Parturition Flashcards
(27 cards)
What is the Estimated Date of Delivery?
40 weeks from the first day of Last Menstrual Period
When is pre-term and post-term?
Pre-term is before 37 weeks
Post-term is beyond 42 weeks
How can the first trimester ultrasound be used to date pregnancy?
Measurement of gestational sac volume and crown-rump length
What is the ultrasound in the second trimester for?
Anomalies and growth
How is the pregnancy state maintained i.e. labour prevented?
Gap junctions down regulated
Oxytocin receptors down regulated
Cervix composed of collagen and ground substance (fibrous)
Low level of prostaglandin biosynthesis
What causes initiation of labour?
Increased oestrogen towards the end of pregnancy causes uterine contractions
Increased prostaglandin production
Increase cytosol-free calcium (for contraction)
Oxytocin is released from pituitary
What is the Ferguson reflex?
The pressure of the foetus pushing down the the pelvic floor stimulates the posterior pituitary to release oxytocin
What occurs during cervical ripening?
Prostaglandin synthesis increases
Increased water content of glycoamioglycan matrix
Myometrial activity causes ‘effacement’ and thinning of cervix
Relaxin upregulates matrix matalloproteinases that breakdown collagen
What are Braxton hicks contractions?
Uncoordinated, non painful contractions
What does primiparous mean?
First birth
What happens in the first stage of labour?
Onset of regular contractions –> fully dilated cervix
What happens in the latent phase of stage 1 of labour?
Onset of painful contractions (5-10 minute intervals)
Cervical ripening and effacement
Cervix slowly dilates up to 3-4cm
What happens during the active phase of stage 1 of labour?
Cervix dilates 0.5-1cm per hour
Increase in frequency and strength of contractions
Presenting part descends
Rupture of membranes
What happens in the second stage of labour?
Cervix fully dilated (10cm) Contractions stronger and every 2-5 minutes Presenting part descends Women has an urge to bear down Ferguson reflex occurs Delivery
What happens in the third stage of labour?
Expulsion of the placenta and membranes
Normally takes 5 minutes
What causes separation of placenta from endometrium?
Forceful uterine contraction cuts of placental bed which reduces bleeding
Where are prostaglandins released from?
Uterine decidual cells
What is the function of prostaglandins?
Stimulate uterine contractions
Soften, thin and dilate cervix
Potentiate contractions induced by oxytocin
Increase number of gap junctions
What is the function of oxytocin?
Triggers phospholipase C cascade resulting in release of Ca2+ from SR stores in uterine smooth muscle –> causing contraction
Stimulates PGF2a production
Constricts uterine blood vessels at site of placenta
Foetal oxytocin induces labour
Where is relaxin produced?
CL, placenta, decidua
What is the role of relaxin in labour?
Increases right before labour Softens ligaments (via collagen metabolism) and helps cervix dilate
How may mechanical stretch affect labour?
Stretch of uterus by foetus may stimulate uterine contractions via a smooth muscle stretch reflex
Explain the positive feedback in uterine contractions
Uterine contractions stimulate prostaglandin release which increases intensity of uterine contractions
Uterine contractions stretch the cervix which stimulates oxytocin release and further uterine contractions
What are the 4 stages of delivery?
Engagement and flexion of the head
Internal rotation
Delivery by extension of head - nose scrapes blanket
Delivery of shoulders
