Chapter 5 Disorder of the Gestation Period

 

 

   

5.1 Resource Material

A. Reading Assignment

• 1. Arthur, et al. - Chapter 4 - Anomalies and Development ofthe Conceptus - pgs. 114-126, Chapter 5 - Prolapse of the Vagina - pgs 127-131.

B. Other References

• 1. Roberts, Chapter V - Disorders and Accidents During the Gestation Period - pgs. 123-124, & 213 242.
• 2. Sloss & Dufty - Chapter 7 - Disorders of Gestation, pgs. 88-97.
• 3. Current Therapy in Theriogenology 2 - Section V - pgs. 208- 209

C. Other

• 1. Syllabus

5.2 . Objective

Given the resource material and following a series of lectures, the student will be able to:

• 1. Define abortion, prematurity, and still birth
• 2. Discuss some of the cause of abortion
• 3. Discuss fetal mummification with emphasis on etiology, pathophysiology, diagnosis and treatment.
• 4. Discuss fetal emphysema and maceration with emphasis or patho-physiology, diagnosis, management and prognosis
• 5. Differentiate hydrops amnion from hydrops allantois based on etiology and clinical signs
• 6. Discuss the treatment, sequelae and prognosis of hydrops amnion and hydrops allantois.
• 7. Diagnose and develop a treatment plan for the various types of hysteroceles encountered in the large domestic species.
• 8. Discuss the diagnosis and management of torsion of the uterus.
• 9. Discuss the etiology, clinical signs, evaluation and prognosis of vagino-cervical prolapse in the large domestic species.
• 10. Discuss the more common dropsical conditions of the fetus that may predispose to difficult birth.

 5.3 Abortion

Abortion is the expulsion from the uterus of a living fetus before it reaches a viable age, or more commonly the expulsion of a dead fetus of recognizable size at any stage of the gestation period. Early death and unseen expulsion of the embryo or fetus is usually classified as infertility. In the cow and mare pregnancy usually progresses from about l l/2 to 3 months before the expelled fetus is largeenough to be recognized. In the cow, abortions occurring before the fourth month of gestation are seldom followed by retention of the fetal membranes, while those occurring after the fourth month are frequently characterized by retention.

Abortions are usually caused by agents affecting the fetus or its membranes or both. These may be classified as follows:

• A. Infectious Causes - bacteria, viruses, mycotic and protozoal organisms.
• B. Noninfectious Causes - chemical, drugs, poisonous plants, hormones, nutrition, genetic, physical causes, twinning, etc.

Economically, abortions are of great concern to the farmer, because the fetus is lost. A prolonged period of uterine disease and infertility may follow; the unproductive female must be maintained for a long period of time or sold, and if the cause of the abortion is infectious, the remainder of the herd is threatened.

Diseases of the uterus and pregnant uterus do not always result in fetal death. The fetus may be expelled prematurely or at term and live or it may be weak and diseased and die shortly after birth. In most abortions, the fetus dies in utero and is expelled within 24 to 72 hours by which time varying degrees of postmortem changes have developed. These changes are helpful in determining how long the fetus has been dead. At 12 hours after death the fetal corneas are cloudy and gray; at 24 hours the kidneys are soft and the abomasal contents are cloudy, mucoid and yellowish. From 36 to 96 hours after fetal death color changes occur in the skin, the subcutis is gelatinous and blood tinged, the liver is soft and the abomasal contents are cloudy, mucoid and reddish. As a sequelae to some cases of intrauterine fetal death, especially of one or more of a number of fetuses in multipdrous animals, failure of expulsion may occur resulting in fetal mummification or fetal maceration. Mummification of the Fetus 

5.4 Bovine Mummification

Fetal death in domestic animals occurring during the middle or last trimester of pregnancy that does not result

in involution of the CL and abortion of the fetus within the next 7 to 10 days, or decomposition or maceration of the fetus within the next several months is followed by autolytic changes in the fetus, absorption of placental and fetal fluids, involution of the maternal placenta, and mummification of the fetus. Conditions necessary for the occurrence of fetal mummification include the maintenance of the dead fetus within the uterus by the presence of a normal viable fetus or fetuses, or the persistence of the CL of pregnancy associated with a single or rarely, twin bovine fetuses. One or more mummified fetuses present in the uterus with one or more viable fetuses is frequently observed in swine, and is occasionally encountered in dogs and cats. Fetal mummification is also encountered in ewes and mares with twin fetuses.

