Trying to Conceive with PCOS: What Works, According to the Evidence

The honest picture, with numbers

PCOS is one of the most common endocrine conditions in women of reproductive age. Reported prevalence ranges from 2.2% to 26% depending on the diagnostic criteria and population studied, and NICE notes many affected women are undiagnosed.

The reason PCOS affects conception is specific and worth being precise about: it is the most common cause of anovulation — cycles where no egg is released. Ovulatory disorders account for about 25% of infertility in couples, and PCOS is responsible for most of them. This matters because it tells you what the problem usually is not. In most cases with PCOS, the eggs, tubes and uterus are not the issue. The issue is that ovulation is irregular or absent, and ovulation is one of the more treatable problems in fertility medicine.

The headline number worth holding onto: in the Cochrane review of ovulation induction in PCOS, women given letrozole had higher live birth rates than women given clomiphene citrate — odds ratio 1.72 (95% CI 1.40 to 2.11), high-certainty evidence across 11 trials and 2,060 participants. In practical terms, where a 20% live birth rate would be expected on clomiphene, letrozole would give 27% to 35%. The number needed to treat for one additional live birth is 10.

What actually affects it

Ovulation, not "fertility" in the abstract

If you have PCOS and your cycles are irregular, the practical problem is that you do not know when — or whether — you ovulate, so intercourse timing becomes guesswork. NICE advises that where cycles are prolonged and irregular, a serum progesterone test may need to be taken later in the cycle (for example day 28 of a 35-day cycle) and repeated weekly until the next period starts. A single day-21 test on a 40-day cycle tells you almost nothing, and a "normal" result from one badly timed test is a common reason women are wrongly reassured.

Weight, honestly stated

This is where PCOS advice most often goes wrong, so here it is as the guidance actually puts it. NICE states that a BMI of 30 or over is associated with taking longer to conceive, and that where a person is not ovulating, losing weight is likely to increase the chance of conception. NICE also states that a group programme involving exercise and dietary advice leads to more pregnancies than weight-loss advice alone — which is a quiet acknowledgement that being told to lose weight, without support, does not work.

What that guidance does not say is that weight causes PCOS, that you would ovulate if you tried harder, or that treatment should be withheld until a BMI target is met. If you have been refused referral pending weight loss, that is a local commissioning decision, not a clinical inevitability, and you can ask for it in writing.

Medication that works

The 2023 International Evidence-based Guideline — developed by an international collaboration including ASRM, ESHRE, the Endocrine Society and the European Society of Endocrinology — recommends letrozole as the first-line pharmacological treatment for ovulation induction in anovulatory women with PCOS and no other infertility factors. Metformin, clomiphene citrate and combinations may be considered, but as less effective options. Second line is low-dose gonadotrophins or laparoscopic ovarian surgery; IVF is third line.

The NHS PCOS page still lists clomifene, metformin and laparoscopic ovarian drilling, and does not mention letrozole. If letrozole is not offered to you, it is reasonable to ask why, citing the international guideline.

What the Cochrane data says about safety

Two reassurances with high-certainty evidence behind them. Miscarriage rates per pregnancy were essentially the same on letrozole and clomiphene (24% versus 25%). Ovarian hyperstimulation syndrome occurred in 0.5% of women in both arms. Multiple pregnancy rates were also similar (1.6% versus 2.2%).

What to do next

1. Establish whether and when you ovulate. Ask for progesterone testing timed to your actual cycle length, repeated weekly if your cycle is long, rather than a single day-21 test.
2. Ask about letrozole by name. It is the first-line recommendation of the 2023 international guideline for anovulatory PCOS with no other infertility factor.
3. Have a semen analysis done in parallel. "No other infertility factors" is a condition of that recommendation, and it cannot be established without testing your partner.
4. Do not rely on ovulation predictor kits alone. Elevated LH is common in PCOS, so urine LH tests can read positive repeatedly without ovulation following.
5. Ask for a structured support programme rather than a weight-loss instruction, if weight is being discussed — that is what the evidence supports.

Tracking ovulation when your cycles are irregular

Most cycle-tracking advice assumes a predictable cycle, which is precisely what PCOS removes. A few adjustments make the standard methods more useful:

• Ovulation predictor kits are less reliable in PCOS. LH is often persistently elevated, so tests can read positive repeatedly across a cycle without ovulation following. Several positives in a row is a known PCOS pattern rather than evidence of repeated ovulation.
• Basal body temperature can only confirm ovulation after it has happened, and NICE advises against using BBT charts to confirm ovulation clinically. Across several anovulatory cycles you may see no rise at all — which is itself information worth taking to an appointment.
• Cervical mucus can show prolonged patchy fertile-type patterns during long anovulatory stretches, never reaching a clear peak.
• Intercourse every 2 to 3 days is NICE's recommendation and is particularly well-suited to irregular cycles, because it removes the need to predict a day you cannot reliably predict.

The practical conclusion: with PCOS, home tracking is poor at answering the central question. A correctly timed progesterone blood test answers it, and that is worth pressing for rather than buying more test strips.

Metformin, insulin and where they fit

Metformin appears in almost every PCOS discussion, so it is worth placing accurately. The NHS describes metformin as a type 2 diabetes medicine used in PCOS to help with tiredness and weight problems. The 2023 international guideline lists metformin among the options that may be considered for ovulation induction, but explicitly as one of the less effective agents compared with letrozole. It has a role, particularly where metabolic features are prominent, but it is not the first thing to reach for when the goal is ovulation and conception.

The order that the evidence supports is: letrozole first line; low-dose gonadotrophins or laparoscopic ovarian surgery second line where there is clomiphene resistance and no other infertility factor; IVF third line. Knowing that sequence lets you ask where you are in it, rather than accepting whatever is offered first.

When to seek help

PCOS changes the timetable. NICE recommends referral at first presentation where either partner has a known or suspected clinical cause of infertility. A PCOS diagnosis is exactly that. Healthdirect Australia likewise advises seeing a doctor sooner than the usual 6 or 12 months if you have a known condition such as PCOS.

You do not need to complete a year of trying first. If you have irregular or absent periods and you are trying to conceive, that is the referral trigger on its own.

Bring to the appointment: your cycle lengths over the last six to twelve months, the date of your PCOS diagnosis and how it was made, any previous progesterone or hormone results, and any medication you have already tried and for how long.