6.2 labour & puerperium? Flashcards
what is the definition of labour?
onset of regular uterine contractions that lead to cervical effacement & dilatation with concomitant descent of the presenting part of the foetus through the enlarged cervix
Uterus becomes more sensitive to _______ as term approaches (37 – 42 weeks) → sensitivity is determined by the degree of ____________ (increased with twins, polyhydramnios) & the ____________ ratio
oxytocin;
myometrial stretch;
oestrogen : progesterone
The foetus controls the initiation of parturition/labour via increased secretion of CRH & ACTH:
• Increased foetal serum cortisol levels produces two effects:
o Increased ______________ production → formation of ________________ on the uterine muscle cell membrane
o Decreased placental ______________→ initiation of contraction
• Contractions increase pressure on the cervix → mechanoreceptor signals to brain → triggers maternal oxytocin secretion → uterine smooth muscle secretions o \_\_\_\_\_\_\_\_\_\_\_\_\_ (positive feedback loop): increased cervical pressure causes greater release of oxytocin → increased contractions • After initiation of labour: cervical stretch & trauma to the decidua causes further release of \_\_\_\_\_\_\_\_\_\_\_\_ that augments the strength of contractions Note: denervation of uterus does not stop normal onset of labour (controlled by hormones)
placental oestrogen;
oxytocin receptors;
progesterone production;
Ferguson reflex ;
oxytocin & prostaglandins
what occurs during the 1st stage of labour and how long does it occur for?
- Less than 16h
- Onset of regular painful contractions leading to progressive dilatation of the cervix
what occurs during the 2nd stage of labour and how long does it occur for?
- 1h (primigravid); significantly shorter if multigravida
- Full dilatation of the cervix (10cm) to delivery of the foetus
what occurs during the 3rd stage of labour and how long does it occur for?
- 10 – 60 min
- Delivery of the foetus to delivery of the placenta
[1st stage of labour (latent phase)]
Cervix effaces & dilates slowly for the ______________ :
• Uterine contractions are initially relatively painless (occur at intervals of ______________ min) & do not distress the patient
• Contractions increase in frequency & intensity as labour progresses
• May take several hours in primiparous women
first 3cm;
5 – 10
[1st stage of labour (active phase)]
Commences when cervix is ______________ (rate of 0.5 – 1cm/h in nulliparous women; 2cm/h in multiparous women):
• 3 – 4 strong contractions every 10 min (1 contraction every __________) lasting ____________ → assessed by palpation of the uterus
• Foetal head descends further into the pelvis & ___________
• Contractions become increasingly painful & many women have the desire to push → assess cervix to determine full dilatation
3 – 4cm dilated;
3 – 4 min;
40 – 50s;
flexes
Foetal asphyxia: uterine contractions causes ______________
- Results in a ____________ in the 1 st stage that continues until full cervical dilatation –> accelerates once maternal bearing down (pushing) commences
- Very prolonged 2nd stage thus results in some degree of foetal asphyxia
- Management: auscultation of foetal heart (to determine changes suggestive of foetal hypoxia as acid base changes activates the ANS to cause altered foetal heart pattern) –> expedite 2nd stage via _______________
mild foetal hypoxia;
slow decline in foetal pH;
instrument delivery
[2nd stage of labour
After full cervical dilation, the foetus progresses through the maternal pelvis due to uterine contractions & maternal expulsive forces (increases intrauterine pressure to 100 – 120mmHg):
1. Foetal head engages into the pelvis in the ______________ position (transverse diameter of inlet > AP diameter)
- Head flexes → descends & _____________ → occiput lies anteriorly under the maternal pubic symphysis
• Crowning is the ___________________ → foetal parietal bones become visible - Maternal expulsive forces propels the foetal head → head extends & delivers (birth attendant applies gentle pressure on the head to maintain flexion)
occipito-transverse (OT);
internally rotates;
appearance of the foetal head at the perineum
