Dystocia Flashcards
What does dystocia mean?
- difficulty giving birth
What % of calvings are affected by dystocia?
8-10%
Causes of dystocia
At conception or early gestation
- foetal sex
- foetal abnormalities
- twins
- sire factors (e.g. breed, calving ease)
- dam factors (e.g. parity, calving history)
At late gestation
- gestation length
- foetal oversize
- dam undersize
- hypocalcaemia
- peri-parturient stress
At parturition
- foeti-maternal disproportion
- uterine torsion
- foetal malpresentation
- uterine inertia
- cervical or vulval stenosis
Most common causes of dystocia
Cattle = foeto-maternal disproportion
▪ 50-80%
Sheep = malpresentations
▪ > 50% of cases
Effects of dystocia
▪Reduced welfare
▪Reduced production
– Cow = subsequent lactation
– Calf = 1st lactation
▪ Stillbirth
▪Dam death
▪Postpartum problems ▪E.g. RFM, metritis, injuries
Options for management of dystocia
▪Manual correction and deliver per vaginum ▪Caesarean section
▪Foetotomy (foetus needs to be dead)
▪Euthanasia of dam +/- foetus
Manual correction and delivery
▪ Will only be successful if foeto-maternal disproportion NOT present
– Malpresentations
– Some soft tissue obstructions (e.g. vulval stenosis)
▪ Correct malpresentation
– Epidural can be helpful (if soft tissue obstructions)
– Consider episiotomy
Indications for c-section
▪ foeto-maternal disproportion
▪malpresentations that cannot be corrected
▪breech calves
▪elective (e.g. high value calves) (ethical q’s re breeding animals knowing they’ll need a c-section, e.g. Belgian blues)
When are c-sections not suitable?
- if calf decomposing→foetotomy
– would contaminate the dams abdomen with bacteria -> very likely to get peritonitis - Alternative approach needed if C-sec performed
Foetotomy (AKA ‘embryotomy’)
▪Foetus will not survive – only suitable if already dead (preferable to C-sec if not fresh) or if euthanasia of foetus required
– but euthanasia of the foetus is very tricky, esp without contamination/damage of the dam as well
▪Epidural recommended→provides analgesia and reduces straining
▪Partial or total
– Partial = removal of part of the foetus only (e.g. head)
– Total = division of the whole foetus into two or more sections
▪ Fetotome prevents soft tissue damage to the dam with the wire
Advantages of foetotomy
- Reduction in foetal size allows easier delivery
- Can be quick (especially partial)
- Can be done without assistance (although assistance recommended if possible)
- Avoids C-sec
– Especially useful if C-sec contraindicated
(emphysematous foetus)
– Better for dam in some circumstances - Can be performed with minimal equipment if required
– Especially sheep
– Partial and subcutaneous need less equipment
Disadvantages of foetotomy
- Risk of iatrogenic injury
– Can be severe or even life-threatening - Can take a long time (especially total)
– Exhaustion of dam and vet - Requires training and technical competency
Percutaneous foetotomy
- Percutaneous = dissection is made through foetal skin
- ‘classic’ technique
Subcutaneous foetotomy
= limb removal without skin
- An incision made in the skin
- Foetotomy knife introduced under the skin and limb dissected away from body
- Easier, less tiring and less equipment needed
Indications for percutaneous foetotomy
- Foeto-maternal disproportion
- Pathological foetal oversize
- Congenital foetal malformations
- Malpresentations that cannot be corrected
NB: these all only apply where the foetus is already dead
Indications for subcutaneous foetotomy
- Same as for percutaneous except correction must be achievable through limb removal only
Less common causes of dystocia
- Dropsical conditions (placental origin)
- Congenital abnormalities (foetal origin)
- Teratogens
What does ‘dropsy’ mean?
= accumulation of fluid
What are the 2 dropsical conditions?
- hydrallantois
- hydramnion
What is hydrallantois?
