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

Abstract

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 1967 to 1997, totaling 1,705,652 births. Method. The total population was analyzed using z-scores for length at birth, birth weight and gestational age. Variation in perinatal mortality by length at birth was studied within birth weight strata (250 g) by logistic regression. Results. Perinatal mortality varied more by birth length than by birth weight or gestational age, especially for values above the population means. Within birth weight strata, the association between perinatal mortality and length was similar in all 250 g birth weight categories above 1500 grams: mortality was lowest at birth lengths 0-2 cm below average, with mortality rates increasing exponentially in either direction. Conclusion. Within all birth weight strata, and adjusted for gestational age, long infants had the higher risk of perinatal death, suggesting that length at birth may be a valuable predictor when assessing the risk of perinatal mortality.