Morbidly adherent placenta (MAP)
It is also called as
" Boston disease" as maximum number of cases reported from Boston area in the early 19th century.
It is a condition in which no line of cleavage between placenta and uterine wall.
1875 - Langhans discovered that the placental separation takes place in the spongy layer of the decidua
1889 - Hart agreed with Langhan's above hypothesis and described a first microscopic account of placenta accreta stating spongy layer of decidua absent as well as absence of Nitabuch fibrinoid layer.
MAP can be,
- Focal
- Partial or
- Complete
Clinical Presentation after vagianl delivery
Milder forms of placenta accreta often manifest clinically as retained placenta or require manual removal of placenta.
Histologic diagnosis
When clinical features suggest MAP, extensive sampling of the basal plate, particularly at the interface between the intact and and disrupted areas than in the blocks taken from wholly intact areas.
Histologically this can be confirmed by finding of myometrial fibres in the basal plate.
Placentas with disrupted maternal surface were more likely to have myometrial fibres in the placenta than those with intact maternal surface.
Myometrial fibres will not be found, in blocks taken from directly over the disrupted areas, but it is probable that the disrupted areas can be so adherent that parts of the placental fragments can be left behind in the uterus, resulting in a disrupted basal plate in the delivered placenta. The absence of myometrial fibres do not exclude the diagnosis.
During histologic examination the blocks should be taken at the interface between intact and disrupted areas. Myometrial fibres will not be found if blocks are taken directly from the disrupted areas.
An block obtained adjacent to a disrupted area rather than with an intact area would provide the most efficient means of detecting myometrial fibres in the placenta.
Placenta accreta and Ultrasound features:
1. Localised thinning of the myometrium
2. Absence of hypoechoic interface between the myometrial and the placental surface
3. Placenta previa with abnormal blood flow within the myometrium is suggestive of MAP.
4. Placental lacunae
5. Loss of retroplacental hypoechoic zone
6. Patients with prevous caesrean and previa
7. Low lying gestation sac (Scar pregnancy)
8. Intraplacental flow with turbulent blood flow
9. Absent decidua basalis and myometrial thickness of <1mm>
10. Focal nodular projections into the bladder (percreta)
11. Lrge echolucencies in the placenta,
12. Loss of the myometrial echolucent stripe near the bladder, and
13. Increased venous structures and flow in the anterior lower uterine segment, are features suggestive of placenta accreta.
The most common feature on ultrasound that would suggest placenta accreta is a "moth-eaten" or "swiss cheese" appearance to the placenta. Ultrasound can be used from 15 weeks gestation, although it is more sensitive at gestations of 20 weeks or more
MRI Protocols in Morbidly Adherent Placenta
* Fast T2 technique *
- Place Coil intensificator in hypogastrium
- Study focus in hypogastrium
- Not in all uterus (better resolution) in anterior or lower placentas, all series must be included,
- Minimum slices should be of 5 mm and not less than that.
- The first one should be a sagittal slice, then a coronal (according to the uterus, not according to the pelvis axis) and finally, the axial slice,
- The axial slice must be done PERPENDICULAR to the posterior wall of the bladder.
- To minimize the artefacts by fetal movement, the operator could use a gathering device or use patients' breath hold technique.
When one should raise the suspicion of MAP?
1. Marked elevations of maternal serum alpha fetoprotien levels (MSAFP) sometimes upto 15 multiples of median (normal <2 nbsp="" p="">
Patient with previous Caesarean + Presence of antrerior placenta previa and + Unexplained raised Maternal Serum Alpha Fetoprotein (MSAFP)
Incidence of MAP
Placenta accreta - 80%
Placenta increta - 15%
Placenta percreta - 5%
Ref : AJOG, 2005; Authors ; Wu and Hibbard et al.
How to improve pregnancy outcome in patients with Morbidly adherent placenta?
- Early diagnosis and planned delivery are the keys to pregnancy outcome in patients with MAP.
- The diagnosis should be thought of, if patient has one or more of the following risk factors;
- Previous uterine surgery
- CS
- Myomectomy
- Uterine curettage
- Hysteroscopy/polypectomy
- Advanced maternal age
- Increased parity
Previous h/o caesarean section and presence of anterior placenta previa, the risk of Placenta accreta is 40%.
If the US findings show, large echolucencies within the stroma of the placenta, loss of the
normal hypoechoic myometrial band beneath the placenta and increased vascularity around the lower
uterine segment, the risk of placenta accreta in such a scenario will be increased from 40% to to 60%.
When to consider MRI in suspected placenta accreta?
1.If the placenta previa was confirmed and the findings of accreta were equivocal, then plan for abdominal and pelvic magnetic resonance imaging (MRI) to clarify the diagnosis.
2 Arrange a follow-up ultrasound examination at 26 - 27 weeks and if this shows a complete placenta previa and confirms all the previously noted sonographic signs of placenta accreta.
A significant association exists between placenta accreta/percreta/increta and elevated MSAFP values. Patients with an unexplained elevation of MSAFP may have an increased risk for placenta accreta and associated blood loss at cesarean hysterectomy.
Maternal serum alpha fetoprotein and MAP
Placenta accreta should also be suspected in pregnant women with elevated maternal serum alpha-fetoprotein (MSAFP) levels, with no other obvious cause. This is a protein found in the blood, at highest concentrations in the foetus. The defect in the layer normally separating the placenta and uterus allows leakage of foetal alpha-fetoprotein into the mother's circulation. Up to 45% of women with placenta accreta have elevated MSAFP levels in the absence of an obvious cause.
Marked elevations of maternal serum alpha fetoprotein levels in midtrimester done as a part serum screening for Down’s syndrome can give a clue in the absence of any fetal anomalies such as NTD.
In a study of 167 women from 25 University hospitals in France, conservative treatment was successful in 78.4% of cases. Spontaneous placental resorption occurred in 75% of women at a 13.5 week follow up.
Surgical techniques were used to remove the retained placenta in 25% of women at a median follow up of 20 weeks. Just over 10% of women had hysterectomies performed within the first 24 hours following delivery and a further 10.8% had delayed hysterectomies.
Conservative management of placenta accreta remains highly controversial as although this technique preserves future fertility and avoids the complications of cesarean hysterectomy, it exposes the woman to potentially life threatening infection and massive hemorrhage.
Points to be discussed during consultation with the patient:
- Risks to the fetus :Prematurity (especially prematurity in the event of maternal antepartum hemorrhage)
- Risks to the mother :
- Substantial risks to the mother, including hemorrhage, the need for blood transfusion, hysterectomy, possible damage to the bladder or other pelvic organs,
- Admission to an intensive care unit, assisted ventilation, pulmonary embolus, and death
- Options for minimizing the risks of life-threatening blood loss at the time of delivery
- Optimization of maternal iron status,
- Pharmacologic stimulation of erythropoiesis,
- Autologous blood donation and transfusion,
- Acute preoperative hemodilution, and
- Use of a cell-saver autotransfusion device at the time of delivery.
- Use of balloons for intravascular occlusion at the time of delivery
- Consider cesarean hysterectomy without attempts to remove the placenta if the patient does not want more children.
