Physiology of Labour Flashcards
Uterotropins (function and 4 examples)
Set the stage for contractions and cervical change (ripen the cervix)
Ex: estrogen, relaxin, Ca dependent phospholipases, arachidonic acid (to make prostaglandins)
What hormone counteracts uterotropins?
Progesterone
Maintains uterine quiescence
Decreased progesterone is involved in cervical ripening
Uterotonins (function and 3 examples)
Directly involved in contraction of myometrial smooth muscle cells
Increase intracellular Ca in myometrium
Ex: oxytocin, prostaglandins (PGF2a), endothelin 1
Do we know what initiates parturition in humans?
Nope!
Where are prostaglandins produced?
Interface of the amnion/chorion and myometrium
Does progesterone activate or inhibit prostaglandin production?
Inhibit
Increases progesterone increases the amount of prostaglandin dehydrogenase
PGE2 function
Cervical effacement
Highest levels of PGE2 are in amniotic fluid just below the presenting forewaters
Cause the breakdown of the rigid structure of collagen fibers (unwinds the fibers)
Softens the ECM
How is PGF2a produced? What is its function?
The thinning of lower uterine segment during active labour causes an inflammatory response, which results in the release of arachidonic acid
This process is also stimulated by oxytocin
PGF2a causes an increase in intracellular Ca (and contraction)
Oxytocin receptors
- When do they increase
- What are they increased by
- What are they down regulated by
- Near term
- Estradiol
- Progesterone
What does oxytocin do?
Increases the amount of intracellular Ca, which helps with contraction
How are gap junctions in the myometrium affected by
- Estradiol
- Progesterone
- Increased
2. Decreased
5 ways to induce labour
Amniotomy (artificially rupture the membranes) Membrane sweeping Prostaglandins Foley catheter in cervix Oxytocin
3 meds to give to prevent labour
NSAIDs (but only for 2 days because dont want to close PDA)
Progesterone
Ca channel blockers
Definition of labour
Progressive cervical dilation, effacement, or both, resulting from regular uterine contractions every 5 mins lasting 30-60s
First stage of delivery
Onset of involuntary painful regular contractions to full dilation
Has latent and active phase
Latent phase
Onset of regular painful contractions every 5 mins lasting 30-60 s
Cervix is less than 3 cm dilated
Extremely variable duration
Active phase
Regular painful contractions every 2-3 mins lasting 45-60s
Cervix 3-4cm to fully dilated
A bit faster in women who had more than one pregnancy
Second stage of delivery
Full cervical dilation to the delivery of fetus
Maternal pushing increases forces directing fetus downwards and outwards
Third stage of delivery
Delivery of baby to delivery of placenta
Can take 0-30 mins (most deliver by 15 mins)
4 signs of placental separation
Gush of blood
Lengthening of cord
Fundus rises up
Uterus becomes firm and globular
3 ways to reduce the risk of postpartum hemorrhage in the third stage
Give uterotonics with delivery (oxytocin, misoprostol)
Gentle, controlled cord traction
Maybe early cord clamping
Fourth stage
The 1-1.5 hours after the delivery of placenta Bleeding slows Uterus remains contracted Maternal stabilization and bonding First attempt at breastfeeding
Puerperium phase
6 weeks following delivery
Most physiological changes return to non-pregnant state
Uterine bleeding stops by contraction of muscle around vessels and thrombus formation
Involution of uterus (gradual)
Cervix lengthens
Diuresis of increased circulatory volume
How does milk produced after the delivery of the placenta?
Delivery of placenta
Decrease in the amount of estrogen and progesterone
Increase in prolactin from anterior pituitary
Milk production
Suckling stimulates what hormone?
Oxytocin
Causes myoepithelial cells around alveoli in breast glands contract
Milk ejected
A decrease in what hormone causes menses to resume?
Prolactin
