Choriodecidual inflammatory syndrome (CoDIS) is the leading, and under recognised, cause of early preterm delivery and second trimester miscarriage.

Severe preterm birth (delivery before 32 completed weeks of gestation), with or without preterm premature rupture of the membranes (PPROM), remains the leading cause of perinatal mortality. It is proposed that localized inflammation of the chorion and decidua in the membranes immediately above the internal cervical os, with or without amniotic cavity infection and inflammation, is the leading, but under recognised, cause of second trimester miscarriage and severe preterm delivery. The term 'CoDIS' (choriodecidual inflammatory syndrome), may provide a better understanding of the underlying pathophysiology than currently used terminology which over emphasizes the importance of overt intra-amniotic infection as opposed to localized extra-amniotic inflammation which stimulates uterine evacuation. Copyright 2001 Harcourt Publishers Ltd.