Fertility Overview

Fertility Overview

Be in the Know. Fertility at a glance.

  • A person’s fertility, or reproductive ability to have children, changes throughout his or her lifetime.
  • The male reproductive system produces and transports sperm, releasing multiple hormones, including testosterone, necessary for those functions.
  • The female reproductive system selects and releases eggs for fertilization, releasing multiple hormones, including estrogen and progesterone, necessary to prepare the uterus for pregnancy and for ongoing bone and heart health.
  • Infertility can be due to abnormalities in sperm, eggs, fallopian tubes, uterus, other endocrine organs, or even combinations of these factors.
  • Patients should seek treatment for infertility if they have been unable to get pregnant after 12 months if the woman is under age 35, six months if she is age 35 or older, or if there are concerns for abnormalities of sperm, egg, uterus, tubes, or whole health.
  • LGBTQ+ individuals and couples have many options for fertility treatments to build their families.
  • Age affects sperm, eggs, and reproductive anatomy, but eggs decline in quality and quantity over time, whereas sperm can continuously be produced but declines in quality.
  • Certain lifestyle practices can optimize fertility, such as eating a balanced diet, maintaining a healthy weight, not smoking, not using drugs, minimizing alcohol consumption, and limiting caffeine intake.
  • Environmental toxins and chemicals can negatively impact fertility.

What Factors Affect a Person’s Fertility?

Fertility is a person’s ability to conceive children. In general, fertility declines overtime for all individuals.

Fertility can be affected by a number of factors, including:

  • Structural abnormalities and medical conditions impacting the reproductive system
  • Age
  • Hormonal changes
  • Illness
  • Lifestyle choices
  • Surgical history
  • Family history
  • Environmental exposures.

Male Reproductive System & Fertility

The organs involved in the male reproductive system include the testes, penis, epididymis, vas deferens, ejaculatory ducts, and urethra.

These organs contribute to the production of hormones and sperm and its transport.

The hypothalamus and the pituitary gland also play a role in male reproduction. These areas of the brain regulate the production of the key hormones:

  • Follicle-stimulating hormone (FSH)
  • Luteinizing hormone (LH).

FSH and LH from the brain stimulate the production of sperm and testosterone from the testicles. Abnormal levels of these hormones can negatively impact sperm production and, therefore, fertility.

The following processes make up male fertility.

Production of Sperm

Sperm start their development in the testicles and then move to the epididymis where they are stored and matured. Healthy sperm are those that have a normal shape, size, and ability to move, which allows them to reach the egg for fertilization. But not all normal-appearing sperm are healthy.

Several glands inside the body also contribute to the production of healthy sperm, including the seminal vesicle and the prostate gland.

Transport of Sperm Out of the Body

The vas deferens is a long, muscular tube that carries sperm from the epididymis into the urethra, which is located inside the penis. The openings to the urethra are called the ejaculatory ducts.

During sexual intercourse, semen is ejaculated out of the urethra through the head of the penis. In addition to problems that can occur with this system of sperm transport, erectile dysfunction can prevent a man from being able to maintain an erection to deliver sperm, and ejaculatory dysfunction can prevent a man from depositing sperm within the female reproductive tract.

Creation of Sex Hormones

FSH from the pituitary gland is responsible for signaling the testes to produce sperm in a process called spermatogenesis. LH, also produced in the pituitary gland, stimulates the testes to produce testosterone.

Testicular testosterone is required for sperm production. It helps sperm mature and also regulates muscle size and strength, as well as red blood cell production in men.

Female Reproductive System & Fertility

The female reproductive system is made up of the ovaries, fallopian tubes, uterus, cervix, and vagina.

These organs contribute to the selection and maturation of eggs (also called oocytes), the transportation of these eggs before fertilization and embryos after fertilization, the production of hormones, and the establishment and maintenance of a pregnancy.

Our current understanding is that a woman is born with every egg she will have, and each month a portion is stimulated and a single egg is selected from this group for release. The remaining eggs that have started stimulation for the month die off and will not be used.

