Morbidly Adherent Placenta with Haemorrhage

Morbidly adherent placenta (placenta accreta spectrum: accreta, increta, percreta) arises when the placenta implants abnormally into the myometrium, because of a defective decidua basalis (usually after uterine scarring). Incidence has risen to about 1 in 300 to 500 deliveries, driven by caesarean rates.

It is a leading cause of major obstetric haemorrhage (blood loss often 3 to 5 L or more), peripartum hysterectomy, bladder and ureteric injury, DIC, ICU admission and maternal death (about 7% where undiagnosed).

Placenta praevia with a previous caesarean section carries accreta risk of about 3% (one prior), 11% (two), 40% (three), and over 60% (four or more). Other risk factors: previous uterine surgery (myomectomy, curettage), Asherman syndrome, IVF, advanced age, and multiparity.

Haemorrhage occurs antepartum (praevia with accreta; bleeding in the third trimester), at attempted placental delivery, or following manual removal.

• Antenatal: painless vaginal bleeding in the third trimester in praevia; often asymptomatic when diagnosed on ultrasound
• Placenta percreta: haematuria, bladder invasion, abdominal pain, uterine rupture (spontaneous haemoperitoneum) in the second or third trimester
• Intrapartum: failure of placental separation with torrential haemorrhage when attempting removal; lack of cleavage plane
• Postpartum: massive haemorrhage with hypotension, coagulopathy and shock; retained fragments with delayed haemorrhage

• Ultrasound (grey scale and colour Doppler) at 18 to 24 weeks and 28 to 32 weeks in at risk women. Sensitivity is about 90%, specificity about 95% when performed by experts.
• Ultrasound findings: loss of the retroplacental clear zone, placental lacunae (irregular vascular spaces, "Swiss cheese" pattern), thinning or interruption of the bladder wall, myometrial thickness below 1 mm, bridging vessels, and exophytic mass.
• MRI (T2) for posterior placentas, suspected percreta, parametrial invasion: dark intraplacental bands, uterine bulging, focal interruption of myometrium, tenting of the bladder
• Cystoscopy for suspected bladder invasion
• Laboratory: full blood count, iron status, coagulation, group and screen with antibody status
• Clinical grading at surgery: grade 1 (abnormal adherence), grade 2 (abnormal invasion), grade 3 (percreta)

• Antenatal planning (multidisciplinary, in a specialist accreta centre). Correct anaemia (oral or IV iron, ferric carboxymaltose 15 mg/kg up to 1,000 mg, erythropoietin if needed). Give antenatal corticosteroids (betamethasone 12 mg IM, two doses 24 hours apart at 34 to 35 weeks). Plan caesarean hysterectomy at 34 to 36 weeks 6 days (earlier for bleeding or labour).
• Arrange blood products (10 units red cells, plasma, platelets, cryoprecipitate), cell salvage, interventional radiology, urology, vascular and general surgery, anaesthesiology, and ICU. Admit at 32 to 34 weeks if bleeding or high risk (placenta praevia with bleeding).
• Surgical technique (caesarean hysterectomy). General anaesthesia (or regional with conversion), large bore access, midline or high transverse incision. Make a fundal or posterior uterine incision above the placenta. Deliver the baby without disturbing the placenta, leaving the placenta in situ, then proceed to immediate hysterectomy (total or subtotal depending on cervical involvement).
• Adjuncts: preoperative ureteric stents or prophylactic occlusion balloon catheters in iliac or uterine arteries (use is selective; benefits are unproven), systemic tranexamic acid 1 g IV, and uterine devascularisation.
• Uterus conserving alternatives (for focal accreta, young women desiring fertility, and where expertise exists). Options are:
  • Leaving the placenta in situ with methotrexate (not effective).
  • Expectant management with delayed hysterectomy or spontaneous resorption (risk of delayed haemorrhage and infection in about 30 to 60%).
  • The triple-P procedure (perioperative placental localisation, pelvic devascularisation, placental non-separation with myometrial excision and reconstruction).
  • One step conservative surgery.
• Haemorrhage control. Massive transfusion protocol in 1:1:1 ratio, fibrinogen concentrate or cryoprecipitate targeting fibrinogen above 2 g/L, tranexamic acid, calcium, warming, and monitoring by ROTEM or TEG. Use uterine artery or internal iliac embolisation, aortic occlusion balloon (REBOA) in extremis, and pelvic packing with delayed closure.
• Emergency unplanned presentation. Stabilise, transfuse, and consider transfer. If the placenta is unexpectedly adherent at delivery, do not force removal: leave in situ with uterotonics, give antibiotics, and arrange transfer or hysterectomy.
• Postoperative. ICU care, antibiotics, thromboprophylaxis (enoxaparin 40 mg daily from 12 to 24 hours after surgery once bleeding controlled, and mechanical measures), and monitoring for bladder or ureteric injury, sepsis, and renal impairment. Offer psychological counselling.