Unless specific risks have been identified in a prenatal veterinary examination, it is generally unnecessary to intervene during whelping. However, sometimes the best made plans can go awry, and early veterinary intervention may minimise foetal losses.
In this article, Dr. Andrea Muennich discusses the most common causes of dystocia in the bitch and explains what to look for in terms of when to intervene. Specific foetal and maternal causes for dystocias and neonatal mortality will be investigated as well as key things to look out for that would indicate trouble brewing.
Delivery and Neonatology - Obstetric Problems and Main Causes of Disease in Newborn Puppies
Dystocia, or abnormal parturition, occurs when the mother is not able to expel a foetus through the birth canal in good time. Normally, delivery starts from the uterine horn that contains the most foetuses, and pups will be expelled alternately from the two horns. Breeders may engage the help of a veterinarian for possible dystocia resulting from failure to start parturition on time, or because of failure to continue with the normal delivery of puppies once labour has begun.
Disturbed parturition can be classified as maternally or foetally induced, and sometimes both.
Dystocia of Foetal Origin
Absolute foetal oversize is also more common in primigravid bitches (maiden pregnancy) and in single pup pregnancies. Puppies of certain breeds are also predisposed to have a big head and some bitches a narrow pelvis (Scotch and Sealyham Terrier, Corgis, brachycephalic breeds).
The most common cause of foetal dystocia is a faulty position of the foetus at the beginning of delivery.. Transverse presentation may develop when a foetus is too big in relation to the birth canal, enters the opposite horn (which may occur when the cervix is not dilated enough) or if the cervix closes too early, before all the foetuses have been expelled.
The most common abnormalities in posture concern the head: lateral deviation, breast-head posture (nose angled down), deviation of the neck (or vertex posture), and often combined with uterine inertia (uterine contractions cease). Oversize foetuses can be the result of various malformations. Anasarca (Hydrops universalis), and Siamese twins are typical examples for pathological enlargement of the foetal body. During prolonged parturition, dead foetuses can become infected by aerobic and anaerobic bacteria and develop emphysema of the entire body as a result of gas accumulation. The formerly normal-sized pup or kitten becomes oversized as a result. Small breed bitches tend to be more predisposed to dystocia than larger breed bitches simply because of the size of their pelvic canal.
Dystocia of Maternal Origin
In terms of uterine issues, inertia is the most common form of dystocia in the dog. Primary uterine inertia is characterised by the absence of signs of the second stage of labour. In addition to myometrial defects like overstretching (hyperfetation), loss of contractility after pathological conditions such as systemic illness, infections, or fatty infiltrations can be implicated. Interestingly, unicornual pregnancy (i.e. foetuses located in only one uterine horn) often leads to problems during delivery, in particular uterine inertia or arrest of contractions One probable explanation is the failure of the expulsion modus (i.e. alternate expulsion of foetuses from each uterine horn).
Secondary uterine inertia is most often the result of failure of the uterine muscles to contract (e.g. after large litters and intensive labour), and also after uterine rupture, torsion of the uterine horn(s) , and/or uterine prolapse. Last, but not least, uterine inertia can be caused by all conditions that lead to cessation of labour, including obstruction, enlarged foetuses, or a narrow pelvis. In these cases, inertia would only be a sign and not the causative agent for dystocia. Finally, in spastic conditions (such as a hypertonic uterus after an overdose of oxytocin for example), inertia can be simulated. Stress leads to a release of adrenalin, which occupies the same receptors for oxytocin and so leads to inertia.
The history from the owner is very important for the veterinarian. Clinical signs of an obstetric problem that can be observed by breeders include:
- abnormally prolonged gestation time (particularly with single pup pregnancy, especially in larger breeds)
- strong and persistent labour for more than 30 to 40 minutes without expulsion of a pup
- weak and infrequent unproductive labour for 2-3 hours
- more than four hours between the expulsion of a puppy in a confirmed multiple pregnancy
- large quantities of green discharge before the first puppy is born
- obvious signs of sickness of the bitch.
Digital exploration of the birth canal with one or two lubricated fingers can give valuable information on the cause for an obstetrical problem. The veterinarian will use X-Ray and/or ultrasonography to confirm the presence or absence of foetal viability. Foetal distress can be predicted. Tocodynomometry is a novel approach to obstetrical monitoring whereby the force of uterine contractions as well as foetal viability can be assessed.
