Preconception Nutrition Notes

Chapter 2: Preconception Nutrition

Learning Outcomes

  • Miscarriage: Loss of a conceptus in the first 20 weeks of pregnancy.
  • Infertility & Subfertility: Know the difference between the two.
  • Puberty: The period when humans become biologically capable of reproduction.
  • Menstrual Cycle: Understand its phases.
  • Hormones: Identify the six major hormones involved in male and female fertility regulation, including their sources and effects.
  • Nutrition-Related Factors: Describe the potential effects of body fat content, iron status, and alcohol intake on fertility in women and men.
  • Nutrient Intake: Cite four examples of relationships between nutrient intake and nutritional status during the periconceptional period and pregnancy outcomes, especially folate.
  • Menu Planning: Develop a one-day menu for pre-conceptional individuals based on Canada’s Food Guide.
  • Contraceptives: Identify nutrition-related consequences related to combination hormonal contraceptives and estrogen or progestin contraceptives.

Introduction

  • Adequate health and nutrition are essential for successful reproduction in both males and females.
  • Disruptions in health or nutrition can reduce reproductive capacity.

Preconception Overview

Miscarriage
  • Definition: Loss of a conceptus in the first 20 weeks of pregnancy.
  • Causes:
    • Defects in the fetus.
    • Maternal infection.
    • Structural abnormalities of the uterus.
    • Endocrine or immunological disturbances.
Subfertility
  • Definition: Reduced level of fertility characterized by a long time for conception.
  • Examples:
    • Multiple miscarriages.
    • Sperm abnormalities.
    • Infrequent ovulation.

Reproductive Physiology

Key Concepts
  • Puberty: The period when humans become biologically capable of reproduction.
  • Ova: Eggs produced and stored within the ovaries of females.
  • Menstrual Cycle: An approximately four-week interval where hormones direct the buildup of blood and nutrient stores within the uterine wall, leading to ovum maturation and release.
    • If the ovum is fertilized, the stored blood and nutrients support its growth.
Development of Reproductive Systems
  • Begins during the first months after conception.
  • Continues through puberty.
  • Capacity for reproduction is established during puberty via hormonal changes.

Female Reproductive System

Menstrual Cycle
  • Prepares an ovum for fertilization and the uterus for implantation.
Hormonal Effects
  • Gonadotropin-Releasing Hormone (GnRH):
    • Stimulates the pituitary to release FSH and LH.
  • Follicle-Stimulating Hormone (FSH):
    • Stimulates growth of ova.
  • Luteinizing Hormone (LH):
    • Stimulates secretion of progesterone.
Phases of the Menstrual Cycle
  • Follicular Phase:
    • First half of the menstrual cycle.
    • Involves follicle growth and maturation.
  • Luteal Phase:
    • Last half of the menstrual cycle.
    • Begins after ovulation.
    • Involves the formation of the corpus luteum.

Male Reproductive System

Reproductive Capacity
  • Complex interactions among the hypothalamus, pituitary gland, and testes.
  • Process is ongoing rather than cyclic.
  • Androgens (e.g., testosterone) stimulate sperm maturation.
  • Sources of disruptions in fertility should refer to Table 2.3 (Not included here).

Nutrition and Fertility

  • Nutritional factors generally exert a temporary influence on fertility.
  • Normal fertility typically returns once the nutritional problem is addressed.

Undernutrition and Fertility

Undernutrition in Women
  • Associated with a decline in fertility, which recovers with improved food intake.
  • Food shortages have been linked to dramatic declines in birth rates (e.g., Europe, Holland).
Body Fat and Fertility
  • Excessive and inadequate levels of body fat are related to declines in fertility in both women and men.
  • Excessive body fat increases the likelihood of subfertility.
  • A critical level of body fat is needed for reproductive functions.
Weight Loss and Fertility
  • Weight loss exceeding 10-15% of weight decreases estrogen, LH, and FSH levels.
    • Results in amenorrhea, anovulatory cycles, and short or absent luteal phases.
    • Treatment with fertility drugs like Clomid may not improve fertility until weight is gained.
Weight Loss and Fertility in Males
  • Studies during World War II showed a 50% decrease in male fertility during starvation.
  • Sperm viability and motility decrease when weight reaches 10-15% below normal.
  • Spermatogenesis ceases when weight loss exceeds 25% of normal weight.

