Logo-white SAFE
26.07.25

Infertility vs. Subfertility: What’s the Difference and Why It Matters

Infertility vs. Subfertility: What’s the Difference and Why It Matters

Many people have heard the terms “Infertility” และ “Subfertility” and often use them interchangeably, which can cause confusion. Are they the same, or do they have important differences worth noting?

In this article, SAFE Fertility Group PCL will help clarify the meaning of both terms and explain what causes fertility challenges—and how you can plan appropriate treatment based on your condition.

What Is Infertility?

Infertility is defined as the inability to achieve pregnancy after at least 12 months of regular, unprotected intercourse. According to medical guidelines, this timeframe is appropriate to consider fertility testing and evaluation.

Infertility may be due to factors related to the female partner, the male partner, or both. Common causes include:

  • Structural or functional reproductive problems, such as blocked fallopian tubes in women or absence of sperm (azoospermia) in men
  • Severe medical conditions, such as advanced endometriosis, severe PCOS, or chromosomal abnormalities
  • Irreversible reproductive damage, such as removal of the ovaries, or previous chemotherapy/radiation therapy affecting fertility

Infertility does not mean pregnancy is impossible—it simply means the chances of conceiving naturally are lower than average, and advanced treatment is often needed.

Medical evaluation for infertility may include:

  • Female hormone profile
  • Ovulation tracking via ultrasound
  • Fallopian tube patency tests
  • Semen analysis
  • Sperm DNA fragmentation test (especially if standard semen results are normal, but fertilization has not occurred)

Fertility treatments often recommended for infertility:

  • Ovulation induction medication
  • Intrauterine insemination (IUI)
  • In vitro fertilization (IVF)
  • Intracytoplasmic sperm injection (ICSI)

These assisted reproductive technologies (ART) are designed to increase the likelihood of pregnancy in cases with significant underlying reproductive challenges.

Once a cause is identified, doctors may recommend suitable treatments for either partner, such as ovulation induction, intrauterine insemination (IUI), or in vitro fertilization (IVF/ICSI) to enhance pregnancy chances.

What Is Subfertility?

Subfertility refers to reduced fertility or delayed conception, even though natural pregnancy is still possible. Subfertile couples may eventually conceive without medical intervention, but it typically takes longer than average—over 12 months for women under 35, or over 6 months for women over 35.

Common Causes of Subfertility:

In women:

  • Age-related decline in egg quality, particularly after age 30–35
  • Irregular periods or mild PCOS
  • Being underweight or overweight, which disrupts hormone balance
  • Chronic stress or poor sleep habits
  • Smoking, alcohol, or medications that affect hormone levels

In men:

  • Poor sperm quality: slow motility, abnormal shape, low count, or high DNA fragmentation
  • Lifestyle risks such as smoking, alcohol, or heat exposure around the scrotum
  • Medical conditions like diabetes or hormonal imbalances

For both partners:

  • High-stress lifestyles
  • Exposure to pollutants or toxins
  • Long-term use of birth control or certain medications
  • Infrequent or mistimed sexual intercourse

A Side-by-Side Comparison between Infertility vs. Subfertility

Infertility
A road blocked by a wall 		Subfertility
A bumpy road—still passable, but more difficult

Definition

No pregnancy after 12+ months of trying

Delayed or reduced chances of conception

Diagnosis

Requires specialized fertility testing

Often assessed through history, symptoms, and basic testing

Severity

More severe; clear reproductive barriers

Less severe; often multifactorial (e.g., irregular ovulation)

Chance of Pregnancy

Often requires ART like IVF/ICSI

May conceive naturally with time and lifestyle adjustments

Initial Treatment

Typically Assisted Reproductive Treatment from the start

May begin with behavior change, medication, or IUI

Diagnosis: Where to Start

If you suspect you may have difficulty conceiving, the first step is to consult a fertility specialist. Recommended tests may include:

  • Hormone and ovarian reserve testing
  • Ultrasound of the uterus and ovaries
  • Semen analysis and sperm DNA fragmentation test
  • Fallopian tube assessment

Learn more: Our Couple Fertility Pre-screening Program

Treatment Options

Depending on the cause identified, treatment may include:

  • Ovulation stimulation
  • Intrauterine insemination (IUI)
  • IVF/ICSI
  • Lifestyle modifications such as weight management, improved sleep, or quitting smoking
  • Nutritional optimization and hormone balancing

Depending on the severity, your doctor may suggest simple interventions like IUI or more advanced procedures. You can learn more about the difference between IUI and IVF to see which path might be right for you.

Explore available treatment programs: Our ICSI/IVF & Fertility Programs

Understanding the distinction between infertility and subfertility can help you take the right action at the right time. With advances in reproductive medicine, there are many options available to help you achieve your dream of building a family.

If you’ve been trying to conceive for over a year (or 6 months if over age 35), it may be time to speak with a fertility expert. The earlier you begin, the better your chances.

At SAFE Fertility Group PCL, our specialists are here to provide tailored diagnostics, treatment, and compassionate multilingual support—every step of the way.

Article by: Peangpailin Voradithi, M.D. (Dr.Tangmo)

SAFE Fertility Group PCL, Gaysorn Amarin Branch Medical License Number 46855

References

Back