6/21/2022
AIMS
describe the normal physiological mechanism of placental
separation, descent and expulsion, including factors that facilitate
haemostasis
• present evidence on the types, use and side-effects of uterotonic
drugs in active management of the third stage
• discuss the evidence relating to timing of clamping the umbilical
PHYSIOLOGY AND CARE DURING THE THIRD
cord, and controlled cord traction
STAGE
• describe the risk factors most commonly associated with PPH
OF LABOUR
and discuss the current evidence-based management strategies for
prevention and treatment
• discuss the midwife’s care of the mother and family unit, during
and immediately after separation and expulsion of the placenta
and membranes.
PHYSIOLOGICAL PROCESSES
The third stage can be defined as the period from the birth of the The midwife’s knowledge and evidence-based skills play a crucial
baby to complete expulsion of the placenta and membranes. role in ensuring that the care received by the woman works with,
It involves the development of the relationship between mother, not against, physiological processes.
baby and father, the separation, descent and expulsion of The placenta may shear off during the final expulsive contractions
the placenta and membranes, the control of haemorrhage accompanying the birth of the baby or remain adherent for
from the placenta site, and sometimes, the initiation of some time.
breast-feeding. The third stage usually lasts between 5 and 15 minutes, but
Although traditionally labour is divided into three distinct any period up to 1 hour may be considered normal.
component parts to aid comprehension, it should be viewed as one
continuous process.
1
, 6/21/2022
SEPARATION AND DESCENT OF THE PLACENTA
Mechanical factors As this occurs, the placenta becomes compressed and the blood
The unique characteristic of uterine muscle lies in its power of in the intervillous spaces is forced back into the spongy layer of
retraction. the decidua basalis.
During the second stage of labour, the uterine cavity Retraction of the oblique uterine muscle fibres exerts pressure on
progressively empties as the baby moves down, enabling the the blood vessels so that blood does not drain back into the
retraction process to accelerate. maternal system.
Thus, by the beginning of the third stage, the placental site has The vessels during this process become tense and congested.
already diminished in area by about 75% (Baldock and Dixon With the next contraction the distended veins burst and a small
2006). amount of blood seeps in between the thin septa of the
spongy layer and the placental surface, stripping it from its
attachment
As the surface area for placental attachment reduces, the relatively If separation begins centrally, a retroplacental clot is formed
non-elastic placenta begins to detach from the uterine wall. This further aids separation by exerting pressure at the midpoint
The majority of placentas are situated on the anterior or of placental attachment so that the increased weight helps to strip
posterior wall of the uterus, and separation usually starts from the adherent lateral borders and peel the membranes off the
the lower pole of the placenta and moves gradually upwards uterine wall so that the clot thus formed becomes enclosed in a
(Herman et al 2002). membranous bag as the placenta descends, fetal surface first.
Fundal placentas separate first at both poles, followed by the
fundal part.
The length of the third stage may be approximately 2 minutes
shorter when the placenta is located at the fundus (Altay et al
2007).
2
, 6/21/2022
This process of separation (first described by Schultze) is This process (first described by Matthews Duncan in the
associated with more complete shearing of both placenta and nineteenth century) takes longer and is associated with
membranes and less fluid blood ragged, incomplete expulsion of the membranes and a higher fluid
If the placenta begins to detach unevenly at one of its lateral blood loss
borders, the blood escapes so that separation is unaided by the Once separation has occurred the uterus contracts strongly, forcing
formation of a retroplacental clot. placenta and membranes to fall into the lower uterine segment and
The placenta descends, slipping sideways, maternal surface finally, into the vagina.
first.
3
, 6/21/2022
Haemostasis They are:
The normal volume of blood flow through the placental site is 1. Retraction of the oblique uterine muscle fibres in the
500–800 ml/min, but this is considerably reduced once the baby is upper uterine segment through which the tortuous blood vessels
born and the placental site on the uterine wall has diminished intertwine – the resultant thickening of the muscles exerts
(Baldock and Dixon 2006). pressure on the torn vessels, acting as clamps, and preventing
At placental separation, blood flow has to be arrested swiftly, or haemorrhage .
serious haemorrhage can occur. It is the absence of oblique fibres in the lower uterine segment that
The interplay of four factors within the normal physiological explains the greatly increased blood loss usually accompanying
processes that control bleeding are critical in minimizing placental separation in placenta praevia.
blood loss and preventing maternal morbidity or mortality. 2. The presence of vigorous uterine contraction following
separation – this brings the walls into apposition so that further
pressure is exerted on the placental site.
CARING FOR A WOMAN IN THE
THIRD STAGE OF LABOUR
3. The achievement of haemostasis – there is a transitory Midwives should ensure that, in order to facilitate informed
activation of the coagulation and fibrinolytic systems during, and decision-making by the woman, adequate time for deliberation and
immediately following, placental separation. questions is made available, where possible, during the course of
It is believed that this protective response is especially active at her routine antenatal consultations.
the placental site so that clot formation in the torn vessels is Information on types of uterotonics, explanation of their
intensified. different routes of administration, benefits, risks and side-
Following separation, the placental site is rapidly covered by a effects involved, and timing and method of placental birth
fibrin mesh utilizing 5–10% of circulating fibrinogen. or delivery should be given.
