Physiological Changes During Pregnancy Flashcards
What are the major physiological changes that occur with pregnancy?
- ↑organ weight
- ↑respiratory rate
- ↑urinary output
- ↑heart rate & stroke volume
- ↑blood volume & RBC
- ↑blood lipids
- ↑insulin resistance
- ↑BMR
- relazed GIT muscle tone (fart more)
What are the phases of physiological changes during pregnancy?
- maternal anabolic phase: 0-20 weeks
- maternal catabolic phase: 20 weeks-brith
What happens in the maternal anabolic phase?
“building up” of mother’s body to supply increased needs of fetus and infant so a lot of extra energy goes to mom here first
* ↑ blood volume, growth of maternal organs
* ↑ fat, glycogen, nutrient stores
* ↑ appetite, decreased exercise tolerance
* ↑ anabolic hormones
How much fetal growth occurs in the maternal anabolic phase?
10%
What happens in the maternal catabolic phase?
Delivering stored energy and nutrients to the growing fetus
* mobilization of stores
* accelerated fasting metabolism
* increased appetite and food intake (declines near term) and exercise tolerance
* increased catabolic hormones
What drive the maternal catabloic phase?
the placenta
What is the single best predictor of
a baby’s health at birth?
Birth Weight
What is an indicator related to an infants birth weight?
weight gain in mother is related to infant birth weight
* link between optimal weight gain and optimal health
What is the gestational weight gain for different weight categories?
What is the weight gain expected for the first, second and third trimesters?
- 1st trimester: ~0.5 to 2kg, little weight gain expected
- 2nd & 3rd trimester: ~0.4 kg/week healthy weight
Where does the added weight go?
- metabolic changes (~58%)
- things to support baby (~42%)
What are the metabolic changes associated with weight gain?
- extra blood, fluids and protein
- breasts and energy stores
- uterus
What things to support the baby contrinute to weight gain?
- placenta
- baby
- amniotic fluid
What is healthy weight gain during pregnancy?
Weight gain within the guidelines is associated with the best pregnancy outcomes and reccommendations should be a weight range for all pregnant women and should be monitored
Where are some considerations for weight gain?
subsets of populations
* adolescents
* multiple pregnancy
What is the risk of low or excessive gestational weight gain on fetus/infant?
low or high birth weight
What is the risk low or excessive gestational weight gain on the mother?
- nutritional status
- gestational diabetes
- pre-enclampsia
- complications during pregnancy
- post-partum weight retention
What is the association vs. causation of maternal weight gain and infant weight gain?
Association between maternal weight gain and infant birth weight does NOT mean that maternal weight gain CAUSES fetal weight gain
* Fetal weight gain is compilation of many different factors – nutrient availability, placental transfer capacity, fetal growth factors, etc.
What is the overall energy balance during pregnancy?
positive energy balance of 80,000 kcal over the course of pregnancy
What is energy required for?
- Increases in maternal tissue: breast tissue, uterine muscles, placenta, fat stores
- Fetal tissues
- Increased BMR to meet new energy “cost” of metabolic needs of new tissue
- Increased cost of physical activity: carrying more
What are the adaptive responces to achieve positive energy balance?
- Increased intake
- Decreased energy expenditure
- Metabolic adaptations
Energy balance in pregnancy for healthy weight women
BMR increases throughout pregnancy (particularly later)
Energy balance in pregnancy for underweight women
decreased BMR
* may allow continuation of pregnancy, but compromise fetal growth
Energy balance in pregnancy for overweight/obese women
Greater increase in BMR (about 20%) to offset further fat accumulation
Kcal recommendations during 2nd and 3rd trimesters
Additional servings: 2-3/day
* 2nd: 340 kcal/d
* 3rd: 452 kcal/d
How is appropriate intake monitored?
Weight gain during pregnancy
What hormones play a key role in pregnancy?
- human chorionic gonadotrophin (hCG)
- human placental lactogen (hPL)
- estrogens
- progesterone
Role of hCG?
human chorionic gonadotrophin
* secreted within days of implantation
* maintains corpus luteum
* little effect on metabolism
Role of hPL
human placental lactogen
* effects on carbohydrate and lipid metabolism
* mediates insulin resistance
* fetal/placental growth factor?
* only around when there is the placenta
Role of estrogens
- influences reproductive organs, ↑binding hormones
- influence macronutrient and bone metabolism
Role of progesterone
- relaxes smooth muscle (GI, urinary tract)
- Results in some of the exercise intolerance as it acts on muscles and bones
How do hCG, hPL, estrogen and progesterone change throughout pregnancy?