  • The ovaries, where eggs are selected, are 1- to 2-inch oblong organs just below the fallopian tubes on each side of the uterus.
  • The fallopian tubes are passageways between the ovaries and the uterus. They are not directly attached to the ovaries but are attached to each side of the uterus. The far ends of the fallopian tubes have fimbria, finger-like projections responsible for sweeping eggs released from the ovaries into the tube. The far end of the tube is where an egg is fertilized by sperm before the fertilized egg (embryo) moves through the fallopian tube to the uterus.
  • The uterus is where a fertilized egg (an embryo) implants and where a baby develops during pregnancy.
  • The lining of the uterus (the endometrium) thickens in preparation for a potential pregnancy during the beginning of the menstrual cycle. If pregnancy does not occur, the normal progesterone secreting ovarian cyst (the corpus luteum) dissolves and the endometrium is shed, which is what is called a period.
  • The cervix is a muscular canal that connects the uterus to the vagina, and thus to the outside of the body.
  • The vagina is also called the birth canal because it carries a baby out of the body during childbirth. It also receives the penis and ejaculated semen during intercourse.

Hormones’ Role in Female Fertility

Sex reproductive hormones include:

  • FSH
  • LH
  • Estrogen
  • Progesterone
  • Testosterone.

Hormones play an important role in egg development, uterine preparation, and fertility.

  • At the beginning of the menstrual cycle, FSH signals the follicles in the ovaries to select eggs. This is called the follicular phase of the menstrual cycle. As the eggs are maturing, estrogen is released, but progesterone levels remain low. As the FSH levels drop, a single egg is selected and the other eggs developing for the month die off.
  • Around day 14 of a woman’s menstrual cycle, a surge of LH triggers the release of an egg from the ovary, which is called ovulation.
  • After ovulation, the follicle where the eggs were developing becomes a progesterone secreting cyst or corpus luteum. Progesterone prepares a woman’s uterus to accept the egg if it’s fertilized by sperm. This is called the luteal phase of the menstrual cycle and is generally well fixed at 14 days. If an egg is not fertilized by sperm it will degrade, and if pregnancy does not occur the lining of the uterus is shed and the cycle begins again.
  • Testosterone is one of the androgen group of hormones, and though often incorrectly associated only with men, testosterone can affect a woman’s fertility and ovulation. Estrogen is created by the conversion of androgens, like testosterone, into the final estrogen hormone.

How Age Affects Fertility in Women

Although women are born with millions of eggs in their ovaries, only a few hundred reach maturity and are ovulated over the course of the lifetime.

Women are born with all of their eggs in their ovaries, but only start to release eggs for fertilization during puberty.

Egg Quantity & Quality

As women age, the number of eggs decreases. The quality of these eggs also decreases, making it more difficult to become pregnant and increasing the chances of miscarriage. A woman’s fertility is constantly declining from birth but starts to change more abruptly in the mid-30s.

Menopause & Perimenopause

Menopause is defined as no period for a year in the setting of low egg supply. The average age of menopause is 50, but the quality and reproductive potential of eggs sharply decrease 8-10 years before menopause.

In the time frame before menopause, often referred to as perimenopause, women will have a reduction of their egg quality and quantity. They may experience shorter menstrual cycles leading to missing periods. After menopause, women can no longer become pregnant using their own eggs. However, with the use of third party reproduction including donor egg or donor embryo, menopausal women are able to carry a pregnancy.

How Age Affects Fertility in Men

In contrast to women who never produce more eggs, starting at puberty, men continually produce sperm. As men age, they may produce fewer sperm with lower motility (ability to move) and reduced ejaculate volume (amount of fluid that comes out). After age 40, a man’s sperm has an increased rate of genetic abnormalities (single-gene disorders) that can cause birth defects as well as developmental problems for their offspring.

Chances of Getting Pregnant When Trying to Conceive

The chances of becoming pregnant for a sexually active couple with normal exposure of eggs to sperm under the age of 30 is 15-20% each month. This likelihood goes down as the couple ages and can be lower if the individuals have health conditions that affect their fertility.

This means that getting pregnant can often take several months, even for those at the peak of their fertility.

Lifestyle Factors that Can Affect Fertility

Lifestyle factors, such as what a person eats, environmental exposures, stress levels, and exercise can impact fertility.

