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

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