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3 Physiology of Normal Pregnancy and the Effects of Undernutrition
Pages 103-124

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From page 103...
... . Some of this Lance is due to Me manipulation of weight gain by restriction of food intake; the influence of age, pang, and pregravid body weight, and the presence or absence of excessive water retention.
From page 104...
... Pregnant women with edema, particulars generalized edema, may gain substantially more water. Sodium and other minerals also accumulate during pregnancy, but their direct contribution to the total weight gain is minimal.
From page 105...
... Carbohydrates are stored as glycogen in the liver and in muscle tissue Maternal Energy Expenditure and Every Balance Studies from Lee Gambia suggest that the nutritional state of the mother may influence the change in resting metabolism. At term, the cumulative change in RMR totaled 13,000 kcal In supplemented women, whereas RMR increased by only 1,000 kcal in unsupplemented women.
From page 106...
... (1987) also evaluated the effect of food supplementation and seasonal energy demands on total fat gain dunag gestation in Gambian women In unsupplemented women, there was no gain in body fat, as estimated from changes in total body water, throughout pregnancy.
From page 107...
... showed that they reduced their energy expenditure to 75 percent of that of nonpregnant women in the last month of pregnant y by reducing the amount of housework and heavy fann wore Me total time spent fang was unchanged, however. The response to food supplementation is also of interest A net ins rease of 723 kcalJday during lactation did not affect breast mink volume or milk energy content (Prentice, 1984~.
From page 108...
... The energy cost of physical activity did not increase with food supplementation (Lawrence et al., 1985~. It is possible that all pregnant women, regardless of nutritional state, reduce then work intensity.
From page 109...
... The concentrations of triglycendes, cholesterol, and phospholipids increase, with the concentrations of phospholipids and triglycerides tending to level Odin We third t~ester "d the cholesterol concentration continuing to rise (Knopp et al., 1978~. Undernutrition, Blood Volume Expansion, and Placental Blood flow in Animal Models Acute food restriction in pregnant rats lets the expansion of blood volume (Rosso and Streeter, 1979)
From page 110...
... The tong of the onset of maternal fob restriction can have deferent effects on uteroplacental blood Skew, depending on the distn~ution of the cardiac output. It is unclear whether a reduction in placental blood flow caused by food restriction significantly reduces nutrient transfer to the fetus.
From page 111...
... , a lipolytic hormone that mob~l~ maternal fatty acids and Bus spares glucose for the fetus and placenta (Ki~ller, 1980) , is increased in fasting pregnant women (Kim and Felig, 1971~.
From page 112...
... This increase in the level of absolute oxygen consumption while resting is consistent among species, and it appears reasonable in view of not only the continued growth of the metabolically active conceptus but also the high cost of the extra maternal cardiac and respiratory work and the considerable cost of reasborbing the extra sodium filtered by the raised glomerular filtration rate (Block et al., 1985; Gilbert et al., 1982~. Resting oxygen consumption in early and mid-gestation appears to be highly variable, being lowered or increased depending on previous maternal nutritional status and energy intake.
From page 114...
... In pregnant women in labor, lactic acid concentration normally increases In relation to muscular work with each contraction.
From page 115...
... Undernutrition in Pregnancy: "Accelerated Starvation" While the basal circulating concentrations of major substrates appear to change over a relatively narrow range during pregnancy when food intake is adequate, the combination of increased absolute rates of fuel consumption and the endocrine changes associated with pregnancy appear to predispose pregnant animals toward intolerance of brief fasts that nonpregnant animals would easily accommodate. During pregnancy, the normal metabolic responses to a fast appear exaggerated in both time and quantity.
From page 116...
... More recent work has documented that the flux of actual nutrients appears to be more complicated and varies from simple diffusion as for water, facilitated diffusion, as for glucose; or active transport, as for some amino acids and calcium. Fluxes of some substrates, such as ethanol, appear tO be directly related tO placental blood flow, while fluxes of others, such as glucose and oxygen, are relatively independent of flow until it is markedly diminished (WiLkening and Meschia, 1985; Wilker~ing et al., 1985~.
From page 117...
... Studies in chronically prepared sheep, discussed later in this report, suggest that exercise may result in decreases in uterine and umbilical blood flow unaccompanied by decreases in nutrient flux. Placental Transport in Malnourished Women and Animals The placentas of women from lower socioeconomic groups weigh less, have d~sproponionately large deficits in trophoblastic mass, and have reductions in the surface area of villi.
From page 118...
... Maternal prote~n-calone malnutrition in rats can also limit the normal expansion in circulating blood volume and can result in diminished uterine blood flow (Rosso, 1981~. Deceased uterine blood flow and decreased substrate concentration In combination result in diminished nutrient delivery consistent with diminished nutnent flux from mother to fetus.
From page 119...
... showed that In sheep, despite increased maternal and fetal blood concentration, few lactate metabolism Is not grossly disturbed by moderate maternal exercise. This study also examined fend responses to combined maternal undernutrition and exera set Iron Status and Work Performance Iron is an essential component of hemoglobin, which Is responsible for transporting oxygen to the tissues.
From page 121...
... 1985. Effects of f~st~g on glucose turnover and metabolite levels in conscious pregnant guinea pigs.
From page 122...
... 1981. Effects of obesity, food restriction and pregnancy on fetal and maternal weight and on body composition in rats.
From page 123...
... 1980. Effects of food restriction on cardiac output and blood flow to the uterus and placenta in the pregnant rat.
From page 124...
... 1985. Fetal oxygen uptake, oxygenation and amd-base balance as a function of uterine blood flow Am.


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