When manipulative and/or medical intervention fails to rectify a dystocia, a caesarean section may be required. In some breeds, a caesarean may be required from the outset (e.g. Bulldogs).
If there is high suspicion that the neonates have aspirated amniotic fluid, the neonates should be treated immediately by emptying the nostrils and the stomach, supplying oxygen by face mask, Jen Chung or chest compression. Cardiopulmonary resuscitation for neonates who fail to breathe should start with ventilatory support. If this is ineffective within one minute, positive pressure with a snugly fitting mask or endotracheal intubation is advised. Cardiac stimulation should follow ventilation support, as myocardial hypoxaemia is the most common cause for bradycardia or asystole. Direct transthoracic pressure is the first step, while adrenaline is the drug of choice for cardiac arrest.
Furthermore, the puppies should be checked for (visible) congenital abnormalities. Birth weight is an important factor in terms of survival and reflects their relative maturity (1-4% of the mother’s weight, depending on the size of breed). If puppies lose more than 10% of their birth weight after the first day they should receive supplementary feeding. Daily weight gain is an excellent indicator of general health. Between days 8 and 10, puppies should have doubled their birth weight.
The most common non-infectious causes of neonatal death are: hypothermia, hyperthermia, hypoglycaemia, dehydration, diarrhoea, and congenital malformations. A healthy puppy has a temperature of 35-36.5°C 24 hours after birth. Abnormally low body temperature in neonates (<35°C) predisposes the pup to impaired suckle reflexes, dehydration, depressed gastrointestinal motility, followed by intestinal paralysis or ileus, and increased susceptibility to infections with viruses or bacteria.
Bacterial infection is the most common cause of infectious disease. Many factors are involved in predisposing puppies of this young age, to bacterial infection. E. coli
, streptococci (S. canis
) and staphylococci (S. aureus and S.pseudointermedius), Klebsiella sp., Pseudomonas sp., Proteus sp
. and anaerobes were regularly isolated. The bitches are suspected and often identified as the source of infection for their puppies (bacterial DNA analysis can confirm species relationship). Results from these investigations showed that staphylococcal strains of diseased puppies were found mostly in their mother’s milk and vagina, and about 60% of E. coli
strains from new born puppies were found in vaginal samples from the mothers. In septic puppies that died, identical strains were isolated during necropsy from organs of the pups and their mother’s milk, faeces or vaginal samples. In puppies, clinical appearance includes local infections (skin, intestine, lungs, eyes), and septic conditions, often followed by sudden death.
Viral infections: Canine herpes virus infections are thought to be a more common cause of neonatal puppy losses than other viruses. In infections contracted shortly after birth, puppies are at higher risk of dying in the first 2-3 weeks of life. .An appropriate vaccination schedule should be implemented in breeding populations.
Diagnostic Approaches to Identifying Causes of Disease – the Breeder’s History is Important
The preliminary report from the breeder is useful for identification of probable causes of disease. The veterinarian will perform a clinical examination of the newborn puppy, but the breeder can also identify some symptoms prior to seeing the veterinarian. The mouth should be inspected for a cleft palate and cyanotic, pale or grey mucous membranes (which would indicate oxygen depravation). The evidence of sucking reflex must be checked using a clean finger in the puppy’s mouth. In a healthy puppy, breathing should be regular and unlaboured. Muscle tone in the neck and legs should be strong.
Daily weight gain is an excellent indicator of general health. If the amount of milk being ingested is questionable, the neonate can be weighed before and after nursing. Crying occurs in response to pain, coldness or failure to nurse. It is abnormal for a healthy neonate to cry for longer than 20 minutes. The umbilical region could indicate evidence of infection. The anus should be checked for patency, swelling or redness.
In general, the diagnosis of disease in puppies by the veterinarian is often hampered by the absence of variability of clinical signs combined with the difficulty of obtaining blood and performing diagnostic procedures. In the case of dead puppies the breeder should request that a necropsy be carried out as soon as possible. This can help find the cause of an underlying disease and successful treatment for the rest of the litter.
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