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Demographics of infertility and management of unexplained infertility

Best Practice & Research Clinical Obstetrics & Gynaecology, 6, 26, pages 729 - 738

The cause of infertility is unexplained in about 22–28% of all infertile couples. The prognosis for spontaneous pregnancy in such couples is better than in those with diagnosed causes of infertility. Traditional treatment options in this group have included expectant management, clomifene citrate, intrauterine insemination with (super ovulation plus intrauterine insemination) or without (intrauterine insemination) super ovulation and in-vitro fertilisation. Despite being more expensive, empirical clomifene and intrauterine insemination in an unstimulated cycle do not improve the chances of live birth compared with expectant management. Although unlikely to be more effective than no treatment in couples with a reasonably good prognosis, super ovulation plus intrauterine insemination has been shown to be more effective than intrauterine insemination. Any potential advantage of super ovulation plus intrauterine insemination has to be balanced against the relatively high risk of iatrogenic multiple pregnancy. In-vitro fertilisation remains the treatment of choice in longstanding unresolved infertility and, when coupled with the use of elective single embryo transfer, can minimise the risk of multiple pregnancies. Data from randomised trials confirming the superiority of in-vitro fertilisation over expectant management is limited.

Keywords: unexplained infertility, expectant management, intra uterine insemination, super ovulation, clomifene citrate, in-vitro fertilisation.


Infertility has been defined as failure to conceive after regular unprotected sexual intercourse for 1 year.1 and 2This definition reflects the prognostic approach to this condition, based on the knowledge that, in a general population, 84% of all women are expected to conceive within 1 year of regular unprotected sexual intercourse. This figure rises to 92% after 2 years, and 93% after 3 years. 3 The term ‘unexplained infertility’ refers to infertile couples in whom standard investigations, including tests of ovulation, tubal patency and semen analysis, are normal. The prevalence of unexplained infertility has been shown to vary from 22–28%.4 and 5A more recent study puts the prevalence among couples attending a fertility clinic to be 21% in women aged under 35 years, and 26% in women over 35 years. 6

Standard work-up for infertility

The basic fertility work up needs to balance the cost and invasive nature of currently available investigations against their value in informing clinical decision making. The National Institute for Health and Clinical Excellence in the UK and the American Society of Reproductive Medicine in the USA have recommended the following essential tests: semen analysis, assessment of ovulation and evaluation of tubal patency by hysterosalpingogram or laparoscopy.7 and 8The place of laparoscopy versus hysterosalpingogram continues to be debated, but it is felt that laparoscopy should be considered when severe endometriosis, pelvic adhesions or tubal disease is suspected. 8

The predictive value of the post-coital test has been questioned, and the result of a randomised-controlled trial has not shown improved pregnancy rates in women undergoing this investigation. 9 Tests of ovarian reserve have been shown to be useful in predicting follicular response to controlled ovarian stimulation in in-vitro fertilisation (IVF), but their role in predicting pregnancy outcomes in infertile women is limited. 10

Causes of unexplained infertility

Standard fertility investigations are far from comprehensive and unable to identify subtle abnormalities in the reproductive pathway. The cause of unexplained infertility is, therefore, likely to be heterogeneous, with proposed causes ranging from endocrinological, immunological and genetic factors. 11 In addition, compromised ovarian reserve is a factor which, while not always captured in the diagnostic pathway, can be responsible for a diagnosis of unexplained infertility in older women.

Some investigators have questioned the validity of the term ‘unexplained infertility’, as it is sensitive to the number, nature and quality of the tests used. 12 Others have argued that the limited number of treatment options, and the overwhelming dependence on assisted reproduction, means that increasing the number of expensive and invasive tests is unlikely to change the treatment strategy in these couples. 13


Couples with unexplained infertility have a higher chance of spontaneous pregnancy than those where definite barriers to conception have been identified. 14 A number of prognostic models have attempted to determine factors associated with spontaneous livebirth.14, 15, and 16A synthesis of these models has been produced by Hunault et al.17, 18, and 19and validated in a Dutch population. Prognostic factors are gradually emerging as key to informing clinical decision-making. The chance of pregnancy leading to live birth is influenced by female age, duration and previous pregnancy. 14 For example, a woman aged 28 years with 2 years of unexplained infertility has been shown to have a 36% chance of conceiving over the next 12 months. 14 The decision to treat a couple with unexplained infertility should, therefore, take into account their chances of spontaneous conception.

