Topics in Compan An Med 33 (2018) 12–16
Review Article
Whelping and Dystocia: Maximizing Success of Medical Management Erin E. Runcan, DVM, DACT*, Marco A. Coutinho da Silva, DVM, PhD, DACT Keywords: whelping dystocia pregnancy labor bitch dog Department of Veterinary Clinical Sciences, The Ohio State University College of Veterinary Medicine, Columbus, OH
Dystocia can be defined broadly as “difficult birth” or more specifically as difficulty in the bitch expelli the pups through the cervix, vagina, and vestibule. It is a fairly common emergency presented to t small animal practitioner with an incidence rate of approximately 5%. The incidence of dystocia highest in toy and brachycephalic breeds, and occurs frequently in small litters ( o 3 pups) due to fe oversize and delayed onset of labor. As duration of labor progresses, the mortality of the pups and ev the bitch increases, with the highest number of stillborn pups occurring after 6 hours from the time active parturition. Practitioners should understand the mechanism of normal parturition so th abnormalities can be readily identified and medical or surgical intervention performed in a safe a timely manner. & 2018 Elsevier Inc. All rights reserv
*
Address reprint requests to Erin E. Runcan, DVM, DACT, Department of Veterinary Clinical Sciences, The Ohio State University College of Veterinary Medicine, 601 Vernon L. Tharp St., Columbus, OH, 43210. E-mail:
[email protected] (E.E. Runcan)
Introduction Dystocia is defined as “difficult birth” and can be due to a wide number of factors. It is a common emergency presented to all practitioners regardless of their interest in canine reproduction, and therefore it is important for any veterinarian to be able to recognize the signs of dystocia so that early intervention can be implemented in order to save the dam and pups. Incidence rates of dystocia have been reported to be approximately 5% of all parturitions;1 however, the rate is highly variable within populations (3.7%-28%).2,3 Mortality rates can be high for neonates (upwards of 20%),4 and timing of medical or surgical intervention appears to play a huge factor in neonatal survival.5 To understand dystocia, a basic knowledge of normal canine parturition is essential. In terms of diagnosis and treatment, little has changed through the years, except for perhaps a greater acceptance of surgical intervention for management. The ability for practitioners to perform elective Caesarean section for breeds predisposed to dystocia has increased neonatal survival. The purpose of this review is to provide an overview of the most common causes of dystocia as well as management strategies for nonsurgical methods of dystocia correction.
Gestational Length Determining normal gestation length in the bitch is extremely
The most accurate calculation of gestational age is to use reliable pattern of hormones around the time of ovulation. The su of luteinizing hormone (LH), which triggers ovulation, has be determined to be a finite period in the bitch and is often used determine events such as the timing of ovulation and gestatio length. Following the LH surge, ovulation typically occurs 1-2 d later. Parturition occurs approximately 65 days post LH surge, an recent large-population study evaluating 84 different breeds2 fou slight breed and age variation. Older bitches experienced a prolon gestational length of 0.11 days per year of age. Greyhounds as w were noted to have a significantly longer gestational length, occurr 68 ± 1.5 days post LH, but no other breed variation was noted in t particular study.2 In contrast, in another study performed in 20 Cavalier King Charles spaniels were found to have shorter duration gestation in comparison to other breeds (61 ± 1.5 days), wh interpreting gestational length from the estimated date of ovulatio It should be noted, however, that this gestational length was cal lated from an estimated ovulation date, and not LH surge. Litter s also appears to play a small role in duration of gestation, w gestational length reduced by 0.08 days per pup over average li size for the breed and longer gestation lengths reported for litters w 3 and fewer pups.7,8 When using an estimated date of ovulation to calculate ges tional age, it is important to remember that actual ovulation variable in duration and timing, therefore an absolute number progesterone cannot be used to accurately determine this 100% the time. Typically, practitioners use either an absolute value 7
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difficult for the clinician if appropriate hormonal ovulation timing has not been performed. Clinicians may be presented with a bitch that is “overdue” based on breeding dates and asked to intervene surgically. As the fertile window for the bitch is extremely long, and canine semen can live upwards of 7 days in the reproductive tract, it can be extremely difficult to predict a gestational length based on mating alone. Average gestational length may be anywhere from 56-72 days from the first mating.6 Owing to this high variability, it is not recommended to perform a Caesarean section purely on mating date alone.
