Nicola Fratelli U.O. Ostetricia e Ginecologia 1-2
Spedali Civili di Brescia
Placente ad impianto anomalo:
stratificazione del rischio emorragico,
modalità e sede del parto
• The factors that determine the site of nidation of the human
blastocyst are not fully understood
• The human blastocyst implants normally in the upper
portion of the uterus
• Abnormal implantation may lead to placenta previa
Placental implantation
Benirschke K, 2006
Placenta previa The placenta either totally or partially lies within the lower uterine segment
Complete
placenta previa The placenta completely
covers the internal os
Partial
placenta previa The placenta partially
covers the internal os
Marginal
placenta previa The placenta reaches
the internal os, but does
not cover it
Low-lying
placenta The placenta extends
into the lower
uterine segment but
does not reach the
internal os Schacher, 1709
Placenta con il margine inferiore distante
<20 mm dall’OUI
Epoca gestazionale > 26 settimane
Diagnosi
Risks
Oyelese Y, 2006
Incidence
• from 3 to 5 per 1000 births
• severe bleeding and preterm birth
• need for cesarean delivery
• maternal mortality 3 per 10.000 births
Oyelese Y, 2006
Diagnosis
• Bleeding in the late second trimester or early third
trimester
• Routine US in asymptomatic women, usually
during the second trimester
Women who present with bleeding in the second
half of pregnancy should have a sonographic examination for placental
location prior to any attempt to perform a digital examination
Smith RS, 1997
TVS is superior to TA sonography for the
diagnosis of placenta previa
• FPR and FNR using TA sonography range from 2% to 25%
• In 26% of the cases of suspected placenta previa, the initial
diagnosis may change after TVS
Leerentveld RA, 1990
For an individual patient, it is not
possible to predict whether a bleed
will occur, nor the gestational age
Ghourab S, 2001 Ghi T, 2010 Stafford IA, 2010
• placenta completely covering the os
• placenta with a thick edge (>1 cm)
• cervical length ≤3 cm
The positive predictive
value for previa at delivery increases the later
in gestation that previa is detected
sonographically
Dashe J, 2002
940 ultrasound examinations
714 pregnancies
• At each interval, complete previa is more likely to persist than incomplete previa
• Prior cesarean delivery is an independent risk factor
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15-19w 20-23w 24-27w 28-31w 32-35w
Placenta previa: Gestational age of diagnosis
Placental migration may occur progressively
throughout the third trimester
Oppenheimer L, 2001
There is a place for TVS prior to an otherwise planned
caesarean section
Placenta-cervix distance Migration Rate CS for placenta previa
> 20 mm 100% 0%
Between –20 mm and +20 88% 12%
Overlap >20 mm
0% 100%
rate of migration: 5 mm/week
Management based on likelihood of APH
and need for CS
Vergani P, 2009
Treatment decisions should be based
on the placenta-cervix distance measured by TVS
Oppenheimer L, 2009
Timing of Delivery
Committee Opinion No. 560. American College of Obstetricians and Gynecologists. Obstet Gynecol 2013;121:908–10
Migration of a low-lying
placenta
Benirschke K, 2006
• Placenta grows preferentially toward a better vascularized fundus, whereas the
placenta overlying the less well vascularized cervix may undergo atrophy
• In some cases, this atrophy leaves vessels running through the membranes,
unsupported by placental tissue or cord (vasa previa)
• In cases where the atrophy is incomplete, a succenturiate lobe may develop
• Development of the lower uterine segment
Resolution of a low-lying placenta can be
associated with vasa previa
Low-lying placenta is associated with
increased risk of PPH
Previa or Low-lying placenta has an increased risk of PPH
Fan D, 2017
Abnormally invasive placenta
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Benirschke K, 2006
Le donne col più alto rischio di placenta accreta sono quelle con pregresso taglio cesareo e placenta previa impiantata
sopra la cicatrice uterina Wortman C, 2013
• massive obstetric hemorrhage
• need for emergency hysterectomy
• damage to adjacent organs
• blood transfusion
• postoperative complications
• maternal death (7%)
placenta accreta (AIP) becomes problematic
during delivery when the placenta does not
completely separate from the uterus
La diagnosi antepartum riduce la morbilità emorragica e
le complicanze legate all’ isterectomia d’ emergenza
Centri di eccellenza per placenta
Accreta
In caso di placenta previa che ricopre
l’orificio uterino interno (OUI) (previa maior)
o in presenza di placenta anteriore con il
margine inferiore distante <20 mm dall’OUI
(previa minor) in paziente già cesarizzata
va riferita a Centro nascita adeguato alla
gestione della patologia
Take home message