Hydroxyprogesterone Caproate / Progesterone (Preterm Birth Prevention)

How it works

As a synthetic progestogen it acts on progesterone receptors to promote uterine quiescence and suppress myometrial contractility.

Prescribing in practice

• Restrict use to appropriately selected women and only after counselling, as evidence of benefit for recurrent preterm birth prevention is contested and the licensing position has been reassessed in some jurisdictions; vaginal progesterone is the preferred option in many UK pathways.
• Confirm singleton pregnancy and prior history criteria before initiating, as benefit has not been demonstrated in multiple pregnancy.
• Avoid in active or past hormone-sensitive malignancy, undiagnosed vaginal bleeding, and significant hepatic impairment.

Monitoring

Monitor for injection-site reactions, signs of venous thromboembolism, and ongoing obstetric review of cervical length and gestation.

Counselling the patient

• Report calf pain, swelling, breathlessness or chest pain promptly as these may indicate a clot.
• Attend all planned antenatal scans and appointments so treatment can be reviewed.
• Discuss the uncertainty around benefit so you can make an informed choice.

Evidence & guidelines

UK practice (NICE NG25) generally favours vaginal progesterone for preterm birth prevention, and the efficacy of hydroxyprogesterone caproate has been questioned by later trial data such as PROLONG.