Pregnancy Flashcards
Describe pseudopregnancy in the goat
- Common
- Not always associated with pregnancy loss
- Where no pregnancy loss, due to end of cyclical ovarian activity (with no hydrometra), treatment with PGF2a
- Where associated with pregnancy lost, early embryonic death with persistent CL, wait for CL regression
Describe pseudopregnancy in the bitch
- 100%
- Not associated with pregnancy loss
- Due to prolonged luteal phase and prolactin production meaning pregnant and non-pregnant hormone profiles very similar
- Treatment usually uncessary, may spay or give prolactin-inhibitor
Describe pseudopregnancy in the mare
- 20% of mares
- Can be due to early embryonic death after endometrial cup formation (15 days), just have to wait
- Or mare that was bred, prolonged luteal phase with no conceptus but assume there was an embryo that was lost, treat with PGF2a
Describe pseudopregnancy in the queen
- 20% of queens
- Not associated with pregnancy loss
- Spontaneous ovulation without fertilisation
- No treatment required
Descibe pseudopregnancy in the sow
- Variable, mainly associated with infectious disease
- May or may not be associated with pregnancy loss
- No loss: failure of CL regression e.g. endometritis, inflammation preventing pulses of PGF2a, treat with exogenous PGF2a
- Or loss of pregnancy around day 20 with persistent CL
How is progesterone production maintained in the non-pregnant bitch during the luteal phase?
- Fall in progesterone (as CL runs out of steam) leads to increased prolactin
- Prolactin leads to increased progesterone
- Luteal phase in non-pregnant longer than in pregnant by 5 days
How can oestrus behaviour be induced in the bitch?
- PGF2a administration
- Administration then removal of progesterone
Explain how PGF2a can be used in the bitch to stimulate oestrus behaviour
- PGF2a stmiulates luteolysis
- Reduction in progesterone
- Drop in progesterone stimulates oestrus behaviour and ovulation
Explain how administration then removal of PGF2a can be used in the bitch to stimulate oestrus behaviour
- Drop stimualtes expression of oxytocin receptors
- Stimulation of PGF2a (oxytocin from CL) which will lyse the CL
- Fall in progesterone allows oestrus behaviour and stimulates ovulation
When does maternal recognition of pregnancy occur?
Before luteolysis, as need CL to produce progesterone to maintain pregnancy
Give the embryonic signals for pregnancy recognition in
a. ruminants
b. sow
c. mare
d. bitch and queen
e. women
a. Interferon tau
b. Oestradiol
c. 3, 3 proteins/oestradiol/migration of conceptus
d. non
e. hCG
Describe the general progesterone profile in pregnancy
- Different depending on species
- In most remains high during pregnancy
- Higher in earlier months if no luteopacental shift
- Where there is shift, may increase again near end of gestation
Describe the general oestrogen profile in pregnancy
- Peak of oestrogens at oestrus/ovulation
- In horses have additional peak mid-pregnancy
- Peak near parturition
Describe the hormone profile in the pregnant mare
- Progesterone high throughout
- Peak of oestrogen in mid-gestation
- Peak of eCG at start of gestation
Describe the hormone profile of the pregnant cow
- Oestrogen low, then increase in preparation for parturition
- Progesterone produced by CL and uterus
- Prolactin peaks at parturition
Describe the hormone profile of the pregnant ewe
- Oestrogen low then increase in prep for parturition
- Progesterone increases in later gestation due to luteoplacental shift
Describe the hormone profile fo the pregnant bitch
- Progesterone increasing before ovulation in metoestrus
- Maintain increase before declining gradually
- At parturition, sharp fall in progesterone caused by PGF2a
- Elevated prolactin maintains progesterone
Describe the pregnancy endocrinology of the queen
- Progesterone: rapid rise, divergent from non-pregnant at 21 days, placenta takes over, rapid fall prior to parturition
- No luteoplacental shift
- Placenta producing prolactin which maintains progesterone
- Relaxin also from placenta
How is progesterone maintained in the pregnant animal?
- Maternal recognition of pregnancy inhibits luteolysis.
- Luteoplacental shift may also take place
- LH stimulates production of progesterone
- Cl stimulates to produce progesterone by prolactin
What stimulates production of relaxin?
PGF2a, at parturition
Where is eCG produced?
By the endometrial cups
What stimulates and inhibits prolactin production?
- Inhibited by dopamine
- Stimulated by oestradiol
What are the functions of the placentally produced hormones?
- Stimulate ovarian/uterine function
- Maintain pregnancy
- Modulate foetal growth
- Stimulate mammary funtion
- Assist in parturition
List the hormones produced by the placenta
- Oestrogen
- Progesterone in some species
- Prolactin
- Placenta lactogen
- hCG/eCG
- Relaxin
List the function of progestagens produced by the placenta
- Essential for pregnancy
- Stimulate production of histotroph and uterine milk proteins
- Suppress myometrial contractions
- Stimulates mammary gland development
Describe the oestrogens produced by the placenta
- Distinct oestrogens per species
- Oestriol: women
- Oestrone: ruminants
- Equine specific oestrogens
- Produced by foetal cotyledons
List the functions of the oestrogens produced by the placenta
- Stimulate mammary development
- Stimulate placental growth
- Increase uterine blood flow
- Stimulate myometrial growth
Where is relaxin produced?