Management options

Expectant management

The relatively high possibility of spontaneous pregnancy in unexplained infertility supports the strategy of expectant management (i.e. active medical intervention). Couples are made aware of the fertile period and advised to continue regular unprotected intercourse. Observational data supporting this policy come from a number of sources. Snick et al. 16 reported a cumulative pregnancy rate of 27.4% at 12 months in a cohort of couples seen in primary care, whereas Collins et al. 14 observed a live birth rate of 14.3% at 12 months in the absence of treatment in a secondary- or tertiary-care setting. In a more recent study, most pregnancies occurring in a group of Dutch couples with unexplained infertility were shown to be conceived spontaneously with limited contribution from IVF.20 and 21

In a Scottish randomised-controlled trial, 17% of women, with a mean age of 32 years and a median duration of infertility of 30 months, had a spontaneous pregnancy leading to live birth after 6 months of expectant management. 22 A health-economic evaluation based on data from the same trial suggests that, despite being more expensive, empirical clomifene citrate and unstimulated intrauterine insemination (IUI) do not offer substantially better outcomes in this context. 23 Dutch data on long-term follow up of couples with an intermediate prognosis, randomised initially to a 6-month period of either expectant management or super ovulation and IUI, show no difference in pregnancy rates between the groups, but an estimated saving of 2616 € in those managed expectantly. 24

Clomifene citrate

It is believed that oral clomifene citrate acts in unexplained infertility by correcting subtle ovulatory dysfunction and inducing multiple follicular growth. Women have been traditionally advised to start treatment with clomifene citrate at a dose of 50 mg once daily from day 2–6 of a menstrual cycle. A transvaginal ultrasound scan for follicle monitoring is advisable on day 12 to minimise the chance of multiple pregnancy. Couples are advised to have timed intercourse from day 12 of the cycle. Where excessive ovarian response is suspected, the cycle is cancelled and the couple asked to abstain from intercourse until the next period.

The use of clomifene has been popular in couples with unexplained infertility, mainly because it is inexpensive, non-invasive and requires little clinical monitoring. 25 Concerns about multiple pregnancies induced by clomifene and a potential risk of ovarian cancer, however, underline the need to weigh the risks and benefits. 26 In a randomised-controlled trial comparing clomifene with expectant management, live birth rates in the two treatment groups were comparable (OR 0.79, 95% CI 0.45 to 1.38), suggesting no benefit associated with clomifene use. 22 The number needed to harm with clomifene citrate was 33 (i.e. treating 33 more women with clomifene would yield one less live birth compared with a strategy of expectant management).

A Cochrane review by Hughes et al. 27 was unable to show improved pregnancy rates associated with clomifene citrate compared with expectant management after pooling data from two trials (OR 1.03, 95% CI 0.64 to 1.66). Aggregation of data from two studies where clomifene was used along with a human chorionic gonadotrophin (hCG) trigger also failed to show any benefit after active treatment (OR 1.55, 95% CI 0.58 to 4.60). Multiple pregnancy rates were similar in both the groups (OR 1.01, 95% CI 0.14 to 7.19) ( Table 1 ).

Table 1 Live birth rates, pregnancy rates and multiple pregnancy rates after different interventions in women with unexplained infertility.

Different interventions Number of participants (n = study) Odds ratio Confidence interval 95% Comments Number of participants (n = study) Odds ratio CI 95% Comments Number of participants (n = study) Odds ratio CI 95% Comments
Live birth rates Pregnancy rates Multiple pregnancy rates
IUI v IVF 113 (1) 1.96 0.88–4.36   Not applicable Not applicable Not applicable   Not applicable Not applicable Not applicable  
Expectant management v IVF 35 51 (1) 22 2.56–189.37   86 (2) 3.24 1.07–9.80 Heterogeneity I2 = 80% Not applicable Not applicable Not applicable  
Stimulated IUI v IVF 35 234 (2) 1.09 0.74–1.59 Treatment naive women 232 (2) 1.10 0.60–2.03 Treatment naive women 351 (3) 0.64 0.31–1.29  
Expectant management v IUI 28 334 (1) 1.60 0.92–2.78   334 (1) 1.53 0.88–2.64   334 (1) 0.50 0.04–5.53  
TI in stimulated cycle v IUI in stimulated cycles 208 (2) 1.59 0.88–2.88 Heterogeneity I2 = 72% 517 (7) 1.68 1.13–2.50 1 study: clomiphene citrate

