Introduction

Dystocia and need for Caesarian sections in bitches are a fairly common occurrence in both general practice and emergency practice. Canine dystocia has varying rates of occurrence, depending on the reference, but a recent prospective study suggested only 46% of dogs whelped naturally without assistance.¹ Distinguishing whether fetuses are term, as well as determining urgency of the need for medical management verses surgical intervention for fetal delivery is a skill every small animal practitioner should have some familiarity with.

Defining Dystocia

During triage of a possible dystocia, determining whether fetuses are term is critical before proceeding with assistance via medical or surgical means. Canine gestation lasts approximately 62–64 days from ovulation,² with a very narrow window of fetal survival if delivery occurs prior to 48–72 hours before due. Ovulation timing to determine acceptable due date ranges is ideal, though not always available. Days from breeding date, transient rectal temperature decreases, presence of mammary development or lactation, radiographic appearances, and nesting behavior are not observations that are absolute for determining safety for delivery, though some can be supportive. Ultrasonographic evaluation is an excellent choice to determine fetal maturity if a dystocia presents in practice, in order to better determine if the bitch is aborting rather than having a dystocia at term pregnancy.² This would warrant a very different approach to management.

Canine eutocia consists of three stages. The first stage of parturition generally on average lasts for 6–12 hours, but can range widely, with 36 hours observed in some primiparous bitches.³ Common notes during this stage include restlessness, nesting behavior, panting, and inappetence, but precedes obvious contractions or lochia. The presence of contractions, abdominal contractions, passage of lochia or burst of fluid associated with ruptured fetal sacs will clearly denote second stage labor. Third stage labor in litter bearing species is often following each puppy, with passage of placenta at the time of birth of each fetus. In the event of dystocia, the bitch may show obvious signs of distress, or may simply not be progressing within timelines that would be associated with normal whelping behaviors.

Although the bitch in obvious distress may appear more urgent, both scenarios may require haste to result in successful delivery of live puppies.

Maternal Causes of Dystocia

Uterine inertia can occur as a primary issue, presenting as a bitch that lacks progress into stage two labor. This may present in bitches with singleton or two-fetus pregnancies, or alternatively may present in a bitch that carries past term with a normal litter size. Secondary inertia can also occur, which occurs as a result of prolonged uterine contractions during whelping. Breed-related predispositions are widely associated with brachycephalic-type breeds but can also extend to those with extremely large or small litters, as well as breeds that have more frequently been managed with elective C-sections in recent years. Brachycephalic breeds are 11 times more likely to have a C-section as compared to other breeds.²

Conformation of the bitch can impact her ability to naturally whelp. History of pelvic trauma, pelvic size, and pelvic shape can all impact the patency of the birth canal for natural whelping. Soft tissue structures may also cause dystocia, such as a vaginal stricture or band that may have gone unnoticed during artificial insemination. Other common vaginal impediments include excessive perivaginal fat, vaginal hyperplasia or prolapse, and congenital structural anomalies. Aside from the reproductive tract structures, additionally a ruptured diaphragm or disrupted abdominal wall may indirectly result in non-productive contractions and may present as a dystocia.

Metabolic concerns may prevent normal labor, such as gestational diabetes and pregnancy ketosis. Although these are commonly associated with pregnant bitches specifically, other endocrine or metabolic conditions may result in a primary inability to produce normal contractions and subsequently puppies. Exogenous progesterone supplementation will prevent the normal progression of labor in most bitches. Other causes for maternal whelping failure include pain and fear.

Fetal Causes of Dystocia

Many of the maternal causes of dystocia have some relation to fetal causes in relation to fetal-maternal mismatch. Large fetal size compared to the birth canal may be due to litter size, breed predispositions, prolonged gestation, or genetic factors.³

Fetal presentation, position, and posture can be abnormal and result in dystocia. It should be noted that 60% of canine fetuses are cranial presentation, with 40% caudal presentation.³ Caudal presentation in this species is not considered a risk factor for stillbirth, and doesn’t generally require a different approach to resolution, as it does in some other species.