Two types of mummification have been observed in domestic animals; the hematic type is seen only in cattle and is most commonly encountered in the Channel Island breeds; the papyraceous type occurs in all species.

Fetal mummification may be due to genetic or chromosomal defects, torsion or compression of the umbilical cord, placental defects,infectious agents and abnormal hormonal concentrations. 

5.5 Bovine Hematic Mummification

Bovine hematic mummification is most commonly encountered in the Channel Island breeds and is theorized to be associated with an autosomal recessive gene.

It is theorized that in hematic mummification hemorrhage between the caruncles and cotyledons results in separation of the chorion and endometrium and eventually death of the fetus. The fetus and fetal membranes are stained a dark brown or black and the fetus undergoes mummification.

Diagnosis can be made by examination per rectum. The uterine wall is thick and atonic, and there are no palpable placentomes. The middle uterine artery is small and there is no fremitus. There is an absence of fetal fluids and a hard but poorly defined structure can be palpated within the uterus.

• Treatment:  
• Prognosis: 

5.6 Fetal Emphysema and Maceration

Fetal emphysema and maceration may occur at any stage of the gestation period and has been observed in all species of domestic animals. Early embryonic deaths and maceration are probably caused by a number of organisms including Trichomonas fetus and Campylobacter fetus. In cases of early maceration, the cervix may be tightly closed or a purulent discharge may be present in the vagina or vulva. These cases are very commonly diagnosed as pyometra or endometritis which are quite distinguishable from each other. In multipara, maceration of early embryos and fetuses usually result in their being absorbed. The other fetuses develop normally or occasionally one becomes macerated. More commonly fetal emphysema and maceration follow abortion in the cow in which the cervix is dilated but the fetus is not expelled due to failure of the genital tract to dilate sufficiently or contract normally, or because the fetus is dead and in an abnormal presentation, position, and/or posture. In rare cases fetal maceration may be associated with uterine torsion during gestation.

The two factors of an open cervix and a dead fetus in the uterus at body temperature causes a rapid bacterial invasion of the fetus and fetal membranes, from organisms that are already in the uterus or posterior portion of the reproductive tract and fetal emphysema and maceration develop. If the dead bovine fetus is beyond the third month of pregnancy, and is not expelled from the uterus emphysema develops in about 24 to 48 hours and maceration begins in about 3 to 4 days.

Fetal emphysema occurring during the middle of gestation is usually accompanied by intermittent straining, accompanied by a foul smelling reddish-gray discharge from the vulva.

• Diagnosis of Fetal Emphysema: 
• Treatment: 

In long standing cases of fetal maceration, the acute emphysematous stage has passed. Straining is seldom observed and the cervix is usually quite contracted. There is often a history of a chronic fetid serosanguinous or mucopurulent discharge from the vulva over a period of several weeks or months accompanied by a gradual decrease in milk production and loss of weight.

• Diagnosis: 
• Treatment: 
• Prognosis: 

5.7 Hydropic Conditions of the Fetal Membranes 

Hydropic conditions of the fetal membranes occur most commonly in cattle, it is occasionally encountered in sheep, and is seen only on rare occasions in swine and horses. 

5.7.1 Hydrallantois or Hydrops Allantois

Hydrallantois, which accounts for about 90% of hydrops of the fetal membranes, is characterized by a rapid accumulation of fluid over a period of 5-20 days in late gestation. Abnormal function of the placentomes results in transudation and collection of 80 to 150 liters of watery, amber colored fluid. The rapid accumulation produces a distended, tense, dome-shaped abdomen. Affected animals become anorectic, dehydrated and weak and may have difficulty breathing. On rectal examination, the uterus is greatly distended and tense and fills the abdominal cavity. The fetus and placentomes cannot be palpated through the tense uterine wall. The sudden increase in abdominal weight predisposes the dam to ventral hernias or rupture of the prepubic tendon.

Retention of the fetal membranes and septic metritis are common complications.

• Prognosis: 
• Treatment: 

5.7.2 Hydramnious or Hydrops Amnion

Hydramnious is characterized by a gradual accumulation of 20 to 100 liters of fluid during the last half of the gestation period. The condition is most commonly associated with a genetically or congenitally defective fetus with impaired swallowing. The fluid is viscid and often contains meconium. The abdomen is pear-shaped and less tense, and the fetus and placentome can be palpated. Although retention of the fetal membrane is common, metritis is less common and less serious than hydrallantois.