Making healthy lifestyle choices can often improve fertility. These most commonly include:

  • Maintaining a healthy weight
  • Eating a diet full of nutrient-rich foods
  • Avoiding cigarettes, alcohol, and drugs.

Weight and Fertility

A healthy weight is defined as a body mass index (BMI) between 19 and 25. Having a BMI outside of this range indicates a person is under or overweight and affects reproductive health.

Other Lifestyle Choices that May Improve Fertility

  • Reducing stress levels through activities such as yoga, meditation or Tai Chi
  • Cutting back on processed or pre-packaged foods that are often low in essential nutrients
  • Eating a daily serving of full-fat dairies, such as whole milk or cheese
  • Limiting caffeine intake to a cup of coffee or tea per day (the equivalent of 200 mg of caffeine)
  • Exercising regularly (goal is 150 minutes per week)

Lifestyle Fertility Factors Specific to Men

Men concerned about their fertility should also avoid spending long periods of time in saunas or hot tubs and avoid placing laptops directly on their laps for extended periods of time. Elevated temperatures around the testicles can disrupt the production of sperm and reduce fertility.

Exercise Fertility Factors for Women

Frequent, strenuous exercise, especially by women with low body fat or low body weight, can cause ovulation problems and contribute to infertility. Women who participate in over five hours of vigorous exercise a week and also experience infrequent or no periods may need to reduce the amount or intensity of their exercise to improve their fertility.

Environmental Factors that Can Affect Fertility

Factors in the environment, from air pollution to food contaminants to water quality, can also affect a person’s fertility.

Notably, exposure to the following substances or processes can contribute to infertility.

  • Radiation or radioactivity
  • Secondhand smoke
  • Welding
  • Mercury
  • Pesticides and fertilizer
  • Lead
  • Organic solvents (such as benzene, glycol ethers, and toluene)
  • Carbon monoxide
  • Industrial chemicals
  • Biological agents (such as toxoplasmosis, listeriosis, and hepatitis A and B)
  • Prolonged exposure to anesthetic gases (such as those used in dental and doctors’ offices)


Certain workplaces carry a higher risk of exposure to these toxic chemicals. For example, those who work in laboratories, cleaners, metal industries, car repair shops, shoemaking factories, salons or hospitals may have a higher chance of regular exposure to processes that can affect fertility.

Some chemicals in home cleaning and personal hygiene products can also affect sperm, egg and embryo quality. These are called endocrine-disrupting chemicals (EDCs) and include substances like paraben and phthalates.

To help limit exposure to EDCs, a person can do the following:

  • Wash all fruits and vegetables before eating
  • Reheat food in glass or ceramic containers rather than plastic
  • Choose cleaning products free of chemicals
  • Use paraben-free shampoos and soaps
  • Drink filtered water
  • Limit the use of pesticides.

Diagnosis of Infertility

Six million couples in the United States – 1 in 8 – struggle with infertility.

Infertility is defined as not being able to get pregnant after 12 months of regular egg/sperm exposure for individuals under the age of 35, and for those 35 and older after 6 months of regular egg/sperm exposure.

Individuals should seek earlier evaluation if they are over age 40 or have irregular periods, abnormal bleeding, history of gynecologic surgery, history of pelvic inflammatory disease, endocrine disorders, inability to maintain an erection, inability to ejaculate, or a history of chemotherapy, radiation or toxin exposure.

Infertility in Women

Other signs that a woman may have infertility can include irregular menstrual cycles (number of days between periods is inconsistent), lack of periods, abnormal bleeding during periods or pain during periods.

If a hormonal abnormality is the source of infertility a woman may also experience:

  • Unexplained weight loss or gain
  • Acne or oily skin
  • Hair growth in unexpected places such as the face or chest
  • Thinning hair
  • Changes in sex drive.

Infertility in Men

Men may have infertility if they have the following symptoms:

  • Problems with achieving or maintaining an erection
  • Problems with ejaculation
  • Low sex drive
  • Swollen chest/breast tissue
  • Pain or lump(s) in the testicles.

Any person with these symptoms or a history of illness or medical treatments that could affect his or her fertility should see a fertility specialist.

When to see a reproductive endocrinologist (fertility specialist)

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