- CL in sow
- Placenta in rabbit, mare, dog
List the functions of relaxin
- Softens connective tissue enabling growth of foetus
- Relaxation of pelvic ligaments
- Parturition
- Can be used for pregnancy diagnosis in dogs
Why can relaxin be used for pregnancy diagnosis in bitches?
Is only produced by the placenta, so if relaxin is present must mean that there is pregnancy
Explain the function of eCG
- FSH and LH like activity - leads to formation of an accessory CL
- Increases progesterone
- Stimulate primary CL to produce progesterone, as a result eCG will increase to produce more progesterone and formation of accessory CL
- Maintains the progesterone for a period of time
Why is there a temporary decrease in blood progesterone in the middle of gestation n the mare?
- Progestagens have local actions
- No decrease in production, but a decrease in the amount reaching the systemic circulation
Describe the unique progestagens and oestrogens in the mare
- Main progestagen is 5-alpha pregnane
- Unique oestrogens: foetal androgens converted by placenta
- Rise in mid-gestation and have typical action on pregnancy and mammary gland development
Where is prolactin produced?
Lactotrophs in anterior pituitary
Describe the actions of prolactin
- Induces lobuloalveolar growth in mammary gland and lactogenesos
- In CL (rodents, dogs) stimulates progesterone
- Stimulates maternal behaviour
Where is placental lactogen produced?
Binucleate cells in placenta, released into foetal and maternal circulation
Describe the action of placental lactogen
- Binds to prolactin receptors
- Modulates foetal metabolism
- Mammary gland development
- Can stimulate lactogenesis
Describe pregnancy specific protein B (PSPB) and pregnancy associated glycoprotein (PAG) in ruminants
- Produced by binucleate cells
- Long half life
- Only produced by placenta
- Detected around 6-8 weeks of pregnancy onwards
- Last a long time in circulation so can give false positives in case of pregnancy loss
In what species does the luteoplacental shift take place?
- Cow
- Ewe
- Mare
- Women
Compare the gestation length in species where there is no placental shift to those where there is a shift
No shift usually shorter gestation
Give the gestation length of camelids
11-12 months
Give the gestation length of the bitch
2 months/65 days
Give the gestation lenght of cows
9 months
Give the gestation length of ewes
5 months
Give the gestation lenght of mares
11 months
Give the gestation length of queen
2 months/65 days
Give the gestation lengthof rabbits
1 month
Give the gestation length in sows
3 months, 3 weeks, 3 days (3.8 months)
Give examples of when pregnancy termination may be desirable
- Unintended mating
- Risk to dam’s health
- Owner does not want pregnancy to continue
- Twinning in mare
- Induction of premature parturition
List the key agents for pregnancy termination
- PGF2a or analogue
- Corticosteroids
- Oestradiol
- Dopamine antagonists
- Progesterone receptor antagonists
What agents can be used for induction of premature parturition?
- Oxytocin
- PGF2a
Describe the use of PGF2a in pregnancy termination
- Only where luteoplacental shift has not taken place
- Luteolytic
- Decline in progesterone
- Effective throughout pregnancy in sow, bitch, cat and goat (multiple doses in dogs)
- Effective up to 150 days in cows, up to 45 days in ewes, up to 35 days in mares
Describe the use of oestradiol in pregnancy termination in the bitch
- Prevents zygote transport to uterus
- No longer licenced
Describe the use of oestradiol in pregnancy termination in ruminants
- Luteolytic
- Effective in large doseases after 100 days
- No longer licenced
Describe the use of anti-progesterones in pregnancy termination in the bitch
- Progesterone required for maintenance of pregnancy
- Aglepristone is an example
Describe pregnancy termination using dopamine agonists
- Dogs, cats
- Inhibits prolactin secretion
- Is luteotrophic and stimulates lactogenesis
- Can be used to treat false pregnancies as dopamine agonists prevent secretion of prolactin
Describe pregnancy termination using corticosteroids
- Mimics foetal signal for parturition
- Induces myometrial contractions
- Expulsion of foetus
- Abortive agent (in combination with PGF)
- Induce (early) parturition
Describe the tone of the cervix and uterus at oestrus in the cow
- Cervix tense and narrow
- Uterus oedematous, filled with fluid, increased tone
Describe the effect of progesterone on cervical and uterine tone in the cow
- Cervix softened
- Uterus flaccid
Describe the tone of the cervix and uterus at oestrus in the mare
- Cervix broad and soft
- Uterus soft and oedematus
Describe the effect of progesterone on cervical and uterine tone in the mare
- Cervix hard and narrow
- Uterus small with increased tone (to aid migration of conceptus)
What may cause pregnancy loss in the ewe?
- Toxoplasmosis
- Chlamydia
- Campylobacter
- Stress
- Poor nutrition
- Ingestion of toxic plants
- Weather
- Salmonella
- Listeria
- Schmallenberg
What steps should be taken following an abortion storm?
- Remove placenta and dead lambs
- Isolate ewes
- No cross-fostering
- Treat/cull affected ewe/lamb
