Energy requirements of pregnancy in The Netherlands

Abstract

57 healthy Dutch women were studied longitudinally from early pregnancy until 2 months post partum. Regular measurements were made of energy intake in food, basal metabolic rate, body weight and body fat mass, and levels of physical activity. Some data were obtained before conception in 23 women. The energy cost of pregnancy calculated as the energy deposited as new tissues plus the associated increase in basal metabolism amounted to 286 MJ (1020 kJ/day), which is only 11% lower than the theoretical estimate of requirements of 323 MJ (1 MJ = 239 kcal). Energy intake throughout the first 10 wk of pregnancy was identical to that before pregnancy. Energy intake was only 200 kJ/day higher in late than in early pregnancy (not significant), and the cumulative increase in energy intake over pregnancy was estimated as 22 MJ (about 80 kJ/day). There is, therefore, an energy gap in pregnancy of about 940 kJ/day. It is proposed that the main mechanisms by which the pregnant body is able to save energy and to bridge the energy gap are by adjustments to physical activity and an increase in work efficiency and an adaptation of the metabolic response to food. Savings on physical activity by behavioural adaptations will not exceed 355 kJ/day.

PIP: 57 study subjects, who live in or near the city of Wageningen, The Netherlands, participated in this study designed to determine energy requirements in pregnancy and lactation. The 57 Dutch women, studied longitudinally from early pregnancy until 2 months postpartum, were judged to be healthy by medical histories, blood pressure, blood hemoglobin, and urine analysis. 23 women also were studied prior to conception. The women were from middle-upper socioeconomic levels, worked as housewives, were not obese, and all were white. 53 women delivered at term (gestation 259-293 days), 2 before term (244 and 248 days), and 2 after term (294 and 297 days). Birthweights were judged normal for gestational age in all but 2 children. Food consumption was measured on 54 women at about 11, 23, and 35 weeks gestation. Food intake also was assessed before pregnancy in 20 women. In another subgroup of 31 women additional food consumption measurements were made at about 17 and 29 weeks gestation. Food intake was always assessed over 5 consecutive days by the individual-weighed inventory technique. Basal metabolic rate (BMR) was measured by open-circuit indirect calorimetry with Douglas bagas and calculated with Weir's equation. At each laboratory visit body weight was measured on a beam balance; body fat mass was assessed by the skinfold method and the densitometric method. A subgroup of 18 women kept detailed physical activity diaries for 5 consecutive days simultaneously with the dietary surveys. The body weight at 10 weeks gestation was 1.1 kg higher than before pregnancy (n=23). Throughout the remainder of pregnancy, body weight increased by 10.5 kg (n=57). At about 10 weeks gestation body fat mass was 0.4 kg (not significant) higher than before pregnancy (n=19). In the last 10 weeks of pregnancy body fat mass was 2.1 kg (significant) above the value at 10 weeks (n=42). Body weight and body fat mass remained unchanged from 1-2 months postpartum. The energy cost of pregnancy calculated as the energy deposited as new tissues added to the associated increase in basal metabolism amounted to 286 MJ (1020 kJ/day). This is only 11% lower than the theoretical estimate of requirements of 323 MJ (1 MJ=239 kcal). Throughout the first 10 weeks of pregnancy, energy intake was the same as that before pregnancy. Energy intake was 200 kJ/day higher in late than in early pregnancy (not significant); the cumulative increase in energy intake over pregnancy was estimated to be 22 MJ (about 80 kJ/da). There is an energy gap in pregnancy of about 940 kU/day. Physiological and metabolic adaptions will bring about a lowering of energy expenditure in pregnancy by a reduction in dietary-induced thermogenesis and/or an increase in work efficiency.