Early embryonic loss may take place even before the embryos implant in the lining of the uterus because of unfavorable environmental conditions caused by endometritis or cystic endometrial hyperplasia. Other causes of early embryonic loss are chromosomal abnormalities and fatal genetic defects in the pups.
Pregnancy can be diagnosed at three to four weeks by palpating the bitch’s abdomen. This should only be done by an experienced breeder or veterinarian. Using ultrasonography, it is possible to diagnose pregnancy as early as 18 days after the first breeding, although most breeders wait until 21 to 28 days. Ultrasounds are excellent for diagnosing pregnancies but tend to underestimate the number of puppies.
Checking blood levels of the hormone relaxin may also confirm a bitch’s pregnancy. This is done at about 30 days into the pregnancy. X-rays are usually taken about 45 days into the pregnancy and are excellent for determining how many pups are present.
If a bitch is found to be pregnant and later does not deliver puppies, one of two things must have happened: Either her puppies were reabsorbed or she miscarried (aborted).
Fetal reabsorption can occur at any time from fertilization through about the 40th day of gestation. The products of conception are absorbed back into the mother’s body. Some bitches exhibit malaise, fever, loss of appetite, and a thin, bloody, or purulent vaginal discharge. In early fetal reabsorption, symptoms usually are absent and the pregnancy and reabsorption go unnoticed. Thus the problem is often mistaken for failure to conceive.
Abortion is defined as death of the fetus followed by expulsion of the products of conception. Abortion generally occurs during the last three weeks of gestation. The signs of abortion are vaginal bleeding and the passage of tissue. These signs may not be observed if the bitch is fastidious and consumes all expelled tissue.
A well-recognized cause of third-trimester abortions and stillbirths is brucellosis. Herpesvirus is another cause of late abortions, stillbirths, a decrease in the number of pups per litter, and female infertility. Occasionally, a bacterial infection will cause an abortion. Culprit bacteria include E. coli, camphylobacter, mycoplasma, and streptococcus. Drugs that can induce abortion include corticosteroids and chloramphenicol.
Bitches who suffer repeated early pregnancy losses or abort on successive pregnancies should be suspected of having uterine infection or a progesterone deficiency. Progesterone deficiency (called hypoluteoidism) is caused by failure of the corpora lutea of the ovaries to secrete enough progesterone to support placental attachment. The condition recurs with subsequent pregnancies and becomes a likely consideration when a bitch repeatedly fails to maintain a pregnancy.
Causes of sporadic abortion include a serious illness with a high fever during pregnancy (such as distemper or leptospirosis), violent activities such as jumping from heights, a blow to the abdomen, and improper feeding and pre-natal care.
Breeders may decide to invest in a monitoring system, such as Whelpwise, to keep a close check on a pregnancy if the bitch is prone to problems. The Whelpwise system measures fetal heartbeats and can also track contractions. Dog owners basically rent the equipment to monitor their bitch and are provided with some guidance from the company on results they see. However, this should not be a substitute for the direct guidance of a veterinarian.
Treatment: A bitch who has passed fetal tissue should be examined by a veterinarian. Ultrasonography may be needed to make sure the bitch has not retained fetal or placental tissue. Infectious abortions are treated with antibiotics and supportive measures, as necessary.
It is important to identify and correct the underlying cause whenever possible. Laboratory examination of the fetus and placenta, along with appropriate cultures, will reveal the cause of an abortion in about 50 percent of cases. When such studies are not done, the cause usually is never discovered. For safety, assume that all abortions are infectious. Maintain kennel hygiene and handle all discharges and tissues with disposable rubber gloves.
Bitches who abort should be screened for brucellosis and herpesvirus – if these tests were not already done in preparation for breeding.
Hypoluteoidism is associated with low plasma progesterone levels in early pregnancy. Although conclusive studies are lacking, treatment with a progesterone supplement may prevent recurrent abortion in some bitches with apparent hypoluteoidism. The progesterone must be carefully monitored because of serious risks associated with its use during pregnancy. Whether these bitches should be bred is questionable.