Placenta_Accreta_Flashcards
What is placenta accreta?
Placenta accreta describes the attachment of the placenta to the myometrium due to a defective decidua basalis.
What causes placenta accreta?
Placenta accreta is caused by a defective decidua basalis.
What is the primary risk associated with placenta accreta during labour?
The primary risk associated with placenta accreta during labour is postpartum haemorrhage.
What are the risk factors for placenta accreta?
Risk factors for placenta accreta include previous caesarean section and placenta praevia.
What are the three different types of placenta accreta?
The three different types of placenta accreta are accreta, increta, and percreta.
What characterizes placenta accreta?
Placenta accreta is characterized by chorionic villi attaching to the myometrium rather than being restricted within the decidua basalis.
What characterizes placenta increta?
Placenta increta is characterized by chorionic villi invading into the myometrium.
What characterizes placenta percreta?
Placenta percreta is characterized by chorionic villi invading through the perimetrium.
summarise placenta accreta
Placenta accreta
Placenta accreta describes the attachment of the placenta to the myometrium, due to a defective decidua basalis. As the placenta does not properly separate during labour there is a risk of postpartum haemorrhage.
Risk factors
previous caesarean section
placenta praevia
Strictly speaking, there are 3 different types of placenta accreta, depending on the degree of invasion although this is quite small print:
accreta: chorionic villi attach to the myometrium, rather than being restricted within the decidua basalis
increta: chorionic villi invade into the myometrium
percreta: chorionic villi invade through the perimetrium
A 27-year-old G2P1 woman presents to the emergency department in the second stage of labour. On examination, the foetal head is visible at the vaginal introitus. Her past medical history is significant only for a previous elective lower-segment Caesarean section.
Antenatal imaging suggested an invasion of the chorionic villi into the myometrium but not the perimetrium.
After the foetus is delivered, the patient develops a post-partum haemorrhage.
What is the most likely cause for her post-partum haemorrhage?
Placenta increta
Placenta percreta
Placenta praevia
Placental abruption
Vasa praevia
Placenta increta
Placenta increta - the chorionic villi invade in to the myometrium but not through to the perimetrium
Placenta increta is correct. Placenta increta is a disorder of the placenta in which the chorionic villi, usually limited to the endometrium, invade the myometrium and may cause heavy bleeding in vaginal delivery. Placenta increta is more severe than placenta accreta, in which chorionic villi attach to the myometrium but do not invade, but less severe than placenta percreta, in which chorionic villi invade the perimetrium.
Vasa praevia is incorrect. This describes a condition in which the foetal blood vessels run near the internal opening of the uterus. This classically presents as the rupture of membranes followed by vaginal bleeding and foetal distress. This would also likely to have been detected on antenatal imaging.
Placenta percreta is incorrect, as this is characterised by chorionic villi that invade the perimetrium, the outermost layer of the uterus. Placenta increta is the most severe disorder on the ‘placenta accreta’ spectrum.
Placenta praevia is incorrect. This is characterised by a low-lying placenta that classically causes painless antepartum bleeding. This would likely have been detected on antenatal imaging and does not show an invasion of chorionic villi into the myometrium.
Placental abruption is incorrect. This classically causes painful antepartum bleeding in which vaginal bleeding is disproportionately low in comparison to the patient’s true blood loss. Placental abruption classically presents with a ‘woody’ firm uterus on examination and may have associated foetal distress on cardiotocography.
A 42-year-old female has just delivered her second and final child at 41 weeks gestation. She has currently been in the third stage of labour for 64 minutes. She has so far lost 2800ml of blood. Her previous baby was delivered by elective caesarean-section. Her only past medical history is pelvic inflammatory disease.
Due to her risk factors, an antenatal ultrasound was performed and confirmed the underlying diagnosis. Unfortunately, the results of this scan had not been seen by the delivery team until now.
What is the most definitive treatment of the underlying problem?
Hysterectomy
Oxytocin administration
Ergometrine administration
Traction on the umbilical cord
Wait another 30 minutes
Hysterectomy
Hysterectomy is the recommended treatment for delayed placental delivery in patients with placenta accreta
This patient has presented with a delayed third stage of labour. This is on a background of a likely placenta accreta. This is indicated by the following two risk factors in the patient’s medical history:
Previous caesarean-section
Previous pelvic inflammatory disease
The stem implies this was diagnosed antenatally too on ultrasound.