Nutrient Status and Fertility

Antioxidant Status
  • No reliable conclusions regarding its impact on fertility.
Zinc Status in Men
  • Deficiency can impair normal functions.
Soy Isoflavones
  • Related to reduced sperm count in men and decreased fertility in women.
Iron Status
  • Poor iron status is related to reduced fertility.
Caffeine
  • Conflicting research regarding its impact on fertility.
Alcohol
  • Increases testosterone levels, reduces sperm concentration, total sperm count, and the percentage of sperm with normal shape.
Heavy-Metal Exposure
  • Related to decreased sperm production and abnormal sperm motility and shape.
Physical Activity
  • Intense levels may delay menarche.

Nutrition During the Periconceptional Period

  • Definition: The time around conception (one month before through three months after).
  • This is a critical period when nutritional and other exposures can impact conception, pregnancy maintenance, and the offspring's growth, development, and health.

The Importance of Folic Acid During Pregnancy

Why Folic Acid is Essential
  • Folic acid helps form the neural tube during early pregnancy, which develops into the baby's brain and spinal cord.
  • Adequate intake reduces the risk of neural tube defects (NTDs) such as spina bifida and anencephaly.
  • Recommendations:
    • Women of childbearing age: Consume 400 micrograms (mcg) of folic acid daily.
    • During pregnancy: Recommended intake increases to 600 mcg per day.
    • Prenatal vitamins often contain higher amounts of folic acid to meet these needs.
  • Sources:
    • Natural sources: Leafy green vegetables, citrus fruits, beans, and whole grains.
    • Fortified foods: Bread, pasta, and cereals.

Folic Acid Fortification Regulations in Canada

Fortification Policy
  • Canada mandates the addition of folic acid to certain foods to prevent deficiencies and promote public health.
  • Mandatory Fortification:
    • White flour and enriched grain products must contain 1.5 milligrams of folic acid per kilogram (150 mcg per 100 grams).
  • Benefits of Fortification:
    • Helps ensure adequate intake across the population.
    • Reduces the incidence of neural tube defects and supports overall health.
  • Voluntary Fortification:
    • Manufacturers can choose to fortify other foods like breakfast cereals, juices, and snacks to enhance nutritional value.

Periconceptional Folate Status

  • Intake of folic acid and improved folate status offers several benefits (e.g., reduced neural tube defects).
  • Some individuals have an increased need for folate due to specific gene variants.
  • Those with an increased need for folate, need to make sure to supplement folic acid.
Remaining Risk Group for Neural Tube Defects
  • Women who take the anti-seizure drug valproate without appropriate folic acid supplementation.
  • Women who have previously delivered an infant with a neural tube defect.

Periconceptional Iron Status

  • Iron deficiency is the most common nutritional deficiency.
  • Iron deficiency prior to pregnancy increases the risk of iron-deficiency anemia.
  • Iron status can generally be improved by regular consumption of vitamin C.

Preconceptional Women

  • Recommended dietary intake and healthy dietary patterns:
    • 400 mcg of folic acid.
    • More than 10,000 IU of vitamin A.
    • Limit or omit alcohol-containing beverages.
    • Additional sources: Dietary Reference Intakes (DRIs) and Canada Food Guide.

Influence of Contraceptives on Preconceptional Nutrition Status

  • Contraceptives contain forms of estrogen.
  • Estradiol combined with progestin suppresses the action of LH and FSH, thereby inhibiting ovulation.
  • Progestin blocks LH and ovulation and induces a barrier to sperm by causing cervical mucus to become thick and sticky.

Nutritional Side Effects of Hormonal Contraception

Progestin Only
  • Weight gain and decreased bone mineral accretion.
Combination Contraceptives
  • Altered blood lipid levels, increased blood and insulin levels, and increased risk of stroke.