5-6 ng/ml , a range of 5-10 ng/ml , or an abrupt rise of at le 3 ng/ml in a 24-hour period to estimate ovulation.9 When es mated ovulation date is used for this determination, most bitc will have a gestational length of 63.1 ± 2.1 days.7
Normal Parturition
Normal canine parturition is divided into 3 stages. Stage I is preparation of the uterus and cervix for birth, stage II is act
https://doi.org/10.1053/j.tcam.2018.03.003 1527-3369/ & 2018 Topics in Companion Animal Medicine. Published by Elsevier Inc.
E.E. Runcan, M.A. Coutinho da Silva / Topics in Companion An Med 33 (2018) 12–16
labor, and stage III is the passage of the fetal membranes, which often occurs in conjunction with stage II in the bitch. The normal physiology and timing of these stages is very important as any deviation of normal may be an early sign of dystocia. Parturition in the bitch typically lasts 4-18 hours, and is triggered by maturation of the fetus. Cortisol in the dam peaks 24 hours prior to parturition correlating with maturation of the fetal hypothalamic-adrenal axis and adrenocorticotropic hormone (ACTH) secretion by the adrenal glands. This is followed by an increase in prolactin 12-24 hours before the onset of parturition. It is believed that this prolactin rise is responsible for the restless behavior and prodromal signs noted in the bitch during this stage of labor. Following the cortisol surge in the bitch, serum progesterone levels fall resulting in stage I labor 24-36 hours later.2 As progesterone is thermogenic, an abrupt drop of body temperature of 1.5-2° Fahrenheit (1° Celsius) will be noted in most bitches 12-24 hours before the onset of parturition.10 The dam’s body temperature will return to normal at the time of parturition, so it is important to monitor this temperature frequently in order to establish a baseline. The authors recommend owners monitoring rectal temperature 3-4 times daily beginning 1 week before the expected date of delivery. As the preparturient “temperature drop” is highly variable and at times unpredictable, it should be noted that the decrease in body temperature alone should not be used to plan elective Caesarean sections. One study11 demonstrated an abrupt increase in body temperature to over 101° Fahrenheit 12 hours after the onset of parturition and persisted up to 36 hours postpartum. Therefore, some authors11,12 advocate evaluation of the dam for possible problems should an elevation in body temperature be noted at the end of gestation during the preparatory stage I of labor. Many uterine contractions are taking place during stage I of labor, but these will not be evident externally. The voluntary abdominal press will be absent, and there should be little to no vulvar discharge. Any discharge that is present will be clear and watery. The bitch will become restless, often panting and digging in bedding (known as “nesting”). Stage I is highly variable in length with some maiden bitches taking 24 hours or more. The average duration of this stage is 6-12 hours for most bitches.12 Stage I leads into stage II which is initiated by the rupture of the fetal membranes and ends with the delivery of the last fetus. The dam’s body temperature will have returned to normal during stage I. In a study,5 the majority (61.1%) of bitches showed signs of dystocia before the first puppy was ever delivered, and therefore this time point is highly critical in diagnosing a potential problem. Stretching the pelvic inlet and cervix stimulates the Ferguson’s
Following the rest, labor will resume until all fetuses are born interesting to note that there have been many anecdotal repo live puppies being born up to 36 hours after the onset of St labor, but this is an extremely unique situation and should n considered as normal. Puppies can be born either in anterior or posterior (40%) presentation.13 The passage of placentas is defined as stage III and often o simultaneously with stage II of labor. Placentas are often deli concurrently with puppies, and should be removed from the to prevent ingestion that frequently results in diarrhea, severe cases choke or obstruction. There is no known bene the dam to ingest the placentas. Owing to the tendenc placentas to be passed along with the birth of pups, ret placentas are uncommon in the bitch.15
