Lecture 13 & 14 - Parturition Flashcards
Quiescence
-Want to keep muscle contractions quiet during pregnancy , and cervix closed
Progesterone - main hormone that keeps things quiet
-progesterone from pitutiary and from palcenta
What has influences on gestation length?
-Parity, age, genetics, ethnicity
Stress, infection ect. can shorten gestation length
all the factors add up
38 weeks since last menstrual period
How to get Preterm activation of birth?
Involves the fetal genome
- Uterine growth (e.g twins - preterm uterus cannot be stretched past a certain point)
- up regulation of myometrium
- membrane rupture (e.g due to infection)
- intact HPA axis
Activation of myometrium?
-what can block this?
Activation of myometrium
- increase CAPs - gap junctions (not many in quiesence)
- more power to activate muscle
- prostaglandin and oxytocin receptors
- can block myometrial activity with calcium channel blockers
- can antagonise intercellular connectivity cap junction forming
Activation
Positive feedback loop, causes stimulation
- Progesterone modulates all of this
- Prostaglandins will be effectors
PGs - increase myometrial contractility,
lead to cervix changes,
associated with membrane rupture
Oxytocin
Not essential for initiation of labour
- requires gap junctions to be effective
- used to induce and augment labour
- primary prevention of post partum hemmorage (causes uterus to contract after baby is born)
How cervix changes during pregnancy
Pregnancy is an inflammatory process
- slow changes of cervix
- leads to ECM degraded, practically disappears and then baby can come out cervix
Strong fibrous tough fiber, then this softens, and ripens during
Membranes
amnion and chorion - attached
- site of PG production
- rupture at zone of morphology
- doesn’t need to rupture, but PG are released when this is rupture, so can deliberately rupture this to help the process along
Stages of labour
1st stage - until full dilation
- muscle contractions
- cervical effacement and dilation
- descent of presenting part
- rupture of membrane
2nd stage - full dilation until birth of baby
3rd - birth of baby until delivery of placenta
What happens when baby is born?
- foramen ovale needs to be shut
- Birth thermogenesis - baby has brown fat to help keep it warm
- Baby needs to be warm (can dry the baby)
- Breast feeding - eye contact
-involution - placental separation, cleavage through decidua basalis, contractions to prevent postpartum haemorrhage, increased uterine sensitivity to oxytocin
What is preterm birth?
What are Pre term birth causes
What is it? abnormality - failure of body to keep uterine quiescence (failure to keep baby in until the right time)
preterm labour - occurs when a number of pathogenic factors lead to early activation of the mechanisms associated with term labour
Preterm birth - grouped by pathogenic factors
- Stress
- Bleeding
- Infection
- Stretch
Failure of Quiescence
inflammation or infection - stimulus - more prostaglandins
What are the triggers to cause premature birth?
Infection - can get up into chorion amnion space or may even cross into placenta and enter fetus
-Stretch - membrane disruption, myometrial distention
Tissue damage especially cervix
Placentation - growth of fetus, hormone- progesterone, prostaglandin release, poor attachment - bleeding
Problems with preterm birth
- immature fetus - often unwell (e.g if htere was infectioN)
- often malpresentaito n
- have maternal comorbitiiees
- oftne have complicated caesarean sections
- risk of recurrence
- poorer outcomes
Lung developments
-not fully developed - harder to breathe, not as much surfactant?
Steriod homrones - can make surfactant so babies can breathe
-can give antenatal glucocorticoids - mature a babys lung
