Miscarriage in dogs: signs, causes and treatment

Overview

Pregnancy loss may affect all puppies or only some. An embryo that dies early can be reabsorbed within the uterus, called resorption. During resorption, fluid components that developed during pregnancy are absorbed within the uterus.

Loss before day 35 of pregnancy is termed early embryonic death. A foetus dying later may be expelled or remain in the uterus. Resorption of one embryo does not necessarily stop the other puppies developing.

Normal pregnancy lasts about 63 ± 1 days from ovulation. From mating, the range is considerably wider, at 57–72 days. The mating date alone therefore gives an imprecise estimate of pregnancy duration.

Foetal organs are still maturing during the final week of canine pregnancy. Skeletal development therefore does not reliably show whether a puppy can survive outside the uterus.

Causes

Pregnancy loss may result from infection or another factor disrupting development. A pathogen may ascend into the uterus from the birth canal. It can also reach a developing foetus through the placenta.

Placental inflammation can impair exchange of substances between mother and foetus. A severe systemic infection in the mother can also end a pregnancy without directly infecting the uterus. Brucella canis can cause miscarriage particularly in late pregnancy.

Canine herpesvirus is a recognised infectious cause of pregnancy loss. Salmonella, Campylobacter and streptococci may also be associated with foetal infection. However, finding Escherichia coli in a sample alone does not prove it caused the miscarriage.

A foetal chromosomal or developmental abnormality may prevent normal pregnancy progression. Structural and metabolic problems in the mother are other possible causes. Inflammation or scarring of the uterine lining can make maintaining pregnancy difficult.

Progesterone is essential for maintaining canine pregnancy. During pregnancy, dogs depend on progesterone produced by the ovaries' corpora lutea. A fall in the hormone may also result from infection or uterine disease.

Risk factors

Increasing maternal age has been associated with more embryo resorption. Medicines and toxins affecting pregnancy can endanger puppy development. Nutritional deficiencies in the mother may also disrupt pregnancy.

Raw meat and carcasses have been possible infection sources in Salmonella-associated miscarriages. Some national brucellosis prevention guidance focuses particularly on imported dogs and dogs from abroad used for breeding.

In a group of 25 bitches treated for luteal insufficiency, 21 were Shetland Sheepdogs. This selected treatment group does not estimate miscarriage risk across all pregnancies in the breed.

Of the group investigated for hormone deficiency, 20/25 bitches, or 80%, had previously lost a pregnancy.

Dogs that travel and compete extensively may have greater herpesvirus exposure. Stress can reactivate a latent herpesvirus infection.

Typical symptoms

Possible signs at home include:

• Bloody, greenish or pus-like discharge from the vulva during pregnancy.

• Fever, abdominal pain or obvious general illness.

• Contractions and premature expulsion of a foetus or dead puppies.

• Loss of appetite, vomiting or diarrhoea before pregnancy loss.

• Apathy and a deterioration from usual wellbeing.

Early resorption does not usually cause visible discharge or other outward signs. Loss may become apparent only through changes between successive ultrasound examinations. Sometimes the problem is noticed only when the expected birth does not begin.

Complications and consequences

A dead foetus retained in the uterus can become mummified as fluids are absorbed. In maceration, the foetus instead decomposes in the presence of microbes and oxygen. Maternal infection may involve dehydration, sepsis or circulatory shock.

Some pathogens causing pregnancy loss can also infect people. With brucellosis, foetuses and placentas may release large numbers of bacteria into the environment. Mild general symptoms do not prevent the mother from spreading infection.

In a group of 29 pregnancies receiving progesterone support, treatment failed in 4 cases, or 13.8%. Failures included 3 miscarriages and one pregnancy ending in foetal mummification.

Diagnosis at the vet

The vet reviews the reproductive and health histories of both the bitch and the litter's sire. Dates of ovulation, mating and previous pregnancy examinations help the assessment. The bitch undergoes a reproductive examination as well as a general examination.

Ultrasound and foetal viability

Ultrasound checks whether living foetuses remain in the uterus. It can also assess placental inflammation or separation. Slow growth or a slow heart rate may indicate a poorer outlook for a foetus.

Routine pregnancy ultrasound is most reliable at about days 25–35. An ultrasound before day 21 may give a false-negative result. Foetal skeletons usually become visible on X-rays only from around days 42–45.

Puppy numbers are best estimated with late-pregnancy X-rays after day 55. Ultrasound, however, assesses foetal viability. A blood relaxin test detects the presence of placental tissue from about days 22–27.

Normal foetal heart rate in late pregnancy is about 220–240 beats per minute. A rate below 180 may indicate foetal distress. A brief slowing during a contraction should return to normal within 1–2 minutes.

Samples from the mother, foetus and placenta

Blood, urine and culture samples are collected as soon as possible after the problem is identified. If the mother's condition allows, samples are taken before treatment starts. Finding a bacterium belonging to the normal vaginal microbiota does not establish the cause of miscarriage.

