Birth weight trends in the 20th century

Abstract

Conflicting evidence exists as to the effect of increased birth weight on mode of delivery. Turner et al. in 1990 concluded that there was a direct relationship between high birth weight and the development of dystocia in nulliparas. However, Gordon Smith, in a population study in Scotland, showed no association between increasing birth weights and increasing caesarean section rates in nulliparas. We investigated the trend in birth weights over the past century in the Rotunda Hospital from 1900 to 2000 inclusive. Data were collected from the labour ward registers for the study period. Male and female birth weights were collected on primiparous and multiparous women. Two hundred birth weights were collected at intervals of 5 years, 100 in the first half of the year and 100 in the second half. Only full-term, singleton, live-born babies weighing >1 kg were included. The lowest birth weights across all categories were recorded for 1945. Comparing birth weights from 1900 to 2000, in nulliparous women there was an increase of 300 g in male infants and an increase of 230 g in female infants. There was a further increase in birth weights from 1945 to 2000 in infants of nulliparous women, with an increase of 456 g in male infants and 340 g in female infants. Birth weights in the multiparous women did not show a similar trend.