system is underdeveloped or compromised, as in the case of an unborn baby, somebody with HIV/AIDS or on immuno-suppressant drugs. In such cases, the immune system is unable to restrict the spread of the parasite, which can then cause damage.

Toxoplasmosis during pregnancy

Toxoplasmosis is only a risk to an unborn baby if caught for the first time during pregnancy or within a few weeks prior to conception. An unborn baby who contracts the disease is said to have congenital toxoplasmosis. The degree of risk to the fetus, and the damage caused, depends on when in pregnancy the mother acquired the infection.

If you catch toxoplasmosis for the first time during pregnancy, it does not necessarily mean that your baby will be infected. On average, only four in ten of such infections will pass to the unborn baby. Caught during pregnancy, toxoplasmosis can cause: miscarriage, stillbirth or damage to the baby’s brain and other organs, particularly the eyes. However, most babies born with toxoplasmosis have no obvious damage at birth but develop symptoms, usually eye damage, during childhood or even adulthood. A few will have more serious symptoms such as blindness or brain damage.

Testing for toxoplasmosis during pregnancy

The toxoplasmosis blood test involves taking blood from the mother and does not affect the baby. The blood tests look for antibodies to Toxoplasma. These are the antibodies produced by the body to fight the toxoplasma infection. Depending on what type of antibodies are found, and whether levels are rising, falling or stable, it’s possible to estimate when the infection took place. Local laboratories may refer blood to the Toxoplasma Reference Laboratory to carry out these tests.

Who might have a toxoplasmosis blood test?

You might consider having a blood test for toxoplasmosis if, for example: 

  • You think you might have put yourself at risk of catching toxoplasmosis (for example, by eating raw meat or meat that has not been cooked thoroughly).
  • You are concerned about symptoms (which can sometimes be a bit like flu).

If you feel you may have put yourself at risk in pregnancy or would like to know your antibody status prior to pregnancy, you should discuss the benefits and problems of testing with your GP, midwife or obstetrician. If it is necessary, a blood test will be taken.

At what point is a toxoplasmosis blood test conducted?

Blood tests for toxoplasmosis can be done at any stage before or during pregnancy. The blood test can usually only show possible infection two to three weeks after any risk incident, as it can take this long for antibodies to be detectable.

The blood test involves taking a small amount of blood from the mother. There isno risk to the unborn baby. The blood test aims to show whether certain antibodies indicating toxoplasmosis are present or not, and, if they are present, to determine whether they are there due to a current or a previous infection.

If the tests show that the infection is current or recent, there is a risk that the baby will be infected. The obstetrician or GP will make a recommendation about any further action that might be required. It may take several weeks for the infection to pass from you to your baby. The degree of risk and severity of damage depends on when you were infected.

What do my toxoplasmosis blood test results mean?

A negative result

A negative result means that you have never had toxoplasmosis, are not immune, and need to take precautions to avoid infection before conceiving and during pregnancy.

A positive result

A positive result means that you had toxoplasmosis at some time in your life. Many pregnant women will have a positive result because they contracted toxoplasmosis in the past and built up an immunity before getting pregnant (antibody screen IgG positive). If the test is antibody screen IgM positive, this indicates a current or recent infection. The blood must be sent on from the local laboratory to the Toxoplasma Reference Laboratory, for confirmation and further testing. The Toxoplasma Reference Laboratory will then send the results to your midwife or doctor, who will pass the information to you.

A small percentage of tests will appear positive when in reality a woman has never had the disease.

A positive result due to a current/recent infection

If further tests show that you have a current or recent infection, it means you are suffering from an acute toxoplasma infection. Further action needs to be taken to assess the risk of passing the infection on to your baby.

If you were infected shortly before conception 

Infection caught shortly before conception (within a few weeks before) carries a one percent risk or below of transmission to the baby, but there is a risk of miscarriage if the baby does become infected.

If you were infected in the first trimester (week one to 12)

Infection caught at this stage of pregnancy carries about 10-15 percent risk of transmission to the baby. A baby infected at this stage has a risk of being miscarried or born with severe symptoms such as hydrocephalus (water on the brain), calcifications of the brain, or retinochoroiditis (inflammation of the retina).

If you were infected in the second trimester (week 13 to 28)

Infection caught at this stage of pregnancy brings about 25 percent risk of transmission. A baby infected at this stage is less likely to be miscarried, but is still at risk of developing severe symptoms as above.

If you were infected in the third trimester (week 29 to 40)

Risk of transmitting the infection rises again if toxoplasmosis is caught at this stage of pregnancy, and may be as high as 70–80 percent. Most babies infected will be apparently healthy at birth, but a large proportion will develop symptoms later in life, usually eye damage.

Finding out if the baby has been infected

Further tests can be carried out to find out whether or not the baby is infected, although the tests will not show how severe the damage is. An obstetrician or GP can explain the risks and benefits of conducting these tests.

Amniocentesis is a technique where amniotic fluid is removed by a fine needle from the amniotic sac – the fluid-filled sac around the baby.

