CH.4 - Pregnancy

Embryo

Weeks 3 - 8 after fertilization.

Fetal Age

Counted from conception; average pregnancy lasts 38 weeks.

Gestational Age

Counted from the last menstrual period (LMP); 40 weeks total.

Obstetric Age

Previously based on LMP but now assessed using the Obstetric Estimate of Gestation at Delivery (OE).

Natality Statistics

Used to assess reproductive outcomes and identify trends in birth complications.

Infant Mortality Rate

5.6 per 1,000 live births (ranked 50th globally).

Low Birth Weight (LBW) Rate

8.5% of births, yet 16% of infant deaths are linked to LBW.

Preterm Birth Rate

10.5% in the U.S. (compared to ~8% in Europe).

Desirable Birth Weight

3500 - 4000 grams (7 lb 12 oz - 10 lb).

U.S. Maternal Mortality Rate

~1,200 maternal deaths in 2021 (32.9 per 100,000 live births).

Fetal Age vs. Gestational Age

Fetal Age starts at conception (38 weeks total); Gestational Age starts at the last menstrual period (40 weeks total).

Stages of Development

1. Maternal Plasma Volume Expansion (first). 2. Nutrient Stores Increase. 3. Placental Weight Increases. 4. Uterine Blood Flow Rises. 5. Fetal Weight Gains Last.

Anabolic Phase

First Half of Pregnancy: Blood volume increases, fat stores, nutrients, and liver glycogen build up, lower exercise tolerance, increased appetite.

Catabolic Phase

Second Half of Pregnancy: Mobilization of fat and nutrients, higher blood glucose, triglycerides, and fatty acids, decreased liver glycogen storage, increased basal metabolic rate (BMR).

Increased Plasma Volume

Supports fetal growth, improves nutrient and oxygen transport, helps prevent hypotension.

Nutrient Metabolism Changes Early

Ensures nutrient availability when needed, hormonal shifts prepare the body for fetal demands, establishes energy stores for later pregnancy.

Carbohydrate Metabolism - Early Pregnancy

More insulin production, storing glucose as glycogen/fat.

Late Pregnancy

Insulin resistance rises → More glucose in the bloodstream.

Diabetogenic Effect

Promotes fetal glucose supply.

Accelerated Fasting Metabolism

Fat burning increases to spare glucose for the fetus.

Protein Metabolism

Increased protein conservation.

Fat Metabolism - Early vs. Late Pregnancy

Early: Fat stores accumulate. Late: Fat mobilization increases.

Cholesterol

Rises to support fetal cell membranes and steroid hormones.

Calcium - How It's Managed

Increased maternal absorption.

Calcium mobilized from maternal bones

But replaced postpartum.

Placenta - Function and Glucose Needs

Functions: Hormone production, nutrient/gas exchange, waste removal.

Glucose

The fetus' primary energy source.

The Fetus Is Not a Parasite

Nutrients go to mother first, then placenta, and finally fetus.

Poor maternal nutrition

Affects fetus more than the mother.

Critical Periods of Development

Hyperplasia → Hyperplasia & Hypertrophy → Hypertrophy → Maturation.

Errors during critical periods

Are irreversible.

SGA, dSGA, pSGA - Differences

SGA (Small for Gestational Age): <10th percentile.

dSGA (Disproportionately SGA)

Normal length/head but low weight (caused by late pregnancy malnutrition).

pSGA (Proportionately SGA)

All small (due to early malnutrition).

Miscarriage - Risk Factors

Obesity, underweight, oxidative stress, infections.

40-60% of fertilized eggs

Don't survive to birth.

Preterm Birth - Risks and Prevention

Risks: Neurological issues, organ immaturity, chronic disease.

Prevention

Prenatal care, reduced stress, proper nutrition.

DOHaD - Developmental Origins of Health and Disease

In utero exposure affects long-term disease risk.

Small, thin newborns

Have higher risks of heart disease, diabetes, obesity.

Weight Gain Recommendations

Underweight: 28-40 lbs.

Normal weight

25-35 lbs.

Overweight

15-25 lbs.

Obese

11-20 lbs.

Weight Gain by Trimester

First Trimester: ~3-5 lbs.

Second & Third Trimester

~1 lb/week.

GI Changes and Consequences

Slowed digestion → Heartburn, constipation.

Increased appetite

Nausea, vomiting.

Energy and Macronutrient Needs

+200-300 kcal/day in 2nd and 3rd trimesters.

Carbs

175g/day minimum.

Protein

+25g/day.

Fat

20-35% of calories.

Key Micronutrients

Folate: 600 mcg/day (prevents NTDs).

Vitamin D

Often deficient, needed for bone growth.

Calcium

Absorption increases, no higher RDA.

Iron

27 mg/day; deficiency can cause low birth weight.

Iodine

Critical for fetal brain development.

Food Safety - Risks

Listeria: Found in deli meats, soft cheeses, raw milk.

Mercury

Avoid shark, swordfish, king mackerel.

Exercise Recommendations

150 min/week moderate activity.

Common Pregnancy Issues

Nausea: Vitamin B6, ginger, small meals.

Heartburn

Small meals, avoid trigger foods.

Constipation

30g fiber/day, fluids.