Dystocia in Dogs and Cats

Ronald M. Bright, DVM, MS, DACVS

BASIC INFORMATION Description Dystocia is the inability to initiate the act of labor or the deliv- ery of pups or kittens at the end of a pregnancy. Dog breeds at increased risk for dystocia include the Yorkshire terrier, miniature poodle, Pomeranian, English bulldog, dachshund, Chihuahua, and Scottish terrier. Causes The causes of dystocia can generally be classified into those caused by the mother and those caused by the fetus.

Uterine inertia is a condition in which the uterine muscles either do not contract (primary uterine inertia) or become fatigued during labor (secondary uterine inertia) from persistent straining against an obstruction within the birth canal. Secondary uterine inertia is almost never the sole cause of dystocia.

A narrow birth canal caused by a previous fracture of the pelvis can prevent passage of the fetus. The head of the fetus may be too large to pass through the birth canal, or the fetus may be oversized or malformed. Sometimes an improper position of the fetus as it approaches the birth canal makes passage difficult.

Psychological stress can delay the onset of labor. A rare cause of dystocia is twisting of the uterus on itself (uterine torsion).

Clinical Signs The following are signs of dystocia: Active straining has occurred for more than 30-60 minutes

without the birth of a fetus. Straining for 2 or more hours has not resulted in delivery of a

fetus. The resting stage between expulsion of fetuses is greater than 4

hours and there is no sign of straining even though it is known that more fetuses remain in the uterus.

Signs of systemic illness, such as vomiting, weakness, or fever, are present.

Abnormal vaginal discharge, such as frank blood or pus, is present.

The pregnancy is known to be a high risk (predisposed breed); only one, large fetus is present; or narrowing of the birth canal has occurred from a prior pelvic fracture.

Attempts to expel a fetus are painful. Obvious signs of distress are present.

Diagnostic Tests The diagnosis of dystocia is often derived from the clinical signs and a thorough physical examination. Other tests that may be rec- ommended include x-rays, an abdominal ultrasound, and labora- tory tests, such as measurement of blood calcium levels. Low blood calcium may be associated with uterine inertia. Commercially available external whelping monitors can be used to detect dimin- ished fetal viability (fetal stress) and abnormal patterns in the uter- ine contractions.

TREATMENT AND FOLLOW-UP

Treatment Options The treatment of dystocia varies, depending on the underlying cause. If a fetus has passed part of the way through the birth canal but is now caught, it may be possible to dislodge the fetus through cautious use of fingers or instruments. Administering a tranquilizer to relieve stress in an apprehensive bitch or queen may be helpful.

If uterine inertia is diagnosed, medical therapy may be attempted, provided that the birth canal is a normal size, the cervix is open, the fetus is not too large to pass through the canal, and no other obstruc- tion is identified. Medical therapy involves administration of the hor- mone, oxytocin, to stimulate uterine contractions. If calcium levels are low, supplementation of calcium is indicated, because it enhances uterine contractions and increases the effects of oxytocin.

If medical therapy fails, surgery to perform a cesarean section (C-section) is indicated. Your veterinarian may discuss the option of spaying the mother at the time of the cesarean section. If there are no further plans for breeding the mother or if a uterine rupture is present, ovariohysterectomy (spaying) may be recommended.

Follow-up Care and Prognosis Following resolution of the current dystocia, emphasis must be placed on preventing dystocia during future pregnancies. Such measures include providing consistent and adequate amounts of exercise during the pregnancy and making sure the mother is fed a well-balanced diet.

To increase the chances of an optimal litter size, it is often rec- ommended that bitches be bred 2 days after ovulation. All queens and bitches should be provided a quiet, dark, stress-free, and sani- tary birthing environment.

If you have other questions or concerns about this, or other health topics, please call McFarland Animal Hospital

608-838-3400

Copyright 2011 by Saunders, an imprint of Elsevier Inc. All rights reserved.