4 studies: gonadotrophins

1 study: clomiphene citrate and gonadotrophins

1 study: clomiphene citrate or gonadotrophins
316 (4) 1.46 0.55–3.87 1 study: clomiphene citrate

2 studies: gonadotrophins

1 study: clomiphene citrate and gonadotrophins
IUI in natural v IUI in stimulated cycles 28 396 (4) 2.07 1.22–3.50 1 study: clomiphene citrate; 3 studies: gonadotrophins 396 (4) 2.14 1.26–3.61 1 study: clomiphene citrate

3 studies: gonadotrophins
39 (1) 3.00 0.11–78.27  
Expectant management v IUI in stimulated cycle 28 253 (1) 0.82 0.45–1.49   253 (1) 0.80 0.45–1.42   253 (1) 2.00 0.18–22.34  
Clomiphene v expectant management 27 385 (1) 0.79 0.45–1.38   458 (2) 1.03 0.64–1.66   385 (1) 1.01 0.14–7.19  

IUI, intrauterine insemination; TI, timed intercourse; IVF, In-vitro fertilisation.

Wordsworth et al. 23 evaluated the cost-effectiveness of empirical clomifene compared with expectant management in unexplained infertility. The cost per live birth was £72 (95% CI £0 to £206) after expectant management and £2611 (95% CI £1870 to £4166) after treatment with clomifene. Clomifene was more expensive and less effective than expectant management. 23

Intrauterine insemination

Intrauterine insemination with or without super ovulation has been an important component of the traditional approach to the treatment of unexplained infertility. It is believed that increasing the density of motile spermatozoa within the uterus and bringing sperm in close proximity to one or more eggs has the potential to increase the monthly probability of pregnancy. Intrauterine insemination can be carried out with or without concomitant ovarian stimulation. In a super ovulation cycle, more oocytes are available, thus increasing the possibility of fertilisation and pregnancy.

Where IUI in a natural cycle is planned, women are asked to monitor either urinary or serum luteinising hormone levels daily from day 10–12 of the treatment cycle. A single intrauterine insemination is planned after 20–30 h after the detection of a luteinising hormone surge. Semen is prepared either by a swim-up technique or a density gradient method, and the processed sample is re-suspended in a sperm buffer. Between 0.2 ml and 1 ml of the prepared inseminate is introduced aseptically into the uterine cavity using a fine catheter. Couples are advised to abstain from intercourse from the day of luteinising hormone monitoring until the insemination day. No luteal support is advised.

For super ovulation plus IUI cycles, either oral anti-oestrogens (clomifene citrate), gonadotrophins or, occasionally, a combination of the two are used. 28 The aim of ovarian stimulation is to achieve ovulation from more than one (ideally two) mature follicles.

In stimulation protocols using clomifene citrate, a 50-mg oral dose is given once daily from day 2 to 6 of the treatment cycle. A transvaginal ultrasound for follicle monitoring is planned on day 12. Once a follicle with a diameter of 18 mm is documented, urinary luteinising hormone or serum luteinising hormone levels are estimated to rule out endogenous surge. If no endogenous surge has occurred, an hCG trigger that mimics endogenous luteinising hormone surge is given intramuscularly and an IUI planned 36–40 h later.

For stimulated cycles using gonadotrophins, a day-3 ultrasound is carried out during the treatment cycle. Thereafter, a daily dose of 75 IU of gonadotrophin (human menopausal gonadotrophin intramuscularly or follicle stimulating hormone subcutaneously) is started from day 3 and transvaginal ultrasound is carried out from day 8 to monitor follicular growth.

Once a follicle of 17 mm is documented, urinary or serum luteinising hormone levels are estimated to rule out an endogenous surge and an hCG trigger given. Intrauterine insemination is planned 36–40 h after the hCG trigger. In the case of excessive response (more than three follicles of more than 15 mm), the cycle is cancelled to avoid the risk of high order multiples. 29 Usually no luteal support is advised.

In combination cycles using clomifene and gonadotrophins together, clomifene (50 mgs orally) is started on day 2 and continued until day 6 of the cycle. Gonadotrophins (either human menopausal gonadotrophin or follicle stimulating hormone at a dose of 75 IU) are given on days 3, 5 and 7, and follicular monitoring is carried out on day 8. The rest of the protocol is similar to the gonadotrophin protocol.

