A HIGHER WEIGHT SPECIFIC FETAL MORTALITY RATE (FMR) CAN EXPLAIN LOWER NEONATAL MORTALITY RATE (NMR) IN BLACK PREMATURE INFANTS

Abstract

The low birth weight (LBW) neonatal mortality is known to be better in black than in white population, but the reasons are not clear. To test the hypothesis that a relatively high LBW fetal mortality might be occurring in black LBWs to explain the low NMR, we used a computerized regional perinatal data base, (Spellacy, AM.J.Ob Gyn.’84> and analyzed data from 65,387 births (1982-85). Standard perinatal vital rates weight specific FMR and NMR and their ratios, and log odds ratio of FMR at 250 g b wt intervals in 16,874 black, 35,966 white and 12,547 Hispanic births were analyzed. (Table). The black LBW NMR was significantly lower than white and Hispanic rates, but LBW-FMR/NMR ratio showed that for every 10 LBW neonatal deaths at 1.5-2.5Kg wt. range, (which forms 11.2% of black total births), there were 25 fetal deaths in blacks as compared to 12 fetal deaths in white and Hispanics. The log odds ratios of weight specific NMR models showed that the odds of FMR decreased exponentially with increasing weight in all races, but the slope in the black was 26% flatter, (p<0.01). Because of high LBW rate in the blacks, a higher risk of LBW black FMR can explain why their LBW-NMR is better: A relatively large fraction of black LBW fetuses simply die before birth. (*Black rates significantly different from white and Hispanic rates: Chi square for independent proportions: p<0.05)