Every now and then I have a client come to me in distress because she is pregnant and she has heard that somewhat persistent myth that having a cat will cause you to lose a pregnancy. Now her mother is insisting that she has to get rid of the cat or she will lose the baby.

The concern about cats and pregnancy involves transmission of a one-celled parasite called Toxoplasma Gondii. Toxoplasma can infect most warm-blooded animals and is widespread across the country. The parasite makes a home inside many different tissues in a host including muscle and internal organs. Carnivores become infected from eating prey that has the parasite. Eating raw or undercooked meat, especially pork, is by far the most common way that humans get the parasite. Herbivores tend to get the infection from browsing in areas where an infected cat has passed stool that has the parasite in it.

Most people and animals that have been infected with Toxoplasma have no idea because it rarely causes clinical signs or illness. Severely immune compromised patients are more likely to have problems because they have reduced ability to keep the organism in check. Unfortunately Toxoplasma has the ability to cross the placenta, especially during the first two trimesters of pregnancy, and can cause an infection in a developing fetus that can result in severe birth defects or fetal death.

Cats have a unique place in the life cycle of Toxoplasma. They are the only animals in which the parasite undergoes the part of its life cycle where it can develop oocycts, which are like little microscopic eggs that are passed out of the cat in its stool and left in the environment to be picked up by other animals. Oocysts can live in the environment for up to a year. When a cat eats prey that is infected with Toxoplasma the parasite finds its way to the cat’s digestive tract, where it starts producing oocysts that are shed in the cat’s stool within 2-3 days. After the oocysts are passed out of the cat they still need to mature for 2-3 days before they can cause an infection in another animal that ingests them. Cats will shed oocysts in the stool for only 1-2 weeks after they have been infected and then they will stop.

What this means for a pregnant woman is that it takes a fairly unlikely, but not impossible convergence of factors for her to get Toxoplasma from the cat. The cat has to have been infected itself within a 2 week window, and the woman would have to have contact with that cat’s stool after it has been sitting for at least 2 days, get some on her hands, and perhaps eat a sandwich without washing her hands first. All the same, the consequences of getting toxoplasma during early pregnancy are severe enough to warrant some simple precautions.

1: Don’t let the cat hunt outside. If he isn’t eating wildlife he isn’t getting exposed himself.

2: Be careful about digging in the soil for gardening and eating produce grown in the back yard. Roaming cats will use your garden for a litterbox and it is possible that one could have deposited some oocysts that are still infective today. Gloves and good hand and food washing goes a long way for safety.

3: Cook all meats thoroughly. Of course you should be doing this anyway, but it is especially important during pregnancy.

4: Somebody other than the pregnant woman should clean the cat’s litterbox every day. You know, why don’t we just make that a permanent situation even after the pregnancy. If is unavoidable that the pregnant woman has do the litterbox cleaning then gloves and good hand washing still go a long way for safety.

The fact is that you are more likely to get Toxoplasma from the cat if you actually eat the cat raw, or if you develop a taste for aged cat poop (Lord knows the dog has). If you can resist some of these more unusual cravings that could come with pregnancy and you take these other precautions you should be just fine and there will be no reason to get rid of the cat