MOTHERS BIRTH-WEIGHT AND SURVIVAL OF THEIR OFFSPRING - POPULATION-BASED STUDY

Objective: To test the hypothesis that a baby's survival is related to the mother's birth weight. Design: Population based dataset for two g enerations. Setting: Population registry in Norway. Subjects: All birt h records for women born in Norway since 1967 were linked to births du ring 1981-94, thereby forming 105 104 mother-offspring units. Main out come measures: Perinatal mortality specific for weight for offspring i n groups of maternal birth weight (with 500 g categories in both). Res ults: A mother's birth weight was strongly associated with the weight of her baby. Maternal birth weight was associated with perinatal survi val of her baby only for mothers with birth weights under 2000 g. Thes e mothers were more likely to lose a baby in the perinatal period (odd s ratio 2.3, 95% confidence interval 1.4 to 3.7). Among mothers with a birth weight over 2000 g there was no overall association between mot her's weight and infant survival. There was, however, a strong interac tion between mother's birth weight, infant birth weight, and infant su rvival. Mortality among small babies was much higher for those whose m others had been large at birth. For example, babies weighing 2500-2999 g had a threefold higher mortality if their mother's birth weight had been high (greater than or equal to 4000 g) than if the mother had be en small (2500-2999 g). Conclusion: Mothers who weighed less than 2000 g at birth have a higher risk of losing their own babies. For mothers who weighed greater than or equal to 2000 g their birth weight provid es a benchmark for judging the growth of their offspring. Babies who a re small relative to their mother's birth weight are at increased risk of mortality.