Why Do Cats Miscarry? Causes of Pregnancy Loss in Cats
By Dr. Zubair Khalid, DVM, MS, PhD ·
Pregnancy loss in cats can happen for many reasons, and often the cause is never confirmed. A cat miscarriage (also called feline abortion) is the loss of a pregnancy before the kittens are due. Owners searching for what causes cat miscarriage usually want two things: to understand why it happened and to know whether their cat needs veterinary care right now.
This article is educational and is not a substitute for veterinary diagnosis or treatment.
Quick Answer
- Pregnancy loss in cats can be caused by infections, hormonal problems, genetic abnormalities of the embryos, uterine or placental problems, stress, poor nutrition, and some medications [1].
- If embryonic death happens before about day 35 of gestation, the embryo is usually absorbed and you may see no outward sign at all [1].
- Later in pregnancy, loss shows up as abortion, or as fetal emphysema, maceration, or mummification (the fetus dies and breaks down or dries inside the uterus) [1].
- Fresh blood or dark green discharge from the vulva before any kittens are born is abnormal and needs veterinary attention [2].
- Any cat in labor with strong contractions for more than 1 to 2 hours with no kitten born, or a rest period longer than 4 to 6 hours, should be seen by a veterinarian [2].
What Feline Pregnancy Loss Means in Plain Words
A miscarriage is the ending of a pregnancy before the kittens are developed enough to be born. In cats, this can happen very early, sometimes before you even knew your cat was pregnant. If the embryo dies before roughly day 35 of gestation, the body absorbs it [1]. You might notice nothing except that your cat never seems to get bigger or never goes into labor.
When death happens in the second half of pregnancy, the result is different. The queen may abort the kittens, or the dead fetus may stay in the uterus and become emphysematous (gas-filled and decomposing), macerated (softened and breaking down), or mummified (dried and shriveled) [1]. These are serious situations that can make the mother sick.
Cats are not small dogs when it comes to reproduction. The feline placenta actually produces steroid hormones and corticotropin-releasing hormone, which is different from dogs [3]. That difference matters because it affects how pregnancy is maintained and how it can fail.
Signs a Pregnant Cat Is Losing Kittens
Some losses are silent. Others are obvious. Watch for:
- Bleeding from the vulva. Fresh blood before any kittens are born is abnormal [2].
- Dark green discharge before the first kitten arrives [2].
- Crying, licking, or biting at the vulva, which suggests pain or illness in the mother [2].
- Strong contractions for more than 1 to 2 hours with no kitten delivered [2].
- A resting period during labor lasting more than 4 to 6 hours [2].
- No kittens within 24 hours after her rectal temperature drops below 100°F [2].
- Lethargy, poor appetite, fever, or a swollen, painful belly.
If your cat is not in labor but you notice a sudden decrease in belly size, a return to calling or heat behavior, or a bloody discharge, call your veterinarian. These can signal a lost pregnancy. Unexplained weight loss in a cat that was eating normally also deserves a check, and our guide on why is my cat losing weight covers the general workup.
What Causes Cat Miscarriage?
There is no single cause. Most cases are multifactorial, meaning several things line up to end the pregnancy. Your veterinarian may never be able to name one specific reason, and that is normal.
Infectious Causes
Bacteria, protozoa, and viruses can all interfere with a pregnancy [1]. In cats, the usual suspects include feline herpesvirus, feline calicivirus, feline panleukopenia virus, feline leukemia virus, feline immunodeficiency virus, Toxoplasma gondii, and Brucella species. Infection can damage the placenta, cross to the fetus, or make the mother sick enough that the pregnancy cannot continue.
Because many of these infections also cause other signs, a queen who aborts may also have a fever, nasal or eye discharge, diarrhea, or poor appetite. Testing the mother and, when possible, the fetal tissue helps identify the agent.
Hormonal and Endocrine Causes
Pregnancy depends on the corpus luteum, the structure on the ovary that produces progesterone. If it fails too early, the pregnancy cannot be maintained. This is called hypoluteodism, and it is a recognized cause of pregnancy failure in dogs [1]. In cats, the same mechanism is suspected but less well documented.
Anti-Müllerian hormone (AMH) is another area of active research. AMH levels are higher in pregnant cats than in non-pregnant cats, and one recent study found that supraphysiological (very high) levels may lead to pregnancy loss [3]. The exact role of AMH during normal feline pregnancy is still being worked out [3].
Other endocrine problems, including gestational diabetes and hypothyroidism, are listed as reasons for pregnancy failure in dogs [1]. Whether they cause the same problems in cats is not well established in veterinary research.
