Labour + Birth Flashcards
(45 cards)
What is labour?
The process by which the fetus + its supporting placenta and membranes pass from the uterus to the outside world
Three key processes in labour
- Regular high intensity contractions
- Softening + dilatation of the cervix
- Rupture of the fetal membranes
Timing of labour:
- miscarriage
- premature
- term
- miscarriage: <22 weeks
- premature: <37 weeks
- term labour: 37 weeks +
Timing of a miscarriage
Before 22 weeks
When is baby deemed premature?
Before 37 weeks
What is classified as term labour?
37 weeks +
What are the stages on labour?
- first stage: from the onset of regular uterine contractions until cervix is fully dilated 10cm
- second stage: from full dilatation until birth of fetus
- thirst stage: from birth of fetus until delivery of placenta + membranes
How is the birth canal created?
- softening of the pelvic ligaments
- increase in myometrial activity > contractions
- cervical dilatation + effacement
First stage of labour
From the onset of regular uterine contractions until cervix is full dilated
Second stage labour
From full dilatation until fetus is born
Third stage of labour
From birth of fetus until delivery of placenta + membranes
What is cervical ripening triggered by?
Prostaglandins
E2 + F2a
What is cervical ripening?
- marked reduction in collagen
- marked increase in glycoaminoglycans
- these both decease the aggregation of collagen fibres
- collagen bundles loosen
- influx of inflammatory cells + increase NO output
Movements of baby in labour
Engagement
Descent
Flexion
Internal rotation
Extension
External rotation (restitution)
Anterior shoulder delivery
Posteior shoulder delivery
What happens to the myometrium in pregnancy?
- becomes thicker
- due to increased cell size x10
- glycogen deposition
What hormones are involved in increases frequency + force of contractions inducing labour?
Prostaglandins
Oxytocin
Contractions in early pregnancy
Occur ~30 mins
Low amplitude
What are Braxton-Hicks contractions?
- Noticeable contractions later on in pregnancy
- Reduced frequency but increased amplitude
How do prostaglandins implement the change in contractions starting labour?
Enhancing release of calcium from intracellular stores > produces action potential
How do oxytocin implement the change in contractions starting labour?
Lowers threshold for triggering AP
Where is oxytocin secreted from?
Posterior pituitary gland
What is the Ferguson Reflux?
- brain stimulates posterior pituitary to release oxytocin
- causes smooth muscle lining of uterus to contract
- baby pushes against cervix > stretch
- stretching causes nerve implases to be sent to brain
- process repeats
What is brachystasis?
Myometrial cells contract and shorten, but do not regain their original length upon relaxation > shortness uterus progressively
What is effacement of the cervix?
Thinning of cervix
