6) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Pregnancy Flashcards
How does BMR vary during pregnancy?
Increase
What two factors explain for the increase in BMR during pregnancy?
1) Metabolic contributions of the uterus and fetus
2) Increase in work of the lungs and heart
What is the strongest predictor of BMR? Why?
- Fat-free mass (FFM)
- Because fat mass is not metabolically active
What are the three components of FFM in pregnancy?
1) An increase in blood volume
2) Skeletal muscle mass
3) Fetal and uterine tissues
Which component of FFM
during pregnancy is low energy-requiring?
An increase in blood volume
Which component of FFM
during pregnancy is moderate energy-requiring?
Skeletal muscle mass
Which component of FFM
during pregnancy is high energy-requiring?
Fetal and uterine tissue
By late pregnancy, half of the increment of energy expenditure can be attributed to ________.
the fetus
What are the two additional energy requirements for pregnancy?
1) Energy required to provide for the growth of tissues
2) Energy required for the maintenance of new tissues
How may the energy cost of new tissue deposition be calculated during pregnancy?
- From the amount of protein and fat deposited throughout the pregnancy
- The quantity of protein and fat gained are converted to calories
- The total number of kilocalories gained during pregnancy is divided by the duration of pregnancy
Why is there an increase in the requirement of energy per gram to synthesize protein and fat?
The synthesis of protein and fat requires the addition of energy
How does PAL vary during pregnancy?
Decrease
How does TEE vary during pregnancy?
Increase
What is the median increase of TEE per gestational week?
8 kilocalories
The EER during pregnancy is the sum of which three components?
1) TEE of the woman in a non-pregnant state
2) Median change in TEE of 8 kcals/week
3) Energy deposition of 180 kcals/day
What is the additional energy requirement, in calories, during the first trimester?
- There is little weight gain and variation in TEE
- There is no additional energy required
What is the additional energy requirement, in calories, during the second trimester?
340 kilocalories
What is the additional energy requirement, in calories, during the third trimester?
452 kilocalories
What weeks does the first trimester correspond to?
Weeks 1 to 12
What weeks does the second trimester correspond to?
Weeks 13 to 27
What weeks does the third trimester correspond to?
Week 28 to birth
Which week is used for the multiplication of the TEE during the SECOND trimester to derive the additional energy requirements?
- Week 20 (midpoint of the second trimester)
- 8 kilocalories x 20 weeks
Which week is used for the multiplication of the TEE during the THIRD trimester to derive the additional energy requirements?
- Week 34 (midpoint of the third trimester)
- 8 kilocalories x 34 weeks
What two factors are the basis of the additional protein requirements during pregnancy?
1) The support in growth of maternal and fetal tissues
2) Maintenance of additional protein stores
Why do protein requirements vary with each trimester?
Due to differences in protein needs for growth and maintenance of the additional protein accretion that has accumulated by the end of each trimester
What is the estimate of protein requirements during pregnancy based on?
Growth and body composition at the end of each trimester
What is the additional protein requirement during the first trimester?
- There is low deposition of tissue during the first trimester
- There is NO increase in protein requirement
What is the additional protein requirement during the second and third trimesters? How is it determined?
- EAR: 21 grams of protein per day
- RDA: 25 grams of protein per day
- The additional pregnancy protein requirement during the second and third trimesters are averaged to devise the EAR
How is protein and energy related to low-birth weight infants?
Improving protein and energy nutrition during gestation, and prior to gestation, decreases the risk of low-birth weight infants
Where may omega-6 and omega-3 fatty acids be acquired to become incorporated into placental and fetal tissue?
Obtained from maternal tissues or through dietary intake
How does the AI for omega-6 fatty acids vary during pregnancy?
Increase (12 g/d to 13 g/d)
How does the AI for omega-3 fatty acids vary during pregnancy?
Increase (1.1 g/d to 1.4 g/d)
Which fatty acid is contained in high quantity in maternal and fetal blood of low-birth weight infants? What type of fatty acid is it?
ETA (omega-9)
Which fatty acids are contained in low quantity in maternal and fetal blood of low-birth weight infants? What type of fatty acid are they?
- AA (omega-6)
- DHA (omega-3)
What do high levels of ETA indicate? Why?
- Essential fatty acid deficiency
- If there is a lack of both omega-6 and omega-3 fatty acids, desaturase enzymes produce omega-9 fatty acids (such as ETA) from oleic acid
How is the ratio of omega-6 to omega-3 fatty acids altered by vegetarian diets? What is an adequate ratio?
