How does Letrozole compare with Clomiphene for live birth outcomes?

[Verified against the International Guideline for PMOS (formerly PCOS)] Letrozole should be used rather than clomiphene citrate in women with PMOS/PCOS with anovulatory infertility and no other infertility factors, to improve ovulation, clinical pregnancy and live birth rates (evidence-based recommendation, 5.4.5.2). Note the outcome list: the recommendation covers ovulation, clinical pregnancy AND live birth. It is not merely a surrogate-endpoint advantage. A practical point in clomiphene's disfavour: the risk of multiple pregnancy is increased with clomiphene citrate use, alone or in combination with metformin, and therefore clomiphene cycles may require ultrasound monitoring (practice point, 5.4.2.2). That monitoring burden is a real cost of choosing clomiphene, and it is often omitted from the comparison. Where clomiphene retains a place: it could be used in preference to metformin in women with anovulatory infertility and no other infertility factors, to improve ovulation, clinical pregnancy and live birth rates (evidence-based recommendation, 5.4.2.1). So the hierarchy for this population reads letrozole, then clomiphene, then metformin. The practical constraint on letrozole is regulatory rather than clinical — it remains off-label in many countries, and where its use is not permitted other agents may be used (practice point, 5.3.2). Confirm the position for Indian practice. There is no evidence of increased teratogenicity with letrozole compared with other ovulation induction agents (practice point, 5.3.3), which addresses the concern most often raised against it.