Changes in basal metabolic rate during pregnancy in relation to changes in body weight and composition, cardiac output, insulin-like growth factor I, and thyroid hormones and in relation to fetal growth.

BACKGROUND: The total energy cost of pregnancy is largely due to an elevated basal metabolic rate (BMR). Large variations in the BMR response to pregnancy have been reported, but the factors associated with this variability are incompletely known. OBJECTIVE: The objective was to identify factors associated with variability in the BMR response to pregnancy. DESIGN: In 22 healthy women, BMR, body weight (BW), total body fat (TBF), fat-free mass (FFM), circulatory variables, serum concentrations of insulin-like growth factor I (IGF-I), and thyroid hormones were measured before pregnancy and in gestational weeks 14 and 32. BMR and BW were also measured in gestational weeks 8, 20, and 35. Fetal weight was estimated in gestational week 31. RESULTS: In gestational week 14, the increase in BMR correlated significantly with the corresponding increase in BW and with the prepregnancy percentage of TBF. Together these variables explained approximately 40% of the variability in the BMR response. In gestational week 32, the increase in BMR correlated significantly with the corresponding changes in BW, TBF, FFM, IGF-I, cardiac output, and free triiodothyronine. The increase in BW in combination with fetal weight or with the elevated concentration of IGF-I in serum explained approximately 60% of the variability in the increase in BMR. CONCLUSIONS: Weight gain and the prepregnancy percentage of TBF-ie, factors related to the maternal nutritional situation-are important factors with regard to the variability in the BMR response to pregnancy. Thus, it is important to consider the nutritional situation before and during gestation when assessing pregnancy energy requirements.

[A woman's weight before and during pregnancy is of importance to her infant. USA guidelines would benefit public health in Sweden]. / Kvinnans vikt före och under graviditet har betydelse för barnet. Riktlinjer från USA skulle gagna svensk folkhälsa.

This paper describes weight gain during pregnancy in Sweden in relation to guidelines from the United States. These guidelines take into consideration the fact that optimal weight gain during pregnancy is related to the woman's prepregnant weight in relation to her height. Almost 50 per cent of women delivering babies in Sweden during the year 2000 were obese or overweight. In the three populations studied, less than 50 per cent gained weight in accordance with the US guidelines, while more than 20 per cent gained less weight than recommended. The results indicate that, in Sweden, more attention should be paid to the body weight of women who bear children.