Lecture 31: Placental Pathology

Question 1

What are the key steps in early placental development?

Answer 1

1. Differentiation of trophoblast from outer cell mass of blastocyst
2. Implantation of blastocyst into endometrial stroma
3. Development of lacunae in trophoblast plaque to form eventual intervillous space
4. Invasion of cytotrophoblast cords to form primary villi
5. Ingrowth of vasculogenic villous troma from extraembryonic mesoderm to form secondary villi
6. Formation of villous capillaries defines tertiary villi
7. Tertiary villi undergo continued growth and phased maturation throughout gestation

Question 2

What is a trophoblast?

Answer 2

The cells forming the outer layer of a blastocyst
Provides nutrients to the embryo and develop into the placenta
Includes multiple subtypes:
i. cytotrophoblast
ii. syncytiotrophoblast
iii. intermediate trophoblast

Question 3

What does the trophoblast differentiate into?

Answer 3

1. Outer syncytial layer remodels the endometrium to form intervillous space
2. Inner mononuclear cytotrophoblast layer propagates to form villous

Question 4

What is the significance of uterine spiral arteries?

Answer 4

They perfuse the intervillous space around 12 weeks of gestation after trophoblast plugs recedes

Question 5

What are the precursors to the intervillous space?

Answer 5

Lacunae

Question 6

What are types of disorders of early pregnancy?

Answer 6

1. Spontaneous abortion
   
   • 15% of pregnancies = spontaneous abortion
2. Abnormal implantation
   
   • ectopic implantation
   • greatest risk factor = prior ectopic pregnancy
   • second greatest risk factor = PID

Question 7

What can spontaneous abortion be caused by?

Answer 7

1. chromosomal anomalies
2. diabetes
3. endocrine abnormalities
4. uterus defects

Question 8

What are the causes of abnormal implantation?

Answer 8

PID

Prior ectopic pregnancy

Question 9

How many vessels are in the umbilical cord?

Answer 9

3
1 umbilical vein
2 umbilical arteries

Question 10

What is Wharton’s jelly?

Answer 10

The substance around umbilical vein/arteries
Acts as a shock absorber
Contains a lot of water content

Question 11

What comprises the membranes of the placenta?

Answer 11

3 layers

1. amnion
2. chorion
3. decidua

Question 12

What do we see on the MATERNAL surface of the placenta?

Answer 12

Decidual basalis

Question 13

What is vasculosyncytial membrane?

Answer 13

The membrane that separates fetal blood from maternal blood an allows exchange between the two

Question 14

What is the most common conformation of multiple gestation?

Answer 14

2 chorions
2 amnions
For twins

Question 15

Anytime you have a single chorion, what type of twins do you have?

Answer 15

A monozygous (identical) twin

Question 16

What does the maternal/basal surface of the placental disc look like?

Answer 16

No umbilical cord

Lobular configuration dn covered by decidua basalis

Question 17

Why look at placentas?

Answer 17

Pathologic conditions of the placenta are important causes of intrauterine or perinatal death, congenital malformations, intrauterine growth retardation, maternal death and a great deal of morbidity for both mother and child

Question 18

What are the clinical indcations for requesting placental examination?

Answer 18

1. Maternal indications
   
   • history of reproductive failure
   • maternal disease
2. Fetal and neonatal implications
   
   • still birth
   • fetal growth restriction
   • severe CNS depression of neonate
3. Placental indications
   
   • any gross abnormality such as thrombi, twisting
4. Optional recommendations
   
   • prematurity between 32 nd 36 weeks

Question 19

What are the three mechanisms of disease in the placenta?

Answer 19

1. Inflammation due to infection
2. Vascular lesions
3. Neoplasms

Question 20

What are the two pathways for placental infection?

Answer 20

1. Ascending infection via BIRTH CANAL
   
   • more common
   • bacterial pathogens
2. hematogenous infections (UMBILICAL ARTERY)
   
   • viral pathogens
   • taxoplasma

Question 21

What are the characteristics of ascending infection in placenta?

Answer 21

Bacterial pathogens through cervix
	i. Group B strep
	ii. E. coli
	iii. fusobacterium
Inflammation of the membranes 
	i. chorioamnionitis
	ii. funisitis (inflammation of the cord)
Frequent cause of preterm labor/delivery/sepsis

Question 22

What are the characteristics of hematogenous infection?

Answer 22

1. viral pathogens, toxoplasma, syphilis
2. infection results in inflammation of chorionic villi (villitis)
3. May cause fetal infection, growth restriction and fetal demise

Question 23

What is chorioamnionitis?

Answer 23

Infiltration of inflammatory cells to chorion and amnion

Maternal neutrophils

Question 24

What is villitis?

Answer 24

Maternal inflammatory cells infiltrate the villi via the intervillous space
CMV

Question 25

What are examples of vascular lesions of the placenta?

Answer 25

1. lesions can disrupt flow between uterus and placenta or placenta and fetus
   Knots in the cord

Question 26

What is an abruption?

Answer 26

A retroplacental hemorrhage
A pathological term
Placental detachment
Caused by cocaine

Question 27

If clinician suspects abruption/retroplacental hemorrhage, what must be done?

Answer 27

Caesarian section

Question 28

What is a retroplacental hemorrhage?

Answer 28

Pathologic correlate for clinical term abruption
Characterize by maternal symptoms of pain, bleeding and uterine enlargement
Premature placental separation
Hypertension is associated

Question 29

What is preeclampsia?

Answer 29

Clinical syndrome of maternal hypertension, proteinuria and edema
Can lead to seizures during pregnancy
Acute atherosis of spiral arteries (stenotic spiral arteries)

Question 30

What is the association between preeclampsia and placenta formation?

Answer 30

Superficially implantation of placenta

Incomplete remodeling of uterine spiral arteries

Question 31

What are types of neoplasms in placenta?

Answer 31

Metastatic disease
Leiomyomas
Gestational trophoblastic disease
Metastatic disease
Gestational trophoblastic disease
	-hydatidiform mole
	-gestational trophoblastic tumors

Question 32

What is a chorangioma?

Answer 32

A proliferation of capillaries
Benign neoplasm of placenta
A placental “hemagioma”

Question 33

What are molar pregnancy/hydatidiform mole?

Answer 33

A manifestation of gestational trophoblastic disease
Complete vs. partial
Complete = paternal ONLY

Question 34

What are the key features of COMPLETE molar pregnancy/hydatidiform mole?

Answer 34

Non-viable fertilized eggs implants in uterus and converts normal pregnancy into an abnormal one
Complete = completely PATERNALLY derived
Caused by
	i. sperm fertilizes empty ovum
	ii. 2 sperm fertilize empty ovum
Higher risk of trophoblastic tumors

Question 35

What are the key features of partial molar pregnancy?

Answer 35

Mixed paternal/maternal derivation
2 sperm fertilize normal ovum
Triploid karyotype (not viable but implant anyway)
Lower risk of developing trophoblastic tumors

Question 36

What are the histological features of villitis?

Answer 36

Scarring of the stroma

Complete molar pregnancy happens if sperm fertilizes empty ovum or if 2 sperm fertilize empty ovum

Question 37

What are types of trophoblast derived tumors?

Answer 37

1. invasive mole
2. choriocarcinoma
3. placental site trophoblastic tumor
4. epithelial trophoblastic tumor
5. Choriocarcinoma

Question 38

What is the significance of choriocarcinoma?

Answer 38

Associated with markedly elevated levels of HCG
Higher rate following hydatidiform mole
Can also arise in setting of germ cell tumors
Present with vaginal bleeding
Malignant form of trophoblastic gestational disease