Dystocia
Dystocia is defined as “difficult birth,” or failure for the d successfully pass puppies through the vaginal canal.5 Dysto diagnosed when parturition does not occur as expected or w a timely manner, utilizing a list of criteria (Table). Early recog of dystocia and early intervention is essential for the health dam and pups. Incidence of dystocia is relatively low; how the incidence may approach 100% in brachycephalic breeds.1 Dystocia can be caused by maternal or fetal factors. canine dystocia is maternal in origin accounting for 75. dystocia cases in 1 report.4
Causes of Dystocia
Uterine inertia is the most common cause of dystocia a defined as the inability of the uterus to contract. It can be large number of factors including sepsis, illness, age-re changes, or a genetic inability of myometrial contractility genetic component could serve as an explanation of wh ability for a bitch to give birth on her own without assis (“free whelping”) appears to run in certain lines. Primary in also occurs when there are too few fetuses present to adequ initiate parturition. Extremely low numbers of fetuses (1-2 pies) accounted for 21.5% of cases of dystocia in 1 study,5 and of dystocia cases involving small litters required Caesarean tion.3 Therefore, because of the high incidence of dystocia in small litters, elective Caesarean section is often warrant provide maximal survival to the fetuses. Often bitches
reflex which triggers oxytocin release and abdominal straining. The first fetus is typically delivered within 4 hours of the rupture of the allantochorionic membrane.12 Mild, occasional vomiting is common during stage II labor due to the abdominal press and pressure of fetuses; however, vomiting should not be severe or protracted. Water and food containing glucose and calcium can be offered to help provide adequate nutrition and hydration during this stage. The duration of stage II is variable depending on parity, litter size, and breed, but the average duration is 4-18 hours.10 Puppies are born from alternate uterine horns, with the first fetus being expelled from the horn containing the highest number of fetuses.13 Typically, puppies are born every 30-60 minutes; however, 2-3 hours can occur between puppies without evidence of fetal distress.10 It is not uncommon for the bitch to experience a transient “whelping pause” to allow for the dispersal of lactic acid that has accumulated in the myometrium.14 During this time, the bitch will have no abdominal contractions, will rest, attend to her pups, and display no signs of distress. This is also a good time for the owner to take the bitch outside for elimination purposes. 14
primary uterine inertia will present with a greenish-black v discharge (uteroverdin, produced from the marginal hemat Table Criteria for Veterinary Evaluation of the Bitch in Labor
1-5,12,14,15,18
1. Prolonged gestation length beyond 65 days from ovulation or 72 days the first breeding. 2. Rectal temperature that has dropped more than 1°F-2°F and has return normal, or elevated with no signs of labor. 3. More than 4 hours between the rupture of the fetal membranes and t delivery of the first puppy. 4. More than 30 minutes of hard abdominal straining without delivery o puppy. 5. More than 2 hours between delivery of puppies. 6. Any green-black discharge prior to the delivery of the first pup by more 1-2 hours or increasing amounts of discharge without abdominal contractions 7. Bitches that are ill, febrile, in shock, or collapse during labor. 8. Membranes or fetal parts protruding from vulva without progression. 9. Bitch has been in second-stage labor for more than 12 hours. 10. Bitch has delivered stillborn puppies.
