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.


METHODS
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.
Lof
Marie
M
Division of Nutrition, Department of Biomedicine and Surgery Clinic, Linkoping, Sweden.
Olausson
Hanna
H
Bostrom
Karin
K
Janerot-Sjöberg
Birgitta
B
Sohlstrom
Annica
A
Forsum
Elisabet
E
D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D001481:Basal Metabolism / Q000502:physiology*; D001724:Birth Weight / Q000502:physiology; D001823:Body Composition / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D002302:Cardiac Output; D003903:Deuterium; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D047109:Fetal Development / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D007231:Infant, Newborn; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D009751:Nutritional Requirements; D011247:Pregnancy / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D013963:Thyroid Hormones / Q000378:metabolism
D013963:Thyroid Hormones; D007334:Insulin-Like Growth Factor I; D003903:Deuterium