Progestogen-only pill when oestrogen is unsuitable
The progestogen-only pill contains a progestogen (a synthetic version of progesterone) and no oestrogen, so it is the oral choice when oestrogen is unsuitable.
Remember
When oestrogen is unsuitable, for example in a smoker aged 35 or over or in migraine with aura (migraine preceded by visual or other warning symptoms), switch to an oestrogen-free pill such as desogestrel. Lowering the oestrogen dose or changing the oestrogen in a combined pill (one containing oestrogen and progestogen) does not remove the risk.
Memory aid
If the problem is oestrogen, take the oestrogen out.
A reason to avoid oestrogen points to a pill that contains no oestrogen.
The progestogen-only pill (POP, or mini-pill) contains a progestogen but no oestrogen. It is the oral choice when the combined pill is contraindicated, which means there is a reason it should not be used. Oestrogen adds to the risk of blood clots, stroke and heart attack, and that is why it is the problem.
Recognised reasons to avoid oestrogen include smoking at 35 or over, migraine with aura, a previous venous thromboembolism (VTE, a clot in a deep vein or the lungs), hypertension and significant cardiovascular (heart and blood vessel) risk. The progestogen-only pill is suitable for many people who cannot take oestrogen, but current breast cancer is a contraindication to it.
Altering the combined pill does not remove the problem. A lower oestrogen dose, a different oestrogen such as oestradiol, or taking active tablets continuously still delivers oestrogen. So the reasons to avoid the combined pill remain. Reducing the dose does not remove the problem for a smoker with migraine with aura.
Not every progestogen-only pill works in the same way. The desogestrel pill suppresses ovulation (stopping the ovary releasing an egg) in most cycles. Older pills containing levonorgestrel or norethisterone work mainly by thickening the cervical mucus, the mucus at the neck of the womb, so that sperm cannot pass through. The combined pill, by contrast, works mainly by suppressing ovulation.
Key facts
- What it contains
- A progestogen and no oestrogen, so it works without adding the clotting and cardiovascular risks of oestrogen.
- Smoking
- Smoking at 35 or over is a reason not to use the combined pill, because oestrogen adds to the risk of heart attack and stroke.
- Migraine
- Migraine with aura, rather than migraine alone, is the feature that makes oestrogen-containing pills unsuitable.
- Timing
- A desogestrel pill counts as late only after 12 hours, whereas older progestogen-only pills count as late after only three hours.
- Bleeding
- The progestogen-only pill has no inactive tablets, so it does not give a predictable monthly bleed, and irregular bleeding is a common side effect.
Exam traps
- A combined pill that uses a different oestrogen, such as oestradiol, is still a pill containing oestrogen, so the reasons to avoid oestrogen still apply.
- A lower oestrogen dose in a combined pill does not remove the reasons to avoid oestrogen, because the pill still contains oestrogen.
- Oestrogen absorbed through the skin from a patch still carries the clotting concern, because the patch contains oestrogen as well, like the combined pill.
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