Third stage of labour, PPH

Define third stage of labour

The period from birth of the baby until complete expulsion of the placenta and membranes, along with control of bleeding.

What else occurs during third stage?

Skin-to-skin contact and initiation of breastfeeding.

Main aim of third stage management

Prevent postpartum haemorrhage (PPH).

Why is preventing PPH important?

PPH is associated with significant maternal morbidity and mortality globally.

Typical time for placental separation and expulsion

5-15 minutes, but may take up to 1 hour.

What is uterine retraction?

Shortening and thickening of uterine smooth muscle that remains partially contracted after contractions.

Which part of the uterus retracts in third stage?

Upper uterine segment (fundus).

Why is retraction important in third stage?

Compresses vessels and reduces blood flow to placental attachment site.

What happens to the placenta during uterine retraction?

Placenta becomes compressed and separates from the uterine wall.

How does placental separation occur?

Retraction compresses placenta → blood enters decidua basalis → vessels rupture → placenta peels away.

What happens to spiral arteries during separation?

They are compressed/clamped off.

What stops maternal blood returning through placental circulation?

Placental compression and vascular closure.

What is autotransfusion?

Blood from intervillous spaces is pushed back into maternal circulation during uterine contraction.

What are living ligatures?

Retracted myometrial muscle fibres that constrict uterine blood vessels.

Why are living ligatures important?

They mechanically reduce maternal blood loss.

What happens if retraction is inadequate?

Bleeding continues and placenta may separate poorly.

What allows coordinated contraction of myometrium?

Gap junctions between myometrial cells.

Function of gap junctions

Allow calcium movement and synchronised contraction.

Why can smooth muscle stretch more than skeletal muscle?

Spindle-shaped fibres arranged in a lattice pattern.

What stimulates uterine muscle contraction?

Oxytocin binding to myometrial receptors.

What intracellular process causes contraction?

Oxytocin → calcium release → actin-myosin interaction → muscle shortening.

What is haemostasis?

The process of stopping bleeding and maintaining blood vessel integrity.

Three mechanisms involved in haemostasis

Vasoconstriction, platelet plug formation, coagulation.

What percentage of circulating fibrinogen is activated at placental site?

Approximately 10%.

Why is fibrin important?

Forms mesh/scaffold for clot stabilisation.

What activates coagulation in third stage?

Exposure of damaged uterine vessels.

What is the endpoint of coagulation?

Formation of fibrin.

What converts fibrinogen to fibrin?

Thrombin.

What activates prothrombin?

Factor X.

What does thrombin amplify?

Production of clotting factors V, VIII and XIII and platelet activation.

How quickly can clot formation occur?

As fast as ~15 seconds.

Why are pregnant women naturally more prepared for clotting?

Oestrogen and progesterone increase fibrinogen production.

Why is hypercoagulability beneficial in labour?

Reduces blood loss after placental separation.

Source of oxytocin

Posterior pituitary gland.

Role of oxytocin in third stage

Strengthens uterine contractions and promotes uterine involution.

What stimulates further oxytocin release after birth?

Skin-to-skin contact and breastfeeding.

Why does breastfeeding reduce PPH risk?

Oxytocin causes uterine contraction and reduces bleeding.

What is involution?

Return of the uterus to pre-pregnancy size and shape.

What is delayed cord clamping?

Waiting before clamping/cutting the umbilical cord after birth.

Why delay cord clamping?

Allows transfer of fetal blood and iron to newborn.

Benefits of delayed cord clamping

Reduced neonatal anaemia, Reduced hypovolaemia, Improved iron stores

How long is delayed cord clamping commonly recommended?

Around 1-3 minutes.

When is the cord usually ready for clamping?

When pulsation ceases and cord becomes white/flaccid.

Approximate blood volume remaining in cord and villi

~80 mL.

What is physiological (expectant) third stage management?

Supporting normal physiology without routine interventions.

Features of physiological management

Skin-to-skin, Quiet environment, Semi-upright positioning, Maternal effort to birth placenta, Hands-off approach

Why may upright positioning assist placental birth?

Gravity supports placental descent.

What are the components of active management?

Uterotonic + controlled cord traction.

What is a uterotonic?

Medication that stimulates uterine contraction.

When is uterotonic usually administered?

After birth of baby, before cord cutting.

What is controlled cord traction (CCT)?

Gentle traction on cord with uterine support to assist placental expulsion.

