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    PMOS and trying to conceive: letrozole, metformin, and what the South Asian data actually shows

    Reviewed by HHH Clinical Team · April 2026

    1 section · 2 min read

    Fertility & Treatment
    2 minHHH clinical team
    HOW IS PMOS TREATED WHEN YOU'RE TRYING TO CONCEIVE?

    How is PMOS treated when you're trying to conceive?

    PMOS is the most common cause of anovulatory infertility worldwide, and disproportionately so in South Asian populations where it presents earlier, with more severe metabolic features at lower thresholds. The fertility treatment for PMOS-related has changed substantially in the last decade. Letrozole has displaced clomiphene as first line in most international guidelines. Metformin has a more nuanced role than the 'metformin for everyone' framing of the 2000s. And the question of whether metabolic optimisation (vit D, weight, insulin) makes a meaningful difference is genuinely contested.

    The grey zone

    Letrozole or clomiphene as first-line ovulation induction?

    Standard position · Global

    The 2014 Legro et al landmark RCT and the 2023 international PCOS guideline both support letrozole as first-line ovulation induction in PMOS, ahead of clomiphene. Live birth rates are higher with letrozole.

    Where it gets more nuanced

    What we honestly do not know

    Whether South Asian women respond differently to letrozole or metformin compared to the trial populations (predominantly white European) is genuinely under-studied. Whether vitamin D repletion improves PMOS-related ovulation outcomes is mechanistically plausible but not settled by high-quality randomised data.

    Bottom line

    If you have PMOS and you are trying to conceive, the 2023 international PCOS guideline framework applies to you. If your clinician is defaulting to clomiphene without offering letrozole, asking why is fair. If they are recommending metformin alone for ovulation induction, the evidence does not strongly support that as a sole strategy.

    References

    1. [1] 25006718Legro RS et al. Letrozole versus clomiphene for infertility in the polycystic ovary syndrome. N Engl J Med 2014;371(2):119-129.
    2. [2] 27511809Balen AH et al. The management of anovulatory infertility in women with polycystic ovary syndrome: an analysis of the evidence to support the development of global WHO guidance. Hum Reprod Update 2016;22(6):687-708.
    3. [3] 37580927Teede HJ et al. International evidence-based guideline for the assessment and management of polycystic ovary syndrome 2023.
    4. [4] icmr-pcos-india-2024ICMR National PCOS Task Force Recommendations.

    Browse the full evidence library →

    For your doctor

    Patient with PMOS seeking conception. Requests review of ovulation induction options aligned with 2023 international PCOS guideline (letrozole first-line). Metabolic optimisation discussion: vitamin D, insulin status, weight in context of South Asian-specific BMI thresholds.

    I have PMOS and I'm trying to conceive. I'd like to discuss ovulation induction options including letrozole, and any metabolic things worth checking like vitamin D and insulin levels.

    How did this land with you?

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    References

    1. [1] 27511809Balen AH et al. The management of anovulatory infertility in women with polycystic ovary syndrome: an analysis of the evidence to support the development of global WHO guidance. Hum Reprod Update 2016;22(6):687-708.
    2. [2] 25006718Legro RS et al. Letrozole versus clomiphene for infertility in the polycystic ovary syndrome. N Engl J Med 2014;371(2):119-129.
    3. [3] 37580927Teede HJ et al. International evidence-based guideline for the assessment and management of polycystic ovary syndrome 2023.
    4. [4] icmr-pcos-india-2024ICMR National PCOS Task Force Recommendations.
    5. [5] 22640517Darling AL et al. Vitamin D status in UK South Asian populations. Br J Nutr 2013.

    Browse the full evidence library →

    Reviewed by clinicians

    Authored and reviewed by clinicians from the founding team. Information only, not personalised medical advice.