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Delivery of the Placenta:Physiology & Pathology

Dr/ mahmoud A. Abdel-Aleem

M.D Obst Gynecol, Assiut University

Importance of the subject

• Development of new thoughts about physiology of delivery of the placenta using new imaging modalities.

• Faults in delivery of the placenta exposes the mother to the risk of PPH which is a significant cause of maternal mortality in the developing countries.

This talk about this huge subject will be covered briefly in the coming 10 minutes under the following headings:

I- Physiology II- Pathology

• Normal Mechanism • Definition

• Role of Myometrium • Types

• Role of mediators. • Prophylaxis

• Sonographic study. • Management

• For example; in Egypt, in spite of the drop in maternal mortality ratio from 174/100000 live births in 1992 to 1993 to 80/100000 live births in the year 2000 (MOH 2000), PPH is still the leading cause and responsible for 34% of maternal deaths.

• Duration:

– No consensus. 20-120 minutes.

• US: too short; 20 minutes.

• NICE guidelines: 60 minutes

• Average time: 30 minutes; as there is no increased hemorrhage during this time period.

• Use of prophylactic oxytocic drugs decreased significantly the duration of 3rd stage (15.5 vs 8.8 minutes).

Graphic Representation of the duration of 3rd stage of labour

0

5

10

15

20

25

30

35

40

45

0-15 mins 15-30mins

30-45mins

45-60mins

> 60 mins

% retained placenta withactive management

% retained placenta withexpectant management

Postpartum Blood loss

Physiology of 3rd stage of labourBrandt Herman Krapp

Year 1933 1993 2000

Mechanism A uterine contraction is needed to cause detachment of the placenta from the

decidual bed.

Methodology Intraumbilical sodium iodine with subsequent

X-ray.

Real-time US examination

Gray scale and color Doppler sonography

Division 3 phases:Detachment.Descent.Expulsion

4 phases:Latent.Contraction.Detachment.Expulsion.

3 phases:Latent.-----------Detachment.Expulsion.

I- Role of myometrium

• Functionally, Myometrium is divided into 2 distinct portions (based on site of placental attachment):– Extraplacental myometrium:– Retroplacental myometrium:

• Retroplacental myometrium:– It represents the core for the separation of placenta from the decidual bed.4 different phases (Herman 1993):1. Latent phase : all myometrium contracts except retroplacental myometrium

(remain relaxed). 2. Contraction phase: contraction of retroplacental myometrium.3. Detachment phase: shearing of the placenta from decidual bed.4. Expulsion phase: placenta is expelled from the uterus by uterine contractions

Retroplacental Myometrium

Resting time Latent Phase Contraction/detachment

II- Role of mediators (NO)

• Both portions act differently during 3rd stage of labour due to secretion of nitric oxide (NO) that is produced by NO synthetase in the placenta and myometrium. It acts as a localized inhibitor.

• NO is rapidly metabolized after its formation and so its action is localized to the retroplacental myometrium.

• Real-time US and Doppler US show that:1. Length of 3rd stage is directly proportional to the length of latent phase.2. Failed placental separation is due to failed contraction of retroplacental

myometrium.

– Cases with dysfunctional labour have higher risks of retained placenta and more need for MROP even during CS.

– Blood flow through the myometrium doesn’t decrease leading to increased PP blood loss, increased blood loss during manual removal.

• Two main advantages of the use of color Doppler sonography in the third stage of labor.

1. More rapid diagnosis of placenta accreta enables us to minimize maternal blood loss by early manual removal and curettage.

2. Color Doppler sonography can be used for targeted curettage to avoid retained products of conception.

240s

265s

280s

“Prolonged 3rd stage of labour”

Retained Placenta

Pathology

A series of heterogeneous clinical conditions in which the clinician is confronted with a third stage which lasts more than 30 or 60 min, commonly described as ‘retained placenta’.

This includes:1. a retained already detached placenta (Trapped Placenta)2. An adherent placenta (Non-detached Placenta).3. Placenta accreta complex (accreta/increta/percreta).

