Parturition: Normal birth Flashcards
What three factors influence labor?
Passage, power and passenger
Powers are the most important
What are the five challenges an physiological changes of human parturition?
Quiescence of the uterus growth and distension pressure
Timing for a safe birth
Activation of uterine musculature
Birth changes, fetal-neonatal changes
Involution of the mother, so haemostasis and establishing lactation
What are some anatomical changes in human pregnancy?
Uterus divides into upper (muscular) and lower segments
Cervical changes: ripening, softening, shortening then effacement
then membrane rupture
Facts about uterine quiescence
Poorly synchronised contractions, low amplitude and frequency called Braxton-Hicks
A firm and closed Cervix
Principle hormone involved is progesterone
What factors alter gestation length
Age and parity (larger=smaller)
Race (caucasian 40, african asian 39)
STRESS and associated cytokines
Timing, what is normal?
280 days post LP, 268 days post conception norally.
Epidemiologically 37-42 weeks (280)
What does activation involve?
How?
Activation has a positive feedback loop, which will eventually stimulate pregnancy. Modulated by progesterone.
Fetal genome, uterine stretch, fetal HPA axis, myometrial upregulation, melatonin and circadidan rhythms and abnorm sources such as membrane rupture
An increase in contraction associated proteins called CAPS. They are gap junctions, e.g connexin-43. Also prostaglandin and oxytocin receptors. Movement of quiescence to activation
What do CAPs do and what drugs can antagonise these effects?
- Increase myometrial contractility- Nifedipine
- Increase myocyte excitability , thus ion channels- block with B2 symathomimetics
- intercellular gap junctions- COX1 and COX2 antagonists
What is the link between prostaglandins and labor? (molecular level and functionally)
A decrease in progesterone, prostaglandin increase in uterus.
Phospholipases release arachidonic acid from cell membranes and decidua.
These are made into prostaglandins, prostacyclins and thromboxane. PGF dominates
Increase contractility; lead to cervical change; associated with membrane rupture
Role of oxytocin
In hospital use syntocinon.
Not essential for labour initiation
Needs gap junctions, and is used to augment labor.
Prevention of post partum haemorrhage
What is the model for cervical ripening/softening (normal)
Decrease in P, increase in E Interleukins and TNF-a now inside tissue These increase COX2 and iNOS COX2- PGE2 and iNOS to NO These cause a variety of things such as vacular permeability, apoptosis, MMP's ECM degradation
What are the membranes and how can these be altered to facilitate labor
Chorion and amnion. These produce PG.
Rupture not required for labour, but if it does happens at cervical part, zone of altered morphology.
Can perform amniotomy to help
What are three things are important for a successful labour? These three things good, birth plus mature fetus, timing etc
UTERUS: Reinforcement of contractions
CERVIX: Dilatation
MEMBRANES: Rupture
How can labour preparation be described at all three levels?
Uterus: Increase in coupling, ion channels, CAP’s. These lead to increased contractility, conductivity and less relaxation
Cervix: Inflammatry response causing ECM degradation and ripening
Membranes: ECM degradation and less tissue integrity leading to rupture
Stages of labour
1st- until full dilatation (10cms)
2nd- full dilatation until baby is birthed
3rd- baby birthed until the placenta is delivered
