The information provided below is for readers based in the United States of America. Readers outside of the United States of America should seek the information from local sources.

What is toxoplasmosis?

Toxoplasmosis is a condition caused by a parasite called Toxoplasma gondii. Able to live inside the cells of humans and other animals, T. gondii is a protozoan, meaning that each organism consists of just one cell, but it is a very complex cell, just like the cells of animals and plants. Being very complex, T. gondii has two different life cycles. One such cycle, called the asexual cycle, occurs in many different types of animals, including humans. The other cycle, called the sexual cycle, occurs only in the intestines of cats. Since the sexual cycle produces eggs, it is possible to develop toxoplasmosis from handling kitty litter, or from drinking water that has been contaminated with cat feces. For this reason, pregnant women, and women who are trying to become pregnant, are often advised to leave handling kitty litter to other people in the household. While it may be prudent to follow this advice, its also important to know that kitty litter is NOT the usual way that people become infected with T. gondii. Rather, a much more common way to develop toxoplasmosis is by eating or handling uncooked meat, or by eating unwashed vegetables.

How common is toxoplasmosis during pregnancy?

Studies have found that a very high fraction of teens and young adults have been infected with the toxoplasmosis parasite at some point. The fraction varies from 10 percent to as much as 55 percent depending on the country. In the United States, about 23 percent of young adults have been exposed to T. gondii at some point in the past, and overall one third of humanity is infected. This number is not particularly useful, because most people who have been infected with the parasite prior to pregnancy are protected by the immune system, which protects the embryo/fetus as well. For a healthy woman (a woman whose immune systems are working properly) the danger comes in when she is infected during pregnancy, or just before getting pregnant. This is called a primary infection and it is dangerous because the parasite can transfer to the developing baby. Unfortunately, there is a lot of uncertainty regarding how common this is because its difficult for doctors to tell the difference between a new infection and a past infection unless you are also experiencing symptoms.

How is toxoplasmosis diagnosed?

Diagnosis of toxoplasmosis is actually fairly difficult. Using antibody tests on samples of your blood, it is very easy for your doctor to find out whether you have ever been infected with T. gondii. However, there are different ways that the test can come out. One way that it can come out can tell the doctor for certain that you were infected a long time ago, in which case you do not have toxoplasmosis. Another possible test result would indicate an infection that could be old or new; this is a problem and would have to be followed up with an additional test 2-3 weeks later. The result of this later test either could tell the doctor that your infection is new, or it could still give an uncertain result. If this happens, further blood tests are possible, but some women will still have uncertain results. If you end up in that uncertain category, or if it is found that you definitely have a new (primary) infection, diagnostic tests of the fetus will be carried out with ultrasound to look for evidence of what is called congenital toxoplasmosis, but in one third of such cases, the ultrasounds look normal.

Does toxoplasmosis cause problems during pregnancy?

If you have a primary infection, it is possible that you will develop flu-like symptoms, such as fever. However, it also is possible to be free of symptoms.

Does toxoplasmosis during pregnancy cause problems for the baby?

There are two levels of possible problems. First, if you develop a fever, this itself could be harmful to the developing baby. It can cause low birth weight, premature delivery, or possibly long-term mental problems. Fever is fairly easy to treat with medications, however. A much bigger problem is the possibility of the parasite infecting the baby. In terms of risks and results, there are important differences between early pregnancy (and the 3 months prior to pregnancy) and late pregnancy. Infection during early pregnancy (the embryo period) is rare (less than 6 percent of new infection of the mother), but if this does happen it can lead to problems in the brain and skull (leading to mental retardation or death), blindness, and severe blood disorders. This is called congenital toxoplasmosis and it tends to be milder when it results from the mother being infected later, during the third trimester, but the third trimester is a time when transmission of the parasite from mother to the developing baby is very easy. If you are infected during the 3 months prior to conception, this also can lead to congenital toxoplasmosis, but infection more than 3 months ahead of conception does not harm the baby.

What to consider about taking medications when you are pregnant or breastfeeding:

  • The risks to yourself and your baby if you do not treat the toxoplasmosis. These can be significant
  • The risks and benefits of each medication you use when you are pregnant
  • The risks and benefits of each medication you use when you are breastfeeding

What should I know about using medication to treat toxoplasmosis during pregnancy?

