Birth weight and gestation time in relation to maternal age, parity and infant survival.

This study examined birthweight and gestation time in relationship to maternal age, parity, and infant survival in 13,730 (7037 male, 6693 female) births at an obstetric hospital in 1935-46. Preliminary analysis of the data indicated that nonsurvivors were significantly lighter at birth with shorter mean gestation times and older maternal ages than survivors. Parity in the 2 groups was similar. When infants who died in the 1st 28 days of life were excluded, the association between birthweight and parity was significant. Children of the 1st 3 parities showed a definite decrease in weight with increasing maternal age, but this effect was not present in higher parities. Mean gestation times were shorter by 1-2 days for parities 5 and above. Parabolas gave a good fit to the logarithm of odds on survival for a given birthweight. Survival was greatest among infants in the 7.5-8.5 lb weight group, which was close to the mean value. A 275-89 day gestation period was associated with the highest rates of infant survival, with periods under 260 days less favorable than periods of 305 days or more. The articla also provides tables for estimating infant survival for given weights and gestation times.