Cordocentesis is a technique where a sample of the baby’s blood is removed from the umbilical cord.

These procedures carry a point five to one percent risk of causing miscarriage. They would only be carried out for toxoplasmosis if a recent or current infection in pregnancy had been diagnosed by a previous blood test on the mother. They are normally carried out after 15 weeks of pregnancy. The amniotic fluid or blood from the umbilical cord is then tested at the Toxoplasma Reference Laboratory using a range of specialised tests, which may include:

  • looking for antibodies to toxoplasmosis 
  • a test to look for the parasite’s DNA (molecular testing/PCR).

If this is positive, the baby will be considered to be infected. Results typically take two to five days.A detailed ultrasound scan will show if there is major damage, such as hydrocephalus (water on the brain), but a scan that shows no damage, while reassuring, does not rule out the possibility that the baby is both infected and affected.

Toxoplasmosis infection - treatment during pregnancy

If you have a positive blood test result, you may be prescribed an antibiotic called spiramycin, which reduces the risk of the infection being passed from you to the baby. Spiramycin only reduces the risk of transmission from mother to baby and is not active against the parasite. It therefore cannot limit any damage if a baby has already become infected.

If the baby is found to be infected, a combination of pyrimethamine and sulphadiazine can be taken. These are both stronger antibiotics and help limit any damage to the baby, although again, they cannot undo any damage.

Side effects of treatments

Spiramycin is used routinely in France for treatment of toxoplasmosis in pregnancy, with little evidence of adverse effects. Experts consider that it is safe to use in pregnancy when a baby is at risk. Women taking spiramycin sometimes experience side effects such as nausea or rashes. Pyrimethamine and sulphadiazine can have side effects for both the mother and baby related to red-blood cell production. Although not normally prescribed in pregnancy, they can be used in extreme circumstances. They are taken with folinic acid, which helps to reduce the worst side effects. All babies born to women who have had a recent or current infection in pregnancy should be given a thorough physical examination after birth, followed by blood tests during the first year of the baby’s life.

Toxoplasmosis infection - treatment after the baby is born

Blood sample

A blood sample should be taken from at-risk babies shortly after birth. A blood sample should also then be taken from you to compare the levels of specific antibodies between you and your baby.

Tests will be carried out to look for different types of antibodies to toxoplasmosis in the baby’s blood. Your baby carries some of your antibodies, so a positive result is expected and not necessarily alarming. If additional antibodies are present, this may indicate that your baby is infected.

Other checks/examinations

Babies who are known to be at risk of having congenital toxoplasmosis should be checked for signs of neurological damage. The eyes will be examined for signs of any problem, preferably by an ophthalmologist (eye specialist). Long-term follow-up by an ophthalmologist might be necessary if eye damage is confirmed.

Your baby’s general health will also be checked. If there is any possibility that the baby has brain damage, special head X-rays might be carried out to check for calcifications, enlarged ventricles or any other abnormalities. 

Treatment for babies who have been infected with toxoplasmosis

If blood tests showed that your baby has been infected, antibiotics might be prescribed, even if your baby shows no symptoms. Treatment can sometimes be continued for as long as one year, to help prevent or limit the eye damage that can possibly occur later.

Further tests/examinations

A blood sample taken every few months, up to the age of one year, can show whether your baby’s antibody level is falling. By that age, the level should be completely negative. This means that your baby will have lost the antibodies acquired from you and is not infected. When your baby’s blood sample is completely antibody-negative, it means they are definitely not congenitally infected. A falling antibody level is a good sign, but is not conclusive and tests should continue until the antibody level is completely negative.

Breastfeeding and toxoplasmosis

Transmission of the Toxoplasma organism by breastfeeding has not been adequately demonstrated or documented as yet. Because of this and the added advantage of passing on extra antibodies to your baby through your breastmilk, breastfeeding would be especially beneficial in fighting infection and is therefore recommended. If you are being treated with pyrimethamine this medication should be changed before breastfeeding.

UK government policy on toxoplasmosis screening

The UK National Screening Committee recently reported that screening for toxoplasmosis in pregnancy should not be offered routinely as there is not enough evidence that it would help.

The Committee suggests that getting pregnant women to avoid undercooked or cured meat and communicating the best ways of avoiding infection is a better way of controlling toxoplasmosis than antenatal screening.


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    Infections to avoid in pregnancy

    Most germs are normally harmless, but when trying for a baby, or newly pregnant, you may be more at risk. Some illnesses may be able to affect your growing baby

Last reviewed on October 3rd, 2016. Next review date October 3rd, 2016.

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  • By Midwife @Tommys on 1 Sep 2016 - 13:02

    Most people have an acquired immunity following contact prior to being pregnant , however if you think you are at risk having had the cured ham , it would be advisable to have the blood test anyhow and your GP can organise this. The blood test can usually only show possible infection two to three weeks after any risk incident, as it can take this long for antibodies to be detectable.

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