Neonatal mortality risk related to birth weight and gestational age in British Columbia

To provide gender-specific neonatal mortality grids depicting relative risk in narrow birth weight ranges at each week of gestation. The grids will provide practitioners with clinically relevant information pertinent to pregnancy, delivery, and postnatal care in Canada.

Records from the British Columbia Vital Statistics Agency birth and death registries from 1981 to 2000 were deterministically linked and resulted in a 99.86% linkage rate. Risk ratios were computed by dividing percent neonatal mortality in 250 g birth weight categories at each week of gestation by the overall gender-specific mortality rates for the full period. We adjusted random rate fluctuations that were due to low frequencies in the narrow birth weight and gestational age strata.

Females exhibited greater survival across the full spectrum of birth weight by gestational age strata, but their mortality configurations were noticeably different from those of males. In addition, there were demarcations in both grids that depicted relatively abrupt changes in risk ratios. Although the crude mortality rates in BC decreased during the study period, the use of risk ratios reduced the disparity in crude rates over time.

These gender-specific mortality grids refine and enhance previously available comparisons by portraying neonatal mortality risks in narrow birth weight ranges at each week of gestation.