EVALUATION OF PLACENTA
Dr Lenon J. D’Souza
EVALUATION OF THE PLACENTA
The early gestational sac is first visible at transvaginal sonography at about 4 weeks' menstrual age
Its hyperechoic rim contains developing villi composed of fetal vessels surrounded by the lacunar space, which is the precursor of the intervillous space.
At about 5 weeks' menstrual age, those villi situated opposite the implantation site begin to atrophy, forming a smooth surface (chorion laeve).
The remaining villi, the chorion frondosum, become the placenta, which may be identified at sonography at about 8 weeks
EVAUATION OF THE PLACENTA
PLACENTAL LAKESPlacental lakes represent inter villous space devoid of placental villous trees Hypoechoic structures with evidence of blood flow
PLACENTAWell formed by around 12 weeksMost commonly assessed at 18-20 weeksTHINGS TO ASSESS:
SIZE- >1 cm not >4 cm thick within 24 weeks TEXTURE PLACENTAL SITE N : anterior/posterior /fundal RETROPLACENTAL AREA= N :hypoechoic CORD : SITE OF INSERTION (centre or within 2
cm) NO. OF VESSELS ( N = 3)
Small PlacentasToxemiaHypertensionChromosomal abnormalitySevere diabetes mel1itusChronic infection
Large PlacentasBlood group incompatibilitiesDiabetes mellitusMaternal anemiaFetal neoplasmTriploidyHomozygous alpha-thalassemia
More than 4 : Ischemic thrombotic changeHemorrhageChorioangiomahydrops
NORMAL PLACENTA ON USG
Placental calcium deposition is a physiologic process
Found along the basal plate, in the intraplacental septa, and in collections of fibrin in the intervillous and subchorionic spaces
Exponential increase in placental calcification with increasing gestational age; more than 50% of placentas contain some degree of calcification after 33 weeks.
Placental calcification is more common in women of lower parity.
TEXTURE :GRANNUM CLASSIFICATION OF PLACENTAL
MATURITY
GRADE 0
GRADE 1
GRANNUM CLASSIFICATION OF PLACENTAL MATURITY
GRADE 2
GRADE 3
EVALUATION - MRI During the second trimester, most patients can
tolerate supine imaging. However, in the third trimester, lateral decubitus
imaging may be required Avoid the risk of impaired systemic venous return
caused by uterine compression of the maternal inferior vena cava.
Imaging late in the third trimester can be challenging,1. Positioning the patient2. Placenta is heterogeneous 3. Myometrium thinner and more stretched
PREPARATION
When evaluating the patient for placenta percreta, the bladder should be mildly distended.
Completely collapsed bladder - Anatomic landmarks difficult to identify
Full Bladder - exclusion of Bladder-wall invasion difficult when closely apposed to the uterus.
No other patient preparation is typically required.
EVALUATION - MRIBetween 19 and 23 weeks:
homogeneous on T2
Between 24 and 31 weeks: the placenta becomes slightly lobulatedconspicuous septae appear between placental lobules, leading to increased heterogeneity with increasing gestational age.
The normal myometrium - trilayered appearance on T2-weighted images
The middle layer is a heterogeneously hyperintense vascular layer, with thinner low signal-intensity layers on either side.
Diffusion-weighted imaging:demonstrate the myometrial-placental interface.
Blood oxygen level– dependent (BOLD) imaging:evaluate placental perfusion.
SHAPEFailure of villous regression results in
abnormalities of placental shape. A more common result of failure of villous
regression is the succenturiate (accessory) lobe, which is present in up to 8% of patients
Recognition of succenturiate lobes is important because they may result in complications such as placenta previa, vasa praevia, and retained placenta after delivery.
SHAPE
The membranes of chorionic leave, instead of attaching to margin of placental disc, insert more towards centre of disc
Disproportionate folding of placenta and fetal membranes, results in chorionic plate being smaller than basal plate
CIRCUMVALATE PLACETA
CIRCUMVALATE PLACENTA
SHAPE
Placenta membranacea is a rare anomaly in which almost all the chorion is diffusely covered by villi.
A variant of this condition occurs when aberrant villous atrophy results in a ring-shaped (annular) placenta.
Both entities are associated with recurrent antepartum bleeding.
CONTRACTIONS Transient changes in the appearance
of the retroplacental myometrium and decidua are seen with contractions, which occur throughout pregnancy and are imperceptible to the mother.
These are most commonly seen in the latter part of the first trimester and the early part of the second trimester
Contractions are a source of considerable confusion because they often mimic retroplacental myomas and hematomas
RETROPLACENTAL MASS
ContractionsMyomasRetroplacental hematomasAbruptio placentae
MYOMASWell circumscribed and
hypoechoic. Diagnosis easily confirmed if
multiple myomas are present. Large myomas may have a
complex echotexture as a result of degeneration and/or hemorrhage.
May increase or decrease in size during the course of the pregnancy.
COMMON MACROSCOPIC LESIONS
SUBCHORIONIC FIBRIN DEPOSITION
PERIVILLOUS FIBRINAnechoic-hypoechoic
intraplacental "lakes" are not uncommon and may contain flow
At delivery, these correlate with blood-filled spaces that presumably represent a stage in the evolution of either perivillous fibrin deposition or intervillous thromboses.