• Prognosis: 
• Treatment: 

5.8 Dropsical Conditions of the Fetus

There are several types of fetal dropsy. Those of obstetrical importance include hydrocephalus, fetal ascites and fetal anasarca. 

5.8.1 Hydrocephalus

Hydrocephalus is encountered in all species of animals and is seen most commonly in pigs, puppies, and calves.

Several etiological factors have been cited, including infectious agents, genetic factors and nutritional deficiencies.

Because of the large size of the head there is difficulty at the time of parturition and assistance with the delivery is often necessary.

• Treatment: 

5.8.2 Fetal Ascites

This condition commonly accompanies infectious diseases of the fetus, and developmental defects such as chondroplasia. Occasionally fetal ascites may occur as the only defect. Aborted fetuses from dams affected with hydramnios or hydrallantois often show some degree of ascites. In cases of severe fetal ascites the abdomen may be so severely distended that it causes dystocia.

Treatment: 

5.8.3 Fetal Anasarca

In this condition, the affected fetus is usually carried to term and concern is caused by the lack of progress in the expulsive stage of parturition. This is due to the great increase in fetal size associated with the accumulation of fluid in the subcutaneous tissues particularly the tissues of the head and limbs. 

Treatment: 

5.8.4 Abdominal Hernias Resulting in Hysteroceles

Extensive unilateral ventral hernias in large animals occasionally occur during advanced pregnancy in cows, ewes, and nannies, but are rarely encountered in mares. These hernias are usually due to trauma but may also be associated with increased abdominal weight as occurs in cases of hydrops allantois and are characterized by unilateral sagging of the abdominal floor 6 to 8 inches or more below that of the normal side. Expulsion of the fetus may be difficult due to the inability of the abdominal muscles to contract equally, and with sufficient strength to force the fetus through the birth canal. As a rule, gestation is uninterrupted but the condition becomes grave for the dam and fetus when parturition commences. This is particularly true in the case of the mare. If the fetus is to survive outside help is necessary at the time the expulsive forces of labor begins.

Affected animals may be managed in a manner similar to that used for rupture of the prepubic tendon in the mare. In general, repair of these large hernias is difficult and the breeding life of the animal is terminated. 

5.8.5 Rupture of the Prepubic Tendon Prepubic Desmorrhexis of Pregnancy

Rupture of the prepubic tendon is a rare occurrence in light mares in advanced pregnancy, but is more common in draft mares. It is very rarely encountered in cows due to the presence of the subpubic tendon which lends additional support to the abdominal wall. The condition is usually preceded by an area of marked, tense, painful edema 4 to 6 inches thick on the abdominal wall, extending from the udder to the xiphoid process. Affected mares walk with a stiff gait and refuse to lie down. The teats are carried forward and downward on the abdominal floor. There is elevation of the tail head and ischial tuberosities and a lordosis. In a few cases rupture of the prepubic tendon may occur suddenly due to trauma or violence without the usual development of severe edema. In these cases the animal shows signs of intense colicky pain, sweating, rapid respiration, fast and weak pulse. There is sudden sagging of the ventral abdomen, sinking of the flanks, and possible internal hemorrhage and shock. Collapse and death usually follow within a short period of time.

The prognosis in rupture of the prepubic tendon is poor. Treatment is usually unsatisfactory once rupture occur. 

• Management: 

5.8.6 Torsion of the Uterus

This is usually described as the revolution or twisting of the uterus on its long axis. The condition is more commonly encountered in cows, but it may occur in all species of animals. In multipara torsion of the uterus, usually involves only a portion of one horn containing only one fetus, while in unipara the intercornual ligament and distention of the uterine horns and body with placenta and fluid both gravid and nongravid horns are involved.

There are a number of factors which predispose the uterus of the cow to torsion:

• 1. The lesser curvature of the uterus in advanced pregnancy is supported dorso-laterally by the broad ligament,while the greater curvature lies free in the abdominal cavity resting on the abdominal floor and supported by the rumen, the viscera and the abdominal walls.
• 2. The ovarian end of the gravid horn of the bovine uterus is a relatively narrow base upon which the uterus rests.
• 3. If the non-gravid horn is small or non-functional, the instability of the uterus is increased.