4. Breast-feeding – the release of oxytocin from the posterior The midwife’s care of the mother should be based on an
pituitary in response to skin-to-skin contact between mother and understanding of the normal physiological processes at work,
baby, and the baby’s nuzzling at the breast, causes uterine including having access to as much information as possible
contractions. about the woman’s pregnancy and labour history
4
AIMS
describe the normal physiological mechanism of placental
separation, descent and expulsion, including factors that facilitate
haemostasis
• present evidence on the types, use and side-effects of uterotonic
drugs in active management of the third stage
• discuss the evidence relating to timing of clamping the umbilical
PHYSIOLOGY AND CARE DURING THE THIRD
cord, and controlled cord traction
STAGE
• describe the risk factors most commonly associated with PPH
OF LABOUR
and discuss the current evidence-based management strategies for
prevention and treatment
• discuss the midwife’s care of the mother and family unit, during
and immediately after separation and expulsion of the placenta
and membranes.
PHYSIOLOGICAL PROCESSES
The third stage can be defined as the period from the birth of the The midwife’s knowledge and evidence-based skills play a crucial
baby to complete expulsion of the placenta and membranes. role in ensuring that the care received by the woman works with,
It involves the development of the relationship between mother, not against, physiological processes.
baby and father, the separation, descent and expulsion of The placenta may shear off during the final expulsive contractions
the placenta and membranes, the control of haemorrhage accompanying the birth of the baby or remain adherent for
from the placenta site, and sometimes, the initiation of some time.
breast-feeding. The third stage usually lasts between 5 and 15 minutes, but
Although traditionally labour is divided into three distinct any period up to 1 hour may be considered normal.
component parts to aid comprehension, it should be viewed as one
continuous process.
1
, 6/21/2022
SEPARATION AND DESCENT OF THE PLACENTA
Mechanical factors As this occurs, the placenta becomes compressed and the blood
The unique characteristic of uterine muscle lies in its power of in the intervillous spaces is forced back into the spongy layer of
retraction. the decidua basalis.
During the second stage of labour, the uterine cavity Retraction of the oblique uterine muscle fibres exerts pressure on
progressively empties as the baby moves down, enabling the the blood vessels so that blood does not drain back into the
retraction process to accelerate. maternal system.
Thus, by the beginning of the third stage, the placental site has The vessels during this process become tense and congested.
already diminished in area by about 75% (Baldock and Dixon With the next contraction the distended veins burst and a small
2006). amount of blood seeps in between the thin septa of the
spongy layer and the placental surface, stripping it from its
attachment
As the surface area for placental attachment reduces, the relatively If separation begins centrally, a retroplacental clot is formed
non-elastic placenta begins to detach from the uterine wall. This further aids separation by exerting pressure at the midpoint
The majority of placentas are situated on the anterior or of placental attachment so that the increased weight helps to strip
posterior wall of the uterus, and separation usually starts from the adherent lateral borders and peel the membranes off the
the lower pole of the placenta and moves gradually upwards uterine wall so that the clot thus formed becomes enclosed in a
(Herman et al 2002). membranous bag as the placenta descends, fetal surface first.
Fundal placentas separate first at both poles, followed by the
fundal part.
The length of the third stage may be approximately 2 minutes
shorter when the placenta is located at the fundus (Altay et al
2007).
2
, 6/21/2022
This process of separation (first described by Schultze) is This process (first described by Matthews Duncan in the
associated with more complete shearing of both placenta and nineteenth century) takes longer and is associated with
membranes and less fluid blood ragged, incomplete expulsion of the membranes and a higher fluid
If the placenta begins to detach unevenly at one of its lateral blood loss
borders, the blood escapes so that separation is unaided by the Once separation has occurred the uterus contracts strongly, forcing
formation of a retroplacental clot. placenta and membranes to fall into the lower uterine segment and
The placenta descends, slipping sideways, maternal surface finally, into the vagina.
first.
3
, 6/21/2022
Haemostasis They are:
The normal volume of blood flow through the placental site is 1. Retraction of the oblique uterine muscle fibres in the
500–800 ml/min, but this is considerably reduced once the baby is upper uterine segment through which the tortuous blood vessels
born and the placental site on the uterine wall has diminished intertwine – the resultant thickening of the muscles exerts
(Baldock and Dixon 2006). pressure on the torn vessels, acting as clamps, and preventing
At placental separation, blood flow has to be arrested swiftly, or haemorrhage .
serious haemorrhage can occur. It is the absence of oblique fibres in the lower uterine segment that
The interplay of four factors within the normal physiological explains the greatly increased blood loss usually accompanying
processes that control bleeding are critical in minimizing placental separation in placenta praevia.
blood loss and preventing maternal morbidity or mortality. 2. The presence of vigorous uterine contraction following
separation – this brings the walls into apposition so that further
pressure is exerted on the placental site.
CARING FOR A WOMAN IN THE
THIRD STAGE OF LABOUR
3. The achievement of haemostasis – there is a transitory Midwives should ensure that, in order to facilitate informed
activation of the coagulation and fibrinolytic systems during, and decision-making by the woman, adequate time for deliberation and
immediately following, placental separation. questions is made available, where possible, during the course of
It is believed that this protective response is especially active at her routine antenatal consultations.
the placental site so that clot formation in the torn vessels is Information on types of uterotonics, explanation of their
intensified. different routes of administration, benefits, risks and side-
Following separation, the placental site is rapidly covered by a effects involved, and timing and method of placental birth
fibrin mesh utilizing 5–10% of circulating fibrinogen. or delivery should be given.
4. Breast-feeding – the release of oxytocin from the posterior The midwife’s care of the mother should be based on an
pituitary in response to skin-to-skin contact between mother and understanding of the normal physiological processes at work,
baby, and the baby’s nuzzling at the breast, causes uterine including having access to as much information as possible
contractions. about the woman’s pregnancy and labour history
4
