How to manage the pregnant bitch

September 1, 2003
Johnny D. Hoskins, DVM, PhD, DACVIM
Johnny D. Hoskins, DVM, PhD, DACVIM

Dr. Johnny Hoskins is owner of DocuTech Services. He is a diplomate of the American College of Veterinary Internal Medicine and he is a member of DVM Newsmagazine's Editorial Advisory Board.

Q. Could you review the appropriate care of the pregnant bitch?

Q. Could you review the appropriate care of the pregnant bitch?

A. Dr. Joni L. Freshman at the 140th American Veterinary Medical Association Annual Convention gave an excellent lecture on the care of the pregnant bitch. Some relevant points made in this lecture are provided below.

The pre-breeding visit is important in establishing baseline data and to plan for care during the pregnancy. Older bitches should have a CBC, serum chemistry profile and urinalysis done to evaluate the dog's general health status.

Brucella canis testing and, if desired, canine herpesvirus titer can be performed. Pregnancy is then diagnosed by palpation or ultrasonography. The bitch's body condition is again assessed and her appetite and diet evaluated. Changes in her activity can be discussed and the need for isolation in later pregnancy stressed. A final prenatal evaluation can be done at 10-14 days prior to delivery. Abdominal radiography can help determine fetal count. Ultrasonography can be performed to assess health of the fetal vesicles and monitor fetal heart rate. Digital vaginal examination can be performed on any bitch that had a previously diagnosed vaginal stricture, as some do relax as parturition approaches. Packed cell volume and serum glucose and calcium levels can be measured at this time. This is an excellent time to discuss indications of dystocia with the owner and to instruct in monitoring twice daily body temperature in the dam to help monitor the onset of labor. Success has been seen in monitoring uterine activity in late-term bitches to better determine the onset and normalcy of labor.

Table 1.

The diagnosis of pregnancy may begin with abdominal palpation and then be more accurately diagnosed with ultrasonography and radiography. Abdominal palpation for pregnancy is best performed between 21 and 28 days, when the fetal vesicles can be felt like small "golf balls."

Pregnancy diagnosis

Ultrasonography can identify fetal vesicles as early as 17 days gestation. More reliable identification of gestational sacs is obtained at 25-30 days from the last breeding. Fetal movement and heartbeats can be seen at 28 days gestation. The presence of intestinal gas can interfere with observation of fetal sacs.

Radiography can identify fetal skeletons at 43-45 days of gestation. Because potential disparity between days from breeding and gestational age may exist, lateral and ventrodorsal radiographic views at or after 50 days from last breeding is recommended to prevent false negative results.

The bitch should be radiographed with an empty stomach and colon to enhance the ability to observe all fetuses present. Radiography is relatively insensitive in identifying fetal distress, as fetuses must be dead for at least 24 hours before radiographic signs are present.

Obese bitches should undergo weight reduction before breeding to improve conception rate and decrease risks of dystocia and poor lactation. Pregnancy is never a good time to attempt weight loss.

Nutrition

During the first three weeks of gestation, the well-conditioned bitch may undergo little or no weight gain. The consumption of a high quality adult dog food is sufficient unless the bitch is underweight. Bitches that enter pregnancy excessively thin should eat a growth or performance food to rapidly correct their condition.

At about three weeks gestation many bitches experience a loss of appetite that persists for about a week. Nausea and mild vomiting occasionally accompany the anorexia. Appetite will return at about week four.

Occasionally, bitches have poor appetites throughout pregnancy. During the last half of pregnancy, energy requirements increase, as does the need for protein and carbohydrates. This is usually provided by the increased intake of a feed for growth, pregnancy and lactation. Too rapid alteration of diet may lead to gastrointestinal distress.

The amount of food required by a pregnant bitch in later gestation increases in proportion with litter size and growth. A 40 percent average increase in food consumption accompanies the 20-55 percent increase in body weight. Because of increased intra-abdominal pressure from the enlarging uterus, multiple small meals are easier for the bitch to consume.

Bitches carrying large litters may have abdominal discomfort the last week of gestation and experience a decrease in appetite. Many, but not all, bitches will stop eating 24-48 hours before delivery.

The administration of supplemental vitamins and supplements to pregnant bitches is discouraged. Calcium supplementation is contraindicated.

Although calcium requirements increase in the pregnant bitch, they are met by the increased amount of food ingested. Excess calcium above the amount provided by a high quality diet suppresses parathyroid hormone production and increases the bitch's risk of puerperal hypocalcemia.

Excess vitamin A has been associated with congenital defects, including cleft palates. Folate deficiencies have been associated with fetal defects in humans. While premium dog foods should contain enough folate, supplementation of B vitamins is not harmful. Dogs produce sufficient vitamin C of their own and do not require supplementation. Excess vitamin D may complicate the calcium mobilization ability of the bitch. Supplementation of omega 3 fatty acids will maximize cerebral and retinal development in the fetuses.

Regular exercise during pregnancy is important in maintaining body condition. Brisk walking and short swims are the safest forms of exercise.

Exercise

In late gestation, bitches carrying large litters may need to limit this to short walks. Performance bitches should stop heavy work activities during pregnancy; herding, agility, field and advanced obedience work are discouraged due to the risk of abdominal trauma and the potential stress to the fetuses.

During pregnancy, moderate uterine contractions occur approximately every 20 to 120 minutes and last three to 15 minutes. They are of low amplitude (5-15 mmHg), but do decrease fetal oxygen levels and stimulates fetal ACTH release. During these uterine contractions, the fetus does not breathe or undergo REM sleep.

