Freeze&Fly

Basics of Fertility

Understanding your fertility starts with knowing how your reproductive system works

This page covers the essential concepts of female fertility, including the menstrual cycle, egg reserve, and the role of hormones.

The Menstrual Cycle

The menstrual cycle is a complex interplay of hormones that prepares your body for pregnancy each month. A typical cycle lasts about 28 days, though this can vary from person to person.

1

Menstruation (Days 1-5)

The uterine lining sheds, resulting in menstrual bleeding. Hormone levels are at their lowest.

2

Follicular Phase (Days 1-13)

FSH stimulates follicle growth in the ovaries. Estrogen levels begin to rise, thickening the uterine lining.

3

Ovulation (Day 14)

A surge in LH triggers the release of a mature egg from the ovary. This is when you're most fertile.

4

Luteal Phase (Days 15-28)

The empty follicle produces progesterone. If no pregnancy occurs, hormone levels drop and the cycle begins again.

Ovarian Reserve

Ovarian reserve refers to the quantity and quality of eggs remaining in your ovaries. Women are born with all the eggs they'll ever have—about 1-2 million at birth.

By puberty, this number decreases to about 300,000-500,000. Throughout your reproductive years, you'll ovulate approximately 400-500 eggs, while the rest will be lost through a natural process called atresia.

As you age, both the quantity and quality of eggs decline, especially after age 35. This is why age is the most significant factor affecting fertility.

Age and Fertility

Under 30

Peak fertility, 20-25% chance of conception per cycle

Ages 30-34

Gradual decline, 15-20% chance per cycle

Ages 35-37

Moderate decline, 10-15% chance per cycle

Ages 38-40

Significant decline, 5-10% chance per cycle

Over 40

Sharp decline, 1-5% chance per cycle

Key Reproductive Hormones

FSH

Follicle Stimulating Hormone (FSH)

Produced by the pituitary gland, FSH stimulates the growth of ovarian follicles containing eggs. High FSH levels can indicate diminished ovarian reserve.

LH

Luteinizing Hormone (LH)

Also produced by the pituitary gland, LH triggers ovulation. The LH surge occurs about 24-36 hours before an egg is released.

E2

Estradiol (E2)

The primary form of estrogen, produced by growing follicles. It thickens the uterine lining and influences the quality and development of eggs.

P4

Progesterone (P4)

Produced after ovulation by the corpus luteum (empty follicle). It prepares the uterine lining for implantation and maintains early pregnancy.

AMH

Anti-Müllerian Hormone (AMH)

Produced by small follicles in the ovaries, AMH is the best marker of ovarian reserve. Higher levels indicate a larger pool of remaining eggs.

INH

Inhibin B

Produced by developing follicles, inhibin B is another marker of ovarian reserve. It helps regulate FSH production.

Reproductive Anatomy

Female reproductive anatomy

Key Components:

  • 1
    Ovaries: Almond-sized organs that store eggs and produce hormones.
  • 2
    Fallopian Tubes: Tubes that connect the ovaries to the uterus, where fertilization occurs.
  • 3
    Uterus: Pear-shaped organ where a fertilized egg implants and develops.
  • 4
    Cervix: The lower part of the uterus that connects to the vagina.
  • 5
    Vagina: The canal that connects the cervix to the outside of the body.