What Factors Can Affect Fertility in Men and Women?

What factors can affect fertility in men and women? Learn how age, ovulation, sperm health, weight, lifestyle, medical conditions, and other factors can influence fertility.

FERTILITY

Written by: ReproNexa Health Editorial Team

8/18/20268 min read

What Factors Can Affect Fertility in Men and Women?

Fertility is the ability to become pregnant and, in some contexts, contribute to a pregnancy. It depends on several biological factors involving both partners.

Fertility isn't determined by one thing. Age, ovulation, sperm production, reproductive health, medical conditions, lifestyle, medications, and previous infections or surgeries can all play a role.

According to the NHS, infertility can affect either partner, and sometimes no specific cause is found despite testing. (nhs.uk)

Understanding the factors that affect fertility can help you recognize when medical advice may be useful.

How Fertility Works

For pregnancy to occur naturally, several processes need to happen.

In general:

  1. An ovary needs to release an egg.

  2. Sperm needs to be produced and reach the egg.

  3. The fallopian tubes need to allow sperm and egg to meet.

  4. Fertilization needs to occur.

  5. The fertilized egg needs to implant in the uterus.

  6. Hormonal and reproductive systems need to support early pregnancy.

Problems at any stage can make conception more difficult.

Because these processes involve both reproductive systems, fertility should not be viewed as only a woman's issue or only a man's issue.

Factors That Can Affect Female Fertility

1. Age

Age is one of the most important factors affecting female fertility.

Fertility generally declines with age, particularly because the number and quality of eggs decrease over time. The decline becomes more noticeable after the mid-30s. (acog.org)

Age can also increase the risk of miscarriage and certain pregnancy complications.

This doesn't mean pregnancy is impossible at an older age. It means the probability of conception generally changes with age.

2. Ovulation Problems

Regular ovulation is important for natural conception.

Conditions that interfere with ovulation can make pregnancy more difficult.

Possible causes include:

  • Polycystic ovary syndrome (PCOS)

  • Thyroid disorders

  • Significant weight changes

  • Excessive exercise

  • Certain hormonal conditions

  • Premature ovarian insufficiency

  • Significant physical or emotional stress in some circumstances

Irregular or absent periods can sometimes be a clue that ovulation isn't occurring regularly. (nhs.uk)

3. PCOS

Polycystic ovary syndrome (PCOS) is a common hormonal condition that can affect ovulation.

People with PCOS may have irregular periods because ovulation does not occur regularly.

PCOS doesn't mean pregnancy is impossible. Many people with PCOS become pregnant naturally or with medical treatment when needed. (nhs.uk)

4. Fallopian Tube Problems

The fallopian tubes provide a pathway where sperm and egg can meet.

Blocked or damaged tubes can interfere with fertilization.

Possible causes include:

  • Previous pelvic infections

  • Pelvic inflammatory disease (PID)

  • Certain sexually transmitted infections

  • Endometriosis

  • Previous abdominal or pelvic surgery

Chlamydia and gonorrhea, for example, can sometimes cause reproductive complications if untreated. (cdc.gov)

5. Endometriosis

Endometriosis occurs when tissue similar to the lining of the uterus grows outside the uterus.

It can cause pelvic pain and may affect fertility in some people.

The exact reasons are complex and can involve inflammation, changes to pelvic anatomy, and effects on the ovaries or fallopian tubes. (nhs.uk)

6. Uterine or Cervical Conditions

Certain conditions affecting the uterus or cervix may make conception or implantation more difficult.

Examples include:

  • Fibroids

  • Polyps

  • Uterine abnormalities

  • Certain cervical conditions

Not every fibroid or uterine condition causes infertility. The effect depends on factors such as its location and size. (acog.org)

7. Premature Ovarian Insufficiency

Premature ovarian insufficiency (POI) occurs when the ovaries stop functioning normally before age 40.

It can lead to irregular or absent periods and reduced fertility.

POI is different from normal menopause because ovarian function can sometimes occur intermittently. (acog.org)

8. Weight and Nutrition

Being significantly underweight or overweight can affect ovulation and reproductive hormones.

Very low energy availability can also interfere with menstrual function.

Maintaining adequate nutrition and a healthy body weight can support reproductive health, although there is no single "perfect" weight for fertility.

Factors That Can Affect Male Fertility

Male fertility depends heavily on the production, movement, and function of sperm.

1. Age

Male fertility can also change with age.