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of the placentas) without the subsequent delivery of pups (within 1-2 hours). This is a medical emergency, as the presence of uteroverdin indicates placental separation, and fetal hypoxia and subsequent death may occur if the litter is not delivered in a timely manner.15 Aging bitches are also prone to dystocia, with primiparous bitches over the age of 6 years having a higher incidence of dystocia than bitches younger than 6 years. Advanced age predisposed this group to more single-pup pregnancies, uterine inertia, and prolonged parturition compared with the younger group in 1 study.5 Another study performed in the UK found an age-related association with bitches aged 3-6 years having 3 times higher odds of dystocia compared with younger bitches.2 In Boxer dogs, significantly higher incidence of uterine inertia and other whelping complications were reported in bitches older than 4 years.16
Obstructive Dystocia Obstructive dystocia can occur from a number of factors including uterine torsion, uterine rupture, inguinal herniation, and soft tissue abnormalities of the vagina or vulva. It is recommended that a digital manual examination of the vagina and vestibule be performed prior to whelping to identify any anomalies such as vaginal bands or strictures, which may prevent normal passage of the fetuses through the vagina. These defects may not be readily apparent at the time of breeding, as vaginal or transcervical insemination may bypass the defect. A narrow pelvic canal may lead to obstruction due to the inability of the fetus to pass through normally. A small pelvic inlet leading to obstruction is most often seen with brachycephalic breeds such as the Boston terrier, Pug, and French bulldog, and can also be seen in achondroplastic breeds such as corgis and Scottish terriers. In 1 study, dystocia rates were highest in brachycephalic breeds with French Bulldogs, Boston terriers, and Pugs demonstrating 14.5%-20.6% dystocia rates when compared to other intact bitches of their breed.5 A large skull size in relation to pelvic width is the presumed cause for the high rate of dystocia. Owing to dystocia rates being so high in these breeds, elective Caesarean section is often performed to decrease neonatal mortality. In New Zealand, Hollinshead and Hanlon reported that 87% of all pregnant brachycephalic bitches received Caesarean sections.3 Toy breeds are also prone to small litters and oversized fetuses and accounted for the highest rate of dystocia accounting for 25.8% of all dystocia cases presenting on emergency to clinics in the UK.2 Obstructive
as the greyhound or collie). In transverse presentation, the lim may be palpable but the fetus travels up the contralateral uter horn resulting in obstruction. If the cause of dystocia is not read apparently on manual digital palpation, a radiograph can quic help determine if malposture is present so that adequate mana ment can be selected. Manual removal may be attempted if the fetus is present in appropriate position, and is not too large for the vaginal canal. T bitch’s perineum should be cleaned and adequate lubricat using obstetrical or sterile, water-based lubricant applied to vaginal canal. Lubricant may be applied cranial to the fetus via passage of a red rubber catheter and syringe. The fetus should grasped by the neck or pelvis, as the limbs do not have bo attachment and can be easily pulled from the body. Tract should be applied in a ventral direction (of the dam) to help gu the fetus downward through the caudal vagina and vestibule us a side-to-side wiggling motion to help guide the shoulders a pelvis through the bitch’s pelvic girdle.14 In the case of a vestibulovaginal obstruction, gentle man stretching of the vestibule and vulva may be attempted, and severe cases, an episiotomy may be performed to help facilit passage of the fetus.15 The successful birth of the first fetus w often result in the bitch easily delivering the remaining pups the litter as the vagina and vestibule will be completely dilat This is especially true in primiparous dams. If the fetus deceased, forceps traction can be attempted as a last resort if pup is accessible with caution to avoid damage to the bitc caudal reproductive tract. If the fetus is unable to be introduced into the vaginal can gentle manipulation may be attempted per abdomen (in breeds), or transrectally. Often the fetus needs to be position caudally behind the pelvis to enable enough room for mutati Manipulation should be attempted between periods of abdomi straining to avoid injury to bitch or pup. In the case of a large fe that is unable to engage the pelvic canal, turning the fetus 45° m create sufficient room to allow the fetus to pass through the pel into the vagina.14 Lastly, the bitch may be placed in a “whe barrow” position by raising her hind legs over her pelvis a allowing her to stand for a few minutes. Often this allows grav to pull the uterus and pups cranial which can facilitate appropri repositioning of a pup for delivery.
Medical Management of Dystocia
dystocia can also occur in cases of pelvic fracture, congenital malformation, or skeletal immaturity.