Intrauterine insemination versus expectant management

In a Scottish multicentre trial, 507 couples with unexplained infertility, 34 with mild male infertility and 39 with mild endometriosis (n = 580), were randomised into three arms: expectant management, clomifene citrate and IUI. 22 Live birth rates of 17% (32 out of 193) and 23% (43 out of 191) were obtained after expectant management and IUI, respectively, a difference which did not reach statistical significance (OR 1.46, 95% CI 0.88 to 2.43). The clinical pregnancy rates were also similar in both groups (expectant group 17%vIUI group 23%) (OR 1.41, 95% CI 0.73 to 2.74). The number needed to treat for benefit with IUI was 17, suggesting that 17 women would need to undergo IUI to achieve one extra live birth.

The Cochrane review by Veltman-Verhulst et al. 28 included this trial by Bhattacharya et al. 22 but excluded data from 73 couples with mild male factor and mild endometriosis. The live birth rate in the IUI group was 23% (38 out of 167) and in the expectant management group 16% (27 out of 167). The difference between the two did not reach statistical significance (OR 1.60, 95% 0.92 to 2.78) ( Table 1 ).

Clomifene plus intrauterine insemination versus expectant management

In the Cochrane review by Hughes et al., 27 data from two trials comparing clomifene citrate with IUI versus expectant management were pooled. The results were unable to show any clinical benefit associated with treatment with clomifene and IUI (OR 2.40, 95% CI 0.70 to 8.19).

Super ovulation plus intrauterine insemination versus expectant management

Steures et al. 30 conducted a Dutch, multicentre, randomised-controlled trial comparing super ovulation (gonadotrophin or clomifene) and IUI with expectant management in couples with unexplained infertility and an intermediate prognosis. The live birth rates were comparable in the two groups: 26 out of 127 (20%) and 30 out of 126 (24%) with super ovulation plus IUI and expectant management, respectively (OR 0.82; 95% CI 0.45 to 1.49) ( Table 1 ). The difference in multiple pregnancy rates did not reach statistical significance (OR 2.00, 95% CI 0.18 to 22.34).

In a cross-over, randomised-controlled trial comparing super ovulation (clomifene) and IUI with timed intercourse in a natural cycle, Deaton et al. 31 randomised 67 women with unexplained infertility and surgically corrected endometriosis. Pregnancy rates per patient were 34% (IUI)v14% (expectant management). Despite an odds ratio of 3.20 in favour of IUI, the results were not statistically significant and the wide confidence intervals (95% CI 0.82 to 12.50) reflected the imprecision of the estimate.

Super ovulation plus intrauterine insemination versus timed intercourse in stimulated cycles

The review of super ovulation plus IUI versus timed intercourse by Veltman-Verhulst et al., 28 based on results from two trials, suggests comparable live birth rates (OR 1.59, 95% CI 0.88 to 2.88). Evidence of significant statistical heterogeneity (I2 = 72%), however, were reported between the trials.

The pooled odds ratio for pregnancy based on data from seven trials was in favour of the super ovulation plus IUI group (OR 1.68, 95% CI 1.13 to 2.50). The stimulation protocol reported in the studies included clomifene, gonadotrophin and a combination of clomifene and gonadotrophins ( Table 1 ).

Four trials reported multiple pregnancy rates and the pooled odds ratio obtained after combining the trials was 1.46 (95% CI 0.55 to 3.87).

Intrauterine insemination in a natural cycle versus super ovulation plus intrauterine insemination

The largest multicentre trial evaluating IUI was conducted in the USA by Guzick et al., 32 and included 932 couples with unexplained or male factor infertility. Participants were randomised to four treatment arms: intracervical insemination (ICI), IUI, super ovulation (gonadotrophin) with ICI and super ovulation (gonadotrophin) with IUI. Four treatment cycles were planned for each couple. Pregnancy rates per couple were significantly higher for super ovulation plus IUI (33%) compared with the other three groups (ICI [10%], IUI [18%] and super ovulation plus IUI [19%]). Treatment with super ovulation plus IUI was three times more likely to lead to pregnancy compared with ICI alone and twice more likely to achieve pregnancy than IUI or super ovulation plus ICI.

