Food Animal Obstetrics

What is obstetrics?

The branch of medicine concerned with care of the female during pregnancy, parturition, and uterine involution.

What factors are required for eutocia?

-Appropriately sized fetus

-Normal maternal pelvis

-Adequate expulsive capabilities

-Normal fetal presentation, position, and posture.

What changes may occur during the last few weeks before parturition?

-Udder enlargement

-Colostrum formation

-Relaxation of pelvic ligaments

-Vulvar edema

-Lengthening of the vulvar cleft

When can udder enlargement begin in heifers?

As early as 5-6 months of gestation.

T/F: Preparturient udder enlargement and vulvar edema can accurately predict the exact time of calving.

False

1 multiple choice option

What fetal endocrine system initiates the mechanism of parturition?

Maturation of the fetal hypothalamic-hypophyseal-adrenal (HPA) axis.

What major fetal hormone increases as parturition approaches?

Fetal cortisol

What happens to placental progesterone and estrogen activity as parturition approaches?

Progestogenic activity decreases while estrogen precursors and estrogen increase.

What does fetal cortisol stimulate the placenta to produce?

PGF₂α

What are two major effects of PGF₂α near parturition?

It helps abolish the progesterone block on myometrial contractility and promotes regression of the corpus luteum.

What hormonal changes promote myometrial contractions?

Increased PGF₂α and estradiol

What happens to uterine oxytocin receptors near parturition?

They are upregulated

What fetal orientation normally develops during stage 1 labor?

Cranial longitudinal presentation, dorsosacral position, with the forelimbs extended.

What occurs during stage 1 of parturition?

Uterine contractions begin, the calf positions itself for delivery, and the cervix dilates.

When there is increased cortisol from fetal adrenal glands, what enzyme in the placenta increases in order to decrease placental progesterone?

17a-hydroxylase

What event marks the end of stage 1 labor?

Rupture of the chorioallantois

What are typical signs of stage 1 labor?

-Abdominal discomfort

-Anorexia

-Restlessness

-Arched back

-Raised tail

-Seeking solitude

-Later intermittent abdominal straining

How long does stage 1 labor usually last in cattle?

Approximately 6 hours, although it may last up to 24 hours in heifers.

T/F: Stage 1 labor signs are usually more obvious in mature multiparous cows than in heifers.

False

1 multiple choice option

How open may the external cervical os be in cows up to a week before calving?

Approximately 2-4 fingers

How does cervical dilation before calving differ in heifers?

The cervix usually remains tightly closed until approximately the day before calving.

What occurs during the passive phase of cervical dilation?

Cervical tone decreases, and the internal os begins dilating after dilation of the external os.

When does active cervical dilation begin?

When the external os is large enough for a hand to pass.

What initiates active cervical dilation?

Increased estradiol and PGF₂α with strong uterine contractions forcing the fetus and membranes into the partially dilated canal.

What is the positive-feedback mechanism involving cervical pressure and oxytocin?

Cervical pressure stimulates sensory neurons that signal the hypothalamus, causing posterior pituitary oxytocin release; increased oxytocin increases contractions and therefore further cervical pressure.

When are the forces of myometrial contractions at their peak?

When the head and forelimbs enter the cervix

What marks the end of stage 1?

Rupture of the chorioallantois

What defines stage 2 of parturition?

Release of allantoic fluid with strong abdominal straining by the dam.

What fetal membrane should normally appear after rupture of the chorioallantois?

The intact amnion

What happens to contractions and resting intervals as stage 2 progresses?

Contractions become stronger and rest periods become shorter.

When does maximal expulsive force normally occur?

As the fetal head passes through the vulva.

What is the average duration of stage 2 labor?

Approximately 2-4 hours, with longer durations possible in heifers.

T/F: A fetus can survive up to 10 hours with the umbilical cord intact.

True

1 multiple choice option

Prolonged stage 2 labor for approximately 8-12 hours predisposes to what condition?

