Classification differences and maternal mortality: a European study. MOMS Group. MOthers' Mortality and Severe...

To compare the ways maternal deaths are classified in national statistical offices in Europe and to evaluate the ways classification affects published rates.

Data on pregnancy-associated deaths were collected in 13 European countries. Cases were classified by a European panel of experts into obstetric or non-obstetric causes. An ICD-9 code (International Classification of Diseases) was attributed to each case. These were compared to the codes given in each country. Correction indices were calculated, giving new estimates of maternal mortality rates.

There were sufficient data to complete reclassification of 359 or 82% of the 437 cases for which data were collected.

Compared with the statistical offices, the European panel attributed more deaths to obstetric causes. The overall number of deaths attributed to obstetric causes increased from 229 to 260. This change was substantial in three countries (P < 0.05) where statistical offices appeared to attribute fewer deaths to obstetric causes. In the other countries, no differences were detected. According to official published data, the aggregated maternal mortality rate for participating countries was 7.7 per 100,000 live births, but it increased to 8.7 after classification by the European panel (P < 0.001).

The classification of pregnancy-associated deaths differs between European countries. These differences in coding contribute to variations in the reported numbers of maternal deaths and consequently affect maternal mortality rates. Differences in classification of death must be taken into account when comparing maternal mortality rates, as well as differences in obstetric care, underreporting of maternal deaths and other factors such as the age distribution of mothers.