12 Parturition and Dystocia
Progesterone, a hormone that is necessary to maintain pregnancy, increases body temperature. Just before the bitch goes into labor, the concentration of progesterone falls abruptly. This is reflected as a drop in body temperature, but this drop is not long-lived. To try to catch the temperature drop, take the bitch’s temperature about four times daily beginning about 55 days from breeding. When the temperature drops more than 1 degree from her average value, she will probably go into labor within the next 24 hours.
If you know the ovulation date, whelping occurs 62 to 64 days later. If all you know are breeding dates, identification of the rectal temperature drop, direct measurement of progesterone in blood, or x-rays can be used to determine whether a bitch is at term.
The green pigment comes from the edges of the placentas and indicates placental separation. If the placenta has separated, the pup is getting no more oxygen or nutrients from the dam. During whelping, if no pups have yet been born, green discharge is very significant because it tells you someone’s placenta has separated. Although I tend to intervene fairly quickly if green discharge is present and birth of a pup is not impending, I have known bitches that passed green discharge for a day and still had live pups. If pups already have been born, it is less significant because you know placentas have separated as the pups were born.
Most bitches show a definite change in behavior when they are done whelping: settling down and letting the pups nurse. You can try palpating the abdomen, but be aware that the uterus coils on itself after whelping and can feel like a round, firm pup. Your veterinarian can verify end of whelping for you with palpation or radiographs if necessary.
Retained placentas can cause uterine infection (metritis). Most often, however, they are broken up and passed in the normal postpartum discharge. If the bitch had live pups that are nursing, she is producing oxytocin, which will cause uterine contractions and help expel the tissue.
Not if she has live pups that are nursing. The nursing pups stimulate frequent release of small amounts of oxytocin, which causes milk letdown and uterine contractions. This is better for the bitch than our giving her one big shot of oxytocin.
Ovariohysterectomy (spay) at the time of C-section is a good idea for bitches that have finished their breeding career because it saves the bitch from having to undergo anesthesia more than once. Milk production is stimulated by prolactin, which is released from the pituitary gland at the base of the brain. Dogs do not need their ovaries and uterus to make milk.
I would work a good 30 minutes before giving up. Rub the pup with a soft towel, aspirate all fluid from the mouth and nose, shake the pup gently by the scruff of the neck, and make sure there is not excessive bleeding from the umbilical cord. You can try providing oxygen at home by blowing into the pup’s nose.
Preparation of the bitch and the environment should occur well ahead of the projected whelping date (see Chapter 10). Materials to have on hand prior to whelping include towels, a bulb syringe, sewing thread or dental floss, iodine, a postal scale or small food scale, vanilla ice cream, and your veterinarian’s phone number (Figure 12-1).
Gestation length in dogs most commonly is reported to be 63 days. However, that gestation length is from ovulation, not from breeding. It has been demonstrated that gestation length timed from ovulation in most bitches is from 62 to 64 days. Gestation length timed from breeding can vary from 58 to 71 days. Remember that bitches stand to be bred for a large window of time around ovulation and that spermatozoa may live for more than a week after introduction into the bitch’s reproductive tract. Therefore, if a bitch is bred very early and does not conceive until well after breeding, she will have an apparent prolonged gestation. Conversely, if a bitch is bred late and conceives very soon after breeding, she will have a shortened gestation. Bitches should not be considered overdue until 65 days after ovulation or 72 days from breeding.
In late gestation, bitches may be unable to eat much at one time or to breathe easily because the enlarged uterus puts pressure on surrounding tissues. Some bitches will pass small volumes of clear or tan fluid from the vulva for 1 to 2 weeks before whelping. As long as the volume of fluid is small, there is no odor, and the discharge does not resemble pus, it probably is not a cause for concern. Some bitches have definite mammary development and lactate up to 1 week before whelping; other bitches have no discernible mammary development and no milk at the time of whelping. Both extremes can be normal. Finally, nesting behavior may start up to 1 week before whelping and is not an exact indicator of onset of parturition.
It is the fetuses that initiate labor. The exact sequence has not been determined in the dog, but it is hypothesized to mimic the system found in sheep. In sheep the lamb releases adrenocorticotropic hormone (ACTH) from its pituitary gland. That ACTH enters the ewe’s circulation and causes her adrenal gland to release cortisol. Cortisol starts a hormonal cascade terminating in a decline in progesterone, a slight rise in estrogen, and an increase in prostaglandin (Figure 12-2). This allows uterine contractions to increase in frequency and strength.
A decline in progesterone concentrations is reflected by a decline in body temperature. Progesterone, when present at high concentrations in blood, is associated with high body temperature. When progesterone concentrations fall precipitously, as occurs just before parturition, there is a transient de crease in body temperature. If rectal temperature is measured four times daily, beginning about a week before expected date of whelping, a decline in body temperature of greater than 1 degree often is identified. Most bitches begin whelping within 24 hours of this temperature drop (Figure 12-3). This is not a consistent phenomenon; some bitches apparently have such a gradual decline in progesterone concentration that other thermoregulatory mechanisms prevent the decline in body temperature, and other bitches have several drops in progesterone, each accompanied by a decline in body temperature.
