Birthweight between 14 and 42 weeks' gestation.

Data representing fetal weight gain between 14 and 42 weeks' gestation are presented; firstly to provide suitable curves enabling the growth of the very immature infant to be monitored and secondly to examine the influence of the improved techniques of paediatric and obstetric assessment developed since the publication of previous studies. Data have been collected from the 57 866 livebirths in Sheffield between 1976 and 1984 and from therapeutically terminated and spontaneously aborted fetuses over the same period. It seems that preterm livebirths do not form a different population with respect to weight from the fetus still in utero, at least until the beginning of the third trimester. Previous studies have reported a bimodality of weight distribution in preterm infants at each gestational age which has been attributed to errors in gestational assessment. The pattern of distribution of weight in this study suggests that early ultrasonography and paediatric assessment techniques have exerted a considerable influence on the accuracy of gestational assessment. The mean weights of the sample differ considerably from those of the Gairdner and Pearson chart which are, therefore, considered to be inappropriate for the Sheffield population.