Semen quality may decline gradually as men get older, although the pattern is different from the relatively more pronounced age-related decline in female fertility. (asrm.org)

Age may affect sperm movement, concentration, and DNA quality.

2. Low Sperm Count

A lower-than-normal sperm concentration can reduce the likelihood of conception.

A low sperm count may result from:

  • Hormonal problems

  • Genetic conditions

  • Testicular disorders

  • Certain medications

  • Previous infections

  • Heat exposure

  • Lifestyle factors

  • Unknown causes

A semen analysis is commonly used to assess sperm concentration and other aspects of semen quality. (nhs.uk)

3. Poor Sperm Motility

Sperm motility refers to how well sperm move.

Sperm need to move effectively through the female reproductive tract to reach an egg.

Reduced motility can therefore affect fertility.

4. Abnormal Sperm Shape

Sperm morphology refers to the size and shape of sperm.

A semen analysis can assess sperm morphology as part of an overall evaluation of sperm health.

Importantly, a single semen measurement doesn't always provide the complete picture of fertility.

5. Testicular Problems

The testes are responsible for producing sperm and testosterone.

Certain conditions can affect fertility, including:

  • Varicocele

  • Testicular injury

  • Undescended testicles

  • Infections

  • Testicular surgery

  • Some genetic conditions

A varicocele, for example, is an enlargement of veins around the testicle and can be associated with abnormal sperm production in some men. (urologyhealth.org)

6. Hormonal Problems

Hormones produced by the brain and reproductive organs help regulate sperm production.

Disruptions involving testosterone, the pituitary gland, or other hormones can interfere with sperm production.

Certain endocrine disorders may therefore contribute to male infertility.

7. Erectile or Ejaculation Problems

Fertility can also be affected when sperm cannot be effectively deposited in the reproductive tract.

Examples include:

  • Erectile dysfunction

  • Problems with ejaculation

  • Retrograde ejaculation

  • Certain neurological conditions

These conditions may have medical or psychological causes and can often be evaluated and treated.

Lifestyle Factors That Can Affect Fertility

Lifestyle doesn't determine fertility by itself, but several habits can influence reproductive health.

Smoking

Smoking is associated with reduced fertility in both men and women.

In men, smoking can affect sperm quality. In women, smoking can damage reproductive health and accelerate reproductive aging. (cdc.gov)

Alcohol

Heavy alcohol consumption can negatively affect reproductive health.

For people trying to conceive, limiting alcohol is generally recommended, and there is no safe level of alcohol consumption during pregnancy. (cdc.gov)

Recreational Drugs

Some recreational drugs can affect reproductive hormones, sperm production, or sexual function.

Discuss drug use honestly with a healthcare professional if fertility is a concern.

Physical Activity

Regular moderate exercise supports overall health.

However, very intense exercise combined with inadequate nutrition can interfere with menstrual function in some women. (nhs.uk)

Weight

Both very low and high body weight can be associated with fertility problems.

Gradual, sustainable lifestyle changes are generally more useful than extreme dieting.

Can Stress Affect Fertility?

Stress is often discussed in relation to fertility, but it is important to avoid oversimplifying the connection.

Significant physical or emotional stress can interfere with ovulation in some women. Long-term stress may also be associated with changes in semen quality in some men. (mayoclinic.org)

However, ordinary daily stress does not automatically cause infertility.

People experiencing fertility difficulties should not be blamed or told that they simply need to "relax."

Fertility problems can have genuine medical causes that require evaluation.

Can STIs Affect Fertility?

Yes. Some untreated sexually transmitted infections can damage reproductive organs and affect fertility.

In women, untreated chlamydia or gonorrhea can lead to pelvic inflammatory disease, which can damage the fallopian tubes. (cdc.gov)

Some infections can also affect male reproductive health.

This is one reason STI prevention, testing, and timely treatment are important parts of reproductive health.

Can Medications Affect Fertility?

Some medicines can affect reproductive function.

Examples may include certain:

  • Hormonal medications

  • Chemotherapy drugs

  • Testosterone treatments

  • Other medicines affecting reproductive hormones

This doesn't mean you should stop a prescribed medication.

If you're planning a pregnancy, ask your healthcare professional whether your medications affect fertility or pregnancy.

Can Previous Surgery Affect Fertility?

Certain surgeries involving the reproductive organs or pelvis can affect fertility.

