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Chorioamnionitis
Etiology

mostly bacteria
low virulence organisms , normal flora of vagina or
obvious pathogens such as E.Coli, Mycoplasma, Ureaplasma
Pathogenesis

bacteria ascending from vagina, breaching cervical defenses (mucus plug etc.)
bacterial colonization of intrauterine space through intact or ruptured membranes
maternal and fetal acute inflammatory response,
Epidemiology

clinically evident in 0.5-10% of pregnancies
General Gross Description

membranes and chorionic plate appear cloudy and occasionally have a yellow or green tint
in severe cases the umbilical cord may have small yellow round lesions on its surface which represent foci of PMN's (small abscesses)
•Examples:
Acute Infection of Placenta
General Microscopic Description

Chorioamnionitis: membranes (amnion and chorion + parietal decidua) show neutrophilic infiltrate. PMN's originate from maternal vessels in parietal decidua and migrate into chorion and then amnion.
Chorionitis: chorionic plate shows neutrophilic infiltrate. PMN's orginate from maternal intervillous space and migrate into subchorionic fibrin, chorion itself and then amnion
Funisitis: umbilical cord shows neutrophilic infiltrate. PMN's orginate in the fetal vessels of the umbilical cord and migrate sequentially through the muscular layers of the vessel and then into the Wharton's jelly.
Chorionic vasculitis: chorionic vessels show neutrophils in wall. PMN's originate in the fetal vessels of the chorionic plate and migrate through the walls of the fetal vessels toward the amniotic fluid
•Examples:
Acute inflammation of fetal membranes 10x Acute inflammation of fetal membranes 20x Acute inflammation of fetal membranes 40x
Clinical Correlation

associated with preterm birth
only 8-25% of mothers have symptoms such as fever, chills
fetus may have decreased biophysical profile score or abnormal heart rate pattern
can lead to congenital pneumonia, gastroenteritis, menigitis, sepsis although most infants do not have sepsis even with umbilical cord inflammation
References

Gibbs and Sweet "Maternal and Fetal Infections" (chapter 42) in Creasy and Resnik, Maternal Fetal Medicine: Principles and Practices 3rd edition; Philadelphia: WB Saunders, 1994, p644-646.

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Chorioamnionitis
Synopsis by: Linda Ernst (T88200M41000)[227]
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