Genetic and Embryonic Causes
Abnormal embryonic development and genetic abnormalities of the embryo can end a pregnancy on their own [1]. This is the body's way of stopping a pregnancy that could not produce a healthy kitten. Competition between placental sites can also lead to loss [1]. These causes are usually invisible to owners and are often the reason an early pregnancy simply disappears.
Uterine and Placental Problems
Anything that changes the environment inside the uterus can harm the pregnancy. Cystic endometrial hyperplasia and inflammation of the uterus are listed as maternal factors that alter ovarian function or the uterine environment and lead to pregnancy loss in dogs [1]. Abnormalities of the placenta and uterine torsion also have harmful effects on fetal development [1].
Uterine torsion is rare in cats, but when it happens it is dangerous. In one reported case, a 4-year-old queen in late gestation arrived with acute abdominal pain, lethargy, abdominal distension, and rapid breathing. Doppler ultrasound showed absent or severely reduced blood flow and no fetal heartbeats, confirming the fetuses had died [4]. This is a surgical emergency.
Environmental, Nutritional, and Drug Causes
Environmental stress and malnutrition can harm fetal development [1]. A queen who is underfed, heavily parasitized, or living in a chaotic, crowded environment is at higher risk. Several drugs and medications have embryotoxic or teratogenic effects, meaning they can poison the embryo or cause birth defects [1]. Never give any medication to a pregnant cat without asking your veterinarian first.
Age, Body Condition, and Pregnancy History
Older queens, queens who are too thin or overweight, and queens with a history of pregnancy loss are at higher risk. A cat with a prior difficult birth (dystocia) is also more likely to have problems again [2].
A Note on Contraceptive Research
You may have read headlines about anti-Müllerian hormone being used for cat contraception. In that research, a single injection produced very high AMH levels that lasted for months and were linked to abnormal estrus cycles, ovarian cysts, and pregnancy loss [5]. This is an experimental contraceptive approach, not a treatment or a natural cause of miscarriage in household cats.
How Veterinarians Diagnose Pregnancy Loss
Diagnosis starts with a full history: breeding dates, previous litters, any discharge, appetite, and behavior changes. Then your veterinarian will examine your cat and likely recommend imaging.
Ultrasound is the most useful tool early on. It can confirm pregnancy, show fetal heartbeats, and estimate how far along the pregnancy is. X-rays become useful later, when fetal skeletons are mineralized, and can show how many fetuses are present [2].
If the mother is sick or the pregnancy has clearly failed, your veterinarian may recommend blood work, infectious disease testing, and sometimes testing of the fetal tissue or placenta. In complicated cases, Doppler ultrasound can assess blood flow to the uterus and fetuses, which helps distinguish viable tissue from tissue that has died [4].
Treatment Options for a Cat Losing a Pregnancy
Treatment depends on whether the mother is stable and whether any kittens are still alive.
If the mother and remaining kittens are stable and there is no obstruction, medication can sometimes help labor progress [2]. If the mother or kittens are not stable, if there is an obstruction, if active labor is prolonged, if medication does not work, or if the fetuses cannot be delivered naturally, surgery (cesarean section) is performed [2].
If the pregnancy has already failed and the uterus is infected or the fetuses are decomposing, a spay (ovariohysterectomy) may be the safest option. This removes the source of infection and prevents future problems. Your veterinarian will discuss whether your cat should be bred again or retired from breeding.
Supportive care matters too. Fluids, antibiotics for bacterial infection, pain control, and nutritional support are common. Any medication dose is calculated by your veterinarian based on your cat's weight and health, so never use a leftover prescription or a human drug.
Recovery, Outlook, and Long-Term Management
Most queens recover well after a miscarriage, especially if the loss was early and no infection is present. Recovery time depends on how far along the pregnancy was and whether surgery was needed. Expect your cat to need a quiet, warm space, good food, and a follow-up visit.
The outlook for future pregnancies varies. If the cause was a one-time infection or an embryonic abnormality, future pregnancies may go normally. If the cause was a uterine problem, a hormonal disorder, or a chronic infection, the risk of another loss is higher. Your veterinarian may recommend waiting at least one full estrus cycle before breeding again, or may advise against breeding altogether.
Long-term management often includes:
- Testing and treating any underlying infection.
- Managing body condition so your cat is neither too thin nor overweight.
- Reducing stress in a multi-cat household.
- Reviewing all medications and supplements for safety in pregnancy.
- Considering spaying if repeated losses occur.
If your cat has other health issues, such as skin or coat problems, our article on why is my cat losing hair explains how a veterinarian approaches those signs.
Prevention
You cannot prevent every miscarriage, but you can lower the odds.
Test and treat infections before breeding. Have your queen screened for common feline infectious diseases and parasites.