- Vegetarian: 15:1 or 20:1 (HIGH)
- Mediterranean diet: 4:1 to 10:1 (LOW)
How may vegetarian diets pose risk for the brain development of the fetus?
Vegetarians have higher quantities of AA and lower amounts of DHA
How does metabolic rate vary during pregnancy?
Increase
What four factors cause an increase in metabolic rate during pregnancy?
1) Establishment of the placental-fetal unit
2) Increase in the energy supply for the growth and development of the fetus
3) Increased maternal storage of fat EARLY in pregnancy
4) Energy to sustain the growth of the fetus during the last trimester
What are three adaptations to pregnancy in terms of carbohydrate metabolism?
1) Decrease in fasting maternal blood glucose
2) Development of insulin resistance
3) Tendency to develop ketosis
Why is there an increase in glucose uptake during the second half of pregnancy?
Due to an upregulation of glucose transporters on the fetal portion of the placenta
What is the respiratory quotient (RQ)?
The ratio of CO2 produced by oxygen consumed
How does the RQ vary during pregnancy?
Increases for both BMR and the total 24-hour energy expenditure
How does glucose utilization by the maternal-fetal unit vary during pregnancy?
Increase
What percentage does glucose oxidation account for in the estimated fetal brain’s fuel requirement? What does that indicate?
- 70%
- Indicates that the fetal brain can use keto acids
How does keto acid concentration vary during pregnancy?
Increase
What is the glucose requirement during late gestation? How does that compare to the maternal-fetal glucose transfer rate?
- Glucose requirement is 33 g/d
- Maternal-fetal glucose transfer rate is lower, averaging at 22 g/d
What quantity of glucose transferred from the mother does the fetus utilize?
- Essentially, all of the glucose transferred from the mother
- Glucose transfer rate: 22 g/d
- Fetal brain glucose utilization rate: 23 g/d
What is the carbohydrate requirement during pregnancy based on?
The transfer of an adequate supply of glucose to the fetal brain that is independent of the utilization of keto acids
What is the additional carbohydrate requirement during pregnancy?
35 g/d
What is the coefficient of variation for carbohydrates during pregnancy based on?
Variations in brain glucose requirement
How does the recommendation for fiber vary during pregnancy?
- There is NO variation (AI = 14 grams/1000 kilocalories)
- There is no evidence that the beneficial effect of fiber for pregnant women is different than for non-pregnant women
How does the recommendation for water vary during pregnancy?
The AI increases from 2.7 L/d to 3.0 L/d
How does the recommendation for calcium vary during pregnancy?
The RDA does not change
How does the recommendation for phosphorus vary during pregnancy?
The RDA does not change
How does the recommendation for magnesium vary during pregnancy?
The RDA increases
How does the recommendation for iron vary during pregnancy?
The RDA increases
How does the recommendation for potassium vary during pregnancy?
The AI does not change
How does the recommendation for sodium vary during pregnancy?
The AI does not change
How does the recommendation for thiamine (vitamin B1) vary during pregnancy?
The RDA increases
How does the recommendation for riboflavin (vitamin B2) vary during pregnancy?
The RDA increases
How does the recommendation for niacin (vitamin B3) vary during pregnancy?
The RDA increases
How does the recommendation for pyridoxine (vitamin B6) vary during pregnancy?
The RDA increases
How does the recommendation for folate (vitamin B9) vary during pregnancy?
The RDA increases
How does the recommendation for vitamin B12 vary during pregnancy?
The RDA increases
How does the recommendation for biotin (vitamin B7) vary during pregnancy?
The AI does not change
How does the recommendation for choline vary during pregnancy?
The AI increases
How does the recommendation for pantothenic acid vary during pregnancy?
- The AI increases because the intake of pregnant women is higher
- However, the requirement does not increase
How does the recommendation for vitamin C vary during pregnancy?
The RDA increases
How does the recommendation for vitamin A vary during pregnancy?
The RDA increases
How does the recommendation for vitamin D vary during pregnancy?
The RDA does not change
How does the recommendation for vitamin E vary during pregnancy?
The RDA does not change
How does the recommendation for vitamin K vary during pregnancy?
The AI does not change
When does the majority of the calcium transfer from the mother to the fetus occur? Why?
- During the third trimester
- Corresponds to the period of maximal skeletal grwoth
What is the major physiological adaptation during pregnancy to meet the increased needs for calcium?
An increase in efficiency in intestinal absorption of calcium
How does calcitriol concentration vary during pregnancy? How does it affect calcium absorption?
