Session 10 - Parturition Flashcards
What is Labour? (Aside from being the most awesomest political party ever!)
Expulsion of products of conception after 24 weeks.
So yeh. Actually sounds a bit more like UKIP.
What is a birth <24 weeks called?
Spontaneous aboriton
What is a birth <37 weeks called?
Pre-term
What is a birth between 37-42 weeks called?
Term
Give three different things you should assess about a babies position before labour
Lie
Presentation
Position
What is a babies lie?
- Relationship to long axis of uterus
- Normally longitudinal
- Fetus normally flexed
What is a babies presentation?
- Which part is adjacent to pelvic inlet
- Normally head (cephalic)
- Sometimes buttocks (podalic)
What is a babies position?
• Orientation of presenting part
What occurs in the first stage of labour? (2)
Creation of birth canal
Onset of labour -> Full cervical dilation
What are two main phases of the onset of labour?
Latent phase
Active phase
What occurs in the latent phase of the onset of labour?
Onset -> 4cm dilation
What occurs in the active phase of labour?
Faster rate of cervical change, 1-1.2 cm/hour
Regular uterine contractions
What is the main event of the second stage of labour?
Expulsion of foetus
What is the normal range of time for the second stage of labour?
Up to 1 hour
Outline what happens to the baby in the second stage of labour
- Head flexes as it reaches pelvic floor (reduces presentation diameter)
- Head rotates
- Head sretches vagina and perineum
- Head delivered
- Shoulders rotate and deliver
What occurs in the third stage of delivery?`
Expulsion of placenta
How does the body facilitate the expulsion of the placenta?
Sheared off by strong contractionas of the uterues
Compresses blod vessels to reduce haemorrhgage
Lasts between five and fifteen minutes
What processes are necessary to create a birth canal?
Expansion of soft tissues
Give three tissues which are expanded in creation of a birth canal
Cervix
Vagina
Perineum
What does expansion of the cervix cause
Foetal membranes to rupture, releasing amniotic fluid
How big is the expansion of the cervix, and what facilitates it?
10 cm
Structural changes and a lot of force
What is the normal diameter of a baby’s head?
9.5cm
What is maximum size of birth canal?
Pelvic inlet typically 11cm
What is the structure and funciton of cervix during pregnancy?
Tough, thick collagen which is coiled to give it strength in order to retain the foetus
What is the process of cervical softening called?
Cervical ripening
What three things does cervical ripening involve?
Reduction in collagen production (Turnover altered)
Increase in glycosaminoglycans (Disrupts the matrix)
Reduces aggregation of collagen fibres (Uncoils)
What is cervical ripening triggered by?
Prostaglandins
PG E2 and F2x
Locally diffused from the uterus
Once released the cervix is ready to be stretched
What happens to myometrium during pregnancy?
Smooth muscles greatly increased in pregnancy
How is force generated by myometrium?
By rises in intracellular Ca2+, which increases due to action potentials.
Triggered by spontaneous signals from pacemakers
What supresses uterine contractions during pregancy?
Progesterone
What maintains corpus luteum in pregancny?
HCG
Describe early uterine contractions
Low amplitude every 30 minutes, mother usually not aware
Describe late uterine contractions
Higher amplitude, less frequent
Braxton-Hicks contractions
What are the contractions of the uteryus made more forceful and frequent by? 2
Prostaglandins (as well as ripening the cervix). Causes increased Ca2+ per action potentional.
Oxytocin
More actionpotentials, threshold lowered
What are prostaglandins?
o Biologically active lipids
o Local hormones
o Produced mainly in the endometrium
What is production of prostaglandins controlled by?
Oestrogen: Progesterone ratio
What happens to prostglandin production when oestrogen > progesterone?
Increased prostaglandins
What happens to prostaglandins when oestrogen < progesterone
Low prostaglandins, feature throughout pregnancy
Where is oxytocin secreted?
Posterior pituitary
Outline the ferguson reflex
Mechanical stimulation of the cervix due to prostaglandin contractions increases oxytocin secretions, strengthening contractions, stimulating the cervix more, releasing more oxytocin
When is oxytocin more effective?
Oestrogen > Progesterone
More smooth muscle receptors
What is brachstasis?
Uterine smooth muscle relaxes less than it contracts.
o Unique feature of uterine smooth muscle
o Fibres shorten in the body of the uterus
o Drives the presenting part of the fetus to the cervix
Give the normal physiological processes which initiate labour? (8)
o ↑ Fetal Cortisol (?)
o Oestrogen > Progesterone
o ↑↑↑ Prostaglandins from Endometrium of Uterus
o Increased force of uterine contractions
o Cervix Stretched
o Oxytocin released from Posterior Pituitary under the Control of Hypothalamus
Ferguson Reflex
o Increased frequency of uterine contraction
o Cervix stretched more
What causes neonate to take first breath?
Multiple stimuli, such a trauma from the birth and cold cause the neonate to take its first breath
What are the two main change causing features of first breath
Reduction in pulmonary vascular resistance
Increased arterial pO2
What are the three features of a reduction in pulmonary vascular resistance?
Blood fills lungs, increased return to LA
Pressure in LA > RA
Foramen ovale closes
What does increased arterial pO2 cause?
Ductus Arteriosus contracts
How is condition of a neonate scored?
Apgar score
What limits maternal blood loss after birth?
Contraction of the unterus, which shears off and expels the placenta (normally after 10 minutes)
Why can bleeding after birth be severe?
Blood flow through placenta is normally 500-800ml/minute (10-15% cardiac output).
How can post-partum bleeding be treated?
Oxytocic drug
What is the most common presenation of a baby?
Most commonly the baby lies longitudinally, in a cephalic presentation, well flexed so that the vertex presents to the pelvic inlet`
What are the three P’s of labour, problems with which can cause a difficult birth?
Powers
Passage
Passenger
What are the powers of labour?
Delivery dependent on myometrium
Contraction and retraction of multidirectional smooth muscle fibres casues progressive shortening
In what three ways can uterine contractons be assesed?
Frequency, amplitude and duration
What is the passage made up of?
Pelvic inlet
Pelvic cavity
Pelvic outlet
What are the measurements of pelvic inlet?
Shorter in the anterior-posterior plane
10.5cm diameter
What are the measurements of pelvic cavity?
Circular
12cm diameter
What are the measurements of the plevic outlet?
o Pelvic Outlet
Shorter in the medio-lateral plane
11cm diameter
What is the passenger?
The size and presentation of the foetus
What are the main tree reasons labour is unable to progress?
o Inadequate Power Insufficient uterine contraction o Inadequate Passage Abnormal bony pelvis Rigid perineum o Abnormalities of the Passenger Fetus too big
How can labour be induced?
Labour can be induced by giving the mother Prostaglandins and Oxytocic drugs. These drugs will cause the cervix to begin to ripen and the uterus to begin its contractions.
How can the physiological state of the foetus be monitored?
During labour fetal heart rate can be assessed using a Fetal Scalp Electrode.
Describe a C-section
Subrapubic Incision
o Linea alba and anterior layers of the rectus sheaths are transected and resected superiorly,
o Rectus muscles are retracted laterall or divided through their tendinous parts allowing reattachment without muscle fibre injury
Give two methods of operative delivery?
Forceps
Vacuum extraction
