Lecture 12: Parturition (Kelleman) Flashcards
Clicker Q: Which of the following are polyestrus and thus have repeated estrous cycles throughout the entire year? A’s: Queens, mares, bitches, cows, or wes
Ewes
Clicker Q: Is progesterone high or low in diestrus?
high
Clicker Q: Melatonin suppresses GnRH in which animal?
Mares
Clicker Q: Luteinizing hormone (LH) causes:
ovulation
Ferguson Reflex
Neuro-endocrine loop causing oxytocin release
Main hormone for maintaining pregnancy
progesterone
cervical closure fx. Maintained by which hormone?
Keeps contents from falling out and infection from getting in during preg. Progesterone
Where is progesterone produced?
CL and placenta
Which species have high progesterone throughout most of pregnancy?
ewe, sow, cow. Decreases in late-gestastion with estradiol peak
rising estradiol –> progesterone
decreases
HPA axis stands for
hypothalamic-pituitary-adrenal axis
Activation of fetal HPA axis increases what 3 hormones
1) Corticotrpoin releasing hormone (CRH)
2) Adrenocorticotropin Hormone (ACTH)
3) Cortisol***
Types of fetal stress
hypoxia, overcrowding, nutritional compromise
Fetal HPA axis:
Name the 3 organs involved
hypothalamus –> anterior pituitary –> adrenal gland (cortex)
Fetal HPA axis:
what hormone is released by the hypothalamus to stimulate the anterior pituitary?
CRF
what hormone is released by the anterior pituitary to stimulate the adrenal gland?
ACTH
Name the 3 functions of cortisol on the fetus:
- induce enzymatic changes in the placenta ie “communicates” with mom
- promotes prostaglandin synthesis
- fetal maturation
main action of progsterone
“pro-gestational”
“hormone of pregnancy”
main function of estrogen
increased uterine “responsiveness”
main function of PGF2-alpha
luteolysis and contractions
main function of oxytocin
contractions
main function of relaxin
genital tract softening
Upon stimulation, what hormone can progesterone be converted to?
estradiol
what hormone induces placental enzymes which convert progesterone to estradiol?
fetal cortisol
what hormone is progesterone converted to before its final conversion to estradiol?
testosterone
progesterone –> testosterone –> estradiol
21 carbons –> 19 carbons –> 18 carbons
3 ways in which progesterone falls
1: enzymatic - fetal cortisol induces placental conversion of progesterone to estrogen
2: luteolysis - via PGF2-alpha and uterine contractions
3: removal of “progesterone block” (keeps fetus quiet during gestation)
“progesterone block”
- keeps fetus quiet during gestation
- during the removal of the “progesterone block” cortisol release induces progesterone to estrogen thereby decreasing progesterone and increasing estrogen.
what way can estrogen can be increased (during parturition)
enzymatic - fetal cortisol induces placental conversion of progesterone to estrogen
what are the three functions of estrogen?
- increases uterine sensitivity to oxytocin
- increases lubrication and sofening
- promotes release of PGF2-alpha
2 main functions of prostaglandin in parturition
- causes luteolysis if CL is still present
2. will cause uterine (myometrial) contractions
what is the main function of oxytocin
myometrial contractions
these contractions can subsequently promote more oxytocin and PGF2-alpha release.
what is the main function of relaxin in parturition?
encourages pelvic, genital tract and cervical softening to facilitate parturition
- this can be externally assessed as parturition nears: vulva, perineum and pelvic ligaments
The Ferguson reflex
the sensation of distension of the cervix, uterus and vagina by the fetus results in a neuroendocrine reflex which causes the release of oxytocin (from posterior pituitary).
oxytocin causes uterine contractions resulting in further distension, which increases oxytocin, causing further distension and contraction and so on…..
Name the 3 stages of parturition
Stage I: “preparation”
Stage II: fetal expulsion with “true labor”
Stage III: expulsion of the fetal membranes
what happens in stage I of parurition
- cervical dilation, myometrial contractions, some fetal positioning
- behavior: nest building behaviors in dog & cat. cattle and sheep isolate themselves. mare shows colic-like signs (poor appetite and restlessness)
what happens in stage II of parturition
start: rupture of the chorioallantois
finish: complete expulsion of the fetus
- myometrial and abdominal contractions.
- chorioallantois breaks (1st fluid expulsion).
- fetus is seen within the amnion. amnion breaks and amniotic fluid is released (2nd fluid expulsion).
Stage III of parturition
expulsion of fetal membranes
in species that are polytocus (more than one fetus), phase II and phase III often follow each other with each fetal passage.
- mom experiences vasoconstriction and inflammation
typical position of fetus upon actual parturition
anterior, dorsosacral, forelimbs extended.
species variability in length of each stage of parturition
general - no specific numbers
cow - slow
heifer - even slower
horse - fast, “explosive”
define: Lochia
the normal fluid which is passed from the uterus during the purerperium. it consists of cellular (RBC, WBC, bits of tissue, etc) and noncellular debris (fetal fluids, lysed blood, mucus, etc).
- time varies by species
minimal odor!
type of contractions throughout parturition
uterine myometrial (smooth muscle) contractions
abdominal contractions:
- straining against closed glottis
- additive with smooth muscle contractions
time from fetal delivery until complete uterine involution is defined as:
Puerperium
Complete Uterine Involution varies by species. cow? mare? bitch?
uterine involution = transformation from pregnant to non-pregnant state
mare = ~ 2 weeks cow = 1 - 1.5 months bitch = about 2 months or more
Retained Fetal Membranes (RFM)
aka “retained placenta” - when placenta is not expelled in its entirety within a given time for each species.
- incomplete expulsion
- autolysis (rotting)
- minor to serious health problems may result depending upon species
- involution is delayed by RFM
dystocia
“difficult birth”
Equine RFM is how much time after fetal delivery?
3 hours - considered a true emergency - potentially life threatening
Bovine RFM - how much time after fetal delivery?
> 12 hours
General parturition summary
- Fetal HPA activation
- decreased Progesterone
- increased estrogen
- increased oxytocin and PGF2-alpha
relative uterine quiescence changes to dramatic uterine activation!