Secondary uterine inertia due to myometrial exhaustion.

What occurs during stage 3 of parturition?

Detachment and expulsion of the fetal membranes.

How do the chorionic villi detach during stage 3?

Continued uterine contractions cause vasoconstriction of arteries within the villi, allowing them to dislodge from maternal crypts.

Approximately how long normally passes before placental expulsion in a cow?

About 8 hours

When is the placenta considered retained in the cow?

At 12 hours postpartum

When is the placenta considered retained in the mare?

3 hours postpartum

What is dystocia?

A difficult birth in which stage 1 or stage 2 labor is prolonged and assistance is required for delivery.

What is the most common cause of calf loss during the first 96 hours postpartum?

Death due to dystocia from from delivery related injuries

T/F: There is a decreased pregnancy rate for dams with dystocia.

True

1 multiple choice option

What is the #1 underlying cause of bovine dystocia?

Management

What are the three major general causes of dystocia emphasized for beef cattle?

-Fetopelvic disproportion

-Abnormal fetal presentation

-Ineffective labor

What is the most common fetal cause of bovine dystocia?

Fetopelvic disproportion.

Why are heifers particularly susceptible to fetopelvic disproportion?

Relative fetal oversize compared with the maternal pelvis.

What is primary uterine inertia?

Failure of normal uterine contractions to develop adequately.

What conditions may predispose to primary uterine inertia?

-Uterine overstretching by multiple or abnormal fetuses

-Myometrial defects

-Hormonal abnormalities

-Hypocalcemia

What is secondary uterine inertia?

Exhaustion of the myometrium after prolonged contractions against an obstruction.

How is secondary uterine inertia managed?

Remove the obstruction and deliver the fetus.

What are possible sequelae to secondary uterine inertia?

-Retained placenta

-Delayed uterine involution

-Uterine prolapse

T/F: Primary uterine inertia results from exhaustion after prolonged obstructive labor.

False

1 multiple choice option

What maternal birth-canal abnormalities can cause dystocia?

-Inadequate pelvic size

-Pelvic deformities/exostoses

-Incomplete cervical dilation

-Vaginal cystocele

-Neoplasia

-Müllerian duct remnants/persistent bands

-Uterine torsion

-Vulvar/vestibular stenosis

What broad fetal factors cause dystocia?

-Excessive fetal size

-Abnormal presentation/position/posture

-Fetal congenital abnormalities

What is perosomus elumbus?

A congenital deformity in which the fore-half of the calf is nearly normal but vertebrae are absent caudal to the thorax, with flexed/ankylosed hindlimbs and a deformed or flattened pelvis.

During a dystocia exam, you palpate four rigid limbs and exposed abdominal viscera with severe ventral curvature of the fetal spine. What is the diagnosis?

Schistosomus reflexus

A malformed fetus has a relatively normal head and thorax, absent caudal vertebrae, ankylosed hindlimbs, and a deformed pelvis. What is the diagnosis?

Perosomus elumbus

What historical information should be obtained in a bovine dystocia case?

-Previous dystocia

-Gestation length

-Progression/duration of labor

-Previous attempts at assistance

-Possible damage caused during those attempts

What should be assessed during examination of the dam and fetus?

-Fetal presentation/position/posture

-Fetal size

-Calf viability

-Degree of birth-canal dilation

What reflexes can be used to assess fetal viability?

-Interdigital claw reflex

-Swallow/suckle reflex

-Corneal reflex

-Anal tone

In what order are fetal reflexes lost as fetal compromise progresses?

From peripheral to central

T/F: Dramatic exaggerated fetal movement always indicates a vigorous, healthy calf.

False

1 multiple choice option

How long may complete manual dilation of the birth canal take?

Approximately 10-20 minutes

When should assistance be considered during labor?

-No progression for about 1 hour

-Rectal or vaginal bleeding occurs

-The cow's condition is deteriorating

-There are signs of calf distress such as meconium

A cow has been actively straining for an hour without any advancement of the calf, and meconium is visible. What should you do?

