Energy requirements of pregnancy in Scotland.

Measurements of energy intake, basal metabolic rate, body weight and composition, and physical activity were made on 88 women throughout pregnancy. Mean weight gain (from 10 wk to 40 wk gestation) was 11.7 kg, birthweight 3370 g, and placental weight 641 g. Maternal fat gain (from 10 wk) calculated by three methods was 2.1 kg. The total rise in basal metabolism for the whole of pregnancy was calculated to be 126 MJ (1 MJ = 239 kcal). The total increase in energy intake was estimated as 88 MJ. There was little evidence of any changes in either the energy cost of physical activity or the time spent in these activities. The total energy cost of laying down fetal and maternal tissues and the increased metabolism was 281 MJ, which was offset by a possible increase in energy intake of only 88 MJ. The most likely explanation for the deficit of 193 MJ is that many small reductions in energy expenditure occurred which were not detectable by the methods used.