Chapter 4.docx

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10 Apr 2012

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Chapter 4: Nutrition During Pregnancy
- Nutritional status stands out as an important factor affecting fetal growth and development
The Status of Pregnancy Outcomes
- Natality Statistics:
o Summarize important information about the occurrence of pregnancy complications and harmful behaviours, along with
infant mortality and morbidity rates
- ** Refer to chart 4.1 pg 88 Time breakdowns before, during and after pregnancy
Infant Mortality
- Infant mortality rates are highly related to population wide improvements in:
o Social circumstances
o Infectious disease control
o Availability of safe and nutritious foods
- Improvements in these (above) are leading to greater reduction in infant mortality rates, more so than improved technology in
healthcare **See chart 4.2 pg 89 **
- The U.S.A spends more money on healthcare than any other nation yet, ranked 29th in international levels of infant mortality
- Liveborn Infant:
o Outcome of delivery when a completely expelled fetus breaths or shows any sign of life
o 2/3 of deaths to livebirth infants occur within 1st month or during neonatal period (38-42 weeks)
- Low Birth weight, Preterm Delivery and Infant Mortality:
o Low birth weight infants 8.2% of all births, 66% of all infant deaths
o Birth rate increases along with the increase in length of the pregnancy
o Lowest infant mortality rates Singapore 2 in 1000
o Highest infant mortality rates Romania 16.8 in 1000
Reducing Infant Mortality and Morbidity
- This can be done through improvements in the birth weight of newborns
- 7 lb 12oz 10 lbs = least likely to die within first year of life as well as least likely to develop heart disease, diabetes, lung
disease etc.
Physiology of Pregnancy
- Pregnancy begins at conception 14 days before next scheduled menstrual period
- Pregnancy lasts 38 weeks or 266 days (gestation age) more commonly 40 days, this starts at the date of last period (LMP)
(menstrual age)
- Maternal Physiology
o The changes in women during pregnancy were once seen as a problem that needed correction
o However, attempts to bring pregnant body back to non-pregnant state can do more harm than good to the pregnancy
o Order of changes that need to take place sequence of development: **table 4.6 pg 92 **
Maternal plasma volume to be circulate must increase by 20 weeks
Maternal nutrient stores are accumulated next by 20 weeks
Placental weight increase to make room for fetal weight increases by 31 weeks
Blood flow to the uterus by 37 weeks
Fetal weight by 37 weeks
Normal Physiological Changes During Pregnancy
- Changes can be divided into 2 groups:
o First half of pregnancy
Changes here considered “maternal anabolic” they build capacity of the mother’s body to deliver relatively
large quantities of blood, oxygen and nutrients
10% of fetal growth
o Second half of pregnancy
Changes here considered “maternal catabolic” energy and nutrient stores, and the heightened capacity to
deliver stored energy and nutrients to fetus predominate
90% of fetal growth
- Body Water Changes:
o Increased amount due to increased plasma, extracellular fluid and amniotic fluid
o Total increase is ranges from 7-10 liters
o 2/3 expansion of blood and body tissue (intracellular)
o 1/3 fluid in spaces between cells (extracellular)
o Increase in plasma accounts for fatigue felt by many pregnant women increases in 2nd and 3rd months
o Edema:
Swelling, usually of legs and feet, due to increase in extracellular fluid (healthy)
o Birth weight is strongly related to plasma volume high plasma, high birth weight
- Hormonal Changes:
o Placenta is KEY in production of steroid hormones (progesterone, estrogen and testosterone)
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- Maternal Nutrient Metabolism:
o Adjustments are directed toward ensuring that nutrients will be available to fetus during times of high needs
Driven by genetically timed sequence of growth and development
o Carbohydrate Metabolism
Promote availability of glucose (preferred fuel) to fetus
Diabetogenic effect of pregnancy: maternal insulin resistance make women slightly carbohydrate intolerant
in 3rd trimester
In first half of pregnancy estrogen and progesterone stimulate (through carb metabolism) increase in insulin
production and conversion of glucose to glycogen and fat
In second half of pregnancy rising levels of hCS (human chorionic somatotropin: increases maternal insulin
resistance to maintain glucose availability) inhibit conversion of glucose to glycogen and fat
o Accelerated Fasting Metabolism
Glucogenic Amino Acid:
Amino acids such as alanine and glutamate that can be converted to glucose
Metabolic by-products of the breakdown of fatty acids in energy formation
Rapid conversion to fasting metabolism allows pregnant women to use primarily stored fat for energy while
sparing glucose and amino acids for fetal use
o Protein Metabolism
Nitrogen and protein needed in increased amounts for synthesis of new maternal and fetal tissues
2 lbs of protein accumulated during pregnancy
Maternal and fetal needs are met by mother’s intake of protein during pregnancy
o Fat Metabolism
First half of pregnancy changes in lipid metabolism promote accumulation of maternal fat stores
Second half of pregnancy enhance fat mobilization
Blood levels of many lipoproteins increase dramatically!
Plasma triglyceride levels increase to 3x that of non pregnant women (most significant increase)
Increased cholesterol supply used by fetus for nerve and cell membrane formation
MAY be that lowering HDL cholesterol after pregnancy may contribute to increase risk of heart disease
o Mineral Metabolism
Calcium metabolism increase rate of bone turnover and reformation
Sodium metabolism delicately balanced during pregnancy, changes in kidneys account for this
Restriction could lead to functional and growth impairments
The Placenta
- Derived from Latin word for cake
- Develops from embryonic tissue and is bigger than fetus
- Functions of the placenta:
o Hormone and enzyme production
o Nutrient and gas exchange between mother and fetus
o Removal of waste products from fetus
- Structure of the placenta:
o Double lining of cells, separate fetal and maternal blood
o Governs rate of passage of nutrients and other essential things in and out
- Nutrient Transfer
o Placenta uses 30-40% of glucose delivered by maternal circulation
o Nutrient transfer depends on…
Size and charge of molecules available
Small molecules with little to no charge (water, lipids) pass through easily
Lipid solubility of particles
Concentration of nutrients in maternal and fetal blood
o Exchange is unregulated for some nutrients, oxygen, and carbon dioxide
o 3 mechanisms operate for nutrient transfer:
Facilitated diffusion
Active transport
Embryonic and Fetal Growth and Development
Critical Periods of Growth and Development:
- Differentiation:
o Cellular acquisition of one or more characteristics or functions different from that of the original cell
- Critical Periods:
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