Intervene and evaluate the dystocia immediately.

What does fetal presentation describe?

The relationship of the fetal spinal axis to the maternal spinal/birth-canal axis.

What are the four presentations of the fetus?

-Cranial longitudinal

-Caudal longitudinal

-Transverse dorsal

-Transverse ventral

Which fetal presentations can be normal in cattle?

Cranial longitudinal and caudal longitudinal

T/F: Every caudal longitudinal presentation is abnormal and must be corrected before delivery.

False

1 multiple choice option

What does fetal position describe?

The relationship of the fetal dorsum/spine to the quadrants of the maternal pelvis.

What is the normal fetal position for vaginal delivery?

Dorsosacral

What abnormal calf positions may be encountered?

Dorsopubic and right or left dorsoilial.

What does fetal posture describe?

The relationship of the fetal extremities to its own body.

What are common calf posture descriptions?

-Extended

-Flexed

-Retained extremities

What is considered normal PPP for a cranial presentation?

Cranial longitudinal presentation, dorsosacral position, with the head and forelimbs extended.

Attempts to convert a caudal to cranial presentation typically result in what issue?

Uterine tears

What is a true breech presentation?

Caudal presentation with bilateral hip flexion, causing the hindlimbs to be retained beneath the fetus.

Why may a true breech fetus fail to initiate obvious stage 2 labor?

There is inadequate fetal stimulation of the birth canal.

What is a ventrovertical or "dog-sitting" posture?

A difficult malposture in which the fetus is positioned in a dog-sitting configuration

What is the likely delivery method if a ventrovertical posture cannot be corrected?

Cesarean section or fetotomy.

Where is a displaced fetal head most commonly located?

To the left of the fetus

What techniques may be used to manipulate a laterally displaced fetal head?

Grasping the orbital grooves with the thumb and middle finger or using a rope snare around the incisor teeth.

Why can casting the dam help correct a displaced fetal head?

The fetus falls toward the maternal spine and away from the narrow part of the pelvis, allowing the head to be guided toward the vaginal canal.

What is engaged carpal flexion?

The flexed carpus and fetal head are both within the maternal pelvis.

What is disengaged carpal flexion?

The flexed carpus remains cranial to the maternal pelvis.

How is carpal flexion corrected?

Repel the fetus, grasp the metacarpus just proximal to the fetlock, lift dorsally, cup/protect the hoof, and bring the limb into the pelvis.

How is shoulder flexion generally corrected?

Convert it to carpal flexion by manipulating the radius/ulna and then correct the carpus.

What is "elbow lock"?

Shoulder/elbow flexion with the fetal elbows impacted on the pelvic brim, especially in heifers.

What characteristic finding suggests elbow lock?

The fetal head lies directly on top of the hooves.

How is elbow lock corrected?

Repel the fetal body and extend the forelimbs.

What is foot-nape posture?

A fetal foot is positioned over the fetal head/nape.

What important complication is associated with foot-nape posture?

Perineal laceration

How is hock flexion corrected?

Manipulate the metatarsus cranially/laterally until the hoof can be brought caudally and medially into the birth canal.

What is mutation in obstetrics?

The process of restoring an abnormal presentation, position, or posture to normal through repulsion, rotation/detorsion, version, and/or extension of the extremities.

Approximately how long should you attempt mutation before moving on to another delivery method?

About 30 minutes

What is repulsion?

Moving the fetus out of the maternal pelvis and deeper into the uterine cavity to create room for manipulation.

What major complication can result from excessive repulsion?

Uterine rupture

What is rotation or detorsion?

Rotation of the fetus around its longitudinal axis, generally to convert a dorsoilial or dorsopubic position to dorsosacral

What is version?

Turning the fetus on its transverse axis to change its presentation to cranial or caudal longitudinal

Version is generally limited to approximately how many degrees?

90°