Significant mental or physical stress on the bitch can cause adrenaline secretion by the bitch that decreases blood flow to the uterus and placenta, resulting in decreased fetal oxygen and can impair development and threaten survival.

Routine vaccinations (if indicated in bitch's locale) should be current or done prior to breeding. A puppy's early immunity is dependent upon consumption of colostrum containing high levels of antibodies and, therefore, dependent on the bitch's immune status.

Vaccination

Canine distemper and parvovirus titers in the bitch can be measured to assure appropriate levels are present. Administration of modified live vaccines is not recommended during pregnancy.

Toxocara canis larvae encysted in muscle tissue of the pregnant bitch may be reactivated during the last trimester and migrate transplacentally to the developing fetuses. It is important to realize that routine deworming of the bitch will not affect this process.

Parasite control

The infection of developing fetuses can be interrupted by administration of fenbendazole at 50 mg/kg PO from day 40 of gestation to day 14 after whelping. Ancylostoma caninum can also be transmitted transplacentally and is responsive to the above treatment.

External parasites are best controlled with environmental management and using a flea comb on the bitch. Non-toxic environmental controls are now available.

Avoidance of organophosphates and pyrethroids during pregnancy is recommended. The newer flea control products are not, at this time, approved for pregnant bitches.

Microfilaria of Dirofilaria immitis can cross the placenta. Pregnant bitches should be routinely tested for heartworms and maintained on heartworm preventative in at-risk areas. The currently used heartworm preventives are safe in pregnant bitches.

Certain blood values are altered by pregnancy. The PCV may decrease to approximately 40 percent by day 35 of gestation and at delivery time the PCV may be below 35 percent. The anemia is normocytic, normochromic and caused by hemodilution from increased plasma volume. The immune system is moderately depressed during pregnancy, resulting in a decrease in serum IgG. Serum creatinine may decrease by 25-35 percent. Fibrinogen and other coagulation proteins increase during pregnancy.

Laboratory evaluation

Hypoglycemia of pregnancy is also known as pregnancy toxemia. This serious illness is most common in thin, poorly conditioned bitches. These bitches have inadequate fat stores, muscle mass and carbohydrate diets. They often present with nonspecific signs of ADR, gastrointestinal distress or seizures.

Glucose control

Ketonemia and ketonuria without glucosuria often accompany the hypoglycemia. Because hypocalcemia presents with similar signs and can occur in term bitches, serum calcium level should also be evaluated. Treatment of hypoglycemia is with slowly administered dextrose-containing fluids.

Nutritional supplementation will be needed in bitches that do not voluntarily eat. Termination of pregnancy may be necessary in severe cases. Pregnant bitches that are maintained on diets deficient in carbohydrate may develop hypoglycemia in the last two weeks of gestation. This resulted in a significant increase in stillborn puppies and in neonatal death in the first three days of life.

Pre-existing subclinical diabetes mellitus may be aggravated by pregnancy. Sensitivity to insulin is decreased as early as 35 days of gestation and continues to decrease as pregnancy progresses. Insulin should be given if indicated by carefully monitored blood glucose levels.

The varying demands and hormonal alterations during pregnancy and parturition may make glucose control difficult to obtain.

Although uncommon, failure to maintain an appropriate serum progesterone level throughout pregnancy is a potential cause of fetal loss. Monitoring of the serum progesterone level allows accurate diagnosis of this problem. Serum progesterone levels above 2 ng/ml are required to maintain pregnancy.

Hypoluteodism

In a normal pregnancy, serum progesterone reaches peak levels of 15-90 ng/ml by 15-30 days post luteinizing hormone (LH) peak. During the last trimester, serum progesterone concentrations decrease to 4-16 ng/ml before dropping below 2 ng/ml approximately one day before parturition. Monitoring of serum progesterone levels can be performed weekly if the levels are 20-50 ng/ml or daily if they are 5-10 ng/ml.

Treatment of hypoluteodism can be performed with injections of progesterone in oil (2-3 mg/kg IM every 24 hours). Alternatively, ally-trenbolone (Regumate, Hoechst-Roussel Agri-Vet Co.) at 0.088 mg/kg PO daily can be given.

Ultrasonographic monitoring of fetuses can be helpful in assessing fetal viability. Fetal heart rates less than 160 bpm indicate fetal distress, as does decreased fetal movement. Exact timing of ovulation, and, therefore, parturition date, is necessary so that progesterone supplementation can be stopped about 72 hours prior to expected parturition, allowing for an approximation of normal decline of serum progesterone.

The fatal form of canine herpesvirus infection results from exposure of the puppies during the last three weeks of gestation and the first three weeks of life. Canine herpesvirus is most commonly spread as a mild respiratory infection between adult dogs. Titers to canine herpesvirus can be measured in the bitch prior to breeding to determine if she has had previous exposure.

Canine herpesvirus

A naive bitch is at risk for infection during pregnancy, as a previously exposed bitch is not. The puppies are still at risk after birth in either situation. No vaccination is currently available. Unfortunately, no successful treatment is available if the puppies become infected.

Administration of any medication is best avoided in the pregnant bitch. Some drugs have proven to be relatively safe, while others are definitely dangerous to the developing fetus (see lists). Many other drugs carry potential risks that have not been researched or established. The safest course is to avoid any medication of questionable safety and to only administer medication if absolutely necessary.

Drug administration