3rd Stage of Labour Flashcards
What is the definition of 3rd stage of labour (NICE 2023)
The third stage of labour is the time from the birth of the baby to the expulsion of the placenta and membranes
What does retraction and contraction do?
Reduces the size of the uterus and the placental site and simultaneously thickens the uterine wall.
BY the beginning of the third stage what has happened to the placental site?
Has diminished in size by about 75%. This reduction in size continues after the birth of the baby’s trunk and causes the placenta to shear off.
What are the 3 phase of the removal of the placental?
Latent, Detachments, Expulsive.
What is the latent phase?
Delivery of infant until beginning of seperation-placenta free wall thickens (intermittent contractions), minimal thickening of uterine wall over placenta.
What is meant by detachment?
Period of placental separation and detachment from uterine wall, brought about by gradual thickening of the uterine wall over the site of the placental attachment. Myometrium thickens and reduces its surface area (lower edge off placenta). Leads to shearing off, of placenta in that area. Thickening of myometrium gradually rises to the entire placental area has sheared off (normally about 3 minutes).
What is meant by expulsion?
From complete separation to entire expulsion.
* Upper segment contracts strongly.
* Placenta forced to fold on itself.
* Descends into lower segment.
* Then into vagina.
* Gravity and maternal effort, from stimulation of vaginal floor, leads to expulsion of placenta and membranes
What do the umbilical veins carry?
Oxygenated blood from the placenta to the fetus
What do the umbilical arteries carry?
Nutrient depleted deoxygenated blood away from the fetus to the placenta
What is the intervillous space?
Part of the fetal-maternal interfere, where maternal blood enters to provide nutrients and gas exchange
What is the physiology between the separation of the placenta from the uterine wall?
Compression of the placenta causes maternal blood in the intervillous spaces* to be forced back into the spongy layer of the maternal uterine tissue (decidua)
- The vessels become congested and burst. A small amount of blood seeps between the vessels, the spongy layer and placental surface aiding separation. This blood begins the formation of a retroplacental clot.
What does the retraction of the oblique muscle fibres do?
Constrict the blood vessels so that blood does not drain back into the maternal system.
What are the 2 main ways a placenta separates?
Schultze method
Matthew Duncan method
What is the schultze method?
Separation starts in the centre of the placenta and this part descends first
* Retroplacental clot forms which aids separation
* Fetal surface appears first at the vulva with membranes trailing behind, the retroplacental clot is enclosed within the membranes
* Associated with less blood loss(quicker separation)
* Most common (80%
What is the Matthew Duncan method?
Separation at lower edge of placenta.
* Placenta slips down sideways, and the maternal surface appears at the vulva.
* Associated with longer duration, increased blood loss and ragged membranes.
* Less common (20%