Transverse presentation is the only form of presentation considered abnormal in the dog and is rare. Position describes the relation of the mother’s pelvis to the fetus’s spine and is normally dorsosacral. Posture describes the extension or flexion of head and limbs, and all should be extended in normal whelping progression.

Schistosomus reflexus, anasarca, and other fetal structural abnormalities may result in difficulty of the dam to whelp naturally. Alternatively, some fetal abnormalities may result in a normal birth, but would need attention immediately post-delivery.

Physical Examination and Fetal Assessment

Routine physical examination of the bitch’s state upon arrival at the clinic is important to determine more serious complications as a result of dystocia and assess for the stability of the patient depending on need for surgery. Digital examination of the vaginal tract should be performed, with special attention to lochia color, presence of fetus, and ability of the bitch to contract when manipulated. Many bitches who can produce strong contractions will do so as a response to vaginal manipulation during labor.

If a fetus is present in a canal, assessing for the subjective assessment of size, position, and cause for dystocia should be performed quickly. Fetal viability is often difficult to observe, as compared to livestock, due to patient size. Still, immediate delivery of the fetus if past the pelvis can be assisted using lubricant and traction synchronized at the time of uterine contractions. Two handed manipulation of a fetus using one hand vaginally and the other either rectally or by transabdominal pressure can sometimes provide extra help to extract the fetus.⁴ It is important to be gentle with all manipulations, as decapitation or dismemberment are possible if using excessive force.

If a fetus is not present in the canal, assessment of ionized calcium can be pursued. Practical assessment of calcium availability can be obtained by stimulating contractions vaginally. If contractility is strong, transient hypocalcemia is less likely a cause for dystocia. If calcium is low, supplementation via intravenous administration. Oxytocin may be used at microdoses (0.25–2 units) intramuscularly to assist in fetal expulsion if calcium needs appear satisfactory. In the event both calcium and oxytocin therapy fail, C-section should be considered imminently.

Indications for Proceeding to C-Section

If a bitch presents in labor, condition of the fetuses for maturity and stress should be assessed upon arrival. Fetal distress is defined differently amongst varying practitioners, however, any fetus that has a fetal heart rate of less than 180 should be observed repeatedly and is cause for concern. If found to be consistent, considering a C-section should be stressed as best for fetal survival.

Obstructive dystocias should be aggressively moved to surgery if the obstruction is not easily relieved by manipulation measures. Color of lochia should be used as an indication for placental separation, and green fetal fluids should be an indicator for concern if no fetuses have been passed. After fetuses have been delivered, green vulvar discharge is considered normal, and is no longer a way to evaluate the health of the fetuses. Normal progression of fetuses should not exceed 2 hours between deliveries in most healthy bitches.

It is important to remember to assess for the remainder of fetuses. On occasion, owners may have not witnessed the birth of a puppy, and radiographic count of fetuses may not have been accurate. In either case, remaining fetal presence is important to confirm, prior to pursuit of Caesarian section.

Post-delivery Considerations

In many species, dystocia may create an increased risk for post-delivery concerns such as metritis and future fertility. No thorough studies exist describing outcomes; however, the cause of dystocia may have a large impact on expected recurrence or negative impacts. Fetuses delivered under stress may have undergone a period of hypoxia and require more attention immediately after birth than their littermates. Stillbirths may be more frequent in situations where prolonged intervals between puppies are observed.

References

1.  Hollinshead FK, Hanlon DW. Factors affecting the reproductive performance of bitches: A prospective cohort study involving 1203 inseminations with fresh and frozen semen. Theriogenology. 2017;101:62–72.

2.  Lopate C. Estimation of gestational age and assessment of canine fetal maturation using radiology and ultrasonography: A review. Theriogenology. 2008;70:397–402.

3.  Johnston SD, Root MV, Olson PNS. Canine and Feline Theriogenology. Philadelphia, PA: W.B. Saunders Company; 2001.

4.  Jackson PG. Handbook of Veterinary Obstetrics. 2nd ed. St. Louis, MO: Saunders; 2004;141–166.