Pregnancy & parturition Flashcards
MRP
maternal recognition of pregnancy
In most species , the conceptus must provide a timely biochemical signal or the pregnancy will terminate.
Which species do not need pregnancy recognition factors?
bitch and queen
MRP biochemical for sows
conceptus produces estradiol (d11-12)– signal for MRP.
What is the pregnancy recognition factor in cow?
The MRP in ruminant is IFNτ.
IFNτ acts on the endometrium in a paracrine manner to prevent luteolysis, thereby maintaining the CL and production of progesterone.
What is the pregnancy recognition factor in mare?
in the horse, the mechanism underlying MRP remains unknown.
migration of conceptus PGF2α production reduced.
What hormones can be produced by the placenta? (5)
- Progestserone
- Estrogens
- Relaxin
- PGF2α
- Somatomammotropin (placental lactogen/prolactin)
Progesterone is Produced by
corpus luteum and placenta
CL progesterone is important in which species?
sow, bitch, queen, doe, cow (8m)
Placental progesterone is important in which species?
mare (70 d), ewe (50d)
In mares, after day 100 the placenta assumes the major progesterone producing role.
The three stages of parturition are:
Stage I – initiation of myometrial activity (removal of progesterone block)
Stage II – expulsion of fetus
Stage III - expulsion of fetal membranes
eCG
Equine chorionic gonadotropin, also known as pregnant mare serum gonadotropin (PMSG) or equine luteinizing hormone, is a glycoprotein hormone secreted by fetal-origin trophoblastic epithelial cells that form the endometrial cups (EC).
PMSG =
pregnant mare serum gonadotropin
also known as eCG
equine endometrial cups are first seen on what day of gestation?
day 36-40
The cups produce eCG.
Enlarge until d 60 (1.5-2 cm) and start to degenerate on d 70, degenerated on d120-160 .
eCG d. 36-40 , highest d. 60-70 disappear d. 120-150.
What initiates parturition
The fetus via the fetal hypothalamo-pituitary-adrenal axis.
Fetal stress due to a lack of space in the uterus induces
the release of corticotropin releasing hormone and thus fetal adrenal cortex corticoids.
What is P4?
steroid hormone progesterone
Explain removal of the “P4 block”.
Fetal cortisol promotes synthesis of three enzymes:
* 17a hydroxylase,
* 17-20 desmolase and
* aromatase
These enzymes allow the conversion of progesterone to estradiol.
This conversion accounts for a dramatic drop in progesterone with simultaneous elevation of estradiol.
In addition, Fetal cortisol causes the placenta to synthesize PGF2α which will induce myometrial contraction and also contribute to luteolysis.
Various effects of estrogens on the initiation of parturition. (4)
myometrial contractions,
oxytocin receptors,
PGF2a,
cervical and vaginal lubrication
Increased cervical pressure caused by the fetus induces the release of…?
neurons in teh cervis send afferent sensory info to the CNS which then induces oxytocin release from the hypothalamus.
Estrogens activate oxytocin receptors. Uterine contractions increase.
What stimulates release of relaxin?
PGF2alfa typically from the placenta
Also some ovarial in certain species.
What events occur during the first stage of parturition?
- Hormonal changes
- Elevation of cortisol, loss of P4 block, rise of PGF2a, oxytocin, relaxin, E2
- Uterine contractions
- Abdominal pressure
- Opening of cervix
- Positioning of fetus
- Water sac expelled
What events occur during the second stage of parturition?
- Uterine contractions
- Dam usually lying down
- Fetus enters birth canal
- Front feet and head protrude first
- Fetus delivery completed
What events occur during the third stage of parturition?
- Caruncle-cotyledon (button) attachments relax
- Uterine contractions expel membranes
define puerperium
the post-partum period, up to 6 weeks post parturition.
– from parturition until reproductive organs
are in normal unpregnant size and reproductive function is restored so another pregnancy can occur.
Main events of the puerperium period (4)
- Resumption of normal ovarian activity (3-4 weeks)
- Uteine involution – myometrial contractions and expulsion of lochia (25-35 days)
- Endometrial repair (50-60 days)
- Elimination of bacterial contamination of the reproductive tract (4-5 weeks)
Lochia includes
fluids from uterus and vagina containing debris, pieces of placenta and endometrium, blood.
