Pharmacological Control Of Pregnancy and Parturition

Question 1

What are the 3 stages of parurition?

Answer 1

1) initiation of myometrial contraction
2) expulsion of the foetus
3) expulsion of the foetal membranes

Question 2

How is parturition initiated?

Answer 2

Parturition is initiated by hormonal signals from the foetus= foetal cortisol

· Effectively the foetus decides when it is ready to be born.

· The fetus is undergoing stress induced by nutritional needs not being met and size of uterus not being enough.

Question 3

What are the hormones (4) involved in parturition and what happens to them?

Answer 3

Question 4

Why does oestrogen increase and then decrase at parturition?

Answer 4

This elevation initiates the secretory activity of the reproductive tract, particularly the cervix, resulting in the cervix and vagina producing mucus. This washes out the cervical seal of pregnancy and lubricates the cervical canal and vagina to reduce friction, enabling the foetus to exit the reproductive tract with relative ease

Question 5

What is the function of foetal cortisol? (5)

Answer 5

Reduces progesterone levels which:

— Removes the of block on myometrial contractions

— Reproductive tract secretions increase

Foetal cortisol also stimulates uterine prostaglandin production:

— Causes uterine contraction

— Acts on the ovary and causes lysis of the corpus luteum

— Relaxin produced changes structure of cervix (most species except cow) Allows for stretch

Question 6

What are myometrial contractions?

Answer 6

Myometrium consists of:

Non-striated smooth muscle fibres

Nerves, Blood and Lymph

• During pregnancy, Oestrogens stimulate muscle cell hypertrophy.
• Myometrial cells behave as a functional syncytium, being electrically coupled via specialised regions of contact known as gap junctions/nexi.
• The combination of the above factors allows strong, coordinated myometrial contraction.
• Excitation of smooth muscle depends on alteration in membrane potential. Myometrial cells must be depolarised (-50mV) to achive contraction.
• Spontaneous depolarizing pacemaker potentials occur. If the magnitude of these exceeds the critical threshold, a burst of action potentials will fire.
• This causes calcium influx from endoplasmic reticular stores and extracellular fluid.
• Intracellular calcium binds to regulatory sites on actin and myosin, allowing expression of ATPase, thus causing contraction.
• Uterine contractions increase in both frequency and amplitude during labour. This causes an increase in uterine pressure from 10mmHg to 50-100mmHg.

Question 7

What causes oxytocin release?

Answer 7

neuro hormonal reflex

Increasing pressure on the cervix activates pressure sensitive neurons which relay afferent information to the hypothalamus (PVN) and this neural input to the posterior pituitary stimulates oxytocin release which strengthens and initiates contractions.

Question 8

When might it be necessary to induce premature parturition? (5)

Answer 8

• When foetus will not survive once born/congenital abnormality
• When it is a risk to mothers life to go full term
• Accidental matings
• Twins in horses
• Free martinism in cows

Question 9

What are the indications for:

1. Dexafort (dexamethasone?
2. Lutalyse (Dinoprost)?

Answer 9

1. Commonly used to induce abortion/parturition in late term gestation
2. To control oestrus cycle in cows and horses. Induce parturition in pigs

Question 10

What are the indications for use of Estrumate (Cloprostenol) in CATTLE? (10)

Answer 10

Cattle indications

• Suboestrus or non-detected oestrus
• Induction of parturition
• Termination of normal pregnancy
• Termination of abnormal pregnancy
• Mummified foetus
• Hydrops of the foetal membranes
• Chronic endometritis (pyometra)
• Ovarian luteal cysts
• Controlled breeding

Question 11

What are the indications for use of Estrumate (Cloprostenol) in HORSES? (6)

Answer 11

• Induction of luteolysis following early foetal death and resorption
• Termination of persistent dioestrus
• Termination of pseudopregnancy
• Treatment of lactation anoestrus
• Establishing oestrous cycles in barren/maiden mares
• As an aid to stud management

Question 12

What are the indications for:

1. Oxytocin?
2. Proslyin (luprostiol)?

Answer 12

1. stimulation of uterine contraction to facilitate parturition in the presence of a fully dilated cervix
   - to promote involution of the post-parturient uterus and thus aid the passage of retained placenta
   - to aid in the control of post-partum haemorrhage
   - promotion of milk let-down' in cases of agalactia and to facilitate stripping out’ of infected quarters in the treatment of mastitis in cows.
2. Prosolvin is a luteolytic agent. Provided an active corpus luteum is present it will cause luteal regression which will be followed by follicle growth, oestrus and ovulation.

