Introduction

The healthy bitch is the key to a healthy litter. The veterinary nurse may play an important part in premating counselling as well as during first contact with the owner when problems arise during pregnancy or at term. Prebreeding examination of the bitch should be carried out to diagnose and treat any clinical dysfunctions that may interfere with normal pregnancy. Birth canal abnormalities such as vaginal strictures, stenosis from previous pelvic trauma or particular breed conformation (Scottish Terriers) and intravaginal or intrauterine masses (tumours) can cause obstructive delivery problems. In most cases, canal abnormalities can be detected in the prebreeding examination and resolved or avoided by elective Caesarean section. If conditions such as altered thyroid or parathyroid function or diabetes mellitus exist, the bitch should not be bred, likewise if any hereditary malfunctions are discovered that may cause delivery problems.

Foetal Emergencies

Premature labour is defined as uterine activity and cervical changes leading to the loss of pregnancy via resorption or abortion before term, for which no metabolic, infectious, congenital, traumatic or toxic cause is identified. Late-term gestational loss attributed to preterm or premature labour is a controversial topic in small animal reproduction. Inappropriate uterine activity accompanied by cervical changes has been implicated, and the diagnosis is dependent upon evaluation of uterine contractility. A novel approach to veterinary obstetrical monitoring in the United States involves the use of external monitoring devices using tocodynamometry (Healthdyne Inc., Marietta, GA, USA) and a handheld doppler (Sonicaid, Oxford Instruments, England) to detect and record uterine activity and foetal heart rates. Terbutaline (0.03 mg/kg orally q8h) has been used to suppress uterine contractility in bitches and queens with loss of otherwise normal pregnancies preterm. The dose is ideally titrated to effect using tocodynamometry. Therapy is discontinued 24 hours before term.

Prolonged pregnancy resulting in foetal oversize or foetal death may be the case if signs of parturition do not occur at the calculated delivery dates. When the bitch is mated, it is important that the mating time is noted to be able to determine the delivery date accurately. The canine pregnancy lasts approximately 65 days from the luteinising hormone (LH) peak, 63 days from ovulation and 60 days from fertilisation. Hence, the day of parturition depends on the starting point of calculation, and variations in the endpoint may be from 58 to 70 days. If the time of ovulation is not known, some landmarks may be helpful by radiography to determine term date. The foetal skull is seldom visible before day 45 and is almost always visible by day 47-49; pelvic bones are not visible before day 53 and are usually easily seen by day 55. Foetal teeth are not visible in the skull before day 58, but usually by day 63. The observation of foetal teeth indicates that the foetus is mature enough for delivery.

Maternal Emergencies--Signs of Abnormal Pregnancy

High progesterone concentration may induce an insulin-resistant diabetes mellitus. Breeding of bitches with clinical diabetes should always be discouraged. However, some bitches may foster subclinical diabetes, which may become overt during pregnancy due to the effects of progesterone. Diabetes mellitus is a chronic endocrine disorder characterised by high blood sugar (hyperglycaemia) and results when the pancreas is unable to produce enough insulin to meet the animal's requirements. Management of the diabetic bitch is very difficult. A stable patient with diabetes should have a blood glucose range of about 5-12 mmol/l for most of a 24-hour period. If discovered early prior to day 35 the pregnancy should be terminated since these bitches often produce dead or weak puppies. If one decides to manage the pregnant bitch, a special diet and insulin supplementation are necessary during pregnancy. Glucose crosses the placenta freely but, since insulin is produced by the foetal pancreas, the foetuses may become hyperglycaemic, and as a result, oversized foetuses develop, which may not pass the birth canal.

The opposite condition to the hyperglycaemia in diabetes mellitus is the hypoglycaemic situation with low blood sugar arising from a relative lack of carbohydrates and resulting in ketosis. This may occur in the last stages of pregnancy in bitches carrying large litters, in bitches that have been fed diets deficient in carbohydrates or in animals with disturbed carbohydrate metabolism or a poorly managed diabetes mellitus. Ketosis is detected by ketones in urine. Ketones circulating in the blood cause signs of ketoacidosis such as anorexia, nausea and lethargy. Hypoglycaemia and ketoacidosis are potentially life threatening for both bitch and puppies. Hypoglycaemia is an emergency, and if the owner describes restlessness, trembling, shivering and muscle twitching, unusual movements or behaviour ask the owner to provide food immediately. Glucose solution can be made from glucose powder and tap water. One gram of glucose per kilogram body weight should be given (1 teaspoon per 5 kg). The pregnant bitch should be hospitalised for further monitoring and restoration of normal blood glucose levels. Induction of parturition may be attempted if the bitch is close to term, i.e., >58 days.