- hCG rises rapidly to 10 weeks then rapidly declones
- hPL, estrogen and progesterone rise throughout
What is the CHO metabolism in early pregnancy?
mediated through estrogen and progesterone
* enhanced insulin secretion
* glucose → glycogen synthesis and fat storage
What is the purpose of the CHO changes?
To maintain availability of glucose for the fetu
* fetal energy use is preferentially glucose
How does hPL mediate CHO metabolism?
- insulin secretion
- insulin sensitivity
- hepatic glucose production
Describe CHO metabolism later in pregnancy
maternal insulin resistance
* ↑ insulin secretion, but decreased sensitivity of maternal peripheral tissues so less glucose uptake by tissues
* glucose production (glycogen, glycerol)
What does the mother use for fuel later in pregnancy?
fatty acids
* hormonally mediated preferential use of non- glucose fuels (lipolysis) by maternal peripheral tissues
How does the RDA change for CHO with pregnancy?
Increased RDA (minimum amount) from 130 g/d to 175g/d with the extra 45 going toward the infant
Why should pregnant women consume regular small CHO meals?
Regular small CHO meals are important because pregnant women reach fasting levels faster which may result in ketone production which may be toxic to babe.
How much fat gets stored in the anabolic phase?
fat storage is ~35,000 kcal to 20 weeks
Describe fat metabolism during early pregnancy
Anabolic: Estrogen, progesterone and insulin favour fat deposition and inhibit lipolysis
* ↑ levels of triglycerides, fatty acids, cholesterol, phospholipids
* some cholesterol used by placenta for steroid synthesis and fetus for nerve and membrane
How do cholesterol and triglyceride levels change during pregnancy?
both rise from non-pregnancy and throughout
Describe fat metabolism in late pregnancy
Catabolic: hPL favours maternal lipolysis and mobilization of fat stores
* fat oxidation as an energy source conserves glucose and amino acids for fetus
* fetal uptake of fatty acids also occurs
What fatty acids are important for fetal development?
- linoleic acid
- 𝝰-linolenic acid
What are the fat recommendations for pregnancy
Recommendations for total fat and types of fat not different from non-pregnancy but small increases in AI for LA and ALA
* LA: 12 g/d to 13 g/d
* ALA: 1.1 g/d to 1.4 g/d
What are the important LA and ALA essential fatty acids?
AA and DHA important fatty acids for optimal fetal neural and visual development
When are AA and DHA transferred to fetus?
preferentially transferred to fetus later gestation
* concentration in serum will be higher in fetus than in the mom
What is the issue with DHA?
- Conversion of linolenic to DHA is low (~5%)
- Good source of DHA is fish but need to be warry for mercury
Reccomendation of DHA/d
Pregnant women should aim for ~200mg DHA/day
* Recommendation is 2-4 servings per week of fish or shellfish with low risk of methyl mercury contamination
What are the fish to avoid?
Atlantic herring and mackeral, Alaskan pollock, salmon, haddock, sardines, anchovies, shrimp, oysters, clams, scallops, canned light tuna
Describe protein metabolism during pregnancy
Gradual adaptation of protein metabolism with increased nitrogen retention in late pregnancy so more protein synthesis
* ↓ amino acid oxidation
* ↓ urea synthesis & excretion - ↑excretion of other N wastes (due to ↑GFR)
* transfer of amino acids to fetus
What are the reccomended changes in protein RDA?
mostly changes in the 2nd and 3rd trimester to 1.1 g/kg/d (71 g/d)
* from 0.8 g/kg/d (46 g/d)
What is RQ?
Respiratory qoutient used as a measurement of fuel utilization - CO2 produced/O2 consumed
What would the RQ of a pregnant woman (including the fetus) be at the end of pregnancy?
higher
* Maternal and fetal because a lot more glucose being used. Even though she is relying on lipids she is conserving more glucose for baby and that supersedes.
How do the micronutrient needs change during pregnancy?
All micronutrients are important during pregnancy and fetal development
Increased need for micronutrients but not an increase in recommendations for all
What are key micronutrients to consider during pregnancy?
- folate
- iron
- vitamin D
- Calcium
- Vitamin A
Folate reccomendations
Pregnancy RDA is 600µg/d of which 400µg synthetic folic acid/d and the other 200µg from food
* non-pregnant is 400µg/d
* UL of folic acid is 1000µg/d
What is the need for iron in pregnancy?
An average of ~1065mg during pregnancy needed (with variation in each component) with increased utilization:
* 500 mg to increase RBC mass
* 315 mg for fetal/placental use
* in addition to 250 mg for basal loss (non- menstruating adult women)
How is iron status assessed?
