Letrozole or Clomiphene: 4 PPCOS II Trial Checks

The 2014 trial used the name polycystic ovary syndrome, or PCOS. The Endocrine Society¹ announced its replacement name, polyendocrine metabolic ovarian syndrome (PMOS), in May 2026, with a transition extending to the 2028 guideline update. The older name remains in the trial and 2023 guideline discussed here.¹

Who entered?

PPCOS II randomized 750 infertile women aged 18–40 with PCOS and ovulatory dysfunction (irregular or absent ovulation). Eligibility required a patent fallopian tube, normal uterine cavity and a partner’s sperm concentration of at least 14 million/mL with documented motility.²³

The current international guideline recommends letrozole as first-line medication for ovulation induction when infertility is due to anovulation and there are no other infertility factors. It recommends individual consideration of tubal testing when semen analysis is normal.⁴

Bring the results already obtained, rather than assuming that irregular cycles explain everything. Ask which findings established ovulatory dysfunction and which other fertility factors have been assessed. The clinic can then explain whether the trial’s comparison addresses your situation.

What counted as success?

Across up to five treatment cycles, live births occurred in 103/374 women (27.5%) with letrozole versus 72/376 (19.1%) with clomiphene: an 8.4-percentage-point difference (95% CI 2.4–14.4). This was the primary outcome, not a per-cycle probability.²

Ask whether a number offered at the appointment means ovulation, a positive pregnancy test, an ongoing pregnancy or live birth. Also ask whether it describes one cycle or the whole planned course. Keep the answer beside the planned review date so the outcome being discussed does not change from visit to visit.

How complete was follow-up?

Dropout or exclusion affected 73/374 versus 85/376; the primary comparison retained randomized denominators. NICHD/NIH funded the trial. Manufacturers had no role; some authors disclosed consulting or investment ties.²

If travel, blood tests or appointment timing will make a cycle difficult to complete, raise that before treatment begins. Ask whom to contact if a period does not arrive when expected and whether testing can be arranged locally. The schedule should state when the clinic will decide to continue, adjust or stop treatment.

What safety questions remain?

The adverse-event table reported major congenital anomalies in 4/102 with letrozole versus 1/66 with clomiphene. The trial could not exclude a safety difference.²

US Femara labeling covers breast-cancer treatment in postmenopausal women, not ovulation induction. It contraindicates use during pregnancy because of fetal harm and requires pregnancy testing before treatment. Fatigue, dizziness and sleepiness can affect driving.⁵

The fertility guideline says pregnancy must be excluded before ovulation induction and that letrozole should not be given when a pre-existing pregnancy is possible. Off-label use requires a discussion of evidence, concerns and side effects.⁴

Get written instructions from the fertility team for the exact treatment days, pregnancy testing and what to do after a missed period or positive test. Do not use the cancer-treatment schedule as a fertility regimen or restart tablets from a previous cycle without the clinic’s instructions. Tell the team if you are breastfeeding; the label advises against breastfeeding during treatment and for at least three weeks after the last dose.⁵

For the diagnosis itself, our PCOS/PMOS overview explains the symptoms that can prompt assessment. “PCOS Becomes PMOS” in Period, Handled describes the name change, diagnostic features and why bleeding regularly does not necessarily confirm ovulation. It provides background for the diagnostic conversation; the fertility clinic should supply the treatment schedule.