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15 May 2023

Subfertility and Infertility

Article by Dr Greg Phillipson

Subfertility and Infertility


Subfertility and infertility are two similar conditions used to describe difficulties with conceiving a child.  The terms subfertility and infertility are often used interchangeably.

  • Subfertility is where the possibility of conceiving naturally exists, but it takes longer than average. Subfertility refers to the condition in which a couple is having difficulty becoming pregnant despite having regular, unprotected sexual intercourse for at least a year. It is also known as reduced fertility or fertility delay. Subfertility can be caused by a variety of factors, including age, hormonal imbalances, reproductive system disorders, and lifestyle factors such as smoking and excessive alcohol consumption. It can occur for couples that had previously conceived easily and may achieve pregnancy without the need for advanced treatments. Research suggests that up to 25% of couples in New Zealand may experience such a delay even after a straightforward previous pregnancy.


  • Infertility is the inability to conceive naturally after one year of trying. Infertility can be caused by a wide range of factors, including problems with ovulation, sperm quality and quantity, blocked fallopian tubes, endometriosis, and other medical conditions. Often the specific cause of infertility is unexplained.

Both subfertility and infertility can be emotionally and psychologically distressing.


Can you get pregnant with subfertility?

It's important to seek medical advice and support if you are experiencing subfertility. The chances of getting pregnant with subfertility depend on the underlying cause and severity of the condition. For example, if age-related factors cause subfertility, the chances of pregnancy may decrease as a woman gets older. If hormonal imbalances or ovulation disorders cause subfertility, treatment with fertility drugs may improve the chances of conception. There may be medical conditions that need to be addressed. A healthcare provider can help identify the underlying cause of subfertility and recommend appropriate treatments to increase the chances of pregnancy. In some cases, assisted reproductive technologies such as intrauterine insemination (IUI) or in vitro fertilization (IVF) may be necessary to achieve pregnancy.

Infertility is a more severe form of subfertility and affects about 15% of couples worldwide.


When should I see someone to discuss fertility?

Approximately 80% of couples will conceive in the first six months of attempting pregnancy. Peak fertility for women is in their 20s to early 30s. For those couples 35 and older, the monthly percentage of conceiving is decreased. Male sperm counts also decrease but with less effect on the chance of pregnancy until a man is over 40.

Fertility can be discussed with a health care provider at any time couples are considering a family. Discussion of the preconception advice topics listed below are usually reviewed at this time.

Women over 35 should be seen if pregnancy has not occurred within six months without contraception. The discussion and tests to confirm ovulation and ovarian reserve (AMH blood test), a pelvic ultrasound scan, and semen analysis should be considered at this stage. These tests may not be needed for younger couples until 12 months without contraception if regular menstrual cycles are occurring and both partners are well because many achieve pregnancy between 6 and 12 months.

However, if previous investigations show fertility delay in a previous relationship for either partner or concerns regarding endometriosis, pelvic infection or surgery, then earlier assessment is suggested.

Referral to a specialist may not be required depending on the initial assessment or results. However, the important issues of ovulation, pelvic infection or possibility or tubal blockage, or abnormal sperm results could require referral at any stage if they are identified, or there is a possibility from their medical history.


References can be provided upon request.

Dr Greg Phillipson (MB, ChB, FRANZCOG, CREI) is an Obstetrician, Gynaecologist and Subspecialist in reproductive medicine and surgery.

This article is for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment before undertaking a new healthcare regimen.

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