Fetal Malposture Fetal malposture is a relatively common cause of obstructive dystocia. Fetal causes of dystocia can include the presence of a large fetus, as in the case of a singleton puppy or gestational diabetes; or the presence of fetal abnormalities such as anasarca (“water puppy”) or a fetal monster. When the fetus is healthy, normal position for birth is anterior with the head and forelimbs extended. Pups can be born in posterior presentation as well, which should be noted and that this is not a sign of dystocia unless the rear limbs are retained, resulting in obstruction. In some cases, when the first pup is in posterior position, inadequate Ferguson’s reflex and mechanical dilation of the cervix can result in dystocia.14 In the case of malposture, fetuses may present with a head extended but shoulders retained, dorsoventral or lateral flexion of the head and neck (commonly seen in dolichocephalic breeds such
Once the determination has been made that obstruction is present, medical management may proceed. Medical managem is absolutely contraindicated in the case of obstructive dysto due to the chance of uterine rupture.17 As the duration of secon stage labor increases, neonatal mortality increases, and the du tion of this stage of labor had the most important influence neonatal survival irrespective of obstetrical aid.5 In a stud neonatal mortality increased from 5.8%-13.7% if intervention w delayed beyond 5 hours of the onset of stage II labor. It is for t reason that we recommend owners and clinicians readily iden and manage dystocia cases in a timely manner. When the bitch initially presents for dystocia, she should quickly and thoroughly evaluated. A history including breed dates, ovulation timing, prior history of dystocia, and health iss should be taken. A complete physical exam should be perform including digital exam of the vagina to look for the presence o fetus, fetal membranes, vaginal bands or strictures, and to evalu the bitch’s response to feathering. Feathering is the firm strok of the dorsal vaginal wall. Normally, this will elicit the “Ferguso response” or strong contractions of the uterus and vagina response to pressure. If these contractions are absent or we
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hypocalcemia or hypoglycemia are likely. It should be noted that due to the length of the canine vagina, that unless the bitch is very small, it is highly unlikely that the cervix will be able to be assessed digitally. Therefore, assessment of cervical dilation is difficult unless a puppy has already been born. If the bitch is stable, an ultrasound examination is performed to evaluate fetal maturity, character of fetal fluids, and fetal heart rate. Unlike adults, fetal heart rate slows in the event of hypoxia; therefore, it can be a sensitive marker of fetal health. Fetal heart rate of less than 180 bpm indicates fetal stress, and Caesarean section is often warranted. If the fetal heart rate is below 150 bpm consistently, profound fetal stress is evident and a Caesarean section should be performed immediately.18 In cases of financial limitations, and no obstruction noted on evaluation, medical management may be attempted with the owner’s understanding that fetuses may be born dead. A complete blood count and chemistry profile should be performed to evaluate for presence of clinical hypocalcemia or hypoglycemia. If indicated, a urine sample can also be obtained to look for ketones or glucosuria. If medical management is to be attempted, a radiograph is performed to evaluate for the presence of pelvic obstruction and to evaluate fetal number. In cases of dystocia where more than 4 puppies are remaining, medical management is unlikely to be successful due to maternal and uterine fatigue; therefore, Caesarean section is warranted.1 If the bitch is in good condition, has not been in prolonged labor, there is no evidence of obstruction, there is no fetal distress, and there are 4 or less pups, medical intervention may be attempted. The purpose of medical management is to first correct underlying abnormalities. The main pharmacological treatments are calcium, to increase the strength of uterine contractions, and oxytocin to increase the frequency of uterine contractions. Oxytocin is responsible for smooth muscle contraction and has a direct action on the rate of calcium influx into the myometrial cells; therefore, oxytocin and calcium are often used in combination when treating uterine inertia.13 Hypocalcemia is a frequent cause for dystocia and is believed to occur at the myometrial cellular level before becoming deficient in peripheral circulation.19 Hypocalcemia in the whelping bitch is best corrected by administration of 10% calcium gluconate solution. Calcium solutions may be administered as a slow IV bolus (10-20 mg/kg) with concurrent cardiac monitoring for arrhythmias, or administered as a subcutaneous injection (22 mg/kg SQ). If subcutaneous calcium is given, it is important to dilute the