In the Cochrane review by Veltman-Verhulst et al., 28 pooled data from four trials were used to generate a combined odds ratio for live births in favour of super ovulation plus IUI cycles compared with natural cycle IUI (OR 2.07, 95% CI 1.22 to 3.50) ( Table 1 ). 28

Veltman-Verhulst et al. 28 could not conduct a meta-analysis for multiple pregnancy outcomes owing to lack of data from the primary trials. A small randomised controlled-trial by Murdoch et al. 33 (n = 39) found multiple pregnancy rates to be similar in both groups (odds ratio 3.00, 95% CI 0.11 to 78.27) with wide confidence intervals. Guzick et al. 32 reported a multiple pregnancy rate of 29% in the super ovulation plus IUI group and 4% in the IUI group.

Intrauterine insemination versus in-vitro fertilisation

Goverde et al. 34 in a prospective randomised-controlled trial, compared IUI, super ovulation plus IUI and IVF in couples with unexplained or male-factor infertility. The trial included 86 couples in the IUI arm, 85 in the super ovulation plus IUI arm and 87 in the IVF arm; a maximum of six treatment cycles were planned in each arm. The differences in live birth rates between IVF (41%) and IUI (26%) were not statistically significant, with an odds ratio of 1.96 (95% CI 0.88 to 4.36). The wide confidence levels reflect the relative lack of precision of this estimate owing to the small sample size.

Super ovulation plus intrauterine insemination versus in-vitro fertilisation

A Cochrane review by Pandian et al. 35 identified three trials comparing super ovulation plus IUI with IVF. Because of different protocols leading to significant heterogeneity, data from only two of these comparing three cycles of super ovulation plus IUI with one cycle of IVF could be aggregated. The pooled odds ratio was 1.09 (95% CI 0.74 to 1.59), suggesting no clear evidence of improved outcomes associated with either treatment ( Table 1 ).

The multiple pregnancy rates were also similar between both the groups with the pooled odds ratio from the three trials being 0.64 (95% CI 0.31 to 1.29) ( Table 1 ).

In the third trial by Reindollar et al., 36 503 couples with unexplained infertility were randomised into two arms. In the conventional arm, women received three cycles of clomifene with IUI followed by three cycles of gonadotrophin IUI and then IVF, whereas those in the second (accelerated) arm received IVF straight after clomifene with IUI. Higher pregnancy rates were achieved in the accelerated arm (hazard ratio 1.25, 95% CI 1.00 to 1.56). The pregnancy rates per cycle were 7.6%, 9.8% and 30.7% for clomifene citrate plus IUI, gonadotrophin with IUI and IVF, respectively.

Pandian et al. 35 included the trial by Reindollar et al. 36 in their review but did not combine it with data from the other two trials owing to statistical heterogeneity. Live birth rates in the IVF group were significantly higher than those in the super ovulation plus IUI group, with an odds ratio of 2.66 (95% CI 1.94 to 3.63).

Intrauterine insemination: health-economic considerations

Intrauterine insemination versus expectant management

In an economic evaluation of a large multicentre trial, Wordsworth et al. 23 evaluated the cost-effectiveness of IUI compared with expectant management as a first-line treatment option in unexplained infertility. 23 The mean (standard deviation) cost per treatment cycle for expectant management was £0 and £98 (£31) for IUI. The cost per live birth for expectant management was £72 (95% CI £0 - £206) and £1487 (95% CI £1116 to £2155) for IUI. The live birth rates were similar in both groups.

The investigators concluded that IUI was expensive and did not result in higher live birth rates compared with expectant management, and are unlikely to be cost-effective in a National Health Service setting.

Intrauterine insemination compared with in-vitro insemination and super ovulation intrauterine insemination versus in-vitro fertilisation

Goverde et al. 34 evaluated the cost-effectiveness of IUI, super ovulation plus IUI and IVF. The treatment costs included hospital costs (e.g. personal, materials, equipment, and housing) and ambulatory costs (e.g. medication, urinary and luteinising hormone kits). Costs for infertility work-up and antenatal care after 12 weeks were not included.

The cost of a single IUI cycle was 623 Dutch guilders (NLG), NLG 931 for super ovulation plus IUI and NLG 3350 for an IVF treatment cycle. The cost per pregnancy, which resulted in live birth, was NLG 8423 for IUI, NLG 10661 for super ovulation plus IUI and NLG 27409 for IVF treatment.