Anaemia is defined as a decrease in the number of red blood cells (RBCs) or the amount of haemoglobin, resulting in a decrease in the oxygen-carrying capacity of the blood. Anaemia may be due to traumatic blood loss, decreased production of new RBCs or an increase in the rate of their destruction, known as haemolytic anaemia (if caused by autoantibodies this is primary autoimmune haemolytic anaemia (AIHA)). In the normal canine pregnancy plasma volume changes to create a relative anaemic condition. Normal haematocrit calculated as % packed cell volume (PCV) is 45-55%. The clinical signs of haemolytic anaemia are usually gradual and progressive, but occasionally an apparently healthy dog collapses into an acute haemolytic crisis. Pregnant bitches may acquire this condition at any time, but usually after mid-term and close to end of term. The symptoms are usually related to a lack of oxygen, such as weakness, lethargy, anorexia and an increase in the heart rate and respiration rate; heart murmurs and pale mucous membranes are found in severe cases. There may be a fever and jaundice due to an accumulation of bilirubin, one of the breakdown products of haemoglobin. The diagnosis is usually made on these clinical signs as well as a complete blood count (CBC) documenting anaemia, often with misshapen or abnormally clumped RBCs. A Coomb's test to confirm the diagnosis is useful. Blood transfusion and immediate surgery to remove the uterus and its contents are necessary because this is a life-threatening condition for the dam.

Birthing Problems--Dystocia

Bitches usually enter stage I labour within 24 hours of a decline in serum progesterone to below 6-8 nmol/l, which occurs in conjunction with elevated circulating prostaglandins and is commonly associated with a transient drop in body temperature of 1-2°C, usually from 38.5 down to 36.5°C. If the bitch has been distressed for more than 24 hours, or the body temperature has fluctuated or remains low, without the commencement of parturition, the dam should be examined by a veterinary surgeon. Uterine inertia, i.e., an intrinsic lack of ability of the muscle layer of the uterus, the myometrium, to contract sufficiently to expel the foetus, is the most frequent cause of maternal dystocia. Primary uterine inertia results in the failure of delivery of any puppies at term, and is thought to be multifactorial, including metabolic defects (lack of carbohydrates or calcium). A genetic component may be present. Monitoring of uterine contraction frequency and strength by tocodynamometry and/or by ultrasound could be very valuable. If the cervix is fully dilated, oxytocin may be given (2-10 IU/kg i.m, s.c. q30min). Use low doses and a maximum of three injections to avoid overstimulation of the uterus.

Normal stage II labour in the bitch begins when external abdominal contractions can be seen accompanying the myometrial contractions and ends in the delivery of the first puppy. If the owner has observed greenish (uteroverdin)--black discharge from the vulva for more than 30 minutes without delivery of any puppy, the bitch should be brought to the clinic immediately. The greenish discharge may be a sign of impending placental abruption. Furthermore, if contractions have been severe for more than 30 minutes and no puppy has been expelled, or the bitch shows extreme pain, the bitch should be brought in for examination as soon as possible. This may be due to malpresentation, general foetal oversize, too large heads or obstruction due to two puppies being delivered simultaneously from each of the two uterine horns. Stage III labour is defined as the delivery of the placentae. Bitches typically are between stages II and III of labour until parturition is complete.

The clinical examination of the bitch should include rectal temperature, evaluation of mucosal membranes, pulse frequency and strength, vaginal exploration to assess an open or closed cervix, udder examination (milk or no milk), ultrasonography (live or dead foetuses) and X-ray (counting heads and look for visibility of teeth). Furthermore, laboratory results (particularly calcium and blood glucose) should be available if the clinical state of the bitch indicates that some metabolic disorder is present. Results of these tests will determine the emergency patient's readiness for anaesthesia and surgery. Depending on the results, the veterinary surgeon may adjust the doses or type of anaesthetic to be used or advise delaying surgery.

References

1.  Davidson A. Obstetrical emergencies. Lecture notes, postgraduate course in reproduction, obstetrics and pediatrics in dogs and cats. Oslo, Norway, June 8-10, 2007.

2.  Jackson PGG. Dystocia in the dog and cat. In: Handbook of veterinary obstetrics (second edition). Edinburgh: (Saunders) Elsevier Limited, 2004; 141-172.