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Subfertility vs Infertility

Subfertility vs Infertility – what’s the difference?

The terms subfertility and infertility are often used interchangeably but they aren’t quite the same thing. Infertility is the inability to conceive naturally after one year of trying. Subfertility, on the other hand, is where the possibility of conceiving naturally exists, but it takes longer than average. In infertility, the likelihood of conceiving without medical intervention is unlikely.

The causes of subfertility are similar to the causes of infertility:


Ovulation Problems

The most common cause of subfertility is a problem with ovulation. If you have no periods or irregular periods that may be a sign of an ovulatory problem. Without ovulation, an egg won’t be released to be fertilised.

There are several factors that can cause ovulation problems:

  • PCOS (polycystic ovarian syndrome) which can prevent ovulation or cause irregular ovulation;
  • hormonal or endocrine imbalances especially with the pituitary or hypothalamus or pituitary, leading to luteinising hormone and follicle-stimulating hormone dysfunction, in turn affecting ovulation;
  • thyroid hormone abnormalities.

Diminished Ovarian Reserve

A low ovarian reserve or egg count, measured by a low Anti-Mullerian Hormone level, may impact the ability to conceive and lead to infertility or subfertility. A low AMH however does NOT predict chances of natural conception, nor reflect a measure of egg quality.

Causes of low AMH include:

  • female ageing;
  • previous ovarian surgery;
  • previous medical treatment, for example chemotherapy;
  • Premature ovarian insufficiency (POI) in which ovarian function is severely diminished before the age of 40.

Tubal Factors

Tubal factors are another common cause of subfertility. If the fallopian tubes are blocked or there is an abnormal tubal function, sperm are unable to reach and fertilise the egg. This can stem from:

  • Prior bilateral tubal ligation or fallopian tube resection for contraception
  • Endometriosis
  • Pelvic inflammatory disease;
  • Peritubal adhesions or scarring from pelvic/abdominal surgery;
  • Previous ectopic pregnancy;
  • Sexually transmitted infection such as chlamydia, especially if undetected or untreated;
  • Postpartum infection.

In its early days, IVF was mainly used to help women whose tubes were blocked; today it is used to treat a wider range of subfertility and infertility issues.

Abnormalities of the uterus

The most common uterine abnormalities are fibroids, and are often an incidental finding on ultrasound, with no symptoms. Fibroids are benign growths or tumours of the muscular part of the uterus. Fibroids are very common – up to 80% of women have at least one fibroid – and increase with age. Most fibroids do not affect a woman’s fertility and do not require treatment unless the fibroid is in a submucosal location within the uterus, and may distort the endometrial lining, affecting embryo implantation. Large fibroids may also affect tubal function or block the fallopian tubes.

Fibroids that may be associated with subfertility or infertility, can be removed via a hysteroscopic operation which is a minimally invasive, safe, and effective treatment for submucosal fibroids.

Other treatments for fibroids may depend on the woman’s symptoms, size, and location of the fibroid within the uterus.

Other much less common conditions of the uterus include congenital (present at birth) anatomical variations:

  • septate uterus, in which a band of tissue divides the uterus into two sections. This requires surgical resection.
  • bicornuate uterus, in which the uterus has two cavities instead of one. A true bicornuate uterus is quite rare (occurring in less than 0.5% of the population) and may be diagnosed after investigations for recurrent miscarriage, subfertility, or infertility.
  • double (didelphys) uterus, in which the uterus has two cavities, each with its own opening. Double uterus is a rare congenital abnormality. In a female fetus, the uterus begins as two small ducts or tubes. As the fetus develops, the tubes normally join to create one uterus. Sometimes, however, the tubes do not combine and join completely, with each one developing into a separate structure. A double uterus may have one opening (cervix) into one vagina, or each uterine cavity may have a separate cervix. In many cases, a thin wall of tissue runs down the length of the vagina, dividing it into two separate openings. Women who have a double uterus often have successful pregnancies, but the condition can increase the risk of miscarriage or premature birth.

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Problems with sperm production or function

Abnormal sperm production, function, or quality can cause subfertility in men. This may be related to a number of factors, including:

  • sexually transmitted infections for example gonorrhea, chlamydia;
  • HIV;
  • diabetes;
  • previous mumps;
  • cancer and cancer treatment;
  • enlarged veins in the testes called varicocele;
  • genetic diseases or chromosomal variations, such as Klinefelter syndrome;
  • hormonal medications;
  • hormonal disorders leading to abnormalities in hormones produced by the pituitary gland, hypothalamus, and testicles;
  • thyroid hormone abnormalities;
  • iron overload.