Pashayan et al. 37 used a mathematical model to estimate and compare the cost effectiveness of primary IVF with IUI and IVF as a treatment option. The cost-effectiveness ratio for IVF was £12,600. The incremental cost effectiveness ratio for IUI and IVF was £13,100. For 100 couples diagnosed with unexplained or male-factor infertility, six cycles of IUI will cost an extra £174,200, providing an opportunity for an additional 54 IVF cycles and 14 live births. The assumed mean live birth rate for IUI was 3.55 per cycle. The investigators concluded that a primary strategy of IVF was more cost effective than IUI followed by IVF.

In-vitro fertilisation versus expectant management

Hughes et al. 38 conducted a randomised trial in which 139 couples with unexplained infertility or male factor were randomised into two groups: direct IVF or 3 months expectant management. The live birth rates obtained were 20 out of 68 (29%) in the IVF group and one out of 71 (1%) in those managed expectantly. The investigators concluded that the relative probability of live birth was nearly 21-fold higher in the IVF arm than in the expectant group.

Pandian et al., 35 in their Cochrane review, analysed data from couples with unexplained infertility recruited to the trial by Hughes et al. 38 The live birth rate was 11 out of 24 (46%) in the IVF group (single cycle) and one out of 27 (4%) in the expectant group. The difference was statistically significant in favour of the IVF group (OR 22, 95% CI 2.56 to 189.37) ( Table 1 ).

In the randomised controlled trial by Soliman et al., 39 pregnancy rates for couples with unexplained infertility were one out of 21 (5%) and two out of 12 (14%) in the IVF and expectant management group, respectively. The odds ratio for pregnancy rate after pooling data from the two trials was also significantly in favour of the IVF group compared with the expectant management, although the large confidence interval reflects the uncertainty (OR 3.24, 95% CI 1.07 to 9.80).

Contribution of in-vitro fertilisation

The contribution of IVF to ongoing pregnancy rates in an unselected subfertile population in a tertiary care centre was evaluated by Brandes et al. 20 This cohort study included 1391 infertile couples followed up for 5 years. A total of 1001 couples (72%) had ongoing pregnancies, of which almost one-half of all the pregnancies were spontaneous (45.6%), 19.2% pregnancies occurred after ovulation induction, 14.0% after IUI and 21.2% pregnancies after IVF treatment. Thus, only 13% of all the ongoing pregnancies in couples with unexplained infertility were attributable to IVF, suggesting that the role of IVF is often overestimated.


The definition of infertility, which is based on the expectation of spontaneous pregnancy over an agreed time horizon, essentially represents a prognostic, rather than a diagnostic approach to this condition. Unexplained infertility represents an inability on the part of clinicians to identify a definite biological barrier to conception. This uncertainty has traditionally encouraged a degree of permissiveness in the use of treatments of unproven effectiveness. Recent trials have questioned the clinical and cost-effectiveness of empirical clomifene citrate and unstimulated IUI in the treatment of unexplained infertility. Although super ovulation plus IUI has been shown to be more effective than unstimulated IUI, use of ovarian stimulation is associated with high rates of multiple birth. This has highlighted the role of expectant management in couples with a short duration of infertility. The use of IVF for longstanding unresolved unexplained infertility, and judicious use of elective single embryo transfer, can minimise the risk of multiples. Data supporting the use of IVF over super ovulation plus IUI in the management of treatment of naive couples are inconclusive, but IVF seems to be more effective in couples previously treated unsuccessfully with clomifene plus IUI.

Practice points


  • Expectant management has an important role to play in the treatment of couples with unexplained infertility of short duration.
  • Empirical clomifene citrate is ineffective as a treatment for unexplained infertility.
  • The role of unstimulated IUI in the treatment of unexplained infertility is questionable.
  • Super ovulation plus IUI is a more effective treatment option than IUI alone, but is associated with higher risk of iatrogenic multiple pregnancies.
  • For couples with long-standing unexplained infertility, IVF is an effective treatment option.
Research agenda


  • Development of accurate clinical prediction models for spontaneous and treatment associated pregnancy rates in couples with unexplained infertility.
  • Identification of the most appropriate time for transition from expectant to active treatment for couples with unexplained infertility.
  • Randomised comparison of clinical and cost effectiveness of super ovulation plus IUI compared with IVF.
  • Large randomised-controlled trials of IVF versus expectant management in couples with varying prognostic profiles.