Why guard the uterus during CCT?

To reduce risk of uterine inversion.

Schultze method for Placental Expulsion

Placenta delivered fetal side first.

Duncan method for Placental Expulsion

Placenta delivered maternal side first.

Why inspect placenta and membranes?

To confirm completeness and reduce retained tissue risk.

What is retained placenta?

Placenta not expelled within expected timeframe.

Why is retained tissue dangerous?

Prevents uterine contraction and increases bleeding risk.

Why can retained fragments cause ongoing bleeding?

Open vascular bed remains exposed.

Complications of retained tissue

Haemorrhage and infection., Postpartum Haemorrhage (PPH)

Define primary PPH

Blood loss >500 mL within first 24 hours after birth; Mild PPH = 500 mL-1 L, Severe PPH = 1000 mL.

Define secondary PPH

Excessive bleeding occurring 24 hours to 12 weeks postpartum.

Common timing of secondary PPH

Around 10-14 days postpartum.

Best indicator of maternal compromise

Woman's clinical condition, not blood loss volume alone.

Risk factors for PPH

Prolonged first stage, Prolonged second stage, Prolonged active third stage (>30 min), Arrest of descent, Episiotomy, Lacerations, Assisted birth, Use of oxytocics

Why does prolonged labour increase PPH risk?

Uterine muscle fatigue reduces effective contraction and retraction.

Why does prolonged third stage increase PPH risk?

Delayed placental separation and continued bleeding from placental site.

What are the four T's of PPH?

Tone → Trauma → Tissue → Thrombin

Most common cause of PPH

Tone (uterine atony).

What is uterine atony?

Failure of the uterus to contract adequately after birth.

Why does uterine atony cause PPH?

Blood vessels at the placental site are not compressed effectively.

First management step for uterine atony

Fundal massage.

Why perform fundal massage?

To stimulate uterine contraction and expel clots.

Other initial actions for uterine atony

Empty bladder, Oxytocic medication, Bimanual compression (if required)

What is a uterotonic/oxytocic?

Medication that stimulates uterine contraction.

Examples of oxytocics

Syntocinon (oxytocin), Syntometrine, Ergometrine, Carboprost, Misoprostol

Why are oxytocics used in PPH?

To increase uterine tone and reduce bleeding.

Why may ergometrine be contraindicated?

Hypertension.

Maximum carboprost dosing mentioned

250 mcg × maximum 8 doses.

What is bimanual compression?

One hand compresses the uterus externally while the other compresses internally via the vagina.

Purpose of bimanual compression

Temporarily reduce bleeding by compressing uterine vessels.

When is bimanual compression usually considered?

If bleeding continues despite initial measures

What causes trauma-related PPH?

Vaginal lacerations, Cervical tears, Perineal tears, Episiotomy, Uterine inversion, Uterine rupture, Vulval haematoma

Why does trauma cause PPH?

Bleeding occurs from damaged genital tract vessels despite a contracted uterus.

What is uterine rupture?

A tear through the uterine wall.

Common association with uterine rupture

Previous uterine surgery.

Signs of uterine rupture

Sudden fetal heart rate change (bradycardia), Excessive vaginal bleeding, Abdominal tenderness, Maternal tachycardia, Shock out of proportion to visible blood loss

Why is uterine rupture clinically dangerous?

Can cause severe maternal and fetal compromise.

What is tissue-related PPH?

Bleeding caused by retained placental tissue or membranes.

Examples of tissue causes

Retained placenta, Retained placental fragments, Placenta accreta, Placenta increta, Placenta percreta

Retained placenta definition

Placenta not delivered within expected timeframe (often >30 minutes after active management).

Why does retained tissue cause bleeding?

Prevents adequate uterine retraction and vessel compression.

Placenta accreta

Placenta attaches too deeply into myometrium.

Placenta increta

Placenta invades into the myometrium.

Placenta percreta

Placenta penetrates through the uterine wall.

Why do invasive placentas increase PPH risk?

Normal separation cannot occur.

What is thrombin-related PPH?

Bleeding caused by impaired clotting.

Examples of pre-existing conditions

ITP, von Willebrand disease

Obstetric conditions associated with coagulopathy

Hypertensive disorders, HELLP syndrome, Abruption, Sepsis, Fetal demise

Why does coagulopathy cause PPH?

Blood vessels cannot form stable clots.