GDM: Calorie Level (2001)
Recruitment: article selection method not described
Design: Narrative Review
Blinding Used (if applicable): not applicable
Intervention (if applicable): not applicable
Statistical Analysis: not performed
Timing of Measurements: not applicable
Dependent Variables: not applicable
Independent Variables: not applicable
Control Variables: not applicable
Initial N: 29 references cited
Attrition (Final N): 29
Age: not mentioned
Ethnicity: not mentioned
Other relevant demographics:
Anthropometrics:
Location: Worldwide studies
Fetal demand and maternal nutrient supply influence nutrient adjustment.
The fetal demand for nutrients occurs primarily in the last half of gestation when >90% of fetal growth occurs.
The rapid rate of fetal growth during the last half of gestation dictates changes in basal metabolism, protein and mineral accretion.
About 60% of the increase in BMR occurs during the last half of gestation when the metabolic cost of fetal tissue synthesis is the greatest.
Maternal fat stores are gained primarily between the 10th and 30th wk of gestation before fetal energy demands are at their peak. ~3.3 kg fat is deposited in maternal stores, the remaining 0.5 kg fat is deposited in the fetus.
Protein metabolism in early and late pregnancy
Calloway DJ (1974) summarized the results of 17 nitrogen balance studies representing over 200 measurements in women between 20 and 40 wk gestation and calculated a nitrogen retention of
~1.3 g nitrogen/d or 8.1 g protein/d.
Marino DD (1983) studied nitrogen metabolism in 3 groups of women in early pregnancy (10-20 wk gestation), late pregnancy (30-40 wk gestation) or nonpregnant controls. Women in late gestation retained 4x more nitrogen than control women or women in early pregnancy. Nitrogen retention was similar for nonpregnant (0.46+0.28 g/d) and women in early gestation (0.56+0.88 g/d) and significantly higher in late gestation (2.10+0.74 or ~13 g protein/d)(P<0.05).
The increased nitrogen retention in late pregnancy was due to a reduction in urinary nitrogen (1.5 times lower than control women or women in early pregnancy.
Kalhan SC, (2000) demonstrated that the reduction in urinary nitrogen in pregnancy is probably due to a decrease in urea synthesis. Urea synthesis declines by 30% during the 1st trimester and 45% in the 3rd trimester compared to nonpregnant controls.
Plasma amino acids decline ~15-25% in late pregnancy, reflecting enhanced placental uptake. Also, maternal oxidation of branched-chain amino acids for energy decreases in late gestation, increasing the amount of energy available for the fetus.
Metabolic adjustments to meet energy needs
The cumulative energy needed for the increase in BMR for pregnancy is 36,000 kcal and the daily energy need in the last quarter of pregnancy is 230 kcal. To meet the increased demand for energy, the following changes may occur:
1. in the rate of lipid synthesis and maternal fat storage.
2. alteration in the intensity of physical activity.
3. increase in food and energy intake.
King JC et.al., (1994) studied 10 women within normal weight over the course of pregnancy and evaluated resting metabolic rate and dietary intake preconception, 8-10, 24-26, and 34-36 gestation and 4-6 wk postpartum. The energy needs of pregnancy per day over the course of pregnancy were 210 to 570 kcal.
The marked differences in metabolic responses of these women suggest that fetal size and therefore, energy demand, influences the adjustments in energy metabolism made by the mother during gestation.
Pregnancy consists of a series of small, continuous changes that affect the metabolism of all nutrients.
Evidence is accumulating that the prepregnancy period is the best time to prepare f or the demands of pregnancy. Public health policies should be established to ensure good maternal nutrition during all phases of the reproductive cycle—prepregnancy, pregnancy, lactation and postweaning.
| University/Hospital: | University of California Davis |
The studies on protein needs during pregnancy are in agreement with the RDA of an additional 10 grams of protein for pregnancy.
The studies on energy needs during pregnancy show a great degree of variability in ways that women meet energy demands of pregnancy—decreased physical activity, increased intake or limited maternal fat storage during pregnancy.
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Quality Criteria Checklist: Review Articles
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| Relevance Questions | |||
| 1. | Will the answer if true, have a direct bearing on the health of patients? | Yes | |
| 2. | Is the outcome or topic something that patients/clients/population groups would care about? | Yes | |
| 3. | Is the problem addressed in the review one that is relevant to dietetics practice? | Yes | |
| 4. | Will the information, if true, require a change in practice? | Yes | |
| Validity Questions | |||
| 1. | Was the question for the review clearly focused and appropriate? | Yes | |
| 2. | Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? | No | |
| 3. | Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? | No | |
| 4. | Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? | No | |
| 5. | Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? | Yes | |
| 6. | Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? | Yes | |
| 7. | Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? | No | |
| 8. | Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? | Yes | |
| 9. | Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? | Yes | |
| 10. | Was bias due to the review's funding or sponsorship unlikely? | Yes | |