labour Flashcards
define miscarriage
delivery of non-viable infant (usually within 13 weeks due to switchover of blood supply causing failed anchorage)
define term and when it happens
delivery of viable infant (usually 37-41 weeks with labour or elective Caesarean section)
define pre-term and when it happens
delivery of viable infant (usually 23-37 weeks, usually due to early labour or medically compromised so preterm emergency Caesarean section)
define labour and changes to tissue function
fundally dominant contractions (pushing from above) coupled with cervical ripening (cervix becomes soft and flexible) and effacement (cervix thins out and moves sideways)
2 other tissue changes which occur during labour
foetal membrane remodelling, lower segment relaxation
process of labour
cervical ripening and effacement -> co-ordinated myometrial contractions -> rupture of foetal membranes -> delivery of infant -> delivery of placenta -> contraction of uterus
3 labour stages (12-48 hours)
phase 1 (contractions and cervical changes over many hours) -> phase 2 (baby delivered over hours) -> phase 3 (placenta delivered over 30 minutes)
relative durations of consecutive labours
faster
what 4 things could initiate labour (relatively unknown)
oestrogens, low progesterone, CRH, oxytocin
preterm inducers of labour
intrauterine infection, intrauterine bleeding, multiple pregnancy, stress (maternal)
what happens during cervical ripening and effacement
change from rigid to flexible structure, remodelling (loss) of extracellular matrix, recruitment of leukocytes (neutrophils), inflammatory process and local (paracrine) change in IL-8
main inflammatory mediators of cervical ripening and effacement
prostaglandin E2, interleukin-8
what happens during co-ordinated myometrial contractions
fundal dominance, increased co-ordination of contractions, increased power of contractions, key mediators
Prostaglandin F2a (E2) levels increased from fetal membranes
Oxytocin receptor increased
Contraction associated proteins
main pro-inflammatory transcription factor in labour
NF-kB (drives itself forward by production of COX and ILs)
labour overview
many initiators -> NF-kB -> many genes which are mostly inflammatory, as well as oxytocin and prostaglandin receptors
supporting evidence for NF-kB
S50
causes of preterm labour
inflammatory changes e.g. infection
-
-
-
-
-
-
-
-
-
-
describe process of constitutive PGE2 synthesis to support prostaglandin induction of labour
following incubation of foetal membranes, baseline production of prostaglandins already high so couldn’t be increased any further
2 key drivers of term labour
PAF and CRH (upregulate inflammatory pathways in foetal membranes to initiate labour)
evidence for CRH as key driver for term labour
rises sharply in last few weeks of pregnancy, as do COX-2 enzymes (make prostaglandins)
platelet activating factor (PAF) location and how it is a foetal signal of maturity before labour
part of lung surfactant (proteins and complexes produced before birth by maturing lung - last organ to mature before birth), with levels in amniotic fluid increasing near term
what else can PAF and prostaglandins drive
IL-1B which further drives labour
describe hypothesis of parturition
CRH made in placenta -> stimulates cascades in foetal membranes, and goes through umbilical cord -> stimulates release of ACTH from foetal pituitary gland -> cortisol produced in foetal adrenal gland -> enters maternal circulation -> positve feedback up-regulating CRH production in female (-> prostaglandins); adrenal gland also produces steroids which mature lung -> lungs produce PAF (-> prostaglandins); adrenal gland also make precursors for oestrogens -> allow endometrium to contract
things that upregulate labour
S60
what is needed to sustain pregnancy
progesterone
S61, 62
inhibits NF-kB, so labour not inhibited as low progesterone receptor presence
progesterone receptor
S63
summary
S65
why must uterus contract at end of pregnancy
in uterus are remodel spiral arteries which provide lots of blood to placenta, however when placenta is delivered these are open into uterine cavity, and have lost lots of smooth muscle cells so can’t contract in normal way, so uterus must contract to ensure mother doesn’t bleed out
