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722 S P E C I A LT Y P R A C T I C E I N C R I T I C A L C A R E

BOX 26.5 Categories of severity of placenta BOX 26.7 Causes of post-partum
praevia haemorrhage characterised by the 4 ‘T’s

l Type I (low-lying placenta): The placenta is located in the Tone:
lower uterine segment but does not impede on the internal l uterine atony
cervical os. l functional or anatomical distortion of the uterus (e.g.
l Type II (marginal): The placenta edge is aligned with the bi-cornuate uterus)
internal cervical os. Tissue:
l Type III (partial): The placenta lies over and partially covers l retained placental products
the internal cervical os. l abnormal placenta
l Type IV (complete): The placenta is centrally located over
the cervix and completely covers it. Trauma:
l cervical and genital tract damage during delivery
l uterine inversion
BOX 26.6 Types of placenta accreta Thrombin:
l Coagulation disorders
l Placenta accreta: the placenta is abnormally adherent to
the uterine lining
l Placenta increta: the placenta invades the uterine muscle
(myometrium)
l Placenta percreta: the placenta grows through the myome- BOX 26.8 Can PPH be prevented?
trium and into adjacent structures, such as the bladder and The most significant intervention shown to reduce the inci-
ureters
dence of PPH is active management of the third stage of labour.
This represents a group of interventions including controlled
cord traction for placental delivery and prophylactic adminis-
condition, how much functioning placenta remains and
fetal wellbeing, and whether bleeding is ongoing. In tration of a uterotonic at delivery: drugs that cause the uterus
severe cases, the woman is usually taken to theatre for an to contract. Active management of the third stage is associated
emergency caesarean section. with a lower incidence of PPH and a reduced need for a blood
transfusion.
Placenta accreta is a serious complicating condition that
may occur in conjunction with placenta praevia. The
attachment of the placenta to the uterine wall is abnor-
mal and is considered morbidly adherent. There are three Postpartum Haemorrhage
levels of severity, although often all three are referred to Postpartum haemorrhage (PPH), a major cause of mater-
as placenta accreta (Box 26.6). Placenta accreta is strongly nal death in developed and developing countries, is
associated with prior caesarean section and a woman defined as ≥500 mL blood loss from the genital tract after
with an anterior placenta praevia and a prior caesarean the birth of the baby. The incidence and severity of PPH
section should be actively screened for placenta accreta is increasing, in both caesarean and vaginal births. 91,94-96
(by ultrasound or MRI) prior to any elective caesarean PPH rates commonly sit at around 10% of all births.
section. Placental tissue can be very invasive and may Severe PPH lacks an agreed definition, with published
infiltrate local structures like the bladder. Many women definitions ranging from ‘≥1000 mL’ to ‘estimated blood
with placenta accreta undergo emergency hysterectomy at loss ≥2500 mL or transfused ≥5 units of blood or received
the time of caesarean section, as a means to remove the treatment for coagulopathy during the acute event’. 12,97
placenta and control bleeding. An alternative manage- Consequently, the incidence of severe PPH varies depend-
ment is to deliver the baby by caesarean section and leave ing on how it has been defined and ranges from 3.7/1000
the placenta in situ. As long as a portion of the placenta deliveries to 4.6/1000 deliveries. 5,97 Additionally, PPH is
93
does not detach, there will be no bleeding and in most also classified according to the timing of the haemorrhage
cases, the placenta will autolyse and be re-absorbed by in relation to the birth. Primary PPH occurs within the
the woman. first 24 hours after birth whilst secondary PPH occurs
from 24 hours up to six weeks following birth. Primary
PPH is often caused by uterine atony, whilst secondary
Practice tip PPH is more likely to be associated with retained prod-
ucts and associated infection.
Read a woman’s operation report if she has a diagnosis of
placenta accreta to identify the extent to which the placental The causes of PPH are varied and have been classified by
tissue has invaded local structures, such as the bladder, ureters the four ‘Ts’: tone, tissue, trauma and thrombin (Box
and bowel. For example, the bladder is often affected and a 26.7). The cause of the PPH should be identified and
cystotomy may have been required to separate the placenta targeted with specific management, in conjunction with
from the bladder. the general principles of haemorrhage management. See
also Box 26.8.