Episiotomy: cut in the perineum to enlarge the vaginal introitus to allow easier delivery (performed under LA unless _________________ has already been given)
• As the foetal head delivers, the maternal perineal tissue stretches and may tear → involves the anal sphincter & rectum (causing faecal incontinence)
• ______________ is preferable to midline episiotomy
epidural analgesia;
Right mediolateral episiotomy
[3rd stage of labour]
The third stage of labour is characterised by placental delivery (takes 10 – 60 min), which is achieved by strong uterine contractions:
• Uterine contractions cause reduction of internal surface area by more than 50%
• Placenta has a fixed mass & cannot reduce surface area (adherent to uterine wall)
• Bleeding from the spiral arterioles is revealed → placental separation is apparent by a __________________
gush of blood & lengthening of the cord
Active management of 3rd stage: to prevent postpartum haemorrhage from prolonged physiological placental separation
• Offered to all women during childbirth
• Uterotonic drug: given following foetal delivery → causes _______________
• Controlled cord traction (_______________ technique): apply firm traction to umbilical cord with one hand & suprapubic counterpressure with the other (see right)
uterus to contract strongly (aids in separation);
Brandt-Andrews
how does rupture of membranes cause loss of foetal blood flow?
Reduced volume of amniotic fluid around the baby causes loss of the cushioning effect around the foetus:
• Uterine contractions exert direct pressure on the foetal head during descent → reduced cerebral blood flow
• Most commonly in the later part of the 1st stage of labour
how does direct cord pressure cause loss of foetal blood flow?
Compression of the cord leads to decreased flow to the foetus
The rise in intra-myometrial pressure during uterine contraction causes: 1. Trapping of large pool of oxygenated blood (~500ml) in the placenta (due to cutting off of the ___________________ while arterial blood flow continues)
2. Arterial blood flow ceases as intrauterine pressure continues to rise (≥30mmHg) → maternal part of placenta becomes a closed system
3. Foetal circulation continues extracting oxygen from trapped maternal blood → oxygen supply declines steadily with time
4. Pressure falls below 30mmHg as the contraction ends → blood flow resumes and oxygen-depleted blood drains from the _______________
5. Oxygen is only restored to the foetus ________________ → foetus needs to undergo anaerobic metabolism (causes small decline in foetal pH)
o Foetuses with ________________ (e.g. prematurity, growth restriction, maternal pre-eclampsia, placental abruption, hyperstimulation of the uterus) may be more compromised in labour
low-pressure venous drainage ;
intervillous space ;
~1 min after the contraction has worn off;
low metabolic reserve
Labour is monitored using a partogram (graphic display to assess overall progress in labour & changes in maternal & foetal parameters). What is being monitored constantly?
- Maternal details
- Maternal temperature, pulse and blood pressure
- Foetal heart rate
- Amniotic fluid colour
- Cervical dilatation
- Descent of foetal head (station)
- Drugs (including syntocin and epidural)
- Contraction rate
- Maternal urine output
Foetal monitoring entails the assessment of the foetal heart during labour to identify any changes that may suggest foetal hypoxia → urgent intervention if necessary:
• Frequency: _____________ (in 1st stage), __________________ (in 2nd stage)
• Method: Pinard stethoscope or US foetal heart rate monitor (for low risk women), continuous heart rate monitoring with cardiotocograph (for high risk women)
o Cardiotocograph monitors both _____________
every 15 min;
after every contraction;
foetal heart rate & uterine activity
The puerperium is the time during which anatomical, physiological, biochemical changes of pregnancy return to the non-pregnant state:
• Occurs after the ____________ until _____________
• Associated with maternal emotional & psychological changes
3rd stage of labour;
6 weeks postpartum
[Puerperium: Size of uterus]
Involutes from ~1kg at term to ~50 – 100g in puerperium because
• Oxytocin stimulates ______________ → breastfeeding is associated as it causes oxytocin release
• Decreased size of myometrial cells due to increased activity of
