Villous oedema of the placenta: a clinicopathological study

Villous oedema was observed in 259 placentae among 1925 consecutive singleton pregnancies of greater than 19 weeks gestation. It was present in 11 per cent of term placentae in which significant associations with fetal and neonatal death (P less than 0.03), and absence of maternal cigarette smoking (P less than 0.002) were found. In preterm placentae, the oedema was usually more severe, and its prevalence increased from 20 per cent for 33-37 weeks to 40 per cent for less than 33 weeks. Our analysis showed that for a given gestational age, villous oedema was not significantly related to chorioamnionistis, Apgar scores of less than 7 at 1 and 5 min, or neonatal death, an exception was for 33-37 weeks gestation, in the absence of chorioamnionitis, villous oedema was associated with low 1 min Apgar score. Immature intermediate villi are present in premature placentae as a normal developmental stage and in dysmature placentae as a result of villous maldevelopment. Since villous oedema closely resembles the 'stromal channels' in this villous type and shows significant association with prematurity and villous dysmaturity, we postulate that villous oedema is a lesion primarily of the immature intermediate villi. Both fetal and maternal factors are involved in its pathogenesis.