Perinatal mortality in Greece and Greek-born women in Victoria. What does a 'natural experiment' suggest?

A comparison of perinatal outcome in the Greek perinatal mortality survey of 1983 with the outcome of births to Greek born women who had migrated to Victoria, Australia found marked similarities in maternal age, parity, marital status and cigarette smoking. The birthweight distributions were almost identical in the two groups. Despite these similarities the perinatal mortality was substantially higher in Greece. Analysis by cause of death showed the differences to be marginal in all categories except deaths attributed to intrapartum asphyxia which were eight times as common in Greece.