Question 13

What are the contra indictions of dexafort (dexamethasone)? (5)

Answer 13

diabetes, chronic nephritis, renal disease, congestive heart failure, osteoporosis and in viral infections during the viraemic stage

Question 14

What are the contra indications of lutalyse (dinoprost)? (5)

Answer 14

Prostaglandins of the F2α type can be absorbed through the skin and may cause bronchospasm or miscarriage

Animals should not be treated if they suffer from either acute or sub-acute disorders of the vascular system, gastro-intestinal tract or respiratory system

Question 15

How can you NOT inject lutalyse (dinoprost)?

Answer 15

NOT NOT INJECT IV

Question 16

What are the contraindications of oxytocin?

Answer 16

Dystocia due to obstruction

Question 17

What are the contraindications for the use of prosolyin (luprostiol)? (3)

Answer 17

Very few adverse reactions have been seen with Prosolvin. Sweating and a slight respiratory effect have been reported in a small number of horses, but these effects were mild and transient. It is, however, possible for prostaglandins to cause diarrhoea in horses and abdominal discomfort in cattle.

Question 18

Devise a possible treatment plan (including when, which drug(s) and expected time of delivery) for inducing parturition in a cow

Answer 18

Prosolvin Solution for injection: Induction of parturition: In cattle Prosolvin may be used to initiate labour after the 270th day of pregnancy. Calving may be expected within 3 days of treatment.

Question 19

Devise a possible treatment plan (including when, which drug(s) and expected time of delivery) for inducing parturition. For pigs.

Answer 19

In pigs, Prosolvin may be used on or after the 113th day of the gestation period. Parturition will normally follow within 48 hours.

Question 20

Devise a possible treatment plan (including when, which drug(s) and expected time of delivery) for inducing parturition. For horses

Answer 20

Prosolvin may also be used to induce parturition in the mare. Treatment must occur on or after the 330th day of pregnancy and the mare must show relaxed pelvic ligaments and a functional udder with colostrum. Following treatment parturition may be expected within a few hours.

Question 21

Devise a possible treatment plan (including when, which drug(s) and expected time of delivery) for inducing parturition. For sheep.

Answer 21

Dexafort: mimics foetal stress hormone should lamb in 24 hrs of injection.

Question 22

List the potential consequences/complications of inducing early parturition (5)

Answer 22

· Underdeveloped foetus that cannot survive once born

· Uterine hyperstimulation

· Failed induction

· Cord prolapse

· Uterine rupture

If dexafort is used it can cause retained placenta, posisbly metritis and subfertility there after.

Question 23

What drugs can be used to delay parturition/aid obstetrical manoeuvres?

Answer 23

Planipart Solution (CLENBUTEROL) for Injection 30 micrograms/ml Species: Cattle

Ventipulmin Syrup (CLENBUTEROL) antagonizes the effects of prostaglandin F2 alpha and oxytocin.

B2 adrenergic agonist - Inihibits contractions and causes relaxtion. Given to reduce contractions.

Question 24

Why might we want to prevent contractions? (2)

Answer 24

C section

Correct dystocia

Question 25

What are the uses of plipart solution (clenbuterol)? (6)

Answer 25

To relax the uterus in cattle, usually at the time of parturition.

• In heifers to delay delivery to allow full preparation of the soft birth canal.
• As an aid to obstetrical manoeuvres in dystocia e.g. malpresentation and malposture.
• To relax the uterus for caesarean section.
• To delay and therefore programme delivery to permit observation of parturition e.g. avoidance of night time delivery.
• To facilitate the replacement of prolapsed uterus.
• In embryo transfer to ensure less traumatic manipulation of the uterus.