_________________
*Progress: level of __________(soon after birth) → fundus no longer palpable (by 10 – 14 days) → ~normal size (by 6 weeks)
• Uterus remains slightly enlarged due to permanent increase in number of cells & elastin in myometrium, vessels, connective tissues
uterine contractions (may be painful);
uterine collagenase & release of proteolytic enzymes;
umbilicus
[Puerperium: Return of menstruation]
Depends on whether the woman is lactating:
• Non-lactating: return of menses by ____________ & ovulation by____________
• Lactating: by 6 months (lactational amenorrhoea)
6 weeks;
90 days
[Puerperium: Placental site]
After delivery: contracts after placental separation in the decidual layer to 50% of its original area → occludes ______________ to reduce risk of PPH
• Placental bed is invaded by macrophages & other inflammatory cells, causing it to shed its superficial layers
By 7 – 10 days: re epithelialisation of uterine cavity (except for placental bed which does not fully regenerate until 6 weeks postpartum)
• _______________ are shed
• Lochia (uterine discharge): initially ___________ & becomes _______________ → lasts up to 8 weeks
o Lochia remaining red for >10 days is suggestive of improper placental site involution
spiral arterioles;
Trophoblast & decidua;
blood-tinged;
serous and pale
[Puerperium: Cervix involution]
• Immediately after delivery: ______________
• By 1 week: involution to ___________
• By 14 days: internal os has closed, external os is a ___________
enlarged & haemorrhagic;
1cm diameter;
transverse slit
[Puerperium: vaginal involution]
• By end of 1st week: rapid healing of perineum
• By end of 3rd week: regains _____________
• _____________ are the torn hymnal remnants
tone & rugal pattern;
Carunculae myritiformis
[Puerperium: pelvic floor muscles ]
Tone is gradually restored to the voluntary muscles of the pelvic floor:
• Any residual laxity predisposes to __________________
pelvic organ prolapse
In the puerperium, there may be trauma to the urinary tract & diuresis:
• Trauma: _____________ of the bladder base (if labour is prolonged, baby is large, instrumental delivery is performed) → _____________ → difficulty voiding
o Ensure bladder is not over-distended (aggravates damage)
• Diuresis: significant fluid shift (from ___________ to _________-) in the first few days after birth
o Ureters can remain dilated up to 3 months after pregnancy
oedema & bruising;
detrusor denervation;
extracellular space to intravascular component
how does coagulation change during puerperium?
During pregnancy: increase in clotting factors I, II, VII, VIII, IX, X
• After placental separation: clotting factors & platelets are consumed at the placental site
• During puerperium: increased risk of DVT/PE (worse
how does Red cell volume change during puerperium?
decreases by ~14% during delivery & resolves by 8 weeks postpartum
how does white cell volume change during puerperium?
increases in labour (usually neutrophils)
how does plasma cell volume change during puerperium?
may increase in the 1st 3 days postpartum (due to fluid shifts into the intravascular compartment) & resolves by the end of puerperium
how does CO change during puerperium?
remains elevated with stroke volume in the 1st hour & completely resolves by 6 weeks
how does bp change during puerperium?
returns to normal early in puerperium
Progesterone induces reduced gut motility during pregnancy:
• Constipation may be common in the 1st few days postpartum if the mother is __________________
dehydrated and has low oral intake
how does hCS/ hPL levels change during puerperium?
Undetectable levels by day 1 postpartum
how does hCG levels change during puerperium?
Levels of <100 by day 7 postpartum (half-life 9h)
how does progesterone levels change during puerperium?
Below luteal levels by day 3 postpartum
how does prolactin levels change during puerperium?
Gradual rise during pregnancy:
• Non-lactating women: gradual decline over 2 weeks
• Lactating women: increases due to nipple stimulation during breastfeeding → produces anti-gonadotrophic effect at the pituitary level → disturbances in LH release
how does TSH levels change during puerperium?
Very low in the 1st 2 weeks and gradually increases thereafter
