3rd STAGE OF LABOUR
This is the period following delivery of the baby until expulsion of the placenta and membranes and includes control of bleeding. This process is concerned with separation and delivery of the placenta and membranes and the control of bleeding from the placental site. It is hazardous stage due to possibility of haemorrhage. A full bladder may impede normal processes of separation and descent and control of bleeding.
PHYSIOLOGY OF THE 3 STAGE OF LABOUR
Mechanism of placental separation Separation begins with the contraction which delivers the babies trunk and is completed with the next one or two contractions. As baby is delivered, there is a marked reduction in the size of the uterus due to powerful contraction and retraction that takes place. The placental site greatly diminishes in size.
When placental site is diminished by half, the placenta, being inelastic, becomes wrinkled and is shorn off the uterine wall. This happens because it is tightly compressed by the contracted uterus. Some foetal blood is pumped back into the baby’s circulation and maternal blood in the intervillous spaces is forced back into the veins in the deep spongy layer of the decidua basalis. The blood in these veins can’t return to the maternal circulation because of the contracted and retracted state of the myometrium.
The congested veins rupture and this small amount of extravasated blood shears off the villi from the spongy layer of the decidua basalis thereby separating the placenta.
Bleeding is controlled by the action of the interlacing spiral fibres which contract around the torn maternal vessels to prevent further blood loss. This process occurs very rapidly after the birth of the baby.
When separation is complete, the upper uterine segment contracts strongly forcing the placenta into the lower uterine segment and then into the vagina.
Detachment of the membranes begins in the 1 stage of labour when separation occurs around the internal os.
In 3rd stage of labour, complete separation of the membranes takes place assisted by the weight of the descending placenta, which peels them from the uterine wall.
There are two methods by which the placenta separates from the uterine wall:
SCHULTZE METHOD — in the majority of cases separation starts in the centre of the placenta and this part descends first. The foetal surface therefore appears at the vulva with the membranes trailing behind. The retroplacental clot is contained within the inverted sac, thus there is minimal blood loss.
MATTHEW DUNCAN METHOD — less commonly separation starts at the lower edge of the placenta. The placenta slips down sideways and maternal surface appears first at the vulva. This method of separation is usually accompanied by some bleeding per vaginum, since blood from placental site escapes immediately, thus a retroplacental clot does not form. This method results in slower separation of the placenta and bleeding is likely to be profuse.
CONTROL OF BLEEDING
Following separation of the placenta, bleeding from the large torn maternal sinuses in the placental site is controlled by:
1. Contraction and retraction of uterus, action of interlacing fibres constrict blood vessels running through the myometrium.
2. Pressure exerted on placental site by walls of the uterus becomes firmly contracted, with the walls in apposition, once placenta and membranes have been delivered.
3. The blood clots at the placental site, in the sinuses and torn blood vessels.
This allows placental separation to occur physiologically without the use of oxytocic drugs. Expulsion is achieved by maternal effort. Average length of 3 stage is 15-30 minutes.
DIVISION OF THE UMBILICAL CORD
Inch (1985) maintains the cord should be left unclamped which enables compaction and compression of placenta and retraction of muscle fibres to occur unhindered. Clamping the cord causes foetal blood to be trapped within the placenta which produces counterpressure which impedes the physiological process.
Squatting is effective for placental delivery as descent and expulsion are aided by gravity.
If woman breastfeeds her baby oxytocin is released and will assist the physiological process of placental separation and expulsion.
Must wait for signs of placental separation and descent. Watch for signs of relaxation of uterus and excessive blood loss. The longer the placenta remains within the uterine cavity the greater the possibility of bleeding.
SIGNS OF SEPARATION AND DESCENT OF PLACENTA
Sign of separation- a trickle of blood, as uterus contracts and retracts Signs of descent- uterus becomes smaller, narrower and rounder. Fundus rises in abdomen, is harder and more freely mobile, the cord lengthens.
Once separation and descent of the placenta have occurred the placenta can be expelled.
EXPULSION OF PLACENTA
Weight of placenta in vagina causes a sensation of pressure, encourage woman to bear down.