Fertility NZ is a registered charity dedicated to providing information, support and advocacy to people experiencing fertility issues.

Unexplained Infertility

‘Unexplained infertility’ is a common phrase in the reproductive world.  It is the term used when there is no cause found for infertility.  A diagnosis of  unexplained infertility is given to about 15-25% of couples with infertility. It does not necessarily mean that there is no cause – rather, it may mean that the cause has just not been found.

Infertility may be said to be unexplained if the woman is ovulating regularly, has patent fallopian tubes with no adhesions or endometriosis, if the man has normal sperm parameters and the couple have been having frequent intercourse at the time of ovulation for at least one year. The final diagnosis is made only after all the necessary tests have been performed and all results are found to be normal.

Diagnosis of Unexplained Infertility

Although normally investigations are commenced after 12 months of unprotected intercourse without conception, in couples where the woman is more than 35 years old most doctors will recommend commencing investigations after 6 months.

Investigations should include a semen analysis, assessment of ovulation and ovarian reserve, a pelvic ultrasound (female) and tubal patency check by hysterosalpingogram or laparoscopy.

The most accurate way currently to assess ovarian reserve is a serum Anti Mullerian Hormone (AMH) assay. This blood test can be performed at any time of the menstrual cycle and should be very helpful in determining ovarian reserve and likely ovarian response if treatment with ovarian stimulation is recommended.


A couple with unexplained infertility still have a fairly good chance of getting pregnant on their own, without needing treatment at all, although this will be dependent on the age of the woman and the length of timing trying to conceive to date.

The principal treatments for unexplained infertility include expectant management with timed intercourse and lifestyle change, clomiphene citrate or letrozole with or without intra uterine insemination (IUI), lipiodol tubal flushing, and IVF.

Expectant Management and Lifestyle changes

Cigarette smoking, abnormal BMI, and excessive caffeine and alcohol consumption can reduce fertility in the male and female partner.  Both partners should be counselled to achieve a normal BMI and reduce caffeine intake to less than 250mg (2 cups) daily. The age of the female partner will impact the chance of expectant management being successful

Your fertility specialist can discuss these options with you and recommend them if appropriate.

Lipiodol or Laparoscopy
Lipiodol tubal flushing and /or the laparoscopic treatment of mild endometriosis with tubal flushing have been shown in some studies to help couples with unexplained infertility conceive.

Clomiphene citrate
The use of Clomiphene with timed intercourse in patients with unexplained infertility has been shown to only have a small benefit – probably 40 cycles of empiric clomiphene are required to achieve one extra pregnancy

Intrauterine insemination involves placing washed prepared sperm in the uterine cavity at ovulation either on a natural cycle or with stimulation. A recent Cochrane review confirmed that IUI with stimulation increased the live birth rate when compared to IUI alone

This is the most effective treatment for unexplained infertility where simpler options have been unsuccessful. IVF will also give an explanation for the infertility in some couples.  Many IVF clinics recommend ICSI (sperm microinjection) as part of the IVF cycle for long term unexplained infertility, or a 50/50 IVF/ICSI split for inseminating  follicles

In sum
A thorough and timely investigation of couples is required before making a diagnosis of unexplained infertility. Various treatment modalities are available with maternal age and length of infertility with current ovarian reserve (as determined by AMH) being the best predictors of success.