Infants' length at birth: an independent effect on perinatal mortality

Aim. To investigate whether variations in birth length (crown-heel-length) were associated with perinatal mortality rate independent of birth weight. Material. The study population was singleton live- and stillbirths from 16 weeks of gestation compiled in the Medical Birth Registry of Norway from 19 67 to 1997, totaling 1,705,652 births. Method. The total population was analyzed using z-scores for length at birt h, birth weight and gestational age. Variation in perinatal mortality by le ngth at birth was studied within birth weight strata (250 g) by logistic re gression. Results. Perinatal mortality varied more by birth length than by birth weig ht or gestational age, especially for values above the population means. Wi thin birth weight strata, the association between perinatal mortality and l ength was similar in all 250 g birth weight categories above 1500 grams: mo rtality was lowest at birth lengths 0-2 cm below average, with mortality ra tes increasing exponentially in either direction. Conclusion. Within all birth weight strata, and adjusted for gestational ag e, long infants had the higher risk of perinatal death, suggesting that len gth at birth may be a valuable predictor when assessing the risk of perinat al mortality.