Feed a complete, balanced diet. Malnutrition is a known risk factor for pregnancy loss [1]. Use a diet formulated for pregnant and nursing cats.
Keep stress low. Environmental stress can harm fetal development [1]. Give your cat a quiet area away from dogs, loud children, and other cats.
Avoid all unnecessary medications. Many drugs are embryotoxic or teratogenic [1]. Ask your veterinarian before giving anything, including flea products and supplements.
Know the labor red flags. Strong contractions for more than 1 to 2 hours with no birth, a rest period longer than 4 to 6 hours, abnormal discharge, or obvious pain all mean call your veterinarian [2].
Spay if breeding is not the goal. Spaying removes the risk of pregnancy complications entirely and is the standard recommendation for cats not intended for breeding.
| Warning Sign | What It May Mean | Urgency |
|---|---|---|
| Fresh blood or dark green discharge before birth | Possible abortion or fetal death | Same day |
| Strong contractions over 1 to 2 hours, no kitten | Dystocia (difficult birth) | Emergency |
| Rest period over 4 to 6 hours during labor | Stalled labor | Emergency |
| Crying, biting at the vulva, obvious pain | Maternal distress | Emergency |
| No kittens 24 hours after temp drops below 100°F | Labor not progressing | Emergency |
| Lethargy, fever, swollen painful belly | Infection or uterine torsion | Emergency |
Limitations and When to Contact a Veterinarian
Not every cause of feline pregnancy loss can be identified, and some losses happen with no warning at all. Even with testing, your veterinarian may not find a single reason. That does not mean anything was done wrong.
Call your veterinarian the same day if you see fresh blood or dark green discharge from the vulva, if your cat seems painful or unwell, or if you suspect she has lost a pregnancy. Go to an emergency clinic now if she is in active labor with strong contractions for more than 1 to 2 hours and no kitten is born, if she rests longer than 4 to 6 hours during labor, if she has a fever, or if she is collapsed or breathing hard [2]. These signs can indicate dystocia, uterine torsion, or infection, all of which can be fatal without fast treatment [2][4].
Schedule a routine visit if your cat was pregnant and now is not, even if she seems fine. An exam and ultrasound can confirm what happened and check for retained tissue or infection. Every individual case needs a veterinarian who can examine your cat, so use this article as background, not as a diagnosis.
Frequently Asked Questions
Can a cat have a miscarriage without me noticing?
Yes. If the embryo dies before about day 35 of gestation, it is usually absorbed and there may be no visible sign [1]. You might only notice that your cat never grew a belly or never went into labor.
Is bleeding always a sign of miscarriage in cats?
No, but fresh blood from the vulva before any kittens are born is always abnormal and should be checked [2]. It can indicate pregnancy loss, placental problems, or another serious issue.
Can stress cause a cat to lose her kittens?
Stress is listed as a factor that can harm fetal development and contribute to pregnancy loss [1]. Keeping a pregnant queen in a calm, stable environment is one of the few things you can control.
Will my cat be able to get pregnant again after a miscarriage?
Often yes, especially if the loss was early and no infection or uterine damage occurred. Your veterinarian may suggest waiting at least one cycle before breeding again, and repeated losses are a reason to consider spaying.
Can medication cause a cat to miscarry?
Some drugs and medications have embryotoxic or teratogenic effects, meaning they can harm or kill the developing fetus [1]. Never give a pregnant cat any medication, supplement, or flea product without asking your veterinarian first.
Related Articles
- Why Is My Cat Losing Hair?
- Why Is My Cat Losing Weight?
- Cat Hair Loss: Causes and When to See a Vet
- How Often Do Cats Go Into Heat? Feline Estrous Cycle & Signs Guide
- Why Is My Cat Losing Hair in Patches? Causes and Solutions
- Weight Loss For Cats
- Why Do Kittens Die? Newborn and Young Kitten Loss
- False Pregnancy in Cats: Symptoms and What to Do
- Diarrhea in a Pregnant Cat: Causes and When to Worry
References
- "My Bitch Is Empty!" An Overview of the Reasons for Pregnancy Loss in Dogs. Veterinary sciences, 2025.
- Reproductive Disorders of Female Cats - Cat Owners. Merck Veterinary Manual.
- Establishment and Maintenance of Feline Pregnancy-A Comprehensive Review. Animals : an open access journal from MDPI, 2025.
- Doppler Ultrasonography for Assessing Uterine Viability and Fetal Vitality in Uterine Torsion in a Domestic Cat (Felis catus): A Case Report. Animals : an open access journal from MDPI, 2026.
- Gene therapy with feline anti-Müllerian hormone analogs disrupts folliculogenesis and induces pregnancy loss in female domestic cats. Nature communications, 2025.