▪ Excess fluid accumulation in the allantois
▪ 85-90% of bovine cases
▪ Placental origin
▪ Foetus normal
▪Sporadic occurrence
▪Up to 10x expected volume of allantoic fluid
– Normal = 8-15 L
▪Fluid accumulates after mid-gestation
▪ Failure in mechanisms of production and absorption
– Excessive production, little-to-no absorption
▪Reduced number of placentomes
▪ Permanent alteration of endometrium
What is hydramnion?
▪ Excess fluid accumulation in the amnion
▪ ~10% of bovine cases
▪ Foetal origin
▪ Foetal abnormalities present
▪Related to foetal abnormalities
– Failure of swallowing or digestion of foetal fluids
– Future breeding prognosis of dam is reasonable
▪Progressive abdominal enlargement in 3rd trimester
– Slower development than hydrallantois
– Uterus and abdomen accommodates extra fluid better
– Less sick cow
– Placentomes still palpable
▪May go undiagnosed until parturition
– Large volume of thick, syrupy fluid
– Foetal abnormalities
Can hydrallantois and hydramnion occur together?
- yes occasionally
Hydrallantois prognosis
- guarded to poor
- if survives, cull of cow recommended
Hydrallantois CS
▪Bilateral abdominal distention
– Symmetrical
▪Uncomfortable
▪ Inappetant
▪Reduced/absent rumen function
– Due to compression
▪Recumbency
▪Tight uterine wall palpable per rectum
– Could potentially rupture from rectal
Tx of dropsical conditions
▪ Induce/terminate pregnancy
– Prostaglandin / steroids
– Need to provide replacement fluids to cow
-> Prevent hypovolaemia
-> Correct electrolyte disturbances
▪ Euthanasia
– Salvage slaughter if fit to travel
▪ Trochar and drain fluid
– Pass trochar into cervix
– Useful if very close to calving, otherwise would have to repeat frequently
– Rapidly re-accumulation of fluid occurs in hydrallantois
– Need to provide replacement fluids to cow?
-> ongoing debate re whether need to replace fluids
-> risk of hypovolaemic shock BUT it’s extra fluid that shouldn’t be there, so removal may not be an issue
-> IV fluids unlikely to cause harm
Congenital abnormalities
- arthrogryposis
- schistous réflexes
- congenital chondrodysplasia
- hydrocephalus
- large offspring syndrome
- cranial defects
Arthrogryposis
▪ Relatively common malformation
▪ Limb ankylosis (fusion of the joints in unusual directions)
▪ Usually combined with other congenital malformations (e.g. cleft palate)
▪ Liveborn neonates unable to stand → euthanasia
▪ Foetotomy or C-sec usually needed
Causes of arthrogryposis
Genetic
- Autosomasal recessive in Charolais breed
-> Arthrogryposis, cleft palate, scoliosis (spinal twist), kyphosis (spinal rounding)
Viral infection in utero
- Schmallenberg virus
-> Arthrogryposis affecting multiple neonates in same year
->Sheep, goats and cattle all affected.
- Bluetongue virus
-> Ruminants and camelids affected.
->Abortion is more common.
- Akabane virus
-> Not reported in UK
- Viruses are the most common cause, esp if multiple animals affected
Teratogenic plants
- Lupines (not all species)
-> Contain anagyrine.
-> Congenital deformities occur in cattle if ingested between d 40 and 70 of gestation
-> USA.
