Oral anti-oestrogens and medical adjuncts for subfertility associated with anovulation

  • Review
  • Intervention




Infertility due to anovulation is a common problem in women. The first line oral treatment is with anti-oestrogens, such as clomiphene citrate. Unfortunately there may be resistance and alternative and adjunctive treatments have been developed. These include tamoxifen, dexamethasone, bromocriptine and aromatase inhibitors (AIs).


To determine the relative effectiveness of anti-oestrogen agents, with or without medical adjuncts, in women with WHO group 2 anovulation.

Search strategy

We searched the Cochrane Menstrual Disorders and Subfertility Group trial register (searched 5th July 2004), CENTRAL (The Cochrane Library Issue 2 2004), MEDLINE (1966 to June 2004) and EMBASE (1980 to June 2004) for identification of relevant randomised controlled trials (RCTs). Additionally the United Kingdom National Institute for Clinical Excellence (NICE) guidelines and the references of relevant reviews and RCTs were searched.

Selection criteria

RCTs that compare oral anti-oestrogen agents for ovulation induction (alone or in conjunction with medical adjuncts) in anovulatory subfertility, were considered for inclusion in the review. Metformin and other insulin sensitizing agents were not included. Hyperprolactinaemic infertility was not included.

Data collection and analysis

Data extraction and quality assessment was done independently by two reviewers. The primary outcome was live birth, secondary outcomes were: pregnancy, ovulation, miscarriage, multiple pregnancy, overstimulation, ovarian hyperstimulation syndrome and patient reported adverse effects.

Main results

Twelve RCTs were found and included in this review. No trials reported live birth as an outcome. Miscarriage and multiple pregnancy rates were poorly reported. Clomiphene was shown to be effective in increasing pregnancy rate when compared to placebo (fixed OR 5.8, 95% CI 1.6 to 21.5; NNT 5.9, 95% CI 3.6 to 16.7). No evidence of a difference in effect was found between clomiphene and tamoxifen (fixed OR 1.0, 95% CI 0.5 to 2.1). The use of clomiphene in combination with tamoxifen did not find any evidence of effect on pregnancy rate when compared to clomiphene alone (fixed OR 3.3, 95% CI 0.1 to 91.6). The comparison between two AIs (letrozole and anastrozole) did not find any evidence of a difference in effect on pregnancy rate (fixed OR 1.9, 95% CI 0.4 to 8.9). For the intervention of clomiphene plus ketoconazole vs clomiphene no evidence of a difference in effect for pregnancy rate was found (fixed OR 2.4, 95% CI 0.9 to 6.4). For clomiphene plus bromocriptine vs clomiphene no evidence of a difference in effect on pregnancy rate was found (fixed OR 1.0, 95% CI 0.3 to 3.0) rates. However, clomiphene plus dexamethasone treatment resulted in a significant improvement in the pregnancy rate (fixed OR 11.3, 95% CI 5.3 to 24.0; NNT 2.7, 95% CI 2.1 to 3.6) when compared to clomiphene alone as did clomiphene plus pretreatment with combined oral contraceptives (fixed OR 27.2, 95% CI 3.1 to 235.0; NNT 2.0, 95% CI 1.4 to 3.4).

Authors' conclusions

This review shows evidence supporting the effectiveness of the current first line treatment, clomiphene citrate. No evidence of a difference in effect was found between clomiphene and tamoxifen. The use of dexamethasone as an adjunct to clomiphene therapy appears promising as do combined oral contraceptives. This review has highlighted a gap in the literature on effects of these drugs on outcomes such as miscarriage rate. Evidence in favour of these interventions is flawed. RCTs of adequate power and of high methodological quality are required for the older treatments such as clomiphene, alone and with medical adjuncts, and also for the newer drugs such as the AIs.

Plain language summary

Clomiphene and tamoxifen are effective treatments for ovulation induction in women with anovulatory subfertility; dexamethasone and combined oral contraceptives are promising adjunctive treatments

Subfertility due to absence of ovulation is common. However, medical treatment may help these women ovulate. Oral anti-oestrogens, e.g. clomiphene, cause increased stimulation of the ovaries and aid ovulation. They can also be used in combination with drugs such as steroids. The review of studies found evidence for the effectiveness of clomiphene. No evidence of a difference between clomiphene and tamoxifen, a similar drug, was found. Dexamethasone (a steroid) and combined oral contraceptives, both used to supplement clomiphene, show promise. Aromatase inhibitors (e.g. letrozole), a new type of anti-oestrogen, may have potential. Evidence was inconsistent, further research is needed.