Conversely, a normal vaginal sample does not rule out infection inside the uterus. A pathogen's significance is assessed alongside tissue damage and other findings. A whole dead puppy and its placenta are often the best materials for laboratory examination.

Microscopic tissue examination may reveal changes invisible externally. Absence of visible changes does not rule out infection. The cause may remain uncertain despite extensive investigation.

The mother may eat dead puppies or placentas, losing important diagnostic material.

Progesterone monitoring can add to pregnancy assessment. Culture for Brucella, Salmonella and Campylobacter requires special laboratory conditions. A sample collected too late or poorly preserved may fail to reveal the cause.

Sampling the uterus through the cervix is not recommended as a routine investigation. It requires specialist expertise and may increase the risk of uterine injury or infection.

Treatment

The vet chooses treatment according to the mother's condition and the suspected or confirmed cause. Dehydration, sepsis and shock risks are assessed first. An ill, dehydrated mother may need intravenous fluids.

Treating infection and assessing the uterus

Suspected bacterial infection may require antibiotics before a final diagnosis. Symptomatic care supports the mother and may improve survival chances for remaining puppies. Opportunities to save a pregnancy are often limited once loss has begun.

After the whole pregnancy has ended, the vet checks that the uterus has emptied. After partial loss, the remaining foetuses' viability is monitored. Reviews assess vaginal discharge amount and character alongside ultrasound findings.

Medication can help empty the uterus in some circumstances. Surgical removal of the uterus is sometimes needed. Finding a treatable underlying cause may improve the chances of future successful pregnancies.

Hormone support only for an identified need

Progesterone support may be considered if production is insufficient to maintain pregnancy. It requires careful monitoring of the mother and foetuses. A low hormone result alone does not distinguish a primary luteal problem from other causes of miscarriage.

Synthetic progestogens may carry a risk of maternal insulin resistance. Male-type genital features may also develop in female foetuses. Incorrectly timed withdrawal of hormone support can cause prolonged pregnancy and foetal loss.

In the group of 29 pregnancies receiving hormone support, 25, or 86.2%, reached full term. Puppies in these successful pregnancies were delivered by planned caesarean section. Without an untreated comparison group, treatment effectiveness could not be established with certainty.

The successful pregnancies produced 110 live puppies in total. Of these, 104, or 94.5%, survived to weaning at 6 weeks.

Prevention

Some national brucellosis prevention guidance recommends antibody testing for imported dogs and dogs from abroad used for breeding. An infected carrier should not have contact with other dogs. Preventing scavenging of carcasses reduces one possible exposure associated with infectious pregnancy loss.

Careful hygiene when handling raw meat is an important part of infection prevention. Vaccination can protect against some pathogens affecting pregnancy. Where available, a canine herpesvirus vaccine can be used during pregnancy.

Early identification of an infectious cause helps prevent spread to other dogs. Kennel hygiene also influences the risk of clinical herpesvirus disease.

Important for dog owners

Record ovulation and mating dates and all pregnancy monitoring results. Bring details of previous litters, a medicine list and information about the mother's diet. Mention the sire's previous litters, travel abroad, new dog contacts and symptoms in other animals in the household too.

Photograph abnormal discharge and note when symptoms began. Call the practice before handling dead puppies or placentas and ask how to store and submit them for examination. Arrange follow-up for the mother and any remaining foetuses.

Fresh diagnostic samples are usually stored below 4°C. Confirm storage and transport conditions with the testing laboratory. Appropriate protective equipment is needed when handling samples and secretions if infection is suspected.

Frequently asked questions

Can a dog miscarry without discharge?

Yes, early embryo death and resorption may cause no outward signs. The change may be noticed only at a repeat examination when a previously identified pregnancy is no longer present. Later pregnancy loss can sometimes cause few symptoms too. Ultrasound can check for living foetuses in the uterus.

Can other puppies survive after one embryo dies?

Partial embryo loss may allow the remaining puppies to develop normally. After partial loss, ultrasound assesses the remaining foetuses. Supportive care for the mother may improve their survival chances. Monitoring also checks that the rest of the pregnancy progresses as hoped.

Is surgery always needed after miscarriage?

Care includes checking whether the uterus has emptied completely. Medication can help it empty in some circumstances. Hysterectomy is sometimes needed, but the decision is based on examination of the mother. Follow-up may use ultrasound and assessment of vaginal discharge.

Can progesterone prevent miscarriage?

Hormone support is used for progesterone insufficiency assessed by a vet. However, low progesterone can also result from infection or uterine disease. Treatment requires careful monitoring to prevent complications. Incorrectly timed withdrawal can be associated with prolonged pregnancy and foetal death.

Can the cause spread to other dogs or people?

Some causes can spread to other animals or people. For example, Brucella canis infection releases large numbers of bacteria in foetuses and birth secretions. Samples and secretions are therefore handled with appropriate protective equipment. Contact between a Brucella carrier and other dogs should be avoided.