Each type represents a different and distinct entity which requires a specific clinical approach. Each is associated with a different sonographic appearance.

• Retained placenta affects 0.6-3.3% of normal deliveries.

• Case fatality rate:

– UK: 0.0033 %.

– India: 9%.

– Nigeria: 3%

“Lack of facilities for manual removal of placenta”

“A woman with retained placenta has to go 100 miles to reach a hospital where she finds that no facilities do exist for MROP”

Risk Factors For Prolonged 3rd stageOdds ratio

Retained

Placenta

Separated

(Trapped)

Constriction

Ring

53%

Atonic

“failed detachment

phase”

Rupture

Uterus

“Rare”

Non-Separated

Adhesions

(adherens)

47%

Simple

Adhesions

Morbid adhesions (accreta)

1/2510

Increasing risk

Atonic

“failed contraction

phase”

ProphylaxisManagement of normal 3rd stage of labour

• Almost all studies concerned with the medicine of third stage use postpartum blood loss as the primary outcome either in prevention or treatment studies for PPH; this isn’t surprising because bleeding is the certainly important outcome.

• Prevention of retained placenta (or in other words) the need for manual removal of placenta may be sometimes included as a secondary outcome or not mentioned at all.

• Although the use of prophylactic oxytocics reduced the mean length of the third stage, they have no effect on need for manual removal i.e. there is no difference between expectant and active management of 3rd stage of labor in terms of retained placenta or the need for manual removal of placenta.

• Only one study has examined the effect of cord drainage on RP rates and this showed a marked decrease in the number of retained placentas in those who underwent cord drainage (RR 0.28, 95% CI 0.10–0.73).

Expectant management Active management

Components Allowing the natural physiological

process to promote normal separation

ofthe placenta

1- Administration of oxytocicagents at delivery of the anterior shoulder, 2- early clamping of the cord3- delivery of the placentaby controlled cord traction4- Fundal massage

Proponents 1- No increased risk for uterine inversion due to cord traction.2- No increased risk for retained placenta due to entrapment caused by uterotonic agents.3- No extra needs

Strong uterine contractions and leads to faster retraction, placental separation, and delivery, with a decrease in maternal blood loss and rate of postpartum hemorrhage.

Opponents 1- increased length of 3rd

stage.2- increased risk of PPH

1- requires medication.2- requires skilled attendant for injection and CCT.

Oxytocin Ergometrine PGE1 analogue“misoprostol”

Advantages 1- rapid onset of action 2-5 minutes (IM route).2- better safety profile.

1- Low price.2-Duration 2–4 hours.

1- oral or rectal.2- heat stable.

Disadvantages 1- More expensive than ergometrine2- Injections only3- Not heat stable

1- delayed onset (7 minutes) -IM route-.2- Causes tonic uterine contraction3- bad safety profile.4- Not heat stable

1- delayed onset of action.2-RCT failed to prove its superiority over oxytocin in prevention or treatment of PPH

Study Methodology Risk of retained placenta Prolonged 3rd stage >30 minutes

Bristol 1988 Active Vs Expectant management

No increased risk 6.42 (4.9-8.41)

Hinchingbrooke

1998

Active Vs Expectant management

No increased risk 4.9 (3.22-7.43)

Abdelaleem H et al 2010

Uterine massage Vs oxytocin vs combined methods

No increased risk No difference

Hofmyer G, 2008 Systematic review. Role of uterine massage in decreasing PPH

No cases were found in the retrieved trial

No cases were found in the retrieved trial

Ernest 2008 Prophylactic ergometrineVs oxytocin

No increased risk

Begley2008

Active Vs expectant No increased risk

Hora Soltani, 2005 Placental cord drainage after spontaneous vaginal delivery

Decreased risk (intervention bias)

Decreased length

• To determine the effectiveness of uterine massage after birth and before or after delivery of the placenta, or both, to reduce postpartum blood loss and associated morbidity and mortality.

