High Rate of Chronic Villitis in Placentas of Pregnancies Complicated by Influenza A/H1N1 Infection

Table 1

Histological classification of chorioamnionitis, funisitis, and villitis.

Grade	Chorioamnionitis	Funisitis	Villitis
0	No inflammation	No inflammation	No inflammation
0.5	Sporadic PMN in chorionic plate/membranes
1	Frequent PMN in chorionic plate/membranes	Inflammation present in the wall of 1 vessel (vein)	1 section with 1 focus of chronic inflammation of >5 villi
2	Invasion of chorionic plate, large infiltrate in chorionic plate/membranes	Inflammation present in the wall of 2 vessels (vein and artery)	2-3 sections with each having 1 focus of chronic inflammation of >5 villi
3	Same as 2, including microabscesses in chorionic plate	Inflammation present in the wall of 3 vessels (vein and 2 arteries)	3 sections with each having >2 foci of chronic inflammation of >5 villi

PMNs: polymorphonuclear cells.