Classifying perinatal death: experience from a regional survey.

Abstract

OBJECTIVE: To examine problems encountered in classifying perinatal death using the systems proposed by Hey et al. (1986) and Cole et al. (1986). SUBJECTS: 451 deaths from a regional perinatal mortality survey of which 293 had a post mortem examination. METHODS: Documents from each death were reviewed by four assessors, one from each discipline, selected randomly from a pool of obstetricians, paediatricians, general practitioners and midwives. Each assessor classified the cause of death blind to the others. The degree of agreement between assessors was calculated for the full and shortened obstetric and fetal-neonatal classifications using the kappa statistic for inter-rater agreement. RESULTS: The kappa statistic, which is a measure of the proportion of agreement above chance, gave a value of 0.55 for the full obstetric classification and 0.58 for the full fetal and neonatal classification when all four assessors made an assignment. An assignment was omitted in 6.2%, but the kappa value of zero for these omissions suggested that this was a nonsystematic result due to random protocol violations. The grouped (shortened) classifications generated a higher kappa value of 0.62 for the nine point obstetric system and 0.67 for the six point fetal and neonatal (New Wigglesworth) system. Post mortem had little effect on agreement. The best agreement levels observed were for congenital anomaly. CONCLUSION: This survey highlighted the complexity of the 22 and 24 point classifications, the uneven distribution of deaths within their categories, and the variable levels of agreement between professionals classifying deaths, thus questioning the validity of individual maternity units of health districts generating local data in this degree of detail for comparative purposes in regional and national statistics. Grouping the original categories led to greater agreement particularly for the New Wigglesworth classification. The role of post mortems in clarifying the cause of fetal and neonatal death needs further investigation.