  • 1 The Practice Committee of the American Society for Reproductive Medicine. Definitions of infertility and recurrent pregnancy loss. Fertil Steril. 2008;90(5 Suppl.):S60
  • 2 S. Gurunath, Z. Pandian, R.A. Anderson, et al. Defining infertility: a systematic review of prevalence studies. Hum Reprod Update. 2011;17:575-588 Crossref
  • 3 E.R. te Velde, R. Eijkemans, H.D. Habbema. Variation in couple fecundity and time to pregnancy, an essential concept in human reproduction. Lancet. 2000;355:1928-1929 Crossref
  • 4 J.A. Collins, T.C. Rowe. Age of the female partner is a prognostic factor in prolonged unexplained infertility: a multicentre study. Fertil Steril. 1989;52:15-20
  • 5 M.G. Hull, C.M. Glazener, N.J. Kelly, et al. Population study of causes, treatment, and outcome of infertility. Br Med J (Clin Res Ed). 1985;291:1693-1697 Crossref
  • 6 A. Maheshwari, M. Hamilton, S. Bhattacharya. Effect of female age on the diagnostic categories of infertility. Hum Reprod. 2008;23:538-542 Crossref
  • 7 National Institute for Health and Clinical Excellence. Fertility: assessment and treatment for people with fertility problems. (NICE Clinical Guideline, London, 11, 2004)
  • 8 The Practice Committee of the American Society for Reproductive Medicine. Diagnostic evaluation of infertile female: a committee opinion. Fertil Steril. 2012;98:302-307
  • 9 S.G. Oei, F.M. Helmerhorst, K.W. Bloemenkamp, et al. Effectiveness of the post coital test: a randomised controlled trial. BMJ. 1998;317:502-505 Crossref
  • 10 F.J. Broekmans, J. Kwee, D.J. Hendriks, et al. A systematic review of tests predicting ovarian reserve and IVF outcome. Hum Reprod Update. 2006;12:685-718 Crossref
  • 11 A. Pellicer, C. Albert, A. Mercader, et al. The follicular and endocrine environment in women with endometriosis: local and systemic cytokine production. Fertil Steril. 1998;70:425-431 Crossref
  • 12 N. Gleicher, D. Barad. Unexplained infertility: does it really exist?. Hum Reprod. 2006;21:1951-1955 Crossref
  • 13 C. Siristatisdis, S. Bhattacharya. Unexplained infertility: does it really exist? Does it matter?. Hum Reprod. 2007;22:2084-2087
  • 14 J.A. Collins, E.A. Burrows, A.R. Wilan. The prognosis for live birth among untreated infertile couples. Fertil Steril. 1995;64:22-28 Crossref
  • 15 J.M. Eimers, E.R. te Velde, R. Gerritse, et al. The prediction of the chance to conceive in subfertile couples. Fertil Steril. 1994;61:44-52
  • 16 H.K.A. Snick, T.S. Snick, J.L.H. Evers, et al. The spontaneous pregnancy prognosis in untreated sub fertile couples: the Walcheren primary care study. Hum Reprod. 1997;12:1582-1588 Crossref
  • 17 C.C. Hunault, J.D. Habbema, M.J. Eijkemans, et al. Two new prediction rules for spontaneous pregnancy leading to live birth among subfertile couples, based on the synthesis of three previous models. Hum Reprod. 2004;19:2019-2026 Crossref
  • 18 C.C. Hunault, J.S. Laven, I.A. van Rooij, et al. Prospective validation of two models predicting pregnancy leading to live birth among untreated subfertile couples. Hum Reprod. 2005;20:1636-1641 Crossref
  • 19 J.W. van der Steeg, P. Steures, M.J. Eijkemans, et al. Pregnancy is predictable: a large-scale prospective external validation of the prediction of spontaneous pregnancy in subfertile couples. Hum Reprod. 2007;22:536-542
  • 20 M. Brandes, C.J. Hamilton, J.P. de Bruin, et al. The relative contribution of IVF to the total ongoing pregnancy rate in a subfertile cohort. Hum Reprod. 2010;25:118-126 Crossref
  • 21 M. Brandes, C.J. Hamilton, J.O. van der Steen, et al. Unexplained infertility: overall ongoing pregnancy rate and mode of conception. Hum Reprod. 2011;26:360-368 Crossref
  • *22 S. Bhattacharya, K. Harrild, J. Mollison, et al. Clomiphene citrate or unstimulated intrauterine insemination compared with expectant management for unexplained infertility: pragmatic randomised controlled trial. BMJ. 2008;337:a716 Crossref