SITE : PLACENTA PREVIA
6% in the 1 st trimester 0.5% at term Predisposing factors for
placenta previa Advanced maternal age Multiparity Prior cesarean section Uterine curettage Maternal cigarette smoking
PLACENTA PREVIA
MARGINAL PLACENTA PREVIA
PARTIAL PLACENTA PREVIA
COMPLETE PLACENTA PREVIA
COMPLETE SYMMETRICAL
COMPLETE ASSYMETRICAL
COMPLETE PLACENTA PREVIA
LOW LYING PLACENTA
LESS THAN 2 CM FROM INTERNAL OS
THICK: EDGE >1 CM
PLACENTA PREVIA
Misdiagnosed : overdistended maternal bladder
: uterine contractions (pseudo placenta previa
If suspected : confirm with re scanning after voiding or after 20 to 30 minutes
PSEUDO PLACENTA PREVIA
15 min later
RETROPLACENTAL AREA : ABNORMAL INVASION OF PLACENTA
• 1 IN 2500
• Abnormal adherence of placenta• to the uterus
• Failure of separation on dellivery
• Deficiency of decidua basalis
PLACENTA ACCRETA
Absence of the intervening myometrium between the placenta and uterine serosa
Color Doppler image abnormal bladder-uterine wall vascularization
numerous vascular lacunae within the placenta
PLACENTA PERCRETA
Distinguish placenta accreta from increta and increta from percreta - challenge, unless there is direct invasion of adjacent organs.
Abnormal placental attachment to the myometrium may be complicated by postpartum hemorrhage and/or retained products of conception when the placenta fails to cleanly separate from the uterus at the time of delivery
MRI – highly accurate
PLACENTA PERCRETA
PLACENTA PERCRETA
PLACENTA PERCRETA
PLACENTA ACCRETA AND PERCRETA
PLACENTAL HEMMORHAGES
Indirect sign of a hematoma : apparent thickening of the placenta
MARGINAL HEMMORRHAGE
INTRAPLACENTAL HEMATOMA
SUBCHORIONIC HEMATOMA
SUBCHORIONIC HEMMORHAGE
BREUS MOLE
SUBAMNIOTIC HEMORRHAGE
A subamniotic haematomas are classical placental pathological lesions resulting from the rupture of chorionic vessels (allantochorionic vessels) close to the cord insertion.
RETROPLACENTAL HEMATOMA
PLACENTAL ABRUPTION
Premature separation of placenta from the myometrium
Secondary to hemmorrhage into decidua basalis
20 wks to birth If >60 ml blood loss chances of fetal demise more
SONOGRAPHIC SIGNS OF ABRUPTION
Diffuse placental thickness Retroplacental mass Rounded placental edge Separation of placental edge Intra-amniotic hemorrhage Preplacental or subamniotic mass Blood in the fetal stomach
PLACENTAL ABRUPTION
PLACENTAL ABRUPTION
INTRAPLACENTAL LESIONS
ChorioangiomaTeratomaMetastases from maternal neoplasms
Hydatidiform molePartial mole
CHORIOANGIOMA
Hydatidiform mole
An enlarged uterus containing material with multiple anechoic vesicles of varying sizes, in the absence of a fetus, is seen with complete hydatidiform mole
The vesicles represent dilated, hydropic villi that enlarge with advancing gestational age; no normal placental tissue is found.
Moles are believed to result from the abnormal fertilization of an empty ovum by a single sperm with a duplicated haploid genome (46,XX karyotype) or, less commonly, dispermy (46,XY).
A coexistent fetus may occur along with a mole in the case of a twin pregnancy with one empty ovum
TROPHOBLASTIC DISEASE
PARTIAL MOLEAn enlarged placenta with multiple
anechoic lesions - Partial mole Normal villi interspersed with
hydropic villi; the fetus - abnormal. Most partial moles are triploid (69
chromosomes). If they do not abort in the first
trimester frequently cause symptoms of preeclampsia at about 18 weeks.
MOLAR PREGANNCY
PLACENTAL SITE TROPHOBLASTIC DISEASE
Can follow commonly after normal pregnancy
Arises from intermediate trophoblasts
Rarest and most fatalB – HCG not significant
PLACENTAL SITE TROPHOBLASTIC
DISEASE Pt usually presents as focal
myometrial nodule
Persisent trophoblastic neoplasia
Abn uterine hypervascularity and low impedance and av shunting
Floris color mosaic pattern with aliasing
INVASIVE MOLEHIGH SYSTOLIC – LOW
RESISTANCE FLOWPSV > 50/cm AND RI
<0.5NORMALLYPSV <50 cm/s and RI 0.7
The umbilical cord inserts into the fetal (chorio-amniotic) membranes outside the placental margin and then travels within the membranes to the placenta (between the amnion and the chorion).
Remodelling of the placenta as a response to factors that affect distribution of uterine blood flow (a process known as trophotropism).
A marginal cord insertion may evolve into a velamentous cord insertion as the pregnancy progresses
VELAMENTOUS CORD INSERTION
VELAMENTOUS CORD INSERTION
VASA PREVIA
CONCLUSION
The placenta should be evaluated, not only as a necessary organ for fetal growth the development, but also as a potential source of fetal disease and/or compromise.
USG is the modality of choice
Patients with suspected accreta spectrum should undergo MR evaluation
Patients with undiagnosed bleeding may undergo MR to rule out abruption
THANK YOU
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