Pregnancy Flashcards
(43 cards)
Conception
initial stage that allows for establishment of pregnancy.
After sperm has been deposited at the cervix, it I transported to uterus where it fertilise the ovum and implants in uterine stroma.
where must sperm travel for conception to occur
ampulla in fallopian tube
Changes sperm needs to undergo for conception to occur
Oxytocin: stimulates uterine contraction which, alongside sperm propulsive activity, aids in transporting sperm nd helping it travel.
Sperm undergoes capacitation in order to prevent oocyte. Capcitation: sperms tail changes from beat-like action to whip-like to help propel forward
Changes that occur are induced by removal of protein coat exposing acrosome enzymes.
Acrosome reactions allow penetration Zona pellucid
Zon pellucida and sperm interaction
Specific cell surface glycoprotein interacts with sperm and allow calcium to enter spermatozoa- increase in intracellular cAMP.
Acrosome swells and outer membrane fuses -> release of enzymes from acrosome into space surrounding head of sperm
Inner cell membrane of acrosome exposed and glycoprotein holds sperm near egg. Proteolytic enzymes released from acrosome then allow for penetration of Zona pellucida by sperm.
Changes following penetration of Zona pellucida
Penetration allows sperm and oocyte membranes to fuse.
Calcium enters oocytes
Changes in oocyte as result of increased calcium
- egg cell membrane depolarises to prevent polyspermy
- Cortical reaction occurs (cortical granules fuse with membrane and release contents into Zona pellucida)
- egg completes fine meiotic division
labour
physiological process by which a foetus is expelled from uterus to outside world
Braxton Hicks contractions
involuntary contractions of uterine smooth muscle.
Occur irregularly- not regarded as part of labour
initiation of labour
cervical ripening
myocetrial excitability
Oxytocin
Cervical ripening
softening of cervix.
Occurs in response to oestrogen, relaxin and prostaglandins.
Ripening involves
- reduction in collagen
- increase in glycosaminoglycans
- increase in hyaluronic acid-reduced aggregation of collagen fibres
Bishop score
assesses cervical ripeness
Myometrial excitability
Relative decrease in progesterone in relation to oestrogen
-facilitates increase in excitability of uterine musculature.
Progesterone typically inhibits contractions and oestrogen increases contractility.
Mechanical stretching of uterus also helps to increase contractility.
role of oxytocin in initiation of labour
invites uterine contractions.
~36 weeks gestation- increase in number of oxytocin receptors present within myometrium. Uterus begins to respond to pulsatile release of oxytocin from posterior pituitary gland
Oxytocin production increased by afferent impulses from cervix and vagina
stages of labour
First stage
- Latent
- Active
Second Stage
- Passive
- Active
Delivery
Third Stage
First stage of labour
Creation of birth canal.
Beginning ofd labour -> cervix fully dilated.
Contractions every 2-3 minutes
Foetal membranes rupture if they have not already.
Latent first stage of labour
slow cervical dilatation over several hours until cervix has reached 4cm dilatation
Active first stage of labour
Faster rate of cervical dilatation until 10cm is reached
Typical rate
- Nulliparous: 1cm per hour
- Multiparous: 2cm per hour
Should not last longer than 16 hours
second stage of lavbour
Full dilatation of cervix until foetus is fully expelled.
Uterine contractions expulsive and pushes foetus through birth canal
Passive 2nd stage of labour
Head of foetus reaches pelvic floor.
Women experiences desire to push.
Rotation and flexion of head are completed
Active 2nd stage of labour
Pressure of foetal head on pelvic floor results in urge to ‘bear down’
Women push in conjunction with contractions in order to expel foetus.
Typically
- 20 minutes in multiparous women
- 40 minutes in nulliparous women
- > 1hr: spontaneous delivery unlikely.
Hormones associated with contractions
Prostaglandins
- more intracellular calcium is released per AP, increasing force of contractions
Oxytocin: lowers threshold for APs, increasing frequency of contraction
Delivery of foetus
Once head of foetus reaches perineum, it extends in order to come up and out of pelvis.
Following delivery of head, rotes 90 degree to assist with delivery of shoulders.
Anterior shoulder delivers first, coming under pubic symphysis pubis while body flexes laterally and posteriorly to aid passage.
Body then flexes laterally and anteriorly to help deliver posterior shoulder. Rest of the body follows
Third stage of labour
Follows delivery and lasts until placenta has been delivered.
Uterine muscle fibres contract to compress blood vessels supplying placenta, which then shears away from uterine wall.
Contaction continues until placenta and membrane delivered.
Typically lasts;15 mintutes
Up to 500ml blood loss normal
Control of bleeding during 3rd stage of labour
Contraction of uterus constricts blood vessels in myometrium.
Pressure exerted on placental site once it has been delivered by walls of contracted uterus.
Normal blood clotting mechanism.
Induction of labour & methods
Process of initiation labour artificially.
Typically 40-42 weeks gestation
Vaginal Prostaglandins
amniotomy
membrane sweep