  • 23 S. Wordsworth, J. Buchanan, J. Mollison, et al. Clomiphene citrate and intrauterine insemination as first-line treatments for unexplained infertility: are they cost-effective?. Hum Reprod. 2011;26:369-375 Crossref
  • *24 I.M. Custers, M.M. van Rumste, J.W. van der Steeg, et al. Long-term outcome in couples with unexplained subfertility and an intermediate prognosis initially randomized between expectant management and immediate treatment. Hum Reprod. 2012;27:444-450 Crossref
  • 25 Royal College of Obstetricians and Gynaecologists Infertility Guideline Group. The management of infertility in secondary care. (RCOG, London, 1998)
  • 26 The Practice Committee of the American Society for Reproductive Medicine Educational Bulletin. Effectiveness and treatment for unexplained infertility. Fertil Steril. 2006;86:1111-1114
  • *27 E. Hughes, J. Brown, J.J. Collins, et al. Clomiphene citrate for unexplained subfertility in women. Cochrane Database Syst Rev. 2010;1:CD000057
  • *28 S.M. Veltman-Verhulst, B.J. Cohlen, E. Hughes, et al. Intra-uterine insemination for unexplained infertility. Cochrane Database Syst Rev. 2006;4:CD001838
  • 29 A.E.P. Cantineau, B.J. Cohlen, H. Klip, et al., The Dutch IUI Study Group Collaborators. The addition of GnRH antagonists in intrauterine insemination cycles with mild ovarian hyperstimulation does not increase live birth rates: a randomized, double- blinded, placebo-controlled trial. Hum Reprod. 2011;26:1104-1111 Crossref
  • *30 P. Steures, J.W. van der Steeg, P.G. Hompes, et al. Intrauterine insemination with controlled ovarian hyperstimulation versus expectant management for couples with unexplained sub fertility and an intermediate prognosis; a randomised clinical trial. Lancet. 2006;368:216-221 Crossref
  • 31 J.L. Deaton, M. Gibson, K.M. Blackmer, et al. A randomized controlled trial of clomiphene citrate and intrauterine insemination in couples with unexplained infertility or surgically corrected endometriosis. Fertil Steril. 1990;54:1083-1088
  • *32 D. Guzick, S. Carson, C. Coutifaris, et al. Efficacy of superovulation and intrauterine insemination in the treatment of infertility. N Engl J Med. 1999;340:177-183 Crossref
  • 33 A.P. Murdoch, M. Harris, M. Mahroo, et al. Gamete intrafallopian transfer (GIFT) compared with intrauterine insemination in the treatment of unexplained infertility. Br J Obstet Gynaecol. 1991;98:1107-1111 Crossref
  • *34 A.J. Goverde, J. McDonnell, J.P. Vermeiden, et al. Intrauterine insemination or in-vitro fertilisation in idiopathic sub fertility and male sub fertility: a randomised trial and cost-effectiveness analysis. Lancet. 2000;355:13-18 Crossref
  • *35 Z. Pandian, S. Bhattacharya, L. Vale, et al. In vitro fertilization for unexplained sub fertility. Cochrane Database Syst. 2005;2:CD003357
  • *36 R.H. Reindollar, M.M. Regan, P.J. Neumann, et al. A randomized clinical trial to evaluate optimal treatment for unexplained infertility: the fast track and standard treatment (FASTT) trial. Fertil Steril. 2010;94:888-899 Crossref
  • *37 N. Pashayan, G. Lyratzopoulos, R. Mathur. Cost-effectiveness of primary offer of IVF vs. primary offer of IUI followed by IVF (for IUI failures) in couples with unexplained or mild male factor subfertility. BMC Health Ser Res. 2006;6:801-811
  • 38 E.G. Hughes, M.L. Beecroft, V. Wilkie, et al. A multicentre randomized controlled trial of expectant management versus IVF in women with Fallopian tube patency. Hum Reprod. 2004;19:105-109
  • 39 S. Soliman, S. Daya, J. Collins, et al. A randomized trial of in vitro fertilization versus conventional treatment for infertility. Fertil Steril. 1993;56:1239-1244


a Reproductive Medicine Unit, Christian Medical College, Vellore, India

b Division of Applied Health Sciences, University of Aberdeen, Aberdeen Maternity Hospital, Aberdeen AB25 2ZD, UK

Corresponding author.