Nutrition Transfer Across the Placenta

Nutrition During Pregnancy

• General Outcome: Students will become familiar with physiological changes during pregnancy and demonstrate how these changes affect nutritional needs.

• Specific Outcomes:

  • Describe physiological changes during pregnancy.
  • Identify recommended weight gain ranges for underweight, normal weight, overweight, and obese women entering pregnancy.
  • Identify relationships between nutritional status during pregnancy and long-term health outcomes in offspring.

Time-Related Terms

• Periconceptional: Period before conception (approximately 14 days before the next menstrual period).
• Trimester 1: Weeks 0-12
• Trimester 2: Weeks 13-28
• Trimester 3: Weeks 29-40
• Preterm: Born before 37 weeks.
• Very preterm: Born before 32 weeks.
• Term: 38-42 weeks.
• Postterm: More than 42 weeks.
• Perinatal: Period from 20 to 24 weeks gestation to 7 to 28 days after birth.

Important Terms & Definitions

• Fetal death/Stillbirth: Death of the fetus after 20 weeks of pregnancy.
• Perinatal mortality: Death of a fetus between 20 weeks of gestation or death of an infant less than 1 month old.
• Neonatal mortality: Deaths from delivery to 28 days.
• Post-neonatal mortality: Deaths from 28 days after birth to 1 year.
• Infant mortality: Deaths from birth to age 1 year.

Infant Mortality

• Indicator: Number of infant deaths under 1 year old per 1,000 live births.
• Decreased Mortality: Indicates improvements in environmental factors like safe and nutritious food, better public sanitation & infectious disease control.

Child Mortality Rates

• In Malaysia, infant mortality rates have decreased significantly from 41 deaths per 1,000 live births in 1970 to 6.9 in 2017.
• Malaysia has seen improvement in health indicators over time.

Causes of Infant Mortality

• Conditions originating in the perinatal period such as meningits and pneumonia,
• Chronic lower respiratory disease
• Congenital malformations/deformations along with chromosomal abnormalities.

Maternal Mortality

• Definition: Deaths due to pregnancy or childbirth complications.
• Global Trend: Global maternal mortality ratio has decreased by 34% from 2000 to 2020.
• Geographic Considerations: Almost 95% of maternal deaths occur in low and lower middle-income countries.
• Preventable Deaths: More than 80% of pregnancy-related deaths are preventable.

Causes of Maternal Mortality

• Severe bleeding (mostly after childbirth)

• Infections (usually after childbirth)

• High blood pressure during pregnancy (pre-eclampsia)

• Complications from delivery

• Unsafe abortions

• Malaysia trend Shows a decrease from 141 deaths per 100,000 births in 1970 to 21 in 2019.

Physiology of Pregnancy

• Conception: Beginning of pregnancy.
• Pregnancy duration: Approximately 38 weeks (266 days) from conception or from first day of last menstrual period (LMP) – approximately 40 weeks(280 days).
• Gestational age: Duration of pregnancy measured from conception.
• Menstrual age: Pregnancy duration measured form the first day of the last menstrual period (LMP).

Normal Physiology Changes During Pregnancy

• Anabolic phase (0-20 weeks): Increased food intake, lipid absorption, and accumulation; increase in hormones.
• Catabolic phase (20+ weeks): Mobilization of fats and nutrients stores, increase in blood glucose, triglycerides & fatty acids.

Maternal Anabolic Phase (0-20 weeks)

• Blood volume expansion: Increased blood volume and cardiac output, to accommodate increase nutrients.
• Fat buildup: Accumulation of fat, nutrients, and liver glycogen stores.
• Organ growth: Growth of certain maternal organs.
• Increased appetite: Increased hunger as a result of increased need for nutrients.
• Decreased exercise tolerance: Body's need to conserve energy

Maternal Catabolic Phase (20+ weeks)

• Fat and nutrient mobilisation: Fat and nutrient stores begin to be used.
• Increased blood glucose: Blood glucose levels increase
• Triglycerides and fatty acids: Levels of triglycerides and fatty acids increase dramatically during pregnancy.
• Fasting metabolism: Fast metabolism accelerates to provide energy.
• Catabolic hormones: Catabolic hormones also increase

Fetal Growth

• Early growth (first half): Approximately 10% of fetal growth during this period
• Later growth (second half): Approximately 90% of fetal growth during this period

Body Water Changes

• Total body water: Increases from 7 to 10 liters
• Extracellular fluid: Increase during pregnancy to enhance transfer of nutrients and wastes.
• Edema: Swelling (usually in the legs & feet) due to accumulation of extracellular fluid.

Hormonal Changes

• Placenta: Main source of hormones that modify physiological changes in pregnancy.
  • Includes hCG, hCS, estrogen, leptin, and progesterone.

Human Chorionic Gonadotropin

• Function: Stimulates corpus luteum for estrogen & progesterone production and maintains endometrium.

Human Chorionic Somatotropin

• Function: Increases insulin resistance in the mother to maintain glucose for the fetus. Promotes protein synthesis and fat breakdown to supply energy for the mother

Estrogen

• Function: Lipid synthesis & uterine/breast development.

Leptin

• Function: Regulates maternal appetite & lipid metabolism.

Progesterone

• Function: Maintains pregnancy and relaxes uterine muscles.

Carbohydrate Metabolism

• Early pregnancy: Insulin production increases, and glucose is predominantly converted to glycogen and fat.
• Late pregnancy: hCS & prolactin inhibit glucose conversion to glycogen & fat. Increases reliance on fats for energy. Ensures glucose supply for fetus development.

Accelerated Fasting Metabolism

• Fasting: >12 hours
• Fat mobilization: Allows pregnant women to utilize stored fats for energy
• Glucose & Amino Acid sparing: Spares glucose and amino acids for fetal use.
• Ketone bodies: During prolonged fasting, dependence on fetal ketone bodies for energy, causes abnormal growth.

Protein Metabolism

• New tissues: Protein is needed for synthesis of new maternal and fetal tissues (about 925 grams during pregnancy).
• Intake: Mothers need to meet increased protein demands during pregnancy.
• Amino acid conservation: Method to increase protein through reduced nitrogen excretion & protein tissue synthesis.

Fat Metabolism

• First half: Accumulation of maternal fat
• Second half: Mobilization of maternal fat, dramatically increasing blood lipid levels.
• Types of fatty acids: Plasma triglycerides, cholesterol-containing lipoproteins, phospholipids, & fatty acids.
• Cholesterol: Used by placenta for steroid hormone synthesis. High concentrations observed do not promote atherosclerosis.

Mineral Metabolism

• Calcium: Maternal absorption & mobilization from bones increase, for fetal bone development.
• Sodium: Elevated needs, low salt/sodium diets not recommended to prevent impairment.

Placenta

• Definition: Derived from "Latin word for cake"- round or disk like structure.
• Functions: Hormone & enzyme production, nutrient & gas exchange between mother & fetus; Removal of waste products from fetus; Barrier to harmful substances.
• Nutrient transfer: Primarily uses passive/facilitated diffusion across maternal-fetal membranes.
• Mechanisms: Passive diffusion, facilitated diffusion, active transport, and endocytosis.

Fetus is Not a Parasite

• Fetus cannot take unlimited nutrients.
• Nutrient needs are first met by maternal demands, then fetal needs.
• Compromised fetal growth & development due to poor maternal nutritional status.