By Richard Wheeler, DVM
Breeding dogs is not cheap…monetarily, emotionally, or with the amount of time invested. Precious lives are involved. Please breed responsibly.
This is the second of a three part series on C-section delivery in the bitch. My intention is to discuss here Emergency C-sections, deciding to proceed to surgery, risks, consequences, and alternatives. Next month, I will discuss the C-section itself, anesthesia, and neonatal resuscitation.
Innumerable conceivable (and some inconceivable) situations can arise to prompt an emergency c-section. Below are a few plausible situations to consider. In reality, each situation will be different and multiple factors involved which must be considered in making the decision to proceed to surgery.
A bitch is perceived to be “overdue”. Very rarely will a bitch actually exceed normal canine gestation. The problem is determining “normal”. Often, the gestation period of the dog is arbitrarily designated as 65 days. Or 62 days. Or 57 days. Even as long as 72 days. Such variability makes it impossible to predict whelping based on breeding dates. Determining the first day of Diestrus (D1) with vaginal cytology allows more accurate prediction of whelping 57 days later. Even then, there is a variability of 3 days (remember, as we discussed previously, delivery even 2 days premature rarely results in viable puppies). The greatest accuracy in estimating whelping date is 65 days after the Lutenizing Hormone (LH) peak, determined by either serial blood progesterone or LH evaluations. This provides accuracy within 1-2 days of whelping. Ultrasound estimation of fetal age base on fetal measurements in early gestation can improve accuracy to within 1 day when combined with the LH peak.
A bitch’s temperature will commonly drop 1-3 degrees below its normal range (usually to 98 or 99 degrees Fahrenheit) 24 hours before whelping. This temperature drop is a result of a sudden drop in Progesterone, the hormone responsible for maintaining pregnancy. Bitches will also often go off feed the morning prior to delivery. If a bitch exceeds her expected due date or there are no signs of labor within 24 hours of an obvious temperature drop, Primary Uterine Inertia (PUI) should be considered. PUI is a condition in which the uterus fails to contract sufficiently to elicit labor or deliver the puppies. Causes of PUI are poorly understood, but included chemical imbalances (especially calcium or magnesium), poor quality nutrition (which may result in chemical imbalances), excessive uterine stretching (possibly from very large litters or abnormal fluid retention called Hydrops), or most commonly for no apparent reason at all (Idiopathic PUI-which may be genetic and is likely to recur on subsequent litters).
Failure to initiate labor is another possibility for an overdue bitch. It is poorly documented, but clinical impression suggests that very small or singleton litters lack sufficient fetal input to trigger the hormonal changes necessary to initiate labor.
Whatever the cause, adjunctive diagnostics are warranted to determine if whelping is eminent to prevent delivery of premature puppies. Blood progesterone levels and fetal monitoring (by ultrasound) are most critical. Accurate breeding history, especially LH peak, is also very valuable.
Occasionally, medical intervention will suffice, including calcium or magnesium supplementation. However, most commonly, surgery is required. Administration of oxytocin is rarely successful in treating PUI, and is CONTRAINDICATED in the event that the cervix has not dilated.
Dystocia is the malpositioning or oversize of a puppy which prevents normal delivery. Active abdominal pressing and straining for more than 20 minutes without producing a puppy is highly suggestive of a dystocia. Possible situations causing dystocia include a puppy too large to fit through the birth canal, 2 puppies entering the birth canal at the same time, abnormal formation of the puppy, abnormal position of the puppy (side-ways in the birth canal or head bent down in the birth canal).
Diagnosis of the cause of dystocia requires vaginal examination and often X-rays. If the puppy is within the birth canal, occasionally vaginal delivery with ample lubrication and gentle traction is successful. If the puppy cannot be delivered within 30 minutes, C-section is recommended. THE USE OF OXYTOCIN IS CONTAINDICATED IN RELIEVING DYSTOCIA. Stimulation of uterine contraction will increase the pressure against the puppy and may damage the uterus. Increasing uterine contractions will also decrease oxygen perfusion to the remaining puppies.
Secondary Uterine Inertia (SUI) is a condition in which the uterine muscles become exhausted and can no longer contract enough to deliver the puppies. SUI often occurs with persistent contraction during dystocia. It may also result during the delivery of the last puppies in a large litter. This is the only situation, in my opinion, where oxytocin is warranted. And then, if and only if it is certain that the cause of SUI is NOT DYSTOCIA. Calcium supplementation is often necessary in conjunction with oxytocin. If SUI occurs with 3 or more puppies remaining in utero, it may be reasonable to proceed to c-section, as delayed delivery of the remaining puppies may result in fetal hypoxia (suffocation) and death.
Premature placental separation is suspected with the appearance of greenish-black vaginal discharge (Uteroverdin) without delivery of the first puppy. THIS IS AN EMERGENCY! It may be a consequence of PUI or secondary to a dystocia. In either event, at least one and possibly all puppies have decreased oxygen delivery and will soon suffocate. Further diagnostics are seldom warranted and immediate c-section is recommended. Passage of uteroverdin after the first puppy cannot be differentiated from the initial discharge and therefore cannot be used to interpret placental separation later in delivery.
In choosing to proceed to Emergency C-section, it is necessary to determine the risk to the puppies and to the bitch. Maximizing live births is the goal, and the sooner a diagnosis can be made, the better. Proper diagnosis of the cause of failure to deliver utilizing blood chemistry and progesterone, ultrasound, and x-ray, greatly hasten the decision to proceed to surgery. Medical management of C-section with calcium, oxytocin, and manual extraction can be rewarding. However, if several puppies remain in utero when intervention is needed, repeated attempts at non-surgical deliver may be too time consuming and stressful to the bitch and the unborn puppies.
Richard Wheeler, DVM, Diplomate ACT (Board Certified, Reproduction)
Poudre River Veterinary Clinic
Affiliate: CSU Veterinary Teaching Hospital
Fort Collins, CO