Sometimes a question arises as to whether or not a bitch is at term. Ideally, breeding management is done when the dog was in heat, allowing identification of the date of ovulation. Parturition occurs with good regularity 62 to 64 days after ovulation. This coincides with 56 to 58 days from the first day of diestrus (see Chapter 9). Measurement of serum progesterone and radiographs also can be used to determine whether a bitch is at term (Table 12-1). It is important not to try to induce labor or perform a cesarean section too much before term. Pups do not lay down surfactant, the lining of the lung, until the final days of gestation and so will have difficulty breathing and be prone to respiratory tract infection if born prematurely.
|Timing from ovulation or onset of diestrus||Ovulation date is determined by measurement of the LH peak or of progesterone in blood. Whelping occurs 62 to 64 days later. Onset of diestrus is determined by vaginal cytology. Whelping occurs 56 to 58 days later (see Chapter 9).|
|Rectal temperature||A transient decrease in body temperature by one degree or more occurs concurrent with the drop in progesterone just before parturition. Stage 1 labor usually begins within 24 hr of the temperature drop.|
|Measurement of progesterone in blood||Concentration of progesterone must fall before uterine contractions can occur. A decline in serum progesterone to 2 ng/mL is usually followed by onset of labor within 24 to 48 hr.|
|Radiographs||Puppies mineralize from the center of the body outward. The last tissues to mineralize and become visible on radiographs are the paws, bones of the tail, and teeth. If these structures are visible, the bitch is within 4 days of whelping and any pups born probably would survive.|
LH, Luteinizing hormone.
Labor in dogs is described as occurring in three stages. The first stage is cervical dilation, the second is expulsion of the fetuses, and the third is expulsion of the placentas. First-stage labor occurs as a distinct period and concludes with the onset of the hard contractions signaling second-stage labor. Second- and third-stage labor alternate as the bitch passes one or two pups and then one or two placentas alternately until done.
The onset of stage 1 labor may be difficult to define precisely. The bitch’s cervix is dilating, but she is not having strong, coordinated abdominal contractions. She may be restless and panting (Figure 12-4). She usually refuses to eat and may vomit. This stage may last for up to 12 hours in normal bitches. Intervention is recommended if the bitch does not enter stage 2 labor, with obvious contractions, within 12 hours. Prolonged stage 1 labor (i.e., >18 hours) has been associated with increased incidence of stillbirths and neonatal death.
During stage 1 labor, the hormones relaxin and oxytocin contribute to relaxation and dilation of the cervix. Because of the extreme length of the canine vagina, the cervix is not palpable. If a circumferential constriction is felt when a gloved finger is passed into the vagina, it probably is a ring of vaginal tissue, not the cervix.
Stage 2 labor is considered to have started when the bitch starts having obvious, coordinated contractions. Movement of a pup, especially a pup’s hard, round head, into the cervix stimulates release of oxytocin and uterine contractions. If pups are not presenting a firm surface against the internal os of the cervix, this reflex release of oxytocin may not occur and labor may not progress. Rising prolactin concentrations contribute to mothering behavior by the bitch and promote lactation.
Bitches may pass a fair volume of clear fluid from the vulva before a puppy is passed. Green vulvar discharge also may be seen. The green coloration arises from the edge of the placenta and indicates that placental separation has occurred. Pups may be born within a clear sac, or the sac may rupture as the pup moves through the birth canal or be ruptured by the bitch as the puppy passes through the vulva (Figures 12-5 and 12-6). The bitch should vigorously lick the newborn pup to stimulate respiration. She also should shear the umbilical cord with her teeth.
If the bitch does not tear the sac away from the pup and stimulate respiration, you must do it (Figure 12-7). Tear the sac away with your fingers, use a bulb syringe to suck fluid out of the pup’s nose and mouth, and vigorously rub the pup with a towel. The use of the respiratory stimulant doxapram has fallen from favor in human and veterinary pediatric medicine. I do not recommend “flinging” the pup to move fluid out of its respiratory tract by vigorously swinging it with head down. Blowing air into the nose may help to provide oxygen to the pup. Insertion of a needle into the tissue between the nostrils (the Jen Chung acupuncture site) and twisting the needle as it hits bone may stimulate respiration (Figure 12-8). The umbilical cord can be tied off with sewing thread or dental floss. Tie off the cord about 1 inch away from the pup’s body and again 1 inch from there. Cut between the two ties, and clean the exposed tissue with a disinfectant such as iodine.
Bitches that appear to be slowing down in labor may be becoming fatigued. Walking the bitch may stimulate uterine contractions. Some bitches will eat during labor, and this boost in calories might be beneficial. Vanilla ice cream and cottage cheese are foods that commonly are offered.
It may take up to 4 hours for the first pup to be born, and puppies should be born within 2 hours of each other. Intervention is recommended if the bitch has had intermittent straining for 4 hours with no pups born, hard and constant straining for 30 minutes with no pup born, or if it has been more than 2 hours between pups. Accurate record keeping is essential (Figure 12-9).