- Calcitriol (active vitamin D) increases during pregnancy
- The increase in calcium absorption during pregnancy is NOT due to the increase in calcitriol
- The role of calcitriol is unclear
Under normal physiological conditions, what is the function of calcitriol?
- Increases calcium absorption
- Decreases urinary calcium excretion
- Increases calcium resorption from bone
- Increases calcium absorption from the intestine
How does maternal bone mass vary during pregnancy? What does this indicate?
- There are no changes in maternal bone mass, despite the fact that the fetus is utilizing maternal calcium
- This demonstrates that there is an increase in intestinal absorption, and that there is NO NEED for an increase in calcium requirement during pregnancy
What two factors demonstrate that there is no additional requirement for calcium during pregnancy?
1) The lack of correlation between the number of pregnancies and bone mineral density
2) The fact that additional calcium does not provide benefit during pregnancy
Which factor demonstrates that there is no additional phosphorus requirement during pregnancy?
Likely due to the 10% increase in phosphorus absorption in the intestine during pregnancy
How does serum magnesium vary during pregnancy?
Serum magnesium decreases, which may be due to hemodilution
Which two factors demonstrate that there is an increased requirement for magnesium during pregnancy?
1) Serum magnesium decreases during pregnancy
2) There is no data that indicates that magnesium is conserved during pregnancy, or that intestinal absorption is increased
The increase in magnesium requirement for pregnant women is associated with what?
Weight gain, as it is assumed that weight gain results in an increased requirement for magnesium
What are the three factors that increase the requirement for iron during pregnancy?
1) Basal losses
2) Iron deposited in the fetus and related tissues
3) Iron from the expansion of hemoglobin mass
How does the requirement for iron during the first trimester compare to non-pregnant women? How does the requirement for iron during the second and third trimesters compare to non-pregnant women?
- First trimester: requirement is LOWER than for non-pregnant women
- Second and third trimesters: requirement is HIGHER than for non-pregnant women
How does iron absorption vary during pregnancy?
Iron absorption increases during the second and third trimesters
What is severe anemia during pregnancy associated with?
Perinatal maternal mortality
What is moderate anemia during pregnancy associated with?
Twice the risk of maternal death due to heart failure, hemorrhage, and infection
What are possible risks of maternal anemia during pregnancy?
- Premature delivery
- Low-birth weight infants
- Increased perinatal infant mortality
What is high hemoglobin at the time of delivery associated with? Why?
- Adverse pregnancy outcomes (e.g. SGA)
- High hemoglobin may reflect a decreased plasma volume associated with maternal hypertension and pre-eclampsia
The concentration of hemoglobin and adverse pregnancy outcomes follow what kind of relationship?
U-shaped relationship
How does iron deficiency increase the workload of the maternal heart to supply the fetus with oxygen?
1) Limits the expansion of the RBC mass
2) Decreases hemoglobin synthesis
How are women recommended to meet their iron requirements during pregnancy?
- The habitual Canadien diet cannot meet the iron RDA
- Pregnant women are recommended to ingest iron supplements
Iron supplementation during pregnancy assumes what?
- Assumes inadequate pre-pregnancy iron stores
- If a woman possesses normal iron stores prior to pregnancy, a supplement during pregnancy may be unnecessary as storage iron can be used
Which factor demonstrates that there is no additional potassium requirement during pregnancy?
- There is very little potassium accretion during pregnancy
- There is no data to suggest a different requirement for potassium during pregnancy
What are the two reasons that explain why there is an accumulation of sodium during pregnancy?
1) To maintain the increase in plasma volume
2) To provide for the products of conception
Why is there no increase in sodium requirement, if there is an accumulation of sodium over the course of pregnancy?
- The additional sodium required is 0.07 grams/day
- This is so minimal that sodium requirements during pregnancy do not differ from that of non-pregnant women
Is sodium reduction recommended during pregnancy?
Sodium reduction has no apparent benefit in lower BP or preventing pregnancy-induced hypertension
What are the two factors that increase the requirement for thiamine AND riboflavin during pregnancy?
1) An increase in growth of maternal and fetal compartments
2) A small increase in energy utilization
How does urinary excretion of riboflavin vary over the course of pregnancy?
Decreased urinary excretion
If a pregnant women and a non-pregnant women ingest low intakes of riboflavin, the clinical signs of ariboflavinosis appear more frequently in which women?
Pregnant women
What is the factor that increases the requirement for niacin during pregnancy?
- There is no direct evidence to suggest a change in niacin requirement
- The increase accounts for the increase in energy utilization and growth
What is the factor that increases the requirement for pyridoxine during pregnancy?