Schistosomus reflexus
▪‘Inside out’ foetuses ▪Rare, fatal malformation
– Likely genetic
▪Foetotomy or C-sec
▪Be careful not to confuse with uterine rupture
▪ Good CE and vaginal exam will differentiate between this and uterine rupture
Congenital chondrodysplasia
▪‘Bulldog’ calves
– Short legs
– Domed head
– Brachygnathia inferior (undershot jaw)
▪Dexters, Holstein, Jerseys – Likely genetic
– Other breeds reported
▪Does not always = dystocia
Hydrocephalus
▪ Increase in CSF volume → domed head
▪ Calves born alive may have neuro deficits
▪ Teratogenic viruses implicated
– BVDv
– BTV
– Akabane virus (not UK)
▪ May also form part of mixed congenital disorders
▪ Mild cases may calve unassisted
▪ Severe cases = C-sec or partial foetotomy (remove head)
Large offspring syndrome
▪ Also termed ‘abnormal offspring syndrome’
– Varied congenital abnormalities reported
▪ Associated with assisted reproductive technologies – Embryo transfer
– In vitro techniques
– Cloning
▪ Exact mechanisms unclear
▪ Very large neonates
– May be 2x average size
– Dystocia
– Macroglossia (enlarged tongue)
-> can affect ability to suckle and feed
Cranial defects
- Ancephaly
- Otocephaly
- Bicephaly
What is ancephaly?
- no head
What is otocephaly?
- some head structures present but no skull
What is bicephaly?
- 2 heads
What is a teratogen?
- agents causing foetal abnormalities or death
How does the timing of exposure to teratogens influence the outcome?
▪Zygote→affected by chromosomal or genetic abnormalities. Often result in embryonic death
▪Embryo→affected by environmental and infectious agents. Most high risk period for developing abnormalities
▪Foetus→more resistant to environmental teratogens but structures that develop late are still susceptible to being affected (e.g. palate)
Effects of BVD virus on calves
- Abnormalities of the brain, eyes and neurological development
- Foetal death
- PI calves
– May be small but may appear normal
– Increased susceptibility to disease
– May develop mucosal disease
Common viral teratogens (& who they affect)
- BVD virus
- Border disease virus
- Schmallenberg virus
- Bluetongue virus
- Akabane and Aino viruses
Effects of border disease virus on lambs & kids
- Abnormalities of skin, skeleton and neurological system
– ‘hairy little shakers’ - Foetal death
- PI lambs
– Similar to PI calves
Effects of Schmallenberg virus
- Arthrogryposis
- Foetal death
Effects of bluetongue virus
- Arthrogryposis and other deformities
- Foetal death and abortion (more common than malformations)
Effects of Akabane and Aino viruses
- Congenital malformations
- Not currently in UK
- Midge spread→may be seen in future
Examples of environmental teratogens
- Hemlock
- Nitrates/nitrites (nitrate accumulating plants e.g. sugar beet, alfalfa) (nitrite based fertilisers)
- Ergotism (mouldy feed)
- Lead
Effects of hemlock
- Skeletal abnormalities if ingested between days 40-70 of gestation
- Abortion
- NB. is highly toxic to cattle and often causes death of dam
Effects of nitrates/nitrites
- Excess nitrate consumption exceeds rumen capacity for metabolism → nitrate and nitrite absorbed into circulation → interacts with haemoglobin → oxidation to methaemoglobin
- This process can also occur in the placenta → foetal death, weak calves
Effects of ergotism
- reduced size offspring
Effects of lead
- Concentrates in CNS of foetus
– Neurological defects
– Reduced foetal size - Also causes problems in the dam
Examples of pharmacological teratogens
- Benzimidazoles
- Tetracyclines
- Steroids
- Prostaglandins
- Xylazine
Effects of benzimidazoles on sheep
- Abnormalities of the foetal skeleton, kidneys and vascular system
Effects of tetracyclines on all ruminants
- Dental discolouration
Effects of steroids on all ruminants
- Abortifacient
Effects of prostaglandins on all ruminants
- Abortifacient
Effects of xylazine on all ruminants
- Abortifacient in later stages of pregnancy
- Causes uterine contraction -> abortion
- Detomidine also has similar, but less pronounced effects
What is puberty in cattle driven by?
