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38. Placental Adhesive Disorders
Described by Irving and Hertig in 1937 as “the abnormal adherence, either in whole or in part, of the afterbirth to the underlying uterine wall”, this term is used to describe also percreta and increta. It occurs as a consequence of partial or complete absence of the decidua basalis and defective formation of Nitabuch’s layer.
Depending on the degree of invasion, the adherent placentas can be:
Accreta: placental villi attached to the myometrium
Increta: invasion of the placental villi into the myometrium
Percreta: placental villi completely penetrating the myometrium, including breaching the serosa and invading the surrounding structures, such as the bladder, broad ligament or sigmoid colon
Total placenta accreta: involves all lobules
Partial placenta accreta: involves at least two but not all of the lobules
Focal placenta accreta: involves only a single lobule, either a portion or the entire lobule
38.1 A Dreadful Condition
Massive obstetric haemorrhage, leading to disseminated intravascular coagulopathy.
Hysterectomy.
Risk of surgical injury to the ureters, bladder, bowel, or neurovascular structures.
ICU complications: adult respiratory distress syndrome, acute transfusion reaction, electrolyte imbalance and renal failure.
Blood loss: The average blood loss at delivery in women with placenta accreta is 3000–5000 mL [1].
As many as 90% of patients with placenta accreta require blood transfusion, and 40% require more than 10 units of packed red blood cells.
Maternal mortality with placenta accreta has been reported to be as high as 7% [2]. Maternal death may occur despite optimal planning, transfusion management and surgical care.
38.2 Incidence Is Increasing!
Why Is This Happening?
It has been noticed that the rising incidence of placenta accreta parallels rising caesarean section rate [5]. It is possibly the incision on the uterus which causes abnormal vascularization and tissue oxygenation of the scar area resulting in defective decidualization and excessive trophoblastic invasion.
38.2.1 Risk Factors
Categorizing risk factors
Most frequent | Frequent | Infrequent | Non-specific |
|---|---|---|---|
• Previous caesarean [8] • Placenta praevia • Multiple and abrasive D and C | • Anterior placenta and previous iterative caesarean sections • Placental insertion in area of previous uterine surgery • Endometrial infection after abortion | • Endometrial thermablation • Radiation • Placenta praevia and assisted conception techniques | • Tabaquism (TOBACCO ADDICTION) • Age over 35 years |
95% of women have identifiable risk factors, and one should be always aware of this in the history. If a patient has a placenta praevia or low-lying placenta, especially when she has had a previous LSCS, look for it! This is important since only a high degree of suspicion is the key to have a prenatal diagnosis of this condition—in which undiagnosed leads to definite morbidity and even mortality.
38.2.2 Diagnosis: Ultrasound?/Colour Doppler?/MRI?
Prenatal diagnosis and knowledge of the extent of placental invasion are instrumental in optimizing patient outcomes in placenta accreta. Foreknowledge allows for referral to a tertiary care centre, multidisciplinary approach when necessary and meticulous planning.
All antenatal patients need to have a routine ultrasound scanning at 20 weeks of gestation that should include placental localization [9].
38.2.2.1 Ultrasound
In general, greyscale predicts abnormal placentation with a sensitivity of 77–86%, specificity 96–98%, positive predictive value 63–88% and a negative predictive value 95–98%. Suspected diagnosis of placenta praevia at 20 weeks of gestation by abdominal scan should be confirmed by transvaginal scan [9]. TVS will reclassify 26–60% of cases where the abdominal scan diagnosed a low-lying placenta, meaning fewer women will need follow-up. Numerous prospective observational trials have used TVS to diagnose placenta praevia, and none has experienced any haemorrhagic complications, thus confirming the safety of this technique. So, do not hesitate to do a TVS in case of a placenta praevia [10, 11]. With three-dimensional power Doppler, visualizing numerous coherent vessels on the basal view has been reported to have a sensitivity of 97% and a specificity of 92% (Table 38.2).
Ultrasonographic findings
Ultrasonographic findings suggestive of placenta accreta are as follows |
1. Loss of normal hypoechoic retroplacental zone 2. Multiple vascular lacunae (irregular vascular spaces) with placenta giving “Swiss cheese” appearance [12] 3. Blood vessels or placental tissue bridging uterine-placental margin, myometrial-bladder interface or crossing uterine serosa 4. Retroplacental myometrial thickness <1 mm 5. Numerous coherent vessels visualized with three-dimensional power Doppler in basal view [13] |
38.2.2.2 Colour Doppler
Diffuse or focal lacunar flow
Vascular lakes with turbulent flow (peak systolic velocity over 15 cm/s)
Hyper-vascularity of serosa-bladder interface
Markedly dilated vessels over peripheral subplacental zone
The additional use of colour Doppler does not significantly improve diagnostic sensitivity over grey-scale ultrasonography alone.
38.2.2.3 Magnetic Resonance Imaging
Dark intraplacental bands on T2-weighted sequences
Uterine bulging
Heterogeneous signal intensity within the placenta
The American College of Radiology recommends that MRI be used in pregnancy only if the diagnostic information cannot be obtained with ultrasonography [14]. They further specify that MRI contrast agents should not be used, and the use is only justified with “overwhelming potential benefit to the patient or fetus”. The benefits are proper planning and optimizing the maternal outcome. Antenatal ultrasound can be complemented by magnetic resonance imaging in equivocal cases to distinguish those women at special risk of placenta accreta [9].
As of today, the mainstay of prenatal diagnosis for abnormal placentation remains ultrasound with MRI being used only as an adjunct in intermediate cases. An ultrasound or MRI diagnosis of placenta accreta predicts the need for hysterectomy with a sensitivity of 78%, 67% and a specificity of 67%, 50%, respectively [15].
90% of major praevias at this gestation will persist [16].
38.3 Antenatal Management
If women are managed at home, they must have safety precautions in place and have ready access to the hospital. They must report any bleeding, contractions or pain (including vague suprapubic period-like aches). Anaemia corrected by IV iron in the antenatal period/packed cell transfusion where near to term. A haematocrit greater than 30 is a reasonable goal [17]. Most patients who undergo an obstetric hysterectomy will need a blood transfusion, hence ensuring that the patient does not have any rare alloantibodies before delivery is also important.
All these patients have to receive antenatal steroids at 26 weeks of gestation (2 doses of 12 mg betamethasone 24 h apart or 4 doses of 8 mg dexamethasone 12 h apart).
Prolonged inpatient care can be associated with an increased risk of thromboembolism; therefore, mobility should be encouraged together with the use of thromboembolic deterrent stockings and adequate hydration. Limiting anticoagulant thromboprophylaxis to those at high risk of thromboembolism seems reasonable [18].
38.4 Delivery Preparation (Care Bundle)
Referral to a tertiary centre and a multidisciplinary approach is of the utmost importance.
- 1.
Consultant obstetrician planned and directly supervising delivery.
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