- The maintenance of plasma pyridoxal phosphate at non-pregnant values requires an additional intake
- There are no direct problems associated, but the biomarker does decrease
Which B-vitamin is accumulated within the placenta and fetus? During which portion of gestation?
- Pyridoxine
- Particularly during the second half of gestation
What are the two factors that increase the requirement for folate during pregnancy?
1) Single-carbon transfer reactions
2) Nucleotide synthesis (cell division)
What does nucleotide synthesis (cell division) contribute to during pregnancy?
- Uterine enlargement
- Placental development
- Expansion of maternal erythrocyte number
- Fetal growth
What indicates that folate is actively transferred to the fetus?
Umbilical cord blood has a higher plasma folate concentration than maternal blood
What does an inadequate folate intake during pregnancy result in?
Megaloblastic anemia and/or NTDs
How may the absorption of vitamin B12 increase during pregnancy?
Increase in intrinsic factor-B12 receptors
How does serum vitamin B12 vary during the first trimester? What does this indicate?
- Decreases during the first trimester by a significant factor
- Indicates that it is not caused by hemodilution, as hemodilution is sparse during the first trimester
How does serum vitamin B12 vary by the sixth month of pregnancy? What is a probable cause?
- Decreases to half the concentration found in non-pregnant women
- Partially due to hemodilution
What is the sole source of vitamin B12 that is readily transported across the placenta? What does this indicate?
- ONLY the newly absorbed vitamin B12
- Thus, maternal liver stores are a less important source of the vitamin for the fetus
- Current maternal intake is MORE important than vitamin B12 stores
Which biotin metabolite increases over the third trimester?
3-hydroxyisovaleric acid
How does biotin excretion vary during pregnancy?
Decrease in biotin excretion
How does the consumption of raw egg, containing avidin, influence biotin requirement?
Increase in biotin requirement
How does a biotinidase deficiency influence biotin requirement? How?
- Decreases the function of the enzyme, which separates biotin from proteins and enzymes within food components, aiding in the recycling of biotin
- Increase in biotin requirement
How do anticonvulsants influence biotin requirement? How?
- Induce biotin catabolism
- Increasing biotin requirement
The ratio of biotin metabolites to the amount of biotin excreted in urine is (increased/decreased) during pregnancy.
increased
What may deplete maternal stores of choline during pregnancy?
There is a substantial quantity of choline delivered to the fetus during pregnancy
What are consequences of choline deficiency during pregnancy?
Increased concentrations of homocysteine, and potentially birth defects
During pregnancy, there is an increased demand for which choline metabolite?
Phosphatidylcholine
Which trimester demonstrates an increase in maternal choline intake?
The third trimester
How is choline intake related to cortisol during pregnancy?
- A diet that is high in choline decreases the baby’s circulating cortisol
- Alters the methylation state and the expression of genes that regulate cortisol production in the placenta
Which metabolite of choline is used as a methyl donor to convert homocysteine to methionine?
Betaine
How may a sub-optimal level of vitamin B12 and folate negatively influence choline levels?
A deficiency in those nutrients causes the system to utilize betaine, derived from choline, to detoxify homocysteine to methionine
What two factors increase the requirement for vitamin C during pregnancy?
1) The quantity of vitamin C within the plasma decreases with the progression of pregnancy due to hemodilution
2) Active vitamin C transfer to the fetus
The additional requirement for vitamin C is based on which notion?
The quantity of vitamin C to prevent scurvy in young infants
The requirement for vitamin C is increased in certain sub-populations, such as what?
Women who frequently consume street drugs, cigarettes, heavy alcohol, and aspirin
What two factors increase the requirement for vitamin A during pregnancy?
1) The required accumulation of vitamin A in the fetal liver during gestation
2) The assumption that the liver contains half of the body’s vitamin A when liver stores are low, such as in newborns
When does vitamin A accumulate mostly during pregnancy?
During the last three months of gestation
What is the UL for vitamin A based on during pregnancy? What is it based on in non-pregnant women?
- Pregnant women: UL is based on teratogenicity
- Non-pregnant women: UL is based on liver abnormalities
What are the consequences of vitamin E deficiency in newborns?
- Hemolytic anemia
- Hemolysis of RBCs
- Vitamin E prevents oxidants from destroying RBCs
Which factor demonstrates that there is no additional vitamin K requirement during pregnancy?
- There are no reports of vitamin K deficiency during pregnancy
- There is no evidence that maternal supplementation would prevent deficiency symptoms in premature offspring
