A study we did in 2007 on 1614 bitches showed that dystocia is not something uncommon in canines. In fact it concerned 13.7% of the canine deliveries. When this happens, prolonged expulsion of the foeto-placental units leads to puppies suffering from hypoxia. Because of that lack of oxygen, blood modifications occur and create a state of metabolic acidosis (=the body produces excessive quantities of acid). Newborn puppies suffering from this disease often appear weak, lethargic and present orthopnea (=abnormal respiration pattern, like they were trying to swallow air at each breath). In cases of dystocia therefore, neonatal mortality rate peaked at 34.7% vs 10.7% in cases of eutocia (=normal birth). No need to do more maths here : it is crystal clear that in breeding kennels, huge emphasis should be put on management of parturition.
Early detection of any risk factor that could impact the parturition’s outcome is therefore always welcomed. Good news : this is an area where veterinary medicine has made huge progress. Some of those factors that influence the occurrence of dystocia are indeed well identified:
– The breed: Because of their brachycephalic morphology (= large heads, small pelvis) English Bulldogs, French Bulldogs and similar breeds are usually overrepresented in the studies focusing on dystocia in the bitch. They are not the only ones however: 40% of Scottish Terriers bitches are said to suffer from primary uterine inertia, dystocias are also common in Chihuahuas and English Bull terriers. More than the breed, lineage sometimes seems to play a role as well and could therefore affect any breed. Just to give you an example I have dealt in the past with lineages of Labradors that seemed to be somehow predisposed to uterine inertia (= the uterus does not contract at the time of parturition). Had I stopped at the breed, we would not have been able to define the appropriate measures for those given bitches.
– The weight: overweight has been described as a risk factor for dystocia in the bitch. I used to think that this should not be such a problem in breeding dogs, but recent studies pointed out that up to 20% of show dogs are now considered overweight. Another common mistake we see in the field consists in feeding breeding bitches with a diet with higher energy density (like puppy food) since the beginning of pregnancy. It is important to keep in mind that during gestation, the foetuses will take 70% of their final weight during the last 20 days of gestation. Energy intake should therefore only be increased in that last third of pregnancy. When the bitches receive puppy food too early in gestation, the energy in excess is converted into fat that can consequently impact the strength of the uterine contractions.
For more info on how to properly feed a pregnant bitch,please watch this video here
Not always an increased risk if the bitch had a previous C-section
– The parity : primiparous bitches (=bitches giving birth for the first time) are often said to be more at risk. In fact, studies identified that this risk is significant when bitches are bred for the first time after 4 years of age. It is important therefore not to start their reproductive career too late in order to decrease the associated risk.
– History of dystocia: the uterus quickly recovers from a C-section and if the surgical procedure was properly performed and no obvious abnormality was noticed at this time, there is generally no reason why the bitch would need another C-section at the following pregnancy.
I would also always recommend to precisely determine the size of the litter in a pregnant bitch. This parameter is indeed associated with occurrence of dystocia in the bitch.
Importance of the litter size
The more accurate way to accurately determine the litter size in the bitch is by performing X-rays after 45 days of pregnancy. Before that, the foetuses’ skeletons are not calcified yet and are therefore not visible. Practically speaking we often recommend performing X-rays at 50 days post-ovulation, which will allow better visualization and evaluation. Two different views (lateral and ventral views) should always be taken for better appreciation. On the other hand, ultrasounds are NOT an accurate technique to precisely determine the litter size. Ultrasounds indeed only allows to observe sections of the abdomen and in case of larger litters, it is somehow easy to miss a puppy or count one twice. Don’t get me wrong, it is a great tool to assess vitality of the foetuses, but in terms of litter size, it will only give you an estimate.