Dystocia refers to abnormal or difficult birth. Causes include maternal factors (uterine inertia, inadequate size of birth canal) and/or fetal factors (oversized fetus, abnormal orientation as the fetus enters the birth canal). The condition occurs more commonly in certain breeds. In one survey (253 whelpings, 1,671 pups born), a high frequency of dystocia (32% of the individual bitches and 27.7% of all the whelpings) in Boxers was reported, mainly due to uterine inertia but also to fetal malpresentations.
Dystocia should be considered in any of the following situations: 1) animals with a history of previous dystocia or reproductive tract obstruction, 2) parturition that does not occur within 24 hr after a drop in rectal temperature to <100°F (37.7°C), 3) strong abdominal contractions lasting for 1–2 hr without passage of a puppy or kitten, 4) active labor lasting for 1–2 hr without delivery of subsequent puppies or kittens, 5) a resting period during active labor >4–6 hr, 6) a bitch or queen in obvious pain (eg, crying, licking, or biting the vulva), or 7) abnormal vulvar discharge (eg, frank blood, dark green discharge before any neonates are born [indicates placental separation]).
To determine the appropriate therapy, the cause of dystocia (obstructive vs nonobstructive) must be determined and the condition of the animal assessed. A thorough history regarding breeding dates, previous parturitions, pelvic trauma, etc, is desirable. The animal should be examined for signs of systemic illness that, if present, may necessitate immediate cesarean section. The normal vaginal discharge at parturition is a dark green color; abnormal color or character warrants immediate attention. A sterile digital vaginal examination should be performed to evaluate patency of the birth canal and the position and presentation of the fetus(es). Radiography or ultrasonography can determine the presence and number of fetuses, as well as their size, position, and viability.
Medical management may be considered when the condition of the dam and fetuses is stable, when there is proper fetal position and presentation, and when there is no obstruction. Oxytocin (3–20 U in bitches, 2–5 U in queens) given IM up to 3 times at 30-min intervals, with or without 10% calcium gluconate (3–5 mL, IV slowly) may promote uterine contractions. If no response follows, a cesarean section should be performed.
Surgery is indicated for obstructive dystocia, dystocia accompanied by shock or systemic illness, primary uterine inertia, prolonged active labor, or if medical management has failed.