Examples include surgeries involving:

  • Ovaries

  • Fallopian tubes

  • Uterus

  • Testes

  • Pelvic organs

Some procedures can cause scarring or alter reproductive anatomy.

Your medical history is therefore an important part of a fertility evaluation.

Can Environmental Exposures Affect Fertility?

Research suggests that some environmental exposures may affect reproductive health.

Examples include certain:

  • Industrial chemicals

  • Pesticides

  • Heavy metals

  • Occupational exposures

  • High heat exposure to the testes

The effect depends on the substance, dose, duration, and individual circumstances.

People working with potentially harmful chemicals should follow appropriate workplace safety measures.

What About Sexual Frequency and Timing?

Timing and frequency of intercourse can influence the chance of conception.

For people trying to become pregnant, the fertile window around ovulation is particularly important because sperm can survive for several days while the egg is viable for a much shorter period.

The NHS recommends having sex every 2 to 3 days when trying to conceive rather than focusing entirely on one predicted ovulation day. (nhs.uk)

When Should You Have a Fertility Check?

Consider speaking with a healthcare professional if:

  • You have been trying to conceive for a year without pregnancy.

  • You are 35 or older and have been trying for about six months without success.

  • Your periods are irregular or absent.

  • You have severe pelvic pain.

  • You have a history of pelvic infections or reproductive surgery.

  • You have known reproductive conditions such as PCOS or endometriosis.

  • You have concerns about sperm production or sexual function.

  • You have a condition or medication that may affect fertility.

The appropriate timing can vary depending on age and medical history. (acog.org)

Can Fertility Problems Be Treated?

Often, yes.

Treatment depends on the cause.

Depending on the situation, options may include:

  • Lifestyle changes

  • Ovulation medicines

  • Treatment for infections

  • Surgery

  • Treatment for hormonal problems

  • Intrauterine insemination (IUI)

  • In vitro fertilization (IVF)

  • Other assisted reproductive technologies

Not everyone needs fertility treatment, and in some cases no specific cause is found.

A fertility specialist can help determine which options are appropriate.

The Bottom Line

There are many factors that can affect fertility in men and women.

For women, important factors include age, ovulation, PCOS, endometriosis, fallopian tube health, uterine conditions, weight, and certain medical problems.

For men, fertility can be influenced by age, sperm count, sperm movement and shape, testicular health, hormones, medications, and some lifestyle or environmental exposures.

Smoking, heavy alcohol use, untreated STIs, and certain medical conditions can affect reproductive health in both sexes.

Most importantly, fertility difficulties are not always caused by something you did or didn't do. If pregnancy isn't happening as expected, proper medical evaluation can help identify possible causes and treatment options.

Frequently Asked Questions

What is the biggest factor affecting female fertility?

Age is one of the most important factors affecting female fertility because egg quantity and quality generally decline with age. (acog.org)

What is the most common cause of infertility in women?

Ovulation problems are among the common causes of female infertility. Conditions such as PCOS can interfere with regular ovulation. (nhs.uk)

What affects male fertility the most?

Male fertility can be affected by sperm production and quality, testicular health, hormones, age, certain medications, infections, and lifestyle factors.

Can stress cause infertility?

Significant stress can interfere with ovulation in some people, but everyday stress does not automatically cause infertility. Fertility difficulties have many possible causes. (mayoclinic.org)

Can lifestyle changes improve fertility?

In some circumstances, yes. Quitting smoking, limiting alcohol, maintaining a healthy weight, eating adequately, and managing certain medical conditions can support reproductive health.

Can an STI cause infertility?

Yes. Untreated infections such as chlamydia and gonorrhea can cause complications that may affect fertility, particularly when they lead to pelvic inflammatory disease. (cdc.gov)

Does age affect male fertility too?

Yes. Male fertility can gradually change with age, including changes in semen quality, although the pattern differs from the age-related decline in female fertility. (asrm.org)

When should I see a doctor about fertility?

Many guidelines recommend fertility evaluation after 12 months of trying without pregnancy, with earlier evaluation often appropriate depending on age, symptoms, or known risk factors. (acog.org)

Does having irregular periods mean I'm infertile?

No. Irregular periods can indicate irregular ovulation, which may make conception more difficult, but they do not automatically mean that pregnancy is impossible.

Can fertility problems affect both partners?

Yes. Fertility problems can involve the female reproductive system, male reproductive system, both partners, or have no clearly identified cause.

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