Pregnancy Flashcards
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
lactation
maternal physiological response where milk is secreted from mammary glands to feed the infant
breast changes during pregnancy
significant hypertrophy of the ductular-lobular-alveolar system. prominent lobules form and mid-gestation alveolar cells differentiate to be capable of milk production.
Little milk secretion due to high progesterone:oestrogen ratio which favour growth rather than secretion.
regulation of milk production
Primarily under control of prolactin
During pregnancy, high progesterone:oestrogen ratio favours development of alveoli but not secretion.
Delivery of placenta- source of circulating steroids (progesterone) is removed allowing alveoli to respond to prolactin.
Breast milk forms within 24-48 hours
prolactin
Polypeptide hormone
Secreted by anterior pituitary gland
Secretion is controlled by dopamine (prolactin inhibiting hormone) from the hypothalamus
Factors promoting secretion of prolactin reduce dopamine secretion in a negative feedback loop
Also produced by decidual cells
prolactin stimulation
promoted by suckling.
Neuro-endocrine reflex
Suckling mechanically stimulates receptors in the nipple and impulses pass up to the brain stem and to hypothalamus to reduce secretion of dopamine and increase vasoactive intestinal protein (promotes prolactin secretion)
Suckling at one feed promotes prolactin release, which causes production for the next feed. Accumulates in alveoli and ducts
Milk let-Down reflex
mechanical stimulation of nipple is responsible for milk delivery to infant and maintenance of lactation.
Milk is ejected by let-down reflex
In response to suckling, oxytocin is released from pituitary gland which stimulates myoepithelial cells that surround alveoli to contract -> squeezing milk out of breast.
maintaining milk production
sufficient suckling stimulation at each feed to maintain prolactin secretion and to remove accumulated milk
milk suppression
If suckling stops, milk production ceases gradually due to turgor induced damage to secretory cells and low prolactin levels
Can also be achieved via steroids
hyperprolactinaemia
elevated prolactin levels.
Can cause infertility, low sex drive and bone loss
Causes
- prolactinoma
- medicine induced (result of hypothyroidism)
- idiopathic
Treatment: dopamine-receptor agonists (bromocriptine/cabergoline)
endocrine maternal adaptions in pregnancy
Increased oestrogen & increased total T3 & T4
Increased progesterone
Increase in human placental lactogen, prolactin and cortisol levels.
Increase in lipolysis
cardiovascular maternal adaptations in pregnancy
increased progesterone levels
- decreases systemic vascular resistance
- decrease in diastolic BP in 1st & 2nd trimester
- Cardiac output increase by 30-50%
Activation of RAAS, leading to an increase in sodium levels and water retention
-Total blood volume increases
respiratory maternal adaptations in pregnancy
increased metabolic rates
- increased demand for oxygen
Tidal volume and minute ventilation rate increases.
May experience hyperventilation
- increased CO2 production and increased RR caused by progesterone.
- respiratory alkalosis with compensated increase in renal bicarbonate excretion
GI maternal adaptations in pregnancy
Upward displacement of stomach
- increase intra-gastric pressure
- predisposes to GI reflux
Increase in progesterone
- smooth muscle relaxation (decreases gut motility. can lead to constipation)
- relaxation of gallbladder (predisposes to gallstones0
Urinary maternal adaptations in pregnancy
Increased CO causes increase in renal plasma flow.
Increased GFR increases renal excretion
–> lower levels of urea & creatinine
Progesterone
- relaxation of ureter
- relaxation of muscles of bladder
- -> urinary stasis which predisposes to UTIs, commonly pyelonephritis
haematological maternal adaptations in pregnancy
increase in fibrinogen and clotting factors
Decrease in fibrinolysis
Increase in progesterone level (stasis of blood and ventilation)
Increase risk of thromboembolic disease
Plasma volume increases significantly. Red cell mass does not increases as much
- physiological dilution anaemia
Pregnancy anticoagulant of choice
LMWH
Warfarin can NOT be given as it is teratogenic and can cross placenta
Gestational diabetes mellitus
Compensatory increase in insulin levels does not occur resulting in high blood sugar levels.
GDM Diagnostic Criteria and Risk factors
Flasting plasma glucose: 5.6 and above
Two-hour plasma glucose: 7.8 or above
Risk Factors
- Age
- high BMI before pregnancy
- Family history of T2DM
- Snoking
Consequences of gestational diabetes mellitus
Unmanaged
-macrosomia (increased risk of shoulder dystocia)
Managed
- intrauterine growth retardation