If you have toxoplasmosis, but the developing baby has not yet been infected, the treatment is an antibiotic called spiramycin, which does not cross through the placenta. Instead, it accumulates in the placenta, where it destroys any parasites or parasite eggs entering the placenta from the mothers blood. If infection of the baby is confirmed then it is too late to give spiramycin, in which case you would be offered pyrimethamine and sulfadiazine. These are drugs that can harm the developing baby, so they are not given unless doctors are able to confirm infection of the baby, but the risk of harm is less than the risk of harm from the parasite, so they are the best option if infection of the developing baby is confirmed.

Who should NOT stop taking medication for toxoplasmosis during pregnancy?

If you have a confirmed new infection of T. gondii, you must take medication to prevent infection of the developing baby.

What should I know about choosing a medication for my toxoplasmosis during pregnancy?

Spiramycin does not reach the developing baby, so it is safe. Pyrimethamine and sulfadiazine can harm the developing baby but are only used when necessary, namely when the baby is in danger of greater harm, due to congenital toxoplasmosis.

You may find Pregistrys expert reports about the individual medications used to treat toxoplasmosis here. Additional information can also be found in the sources listed at the end of this report.

What should I know about taking a medication for my toxoplasmosis when I am breastfeeding?

The T. gondii parasite is not thought to enter breastmilk or to put a nursing infant at risk through contact. Thus, in the event that you are infected newly with T. gondii after giving birth, you dont need to take medications, unless you have a fever, in which case the needed medications are not harmful.

What alternative therapies besides medications can I use to treat my toxoplasmosis during pregnancy?

Termination of pregnancy through an elective abortion is the only viable alternative to medications if it
is confirmed that you have a primary (new) T. gondii infection. That said, this is an appropriate moment to emphasize that there are preventive options as well. You can reduce your risk of getting a primary infection in the first place through avoidance of raw, undercooked, or cured meat, and unwashed produce. Wash your hands when working with food, and do it correctly. This means scrubbing with soap and not touching with your just-cleaned hands faucets that were in contact with your hands before they were washed. Dont eat in the types of restaurants where you judge that handlers of raw food and produce might not be washing correctly. This hygiene issue is more important than the cat issue, but also keep in mind that indoor cats are much less likely to carry this disease than cats who are permitted to wander about outside.

What can I do for myself and my baby when I have toxoplasmosis during pregnancy?

Cooperate with your doctors by accepting all the recommended tests for toxoplasmosis and consider all medications on the table.

Resources for toxoplasmosis in pregnancy:

For more information about toxoplasmosis during and after pregnancy, contact (800-994-9662 [TDD: 888-220-5446]) or visit the following links:


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General information

It is very common for women to worry about having a miscarriage or giving birth to a child with a birth defect while they are pregnant. Many decisions that women make about their health during pregnancy are made with these concerns in mind.

For many women these concerns are very real. As many as 1 in 5 pregnancies end in a miscarriage, and 1 in 33 babies are born with a birth defect. These rates are considered the background population risk, which means they do not take into consideration anything about the health of the mom, the medications she is taking, or the family history of the mom or the baby’s dad. A number of different things can increase these risks, including taking certain medications during pregnancy.

It is known that most medications, including over-the-counter medications, taken during pregnancy do get passed on to the baby. Fortunately, most medicines are not harmful to the baby and can be safely taken during pregnancy. But there are some that are known to be harmful to a baby’s normal development and growth, especially when they are taken during certain times of the pregnancy. Because of this, it is important to talk with your doctor or midwife about any medications you are taking, ideally before you even try to get pregnant.

If a doctor other than the one caring for your pregnancy recommends that you start a new medicine while you are pregnant, it is important that you let them know you are pregnant.

If you do need to take a new medication while pregnant, it is important to discuss the possible risks the medicine may pose on your pregnancy with your doctor or midwife. They can help you understand the benefits and the risks of taking the medicine.

Ultimately, the decision to start, stop, or change medications during pregnancy is up to you to make, along with input from your doctor or midwife. If you do take medications during pregnancy, be sure to keep track of all the medications you are taking.

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