management has failed, then a Caesarean section is needed puppy is born and normal delivery occurs, the clock “resets the oxytocin protocol can be given again. Oxytocin ma administered every 30 minutes as long as subsequent pu are delivered, or discontinued if treatment fails to contractions.14
Conclusion
The success of nonsurgical management of dystocia is lim Münnich and Küchenmeister reported in their study5 that 5 bitches who began medical management, ultimately ne Caesarean section due to response failure. This study is in a ment with an earlier study performed by Darvelid and L Forseberg4 which reported successful outcome with m management alone at only 27.6%. The chances of success are when a problem is readily identified and addressed b experienced owner and veterinary team. Often a Ceas section is the best option for a speedy outcome of bitch and however, when used judiciously, medical management may to resolve a dystocia. Appropriate medical management needs to be selected on presenting information, and health of the dam and pups to be thoroughly evaluated before the decision is made to pro Medical management with oxytocin should never be used i face of an obstruction, or if the cervix has not dilated. The successful outcomes occur when detection and correctio problems occur within the first 6 hours of the onset of se stage labor; therefore, it is essential that all act quick recognize a problem and intervene appropriately for the outcome for both dam and pups.5 References
1. Pretzer SD. Medical management of canine and feline dystocia. Theriogen 70:332–336, 2008 2. O’Neill DG, O’Sullivan AM, Manson EA, Church DB, Boag AK, McGreevy, Canine dystocia in 50 UK first-opinion emergency-care veterinary prac prevalence and risk factors. Vet Rec 181: 88, 2017 3. Hollinshead FK, Hanlon DW. Factors affecting the reproductive performan bitches: A prospective cohort study involving 1203 inseminations with and frozen semen. Theriogenology 101:62–72, 2017 4. Darvelid AW, Linda-Forsberg C. Dystocia in the bitch: A retrospective stu 182 cases. J Small Anim Pract 35:402–407, 1994 5. Münnich A, Küchenmeister U. Dystocia in numbers – Evidenced-based pa
volume 1:1 with saline, as calcium salts may be irritating when administered subcutaneously, and there is a small risk of granuloma formation or skin sloughing at the injection site. Subcutaneous calcium may take up to 45 minutes to show effect. Regardless of route of administration, calcium may be repeated in 6-8 hours if needed.5,14,18 Owners will often give oral doses of calcium chloride-containing supplements during labor; however, this method of administration is often ineffective during a dystocia due to the slow absorption rate of oral calcium.20 Oxytocin is a hormone released from the posterior pituitary gland and causes smooth muscle contraction, milk letdown, and maternal bonding. It is therefore essential to parturition. Oxytocin should never be given in the presence of an obstructive dystocia as it has the ability to make this type of dystocia much worse and could cause uterine rupture.17 Micro doses (0.25-1 unit) should be used with no more than 5 units administered per bitch of any size. Higher doses result in uterine tetany and fetal hypoxia, and are not as effective. Oxytocin may be administered SQ, IV, or IM. The dose of oxytocin can be repeated in 15-30 minutes.18 If a total of 2-3 doses of oxytocin have been given without a puppy being born (and abdominal contractions have been strong), medical 16
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17. Humm KR, Adamantos SE, Benigni L, Armitage-Chan EA, Brockman DJ, Chan DL. Uterine rupture and septic peritonitis following dystocia and assisted delivery in a Great Dane bitch. J Am Anim Hosp Assoc 46:353–357, 2010 18. Smith FO. Guide to emergency interception during parturition in the dog and cat. Vet Clin Small Anim 42:489 –499, 2012
19. Berstrom A, Fransson B, Lagerstedt AS, Olsson K. Primary uterine inertia in 2 bitches: Aetiology and treatment. J Small Anim Prac 47:456–460, 2006 20. Hjort AM. The influence of orally administered calcium salts on the seru calcium of normal and thyreoparathyroprivic dogs. J Biol Chem 65:783–79 1925