- weight, not age
- puberty occurs at ~2/3 of adult BW
Early unwanted pregnancy in heifers
▪Well grown heifers unexpectedly conceive to mis- mating
– Uncastrated youngstock
– Bulls running with herd
– Entire males escaping
Can lead to:
▪Poor heifer growth
▪Increased risk of dystocia
How can an early pregnancy in a heifer be managed?
- Wait & see
- Elective c-section
- Induce parturition
- Terminate pregnancy
How can an early pregnancy in a heifer be managed - wait & see
- C-sec likely needed→can be less optimal outcomes if performed in emergency
- Can be effective if farmer aware of mis-mating and requests vet assistance as
soon as parturition starts - Only addresses issue of dystocia
How can an early pregnancy in a heifer be managed - elective c-section
- Performed at/near end of gestation before parturition starts
- Need a idea of gestation duration → scan
- Only addresses dystocia
- Justified in this case
How can an early pregnancy in a heifer be managed - inducing parturition
- Aim to induce near/at term for viable but small foetus
- May still need C-sec if calf big
- Requires reliable insemination date → scan
- Only addresses dystocia
How can an early pregnancy in a heifer be managed - terminating pregnancy
- Prostaglandin
- Glucocorticoid steroids (dexamethasone)
- Reliability dependent on stage in gestation → scan
- Early termination can mean limited effects of pregnancy on dam
Pregnancy termination using prostaglandins
▪Lysis of CL→pregnancy loss
– Progesterone needed to maintain pregnancy
▪ Abortion occurs within 7days if given <100 days gestation
– >100 days gestation timing and reliability of abortion reduced
Why is the stage of gestation an important factor when considering the use of prostaglandins for pregnancy termination?
- <100 days gestation = maximal chances (> 90%)
- 101-150 days gestation = moderate chances (~ 60%)
- > 150 days gestation = lower chances (≤ 40%)
– Because placenta also a source of progesterone between days 150-200 - > 270 days gestation to induce parturition → live calf
Pregnancy termination using glucocorticoid steroids
▪Reduces placental secretion of progesterone→ pregnancy loss
– Most effective in last month of gestation
– Can also be used after day 270 to induce parturition →
live calf
▪Dexamethasone
– Give 20-30mg (for most products this is 10-15ml)
What can you give for pregnancy termination for mid-late gestation (i.e. >150d) or if uncertain?
- both dexamethasone AND prostaglandin
- both drugs associated with increased likelihood of retained foetal membranes
- no other adverse effects for the heifers reported
Pregnancy induction - drug choices
- Short acting (corticosteroids)
– 20-30mg dexamethasone - Prostaglandins
- Prostaglandin + corticosteroid combination
- Longer acting corticosteroids
– dexamethasone trimethyl acetate)
Short acting
corticosteroids to induce parturition - advantages
- High efficacy (80-90%) when given within 2 weeks of expected calving date
- Calving occurs within 72hrs of injection
Short acting
corticosteroids to induce parturition - disadvantages
- High incidence of retained foetal membranes (RFM)
Prostaglandins to induce parturition - advantages
- Calving occurs 24-72 (average 45) hours after injection
- Give within 2 weeks of calving date
Prostaglandins to induce parturition - disadvantages
- High incidence of RFM
- Failure of induction common if
given > 2weeks before end of gestation
Prostaglandin + corticosteroid to induce parturition - advantages
- More reliable than steroids or PGF alone
– Especially if dates uncertain - Calving occurs 24-48hrs after treatment
Prostaglandin + corticosteroid to induce parturition - disadvantages
- Retained foetal membranes commonly occur
Longer acting corticosteroids to induce parturition - advantages
- Used if timing of calving more important than calf viability
- Given 1 month before expected calving date
- Calving occurs 4-26 days after injection
- Lower incidence of RFM
Longer acting corticosteroids to induce parturition - disadvantages
- Higher incidence of calf death (up to 45%)
- Dexamethasone trimethyl acetate currently not licensed in UK
