Nutrition During Pregnancy Part I: Weight Gain, Part II: Nutrient Supplements (1990) / Chapter Skim
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17 Vitamins, A, E, and K
17 Vitamins, A, E, and K
Pages 336-350
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From page 336... ...
The primary form of preformed vitamin A is retinyl ester, which is found in foods of animal origin such as liver, fish liver oils, milk, eggs, and butter. Provitamin A carotenoids are mainly of vegetable origin; carrots and darkgreen leafy vegetables are especially rich sources.
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From page 337... ...
Carotenoids can be converted to retinal and retinyl esters in the intestinal mucosa, and both carotenoids and the retinyl esters derived from them are transported via the chylomicrons to the liver. The major storage site is the liver, which normally contains more than 90% of the total body stores of vitamin A in well-nourished people.
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From page 338... ...
In human fetuses, such hepatic concentrations are consistently much lower than those in adults (Montreewasuwat and Olson, 1979; Shah et al., 1987; Wallingford and Underwood, 1986) and correlate with maternal serum retinol levels (Shah et al., 1987~.
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From page 339... ...
it is recommended that nonpregnant adults maintain plasma retinal concentrations higher than 30 ~g/dl in order to maintain body stores; levels less than 20 ~g/dl are associated with increased risk for development of clinical signs and symptoms of vitamin A deficiency (NRC, 1989~. Pregnancy complicates the interpretation of these values, in part because blood levels of REP change with pregnancy (NRC, 1978~.
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From page 340... ...
Whether or not lower doses produce a less evident clinical syndrome is not known. Ingestion of excessive amounts of preformed vitamin A produces a well-defined syndrome, including headache, vomiting, diplopia, alopecia, liver damage, and skin abnormalities (Bauernfeind, 1980~.
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From page 341... ...
population. However, since there is also a wide range of individual intakes, it may be important to assess vitamin A intakes, particularly in women with unusual diets or who habitually avoid dietary sources of vitamin ~ Recommendations for Supplementation Since estimated dietary intake in the United States appears to be sufficient to meet the needs of most pregnant women throughout gestation, routine supplementation during pregnancy is not recommended.
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From page 342... ...
Thus, the vitamin is given to premature infants routinely to meet their special needs (AAP/ACOG, 1988~. The limited evidence that macrocytic anemia results from vitamin E deficiency is based primarily on hemolysis after an in vitro peroxide stress.
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From page 343... ...
There is no evidence that maternal vitamin E supplementation would reduce the incidence of health problems in premature infants. However, if the fetus acquires vitamin E while it is accumulating fat (during the last 8 to 10 weeks of gestation)
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From page 344... ...
Thus, supplementation of healthy pregnant women appears to be unnecessary. Special Considerations Given the low vitamin E levels and the clinical syndrome of anemia believed to result from vitamin E deficiency, it is routine to give premature infants supplements of vitamin E
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From page 345... ...
By contrast, there is considerable evidence that the newborn infant is functionally vitamin K-deficient, as judged both by vitamin K levels and by abnormal clotting (Lane and Hathaway, 1985; Muntean, 1983; Pietersmade Bruyn and van Haard, 1985; Prentice, 1985~. Accordingly, pediatric and obstetric professional groups recommend that all newborns receive parenteral vitamin K immediately after birth (AAP/ACOG, 1988)
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From page 346... ...
Vitamin K may also be of special importance in newborns born to women taking anticonvulsant drugs (Yerby, 1987~. CLINICAL IMPLICATIONS · Routine supplementation with vitamin A, either as retinal (preformed vitamin A)
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From page 347... ...
1966. Syndrome in premature infants associated with low plasma vitamin E levels and high polyunsaturated fatty acid diet.
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From page 348... ...
1986. Persistent low plasma vitamin E levels in premature infants surviving respiratory distress syndrome.
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From page 349... ...
1987. Liver stores of vitamin A in human fetuses in relation to gestational age, fetal size and maternal nutritional status.
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From page 350... ...
1987. Oral vitamin E supplementation for the prevention of anemia in premature infants: a controlled trial.
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