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