• There were no cases of retained placenta in either group.

• We conducted an RCT addressing the value of uterine massage in the management of third stage of labour either alone or combined with oxytocin.

• A total of 1964 pregnant women were randomly allocated to 1 of 3 treatment groups.

• Uterine massage was less effective than oxytocin for reducing blood loss after delivery. When oxytocin was used, there was no additional benefit from uterine massage.

• There was no difference among the 3 study groups for the need for MROP.

• An RCT comparing the effect of prophylactic use of oxytocin and ergometrine in management of the third stage of labor.

• 600 women were assigned to receive either oxytocin or ergometrine in the third stage of labor.

• Results;– No difference as predelivery and potdelivery HCV– No difference as regards the risk of retained placenta.– More SE in the ergomterine group.

Treatment of Retained Placenta

• Unfortunately, there is lack of proper definition, classification of the research work concerning retained placenta.

• No mentioning of the subtype of retained placenta.

Placenta not delivered 30 minutes

1- Edge of the placenta is palpable through tight cervical os

2- Fundus small and contracted.

US: the myometrium is seen to be thickened all around the uterus and a clear demarcation is often seen between the

placenta and the myometrium

Trapped placenta

Tocolytics

“Nitrolgycerin”

Succeeded Failed

MROP

With no bleeding

US. Myometrium will be thickened in all areas except where the placenta is

attached where it will be very thin or even invisible

Adherent placenta

Systemic oxytocics

FailedSucceeded

Intraumbilical oxytocics

Succee

de

d

• To assess the effect of injecting an uterotonic agent in the umbilical vein during the third stage of labor in women with retained placentas.

• They concluded that intraumbilical injection of uterotonics is a noninvasive, effective, and clinically safe method of shortening the third stage of labor in women with retained placentas.

Papingas technique

• A direct solution for the retro-placental contractile failure in retained placenta is the direct delivery of an oxytocic to the retro-placental myometrium through the umbilical vein was first tried in the 1960s.

• It is now considered by the WHO as first line treatment for retained placenta

• Controversies about the optimal dose (10-100 units) and technique.

• Pipingas, using injections of radio-opaque dye into delivered placentas, demonstrated that solutions injected using this technique rarely reached the placental bed. He went on to show that the most effective technique is to inject 30 ml of solution down a infant naso-gastic tube which has been threaded down the umbilical vein.

• Success rate 92%

Pipingas technique

Role of tocolytics“Nitrolgylcerin”

• Recent Cochrane review published 19/01/2011 found that Sublingual nitroglycerin, given when oxytocin fails, seems to reduce both the need for manual removal of placenta and blood loss during the third stage of labour when compared to placebo.

• Authors recommends Further trials are needed to confirm its clinical role and safety.

• Its routine use cannot be recommended based on a single small study. There is no evidence available for other types of tocolytics.

Abdel-Aleem H, Abdel-Aleem MA, Shaaban OM. Tocolysis for management of retained placenta. Cochrane Database of Systematic Reviews 2011 , Issue 1 . Art. No.: CD007708. DOI: 10.1002/14651858.CD007708

Manual Removal of Placenta{MROP}

• An invasive procedure requiring:– Anesthesia– Skill– Aseptic technique.– Well-equipped hospital with possible blood transfusion.

• Timing:A nice survey conducted published In BJOG, 2008 among different European countries shows diversity in the timing of doing MROP.

Placenta Accreta

• Abnormal invasion.

• Degree of invasion.

• Main risk factor.

• Early diagnosis: role of Doppler study.

• Late diagnosis.

• Management.

Firstly, this find could indicate a new funerary practice of ancient Egyptians. If a woman died while giving birth to a child, her afterbirth might have been placed into her body cavity during the mummification process.Secondly, the preservation of the placentacould be evidence of a specific labour complication called placental retention, which involves an abnormally firm attachment of the placenta to the uterine wall.