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Labour, delivery and birth

dilation of cervical canal

allows passage of foetus from uterus through vagina

Myometrial contractions in uterus must be strong enough to push baby out

During first two trimesters uterine muscle remains quiet

Inhibitory effects of high progesterone 

3rd trimester - Braxton - Hicks contractions

increasing strength and frquency 

may cause false labour

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End of Pregnancy

cervical softening/ripening

connective fibres have dissociated

caused by peptide hormone relaxin

relaxes pelvic bones

foetus shifts downwards(dropping)

baby orientated so head is down in contact with cervix

compare with breech birth

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Onset of labour

Coordinated uterine contractions

Increased frequency and discomfort

force foetus agaisnt cervix

baby pushes through birth canal

endocrine factors determine inset of labour -- placental clock

Contraction begins at top of uterus 

cervical stretch receptors - stimulate oxytoxin - more powerful contraction

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Stages of labour - membranes rupture (water breaks)

cervix dilates 10 cm for baby flows

If not the head - medical assistance may be required

Birth of the Baby - 2nd stage once cervical dilation is complete

Infant moves through cervix and vagina 

vaginal stretch receptors activate neural reflex

abdominal wall contracts in sync with uterus

Mother can assist in 'push'

Voluntary contraction of abdominal muscles

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Placenta delivery and Involution

caused by uterine contraction

Placenta separates from myometrium

the expelled through vagina 'AFTERBIRTH'

Shirtests stage is 15-30 mins after birth

constructs uterine vessels 

prevents heammorage

Involution - occurs after delivery

Uterus shrinks 

If material not dispelled it disintegrates 

results in vaginal discharge 

continous through 3-6 months 

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