The definitive management of such a patient is hysterectomy with the placenta left in-situ [1]. This is because the attempts to actively remove the placenta can cause significant haemorrhage.
Medical management (oxytocin and ergometrine) may help manage the post-partum haemorrhage but is not a definitive treatment option.
Cord traction is unlikely to help as the placenta is pathologically implanted into the uterine wall.
It would not be appropriate to wait another 30 minutes due to the risk of further bleeding.
Reference:
[1] https://www.acog.org/Clinical-Guidance-and-Publications/Committee-Opinions/Committee-on-Obstetric-Practice/Placenta-Accreta
A 36-year-old G2P0 woman presents to the clinic at 21 weeks gestation after her routine 20-week scan showed placental invasion into the deeper layers of the uterus. Her medical history includes a uterine curettage after a miscarriage 2 years ago, she has no allergies and is a non-smoker.
The risks of the likely diagnosis are discussed with her, and she elects to undergo early Caesarean delivery at 36 weeks with a subsequent hysterectomy.
Histological analysis after hysterectomy confirms invasion of the chorionic villi into the perimetrium.
What diagnosis can be made now?
Placenta accreta
Placenta increta
Placenta percreta
Placenta praevia
Placental abruption
Placenta percreta
In placenta percreta the chorionic villi invade through the perimetrium
The correct answer is placenta percreta, which is a severe disorder on the placenta accreta spectrum whereby the chorionic villi of the placenta invade through the entire myometrium to the perimetrium or outer serosal layer of the uterus. Previous uterine surgery is a risk factor for placenta accreta spectrum disorders, which carry a significant risk of major postpartum haemorrhage if not treated early. Early identification by ultrasound is important, although it may not be able to characterise the extent of chorionic villi invasion. MRI can be used, but histological analysis of the uterus provides a definitive diagnosis. Caesarean section with a hysterectomy at 35+0 to 36+6 weeks gestation is recommended by RCOG to prevent major haemorrhage, and removal of the placenta from the uterine wall should not be attempted. This patient has confirmed chorionic villi invasion to the perimetrium, therefore she can be diagnosed with placenta percreta, the most severe form of abnormal placentation and a hysterectomy is appropriate.
Placenta accreta is incorrect. This term describes a set of abnormal placentation disorders where the chorionic villi invade beyond the decidua basalis. If differentiating between each of the disorders, the term also refers directly to the first type where chorionic villi attach to the myometrium but not into it (also known as placenta creta or placenta adherenta). As it is difficult to identify the extent of chorionic villi invasion antenatally, decisions about management should take into account the possibility of invasion into or beyond the myometrium. This patient has confirmed chorionic villi invasion to the perimetrium, therefore she can be diagnosed with placenta percreta, the most severe form of abnormal placentation.
Placenta increta is incorrect because this term is used when chorionic villi invade into the myometrium, but not beyond it. It is the medium severity form of placenta accreta but is still associated with significant morbidity and mortality from postpartum haemorrhage. Antenatal management decisions should be discussed similarly to other types of placenta accreta, and often these women require a hysterectomy following an early Caesarean section. This patient has confirmed chorionic villi invasion to the perimetrium, therefore she can be diagnosed with placenta percreta, the most severe form of abnormal placentation.
Placenta praevia is incorrect because this condition is characterised by an abnormal position of the placenta over the internal cervical os, rather than abnormal chorionic villi invasion. It is a significant risk factor for haemorrhage and should be suspected in women presenting with vaginal bleeding in the third trimester as haemorrhage from placenta praevia can be significant, and requires surgical management. This patient’s placental abnormality is a deep invasion of chorionic villi to the perimetrium, therefore she can be diagnosed with placenta percreta.
Placental abruption is incorrect because this term refers to the early separation of the placenta from the uterine wall, resulting in antepartum haemorrhage. Women may not present with bleeding if the haemorrhage does not reach the cervical os, but the bleeding can still be significant enough to cause haemodynamic compromise in both mother and foetus. This patient’s problem concerns the abnormally deep invasion of chorionic villi into the perimetrium, therefore the most appropriate diagnosis is placenta percreta.