Problems with sperm delivery

Problems with the delivery of sperm can make it difficult to conceive. This can be caused by several things, including:

  • blockages of the genital tract (ejaculatory ducts or seminal vesicles) caused by previous infections or injuries;
  • prior vasectomy;
  • genetically inherited conditions, such as cystic fibrosis;


Certain factors increase your risk of being subfertile. Many lifestyle or background disease risk factors are the same for male and female subfertility and may be multifactorial. These include:

  • being a female over the age of 35;
  • being a male over the age of 40;
  • being overweight, obese, or underweight;
  • smoking tobacco or marijuana;
  • excessive alcohol use;
  • excessive physical or emotional stress;
  • certain medications (such as hormonal therapies, chemotherapy, anabolic steroids, some psychiatric medications, antipsychotics);
  • exposure to environmental toxins, such as lead and pesticides;
  • background cardiovascular disease, hypertension, high cholesterol, and metabolic factors.
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A Flinders Fertility Specialist can help diagnose the cause of subfertility. Your doctor will begin by collecting the medical history of both partners and family members in some cases.

The doctor may also perform a physical examination, particularly if there are indications such as abnormal semen analysis results.

A fertility evaluation will also include ordering a number of tests which may include:


  • transvaginal baseline ultrasound to assess the reproductive organs and ovarian antral follicle count;
  • blood tests including baseline hormonal levels, a mid-luteal phase progesterone to assess ovulation, infection screening, thyroid and prolactin levels;
  • pre-conception screening for red blood cell count/anaemia, immunity for rubella/chicken pox, diabetes screen, vitamin D and iron levels;
  • Hystero-salpingo contrast sonography (HyCoSy) to evaluate the condition of the fallopian tubes and uterus;
  • Anti-Mullerian Hormone testing for ovarian reserve testing.


  • semen analysis;
  • blood tests to determine male hormone levels, including testosterone; infection screening, general health assessments.

Depending on your medical/family history and or test results, additional tests may also be requested, including chromosomal analysis. Genetic carrier screening for inherited diseases will be considered.

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Whether you are subfertile or infertile it is still possible to conceive naturally. Treatment for subfertility is focused on lifestyle changes and learning how to increase your chances of getting pregnant. Medical treatments and other options are available if needed.

Boosting your odds of natural conception.

Here are some lifestyle changes and tips that can increase your chances of conceiving naturally:

  • Avoid smoking, which can affect male and female fertility;
  • Stop drinking alcohol and cut back on caffeine;
  • Consider taking prenatal vitamins;
  • Maintain a healthy weight, as being underweight or overweight can affect fertility, increase the risk of miscarriage and fetal growth problems in pregnancy;
  • Ovulation predictor techniques eg basal body temperature monitoring, LH surge kits, plus cervical mucus monitoring to predict ovulation and enhance intercourse timing, although there is little evidence that these techniques increase conception;
  • Avoid excessive heat, such as saunas, which can affect sperm production and motility;
  • Avoid toxic chemicals that can disrupt hormones;
  • Speak to your doctor about your medications, as some may affect fertility or may not be recommended pre-conception or in pregnancy.

You should see a doctor before trying to conceive to assess your general health, medications, vaccination status, and undergo pre-conception screening. Medical treatment will depend on the cause of subfertility or infertility and the treatment varies between males and females.

Treatment for male subfertility

Treatment options for men may involve treating sexual health problems or:

  • medications (multivitamins/antioxidants) to improve testicular function, including sperm count and quality;
  • sperm retrieval techniques to obtain sperm if there are problems ejaculating or when ejaculated fluid does not contain sperm;
  • surgery to repair a varicocele or blockage – this is in fact rare not common;
  • if BMI is outside the normal (20-25) range, optimising diet and embarking on lifestyle changes may help to improve sperm quality.

Treatment for female subfertility

There are many therapies available to help restore female fertility. You may need only one or a combination of treatments to be able to conceive.

These include:

  • ovulation induction medications;
  • surgery to treat uterine problems;
  • if BMI is outside the normal (20-25) range, optimising your diet to achieve this target range may enable you to achieve a healthy pregnancy without further intervention.

Assisted reproductive technology

Assisted reproductive technology (ART) refers to any fertility treatment or procedure that involves the handling of the egg and/or sperm.

One of the most low-intervention forms of ART is intrauterine insemination (IUI), which is placing healthy sperm inside the uterus. IUI is often helpful for couples where timing of intercourse is difficult (eg FIFO workers), or may help overcome some sexual difficulties.

However, the most common ART procedure is in vitro fertilization (IVF). It involves retrieving a woman’s eggs from her ovaries and fertilizing the eggs with sperm, to develop embryos in a specialised laboratory. The embryos are then transferred into the uterus.

Other techniques may be used during IVF to help increase the likelihood of conception. These include:

  • intracytoplasmic sperm injection (ICSI), in which a normal sperm is injected directly into an egg;
  • assisted hatching, which may improve implantation by opening the outer thin shell of the embryo;
  • donor eggs or sperm, which may be used if there are severe problems with either the eggs or sperm.

If you suspect you may be sub-fertile please contact Flinders Fertility to speak to a patient care coordinator, or to book an appointment with one of our fertility doctors.

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