normal birth Flashcards
define parturition
the process of giving birth
- expelling the fetus, placenta and membranes from the uterus
challenges in human parturition
Quiescence - of uterus with growth, distension, pressure
timing - for safe birth
activation - stimulation of uterine musculature changes in genital tract
birth - fetal-neonatal adaptations
involution - haemostasis, establishing lactation
physiological processes
- quiescence
- activation
- stimulation
- involution
anatomical changes leading to pregnancy
uterus - upper and lower segments
cervical changes = ripening
softening shortening effacement
membrane rapture
uterine quiescence
uterine muscle contractions poorly synchronised
low amplitude and frequency
painless
cervix remains firm and closed
hormone responsible = P4 (form corpus luteum and placenta)
mifepristone
drugs which blocks P4 a and b
can be used to induce labour later on in pregnancy
(progesterone is normally a muscle relaxant)
factors that may determine gestation length
- parity
- age
- genetics-maternal and paternal
- race-ethnicity
activation
timing - 37-42 weeks
activation involves fetal genome
- uterine stretch-growth (twins earlier)
- fetal HPA axis
- membrane ruptures
- upregulation of myometrium
activation: up-regulation of myometrium in labour
increased PG receptors
increased oxytoxin receptors
increase in CAPS (gap junctions connexin 43)
contraction associated proteins
increase myometrial contractility
= actin myosin
increase myocyte excitability ion channels
= Ca2+ voltage, regulated
increase intercellular connectivity gap junctions
= connexin 43
PGs and labour
final stage of labour is an inflammatory event through PG
- potent inducer of labour
action of PG in labour
increase myometrial contractility
lead to cervix changes
associated with membrane rupture
cervical ripening
firm hard cervix gets remodelled by numerous cytokines causing extracellular matrix to breakdown and soften. leads to opening of the cervix
cervical ripening
firm hard cervix gets remodelled by numerous cytokines causing extracellular matrix to breakdown and soften. Leads to opening of the cervix
can happen preterm = infection
term = P4 decrease, E2 increase
membranes
amnion and chorion
- site of PG production
- rupture not essential for labour
- method of inducing labour
major changes to the uterus during parturition and success for labour
- increased coupling
- increased ion channels
- increased receptors
- decreased NO
causes
- increased conductivity and excitability
- decreased relaxation
=reinforcement of contractions
major changes to the cervix during parturition and success for labour
- increased inflammatory response
- increased collagenolysis
causes
- increased ripening
= dilatation
major changes to the fetal membranes during parturition and success for labour
- increased ECM degradation
causes
- decreased tissue integrity
= rupture
stages of labour
1st = until full dilatation (10cms)
2nd = full dilatation until birth of baby
3rd = from birth of baby until delivery of the placenta
partogram
graphical description of labour
- looks at progress of labour
- women having first baby have a slower labour than 2nd +
- time against cervical dilatation
1st stage of labour
contractions
cervical effacement and dilatation
descent of presenting part
intrauterine pressure increases (about 25mmHg pain felt)
CVS adaptation in neonate
- closure of foramen ovale
- 100% of right ventricle CO has to go through lungs therefore needs to be a rapid reduction in pulmonary vascular resistance (to allow blood to go through lungs)
- reduction-closure ductus aretiosus (pulmonary to aorta)
things needing to happen at birth
establishing continuous breathing
thermogenesis
intermittent nutrition
cardiovascular adaptations
involution
- placental seperation
- cleavage through decidua basalis
- contractions to prevent postpartum haemorrhage
- increased uterine sensitivity to oxytocin
P4 effect of labour
pregnancy hormones such as P4 put the brakes on myometrium
normal term labour
- inflammatory response
- multiple steps in a cascade
- requires interplay between fetoplacental unit and myometrium
