Miscarriage in Cats

What is miscarriage?

Miscarriage refers to the death of a fetus during pregnancy. This fetal death can occur at any time during pregnancy, though the signs of miscarriage vary depending on the stage at which it occurs.

Some miscarriages occur early, during the first half of pregnancy (before 45 days). In these cases, the embryo is often reabsorbed into the body, and the miscarriage may go completely undetected. Sometimes, one or more kittens in the litter may be miscarried and resorbed, while other kittens in the litter go on to be born normally.

"Sometimes, one or more kittens in the litter may be miscarried and resorbed, while other kittens in the litter go on to be born normally."

Miscarriages may also occur later in pregnancy. These miscarriages may result in a variety of outcomes. Kittens may be passed stillborn, either before their due date or on their due date. In some cases, a deceased fetus may become mummified within the uterus. Mummification occurs when the body creates a protective membrane around the fetus, allowing it to remain encased and walled off within the uterus. In many cases, mummification does not threaten the female; in some situations, however, infection may occur.

What causes miscarriage?

Infection is a common cause of miscarriage in cats. These infections can be viral, bacterial, or parasitic in nature. Most feline miscarriages are caused by viral infections, including feline leukemia virus, feline immunodeficiency virus, panleukopenia, feline herpesvirus, and feline enteric coronavirus. Bacteria are often cultured in cases of miscarriage. However, it is difficult to determine whether these bacteria are the actual cause of miscarriage.

Hormonal shifts or abnormalities may also cause miscarriages. Progesterone is the hormone that is responsible for maintaining pregnancy in the cat. Low levels of this hormone can lead to miscarriage. In some cases, the low progesterone level can be caused by medications (such as in the case of medically induced abortions). It can also be caused by maternal and placental factors.

What are the clinical signs of miscarriage?

Often, there are no visible signs of miscarriage. Early miscarriages typically result in embryo resorption and are only detected if the pregnancy was confirmed on an early ultrasound and a later ultrasound shows no viable pregnancy.

Later-term miscarriages may be associated with clinical signs but may also be asymptomatic. Abnormal vaginal discharge (brown, green, black, or pus-colored) at any time during pregnancy, abdominal pain, and fever are all potential signs of miscarriage or infection. Additionally, some cats experiencing a miscarriage will begin to have contractions and deliver stillborn kittens.

How is miscarriage diagnosed?

If miscarriage is suspected, ultrasound is used to assess the pregnancy and determine whether the fetuses are alive. Progesterone level monitoring can also benefit pregnancy monitoring; abnormal progesterone levels may indicate a failing pregnancy.

"If miscarriage is suspected, ultrasound is used to assess the pregnancy and determine whether the fetuses are alive."

After a miscarriage, testing of both the mother and the fetus may be recommended to look for infectious causes of miscarriage. Blood tests on the mother, cultures of vaginal fluids, and histopathology (microscopic examination) of the fetus may determine the cause of miscarriage.

Finding a cause for the miscarriage, especially if it is a treatable condition, may improve outcomes for the cat’s future pregnancies.

How is miscarriage treated or prevented?

If a cat develops a fever during pregnancy, this may indicate an infection. Infections are typically treated with intravenous (IV) fluids and injectable antibiotics. This may prevent miscarriage or, if a miscarriage has already occurred, may prevent more severe medical complications with the mother.

If hormonal imbalances are suspected, a progesterone supplement may be recommended. This medication is given daily until shortly before the expected due date to help maintain appropriate hormone levels to support pregnancy. This medication requires careful monitoring to prevent complications.