Obstetrics - Causes of Dystocia Flashcards
Maternal causes of dystocia - broad categories
- Abnormalities of the pelvis (size, fracture),
- Cervix (ringwomb), Vagina (vaginal prolapse)
- Uterine torsion
- Uterine inertia
what is ringwomb? what animal is it more common in? what is its etiology and presentation?
failure of cervical dilation, in sheep
-genetic link
-normal hormonal changes dont occur
>no signs of impending labour
-presents as fetal membranes hanging from vulva
when are we more likely to see failure of cervical dilation in cows?
- In association with uterine torsion
- Or if the calf is dead and does not enter pelvic canal (lack of Fergusson reflex)
what is uterine inertia?
inability to trigger uterine contractions
what are primary causes of uterine inertia?
-hypocalcemia
– Overstretching – due to hydrops, multiple fetuses
what are secondary causes of uterine inertia?
– Exhaustion of the myometrium after prolonged and unsuccessful delivery attempt– inability to continue uterine contractions
fetal causes of dystocia - broad categoies?
– Fetal maternal disproportion
* Fetus too big or pelvis too small
– Fetal malalignment
* Presentation, posture or position
– Multiple fetuses (twins, triplets…)
– Fetal monsters
most common cause of dystocia in cattle?
– Fetal-maternal disproportion
when do we see Fetal-maternal disproportion
– Heifers with insufficient pelvic size
– Large fetus too big for normal pelvis
– Large bulls
– Double muscled breeds
– Consider calving ease in bull selection
is fetal-maternal disproportion common in non-cattle species?
uncommon
-sometimes in dogs with a single pup litter
what is fetal malalignment? what species is this the most common cause of dystocia in?
– Fetal malalignment
* Abnormalities of presentation, posture or position
* Most common cause of dystocia in horses and alpacas
what is Schistosomus reflexus?
A fetal monster
Spinal curvature
Thoracic/ abdominal walls not fused - abdominal contents spilled to the outside
ankylosis - of the limbs, challenging to get out
what is Perosomus elumbus?
a fetal monster
Vertebral agenesis
and arthrogryposis
Front half relatively normal
Flexure and ankylosis of hindlimbs
No vertebrae caudal to thorax Pelvis is flat
Hydrocephalus in Friesian and Belgian horses associated with what?
nonsense mutation in B3GALNT2
* Autosomal recessive
what is fetal anasaca? what animal is it more common in?
-generalized edema, fetus becomes too large
-esp. in bulldogs
what is fetal ascites? what is it associated with?
-fetal abdomen full of fluid, assoc with organ abnormalities
-too big to pass vaginally
top 3 causes of dystocia in cows
Fetopelvic disproportion: 45 %
Fetal malalignment: 26%
Dilation, cervix / vagina: 9%
most common causes of dystocia in mares?
> 90% are due to fetal malalignment
– Head and/or limb deviation – 40 – 61%
– Posterior presentations –11 - 50%
– Contracted tendons – 8%
– Transverse – 10-16%
* Fetal oversize, uterine inertia, pelvic or other maternal problem – rare < 10%
most common causes of dystocia in mares?
> 90% are due to fetal malalignment
– Head and/or limb deviation – 40 – 61%
– Posterior presentations –11 - 50%
– Contracted tendons – 8%
– Transverse – 10-16%
* Fetal oversize, uterine inertia, pelvic or other maternal problem – rare < 10%
examples of fetal monsters
hydrocephalus
conjoined twins
Perosomus elumbus
Schistosomus reflexus
common causes of dystocia in the bitch
Uterine inertia (complete): 49 %
Uterine inertia (incomplete): 23 %
Fetal malalignment: 15%
most common cause of dystocia in the queen
unterine inertia 61%
fetal malalignment 15%
most common causes of dystocia in the ewe
fetal malalignment: 50%
obstruction of birth canal: 35%
most common causes of dystocia in the doe
fetal malalignment: 56%
fetopelvic disproportion: 20%
obstruction of birth canal: 12%
uterine inertia: 10%
most common causes of dystocia in the sow
Uterine inertia: 37%
Fetal malalignment: 33%
most common causes of dystocia in the sow
Uterine inertia: 37%
Fetal malalignment: 33%
what is fetal presentation?
Describes the relative association of the LONG AXIS of the fetus with the maternal birth canal
* Which half of the fetus is presented first at the entry to the birth canal
* Normal is:
– Anterior longitudinal
– ? Posterior longitudinal > In cow
How do you know if fetus is coming frontwards, or backwards?
palpate joints
Anterior longitudinal: These joints bend
in same direction (fetlock and carpus of Forelimb)
Posterior longitudinal: these joints bend in opposite directions (fetlock and hock of hindlimbs)
Presentation:
* Anterior Longitudinal – palmar aspects of forelimb hooves should be pointing down (unless fetus is upside-down) – feel for head
* Posterior Longitudinal
– Two hindlimbs (hooves) and tail are presented
– Plantar aspects of hooves should be pointing UP
– Careful palpation of joints
– Considered “normal” in cows but usually requires assistance for delivery – PULL!
what is fetal position?
- Describes the surface of the maternal birth canal to which the dorsal part of the fetus is aligned
- Dorsal-sacral is normal
- i.e. the dorsum of fetus is aligned with the sacrum of the dam
what is fetal posture?
- Describes the disposition of the fetal head, neck and limbs
- Normal is extended head and limbs (forelimbs if anterior; hindlimbs if posterior)
- We only describe the limbs presented
what is a breech birth described as more formally?
Breech is Posterior with Bilateral Hip Flexion
Breech is NOT Posterior Longitudinal
what is the most common and normal fetal alignment for birth?
Anterior longitudinal, dorsal-sacral, extended head and forelimbs
what is a transverse abnormal fetal presentation
fetus lies across pelvic inlet
– dorsal - fetal back at pelvic inlet
– ventral – all four limbs at pelvic inlet
what is a vertical abnormal fetal presentation
– fetus sits vertically in pelvic inlet
* also known as “Dog-Sitting”
what do we expect for the delivery of a dog-sitting fetus?
Delivery appears normal and then progress suddenly stops
-Fetal hindlimbs are also engaged in pelvis and impede delivery
formal term for upside down fetus
- Dorso – pubic
formal name for lateral fetus
Right or left dorsal- ilial
how do we describe an abnomral birth posture regarding limbs?
- Describe the abnormally positioned body part and direction
eg
* Lateral deviation of head and neck
* Ventroflexionofthe head
* Carpal flexion – Uni – or bilateral
* Shoulder flexion – uni or bilateral