These anatomical arrangements together with the manner in which the cow lies down and rises predisposes to torsion. Other factors involved include lack of fetal fluids, violence, rolling, confinement in stables for long periods, a deep spacious abdomen and strong movements of the fetus. The incidence of torsion has been shown to be more common in pluriparous animals than in primiparous animals and is thought to be associated with a lack of uterine tore.

Torsion of the uterus in uniparous animals may occur either to the right (clockwise) or left (counter clockwise). Roughly 60% of torsions of the uterus in cows are to the left or counter clockwise Torsion to the left is most commonly associated with a right horn pregnancy while torsion to the right is associated with a left horn pregnancy.

The degree of torsion varies with the incidence. 

Degree of Torsion	Incidence
180	52%
270	28%
360	9%
90	10%
360>	1%

The majority of uterine torsions in the cow occur during the preparatory (dilation) stage of parturition, the remainder occurs in the early part of the expulsive stage. The torsion site, in most cases is detected upon examination for the cause of dystocia and in most cases is located posterior to the cervix.

In the mare torsion of the uterus occurs in the later stages of gestation and is seldom associated with parturition. It is possibly associated with the mare's rolling or falling or with excessive activity of the fetus. In general, torsion of the uterus occurs less frequently in the mare than in the cow.

The most significant clinical finding in cases of uterine torsion in the cow is that the preparatory stage is abnormally protracted or that it decreases and does not progress to the expulsive stage of parturition. If the torsion does not occur until early second stage, of labor, then ashort period of straining will have succeeded the restlessness but will have ceased abruptly. In the severe cases of torsion (180 >) there may be increasing signs of restlessness but more probably all signs of labor will have ceased and unless the animal was observed, there may be no knowledge that parturition has begun.

In the mare, clinical signs of torsion of the uterus are restlessness, anorexia, abdominal pain, and frequent attempts at urination. These signs resemble those seen in the early stage of parturition, and when these are observed in advanced pregnancy, usually should alert the examiner to evaluate the genital tract.

Diagnosis: 

Prognosis: 

Treatment: 

5.9 Prolapse of the Vagina and Cervix

Eversion of the vagina and cervix occurs in all species but is most commonly encountered in ruminants during late gestation, it occasionally occurs following parturition and rarely occurs unrelated to pregnancy or parturition.

A number of predisposing factors have been cited in the literature. These include:

• a. Hereditary or genetic factors are believed to influence this condition in certain breeds of cattle, this is particularly true in the case of Herefords.
• b. xcessive deposition of fat in the perivaginal tissue tend to increase the intrapelvic pressure, this predisposing to straining and prolapse
• c. Endocrine imbalance in which estrogenic hormones predominate.
• d. Injuries or stretching of the birth passage at the first or subsequent parturition.
• e. The condition is more common in pluriparous than primiparous animals.
• f. Mechanical factors such as increasing intra-abdominal pressure of late pregnancy and gravity acting through the medium of a sloping floor or hilly terrain.

Clinical Signs: The condition is most commonly encountered in the last 2 weeks of pregnancy when relaxation of the vulva and perivaginal structures has begun. The degree of protrusion varies from a mild protrusion of the vaginal mucosa through the vulva when the animal lies down, to a severe necrotic vagino-cervical prolapse containing a greatly distended bladder.

Straining may be absent, intermittent, mild, severe, or nearly constant depending on the degree of prolapse, and the severity of the inflammation and irritation involving the genital canal. Edema of the prolapsed mass is usually present due to irritation and trauma to the exposed tissue, as well as, passive venous congestion.

This edema usually occurs in the submucosa and results in a separation of the mucosa from the underlying thin muscular vaginal wall.

The cervical seal usually remains intact although there may be some dissolustion of it. In cases where there is complete breakdown of the cervical seal and relaxation of the cervix abortion or premature parturition or normal delivery may occur in 24 to 72 hours.

Clinical Evaluation: 

Prognosis: This depends on the severity of the prolapse and the length of time it has existed.

 TABLE II

GESTATION LENGTH IN CATTLE (RANGE 273 TO 296 DAYS)

 TABLE III

GESTATION LENGTH IN MARES (Range 327-357 days)

TABLE IV

GESTATION LENGTH IN ANIMALS (days)