Fetus-Placenta-NewbornNew standards for birth weight by gestational age using family data☆,☆☆
Section snippets
Material and methods
We analyzed data as available in the Medical Birth Registry of Norway. The registry is population based and contains all births in Norway since 1967. In this study we used data for 32 years, 1967-1998, which comprised >1.7 million births. The registry contains all live births and reported fetal deaths at ≥16 weeks’ gestation.
In Norway a unique personal identification number is given at birth to all citizens, and the personal number of the mother is available for all births included in the
Birth weight according to gestational age with family data
To illustrate the strong relationship between sibling birth weights, we present in Fig 1, A, the observed mean birth weight according to gestational age and the observed 10th and 90th percentile values in second births for 2 strata of first birth weights, 2250 to 2749 g and 3750 to 4249 g.
Comment
Sibling birth weights are highly correlated,6 and we showed in this study that the expected birth weight in a second birth varied by >1100 g, depending on the first birth weight. Although the link between maternal and offspring birth weights was weaker,7, 8 maternal birth weight similarly contributed to variation in first birth weight, with an effect of almost 700 g.
Tanner et al9 have suggested family standards for improved prediction of birth weight. However, they reflected that
Acknowledgements
We thank Gunnar Dalseth and Barbro Mork Emblem for valuable programming assistance.
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Cited by (0)
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Supported by the Norwegian Research Council.
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Reprint requests: Rolv Skjærven, PhD, Section for Medical Statistics, Armauer Hansens Bldg, N-5021 Bergen, Norway.