Lecture 31: Placental Pathology Flashcards
What are the key steps in early placental development?
- Differentiation of trophoblast from outer cell mass of blastocyst
- Implantation of blastocyst into endometrial stroma
- Development of lacunae in trophoblast plaque to form eventual intervillous space
- Invasion of cytotrophoblast cords to form primary villi
- Ingrowth of vasculogenic villous troma from extraembryonic mesoderm to form secondary villi
- Formation of villous capillaries defines tertiary villi
- Tertiary villi undergo continued growth and phased maturation throughout gestation
What is a trophoblast?
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
What does the trophoblast differentiate into?
- Outer syncytial layer remodels the endometrium to form intervillous space
- Inner mononuclear cytotrophoblast layer propagates to form villous
What is the significance of uterine spiral arteries?
They perfuse the intervillous space around 12 weeks of gestation after trophoblast plugs recedes
What are the precursors to the intervillous space?
Lacunae
What are types of disorders of early pregnancy?
- Spontaneous abortion
- 15% of pregnancies = spontaneous abortion
- Abnormal implantation
- ectopic implantation
- greatest risk factor = prior ectopic pregnancy
- second greatest risk factor = PID
What can spontaneous abortion be caused by?
- chromosomal anomalies
- diabetes
- endocrine abnormalities
- uterus defects
What are the causes of abnormal implantation?
PID
Prior ectopic pregnancy
How many vessels are in the umbilical cord?
3
1 umbilical vein
2 umbilical arteries
What is Wharton’s jelly?
The substance around umbilical vein/arteries
Acts as a shock absorber
Contains a lot of water content
What comprises the membranes of the placenta?
3 layers
- amnion
- chorion
- decidua
What do we see on the MATERNAL surface of the placenta?
Decidual basalis
What is vasculosyncytial membrane?
The membrane that separates fetal blood from maternal blood an allows exchange between the two
What is the most common conformation of multiple gestation?
2 chorions
2 amnions
For twins
Anytime you have a single chorion, what type of twins do you have?
A monozygous (identical) twin
What does the maternal/basal surface of the placental disc look like?
No umbilical cord
Lobular configuration dn covered by decidua basalis
Why look at placentas?
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
What are the clinical indcations for requesting placental examination?
- Maternal indications
- history of reproductive failure
- maternal disease
- Fetal and neonatal implications
- still birth
- fetal growth restriction
- severe CNS depression of neonate
- Placental indications
- any gross abnormality such as thrombi, twisting
- Optional recommendations
- prematurity between 32 nd 36 weeks
What are the three mechanisms of disease in the placenta?
- Inflammation due to infection
- Vascular lesions
- Neoplasms
What are the two pathways for placental infection?
- Ascending infection via BIRTH CANAL
- more common
- bacterial pathogens
- hematogenous infections (UMBILICAL ARTERY)
- viral pathogens
- taxoplasma
What are the characteristics of ascending infection in placenta?
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
What are the characteristics of hematogenous infection?
- viral pathogens, toxoplasma, syphilis
- infection results in inflammation of chorionic villi (villitis)
- May cause fetal infection, growth restriction and fetal demise
What is chorioamnionitis?
Infiltration of inflammatory cells to chorion and amnion
Maternal neutrophils
What is villitis?
Maternal inflammatory cells infiltrate the villi via the intervillous space
CMV