Physiological increase in plasma volume as well as RBC means hemoglobin concentrations changes throughout pregnancy with hemodilution effect mostly 10-20 weeks
* >110 g/l during 1st and 3rd trimesters
* >105 g/l during the 2nd trimester (maximum volume increase)
Maternal risks of iron deficiency during pregnancy
- fatigue, decreased work performance, impaired resistance to infections
- poor tolerance to blood loss
Fetal risks to iron deficiency during pregnancy
- 2-3 x ↑ risk of preterm delivery/low birth weight
- lower intelligence, language, gross motor, attention tests (5 years)
- low iron stores to fetus, risk of iron deficiency anemia
Problems with iron supplementation
- The larger the dose, the less the absorption
- Less absorption when taken with food, or other supplements
- Increasing absorption as pregnancy progresses
interpret the graph
The greater the dose if iron the less absorption but the small percentage of a higher dose may still be better
Average iron needs in 3rd trimester
5.6mg/d absorbed iron
* 0.9 mg/d absorbed iron for basal lost
* 2.0mg/d absorbed iron for fetus/placenta
* 2.7mg/d absorbed iron for RBC expansion
DRIs for iron during pregnancy
- EAR: 22 mg/d = 5.5 mg absorbed
- RDA: 27 mg/d = 6.75 mg absorbed iron
Recommendations for iron supplement
Health Canada recommends supplementation of 16-20 mg iron throughout pregnancy
* higher amounts if maternal iron deficiency present
Role of Calcium and vitamin D
Maintenance of maternal bones and skeletal development of fetus
DRI reccomendations for Calcium and vitamin D
RDAs and same as for non-pregnant
* Calcium: 1000 mg/d (enhanced absorption, taken from maternal bones but quickly replaced)
* Vitamin D: 600 IU/d (15 µg/d)
What is the supplement recommendation for vitamin D?
Canadian Paediatric Society: consideration
of 2000IU supplement during pregnancy
Vitamin A DRIs during pregnancy
RDA pregnancy 770 ug RAE/d
* Vitamin A deficiency a concern in developing countries; in developed countries Vitamin A toxicity is a concern
* Beta-carotene safer source of vitamin A
What are the 2007 food guidelines for pregnant women?
+ 2-3 servings from any group
* Vegetables & Fruit: 7-8 servings
* Grain Products: 6-7 servings
* Milk & Alternatives: 2 servings
* Meat & Alternatives: 2 servings
What should a supplement contain?
Supplement containing 0.4 mg folic acid and 16-20 mg of iron is recommended
Caffeine recommendations
Maximum 300mg/d
* 250ml coffee: 40-180mg,
* 250 mL tea: 10-110mg
* 355ml Cola drink: 30-60mg
* 56g dark chocolate: 50mg
artificial sweetener reccomendations
- Aspartame, acesulfame-potassium, sucralose, saccaharin and stevia considered safe (usually found in nutrient poor foods though)
- Cyclamates not recommended
Recommendations of herbal productions
- Safety of many herbal products unknown
- Generally considered safe in moderation: ginger, peppermint leaf, orange peel, rose hip, red raspberry leaf
considerations with vegetarianism during pregnancy
A healthy pregnancy can be supported by a vegetarian diet but takes more pre-planning and careful though into nutrients at risk
* adequate energy and weight gain
* protein and iron intake
* B12 supplementation may be required
Why is weight loss not reccomended during pregnancy?
- limits nutrient availability
- promotes ketone formation which may reduced fetal growth and impaired cognitive function
What occurs with accelerated fasting metabolism during pregnancy?
ketone formation and low blood glucose occurs more quickly
* Important to have regular small CHO snacks
What are common cravings and aversions?
- cravings are dairy and sweets → encourage consumption of food from the food groups (not “other foods”)
- aversions are alcohol, caffeine, meats so may need to consume other protein/iron rich foods
Foods to avoid during pregnancy
General principles of food safety and avoidance of raw food that may causes food borne illness
* Listeriosis, toxoplasmosis, salmonella, E. coli
Benefits of regular physical activity during pregnancy
- maintenance of fitness
- promotion of appropriate weight gain
- provide strength for labour
- may also help prevent gestational diabetes and pregnancy induced hypertension
physical activity considerations for pregnant women
- Ensure adequate energy and fluid intake
- Some limitations to type of activity → avoid over-exertion and high risk activity
What hormone might result in intolerance to PA at the start of pregnancy?
progesterone
What screening tool is used to determine PA readiness during pregnancy?
PAR-med-X for Pregnancy
* Contraindications
* Guidelines for exercise based on ‘FITT’
* Heart Rate Ranges
What are the FITT guidelines?
Found on PARmed-X
* frequency
* intensity
* time
* type of activity
What are the heart ranges based on for the PAR-med-X?
Based on age, fitness level or BMI
