Diagnosing and managing canine dystocia (Proceedings)
Most owners lack medical knowledge regarding the birthing process, and as such, they frequently look to the veterinarian to answer questions and to identify potential problems. The emergency clinician must therefore be familiar with normal reproductive behavior in addition to the common complications that may arise. With this goal, we will review the events surrounding normal parturition, the various causes of dystocia, and techniques for managing this type of emergency.
Normal Reproductive Physiology
Normal gestation length in the dog may range from 57-72 days from the time of first breeding, with an average length of 65 days. Because cats are induced ovulators, there is generally less variability in gestation length, which ranges from 63-65 days. Ovulation may not take place after the first breeding however, so in the event of multiple breedings, uncertainties with regards to gestation length may still be present in the cat. As the whelping date approaches, a number of clues may point toward impending parturition. Mammary development, vulvar enlargement, mucous vaginal discharge, and relaxation of the pelvic ligaments are early signs of approaching parturition. Onset of lactation may be noted in primiparous bitches within 24 hours of parturition, but in multiparous bitches may occur several days before parturition. A sudden drop in body temperature (>2°F) is generally noted within 24 hours of parturition in dogs and cats as a result of decreases in progesterone levels, but this finding is not always reliable. In one recent study, nadir temperature occurred >48 hours before parturition in 24% of dogs, and an appreciable drop in temperature (>1° F) was not seen in 35% of dogs.Normal parturition proceeds in three stages. The first stage is characterized by subclinical uterine contractions and progressive dilation of the cervix. During this stage, which typically lasts for 6-12 hours, bitches may show signs of restlessness, apprehension, panting, nesting behaviors, hiding, and anorexia. Queens may be tachypneic, restless, and vocal, or may lay in their nesting boxes, purring. Active expulsion of the fetuses occurs during the second stage of labor. The first fetus is usually delivered within 1 hour of onset of stage 2 labor in cats, and within 4 hours in dogs, with subsequent deliveries every 15 minutes to 3 hours. Active straining generally results in expulsion of a fetus within 15 minutes. The entire process generally occurs over 2-12 hours, but may take as long as 24 hours with large litter sizes. The third stage of labor results in expulsion of the placenta. One placenta should be identified for each fetus delivered. Placentas are usually still attached to the fetus by the umbilical cord and emerge with the fetus, but may emerge within 15 minutes to several hours if they become detached. Lochia, a greenish vaginal discharge, indicates placental separation and may be seen during all stages of labor. Following parturition, the discharge gradually becomes red-brown, decreasing in volume over 4-6 weeks as uterine involution takes place.
Historical and physical exam findings that should prompt a clinician to suspect dystocia are as follows:
A definite cause is apparent (ie. fetus lodged in birth canal, pelvic fractures)
Gestation is prolonged (>70 days) with no evidence of labor
Temperature has dropped to <100° F and returned to normal with no evidence of labor within 24 hours
Lochia is noted and 2 hours have elapsed without expulsion of a fetus
Strong and persistent contractions fail to result in the delivery of a puppy within 30 minutes
Weak and infrequent contractions fail to produce a fetus within 4 hours.
More than 4 hours have elapsed since the birth of a puppy with no evidence of ongoing labor
Signs of systemic illness or severe pain are present