The influence of racial mix on comparisons of perinatal mortality rate between Area Health Authorities.

The proportion of births to women of New Commonwealth origin in different Area Health Authorities (AHAs) varies widely. The influence of this varying proportion in contributing to differences in perinatal mortality rate (PNMR) between authorities is examined. Firstly, it is shown that the two main 'immigrant' groups have adverse PNMRs compared with Europeans, and that there is a positive correlation between the proportion of immigrant births in an Area and the PNMR. Secondly it is shown that immigrants have PNMRs (standardised for birth weight distribution) better than those of Europeans, and that there is a negative correlation between the proportion of immigrant births in an Area and the standardised PNMR of the whole Area. Thirdly, based on data from Birmingham a correction factor is developed and applied to the standardised PNMR to examine the effect of adjusting for racial mix. Factors other than birthweight contributint to variation between races in their PNMRs are discussed. It is concluded that the effect of race in contributing independently of birthweight to variation between Areas in respect of PNMRs is insufficient to invalidate inter-Area comparisons.