Mid-Pregnancy · Preterm Prevention
Vaginal Progesterone for Preterm Birth Prevention
Vaginal progesterone (Cyclogest, Crinone, Utrogestan) reduces preterm birth by ~30% in singleton pregnancies with short cervix or previous PTB. Nightly pessary from 16-22 weeks to 34-36 weeks. Twin pregnancies: no benefit. NICE NG25 / Romero meta-analysis 2018.
Last reviewed 2 June 2026
Vaginal progesterone — PTB prevention
Eligibility, dose, duration
Troubleshooting + common pitfalls
- Pitfall: Continuing 17-OHPC injections.
Solution: PROLONG trial (Blackwell 2020 Am J Perinatol) was negative; FDA withdrew the 17-OHPC indication for PTB prevention in 2023. Vaginal progesterone 200 mg is the current standard. - Pitfall: Progesterone in twins.
Solution: EPPPIC 2021 IPD-MA (Stewart Lancet 2021) showed NO benefit of any progesterone formulation in twin pregnancies. Don’t routinely use. - Pitfall: Initiating after 24 weeks for short cervix.
Solution: Benefit largely limited to initiation 16–24 wk. Late initiation has weaker evidence; consider cerclage instead at 22–24 wk if CL ≤ 25 mm. - Pitfall: Treating CL 26–30 mm.
Solution: Most centres use ≤ 25 mm threshold; some use ≤ 20 mm. Above 25 mm, evidence is weak; surveillance. - Pitfall: Stopping at 32 wk.
Solution: Continue to 36+6 wk (or rupture of membranes / delivery / preterm labour onset). - Pitfall: Oral progesterone for PTB prevention.
Solution: Vaginal route is the evidence-based delivery method; oral progesterone has not been shown effective for this indication. - Pitfall: No cervical surveillance after starting progesterone.
Solution: Continue TV CL every 2–4 weeks; cerclage if CL shortens to ≤ 25 mm before 24 wk. - Pitfall: Co-administered intravaginal antifungals reducing absorption.
Solution: Counsel patients to space at least 6 hours between progesterone pessary and other vaginal preparations. - Pitfall: Patient stops because of discharge.
Solution: Increased discharge is normal with vaginal pessary; not a reason to stop. Counsel up front. - Pitfall: No fetal-anomaly anatomy scan before starting (rare side issue).
Solution: Complete the 20-wk anatomy scan as usual; progesterone doesn’t interfere with imaging. - Pitfall: Cervical pessary used as alternative without evidence.
Solution: Arabin cervical pessary — recent trials (PROMISE 2022, others) have been mixed/negative for short-cervix women without prior PTB. Not first-line. - Pitfall: Forgetting maternal mental health.
Solution: Women with prior PTB live with anxiety about recurrence. EPDS / GAD-7 at the high-risk antenatal review; reassurance is part of treatment.
Educational tool only — not medical advice. Romero IPD-MA AJOG 2018; NICE NG25; SMFM Consult #44; EPPPIC Lancet 2021. Decisions made by obstetric / fetal-medicine team.
What does this mean?
Vaginal progesterone for preterm-birth prevention has two evidence-based indications in singleton pregnancies: (1) short cervix on mid-trimester ultrasound (TVUS CL ≤ 25 mm at 18–24 weeks) without prior preterm birth, and (2) prior spontaneous preterm birth < 34 weeks (now the preferred option after the PROLONG trial showed 17-OHPC was not effective and the FDA withdrew that indication in 2023). The Romero 2018 individual-patient-data meta-analysis showed ~35–40 % reduction in preterm birth < 33 weeks and ~30 % reduction in the neonatal mortality / morbidity composite for the short-cervix indication. Effect is strongest at the shortest cervical lengths. Twin pregnancies are an important exception: the EPPPIC 2021 IPD-MA (10 trials, > 4,300 women) was negative across vaginal progesterone, 17-OHPC, and any progesterone formulation in multiple pregnancies. Don’t use routinely. Practical points: start 200 mg pessary nightly; initiate 16–24 weeks; continue to 36+6 weeks; counsel about expected increased vaginal discharge; continue cervical-length surveillance because cerclage may be added at 22–24 wk if CL shortens to ≤ 25 mm despite progesterone.
Who benefits?
Two evidence-based indications for SINGLETON pregnancies:
- Short cervix on mid-trimester ultrasound (TVUS ≤25 mm at 18-24 wk).
- Previous spontaneous preterm birth <34 weeks.
Progesterone reduces preterm birth before 34 weeks by ~30-35% (Romero meta-analysis 2018).
Twin pregnancies: NO benefit (EPPPIC 2021).
What is it?
Micronised progesterone (natural form) as pessary or gel inserted vaginally. Brands:
- Cyclogest — pessary 400 mg.
- Crinone — gel.
- Utrogestan — capsule taken vaginally.
Most studies: 200 mg daily nightly. Absorbs through vaginal lining directly to uterus + cervix.
How does it work?
- Stabilises the cervix (prevents shortening / opening).
- Reduces uterine muscle contractility.
- Anti-inflammatory at placental interface.
- Immune modulation reduces inflammation.
When to start & stop
- Start: 16-22 weeks when indication identified.
- Short cervix on 20-wk scan: start within days.
- Previous PTB: start 16-18 wk.
- Continue until 34-36 weeks.
How to insert
- Wash hands.
- Lie on back / side with knees bent.
- Push pessary gently as high as comfortable (2-3 inches).
- Stay lying down for 10-15 minutes for absorption.
- Wear pantyliner next day (some leakage).
Bedtime insertion most convenient.
Safe for baby?
Yes. Extensively studied. No increase in birth defects, miscarriage, growth restriction, or long-term neurodevelopmental issues. Natural progesterone form mimics body’s own hormone.
Side effects
Usually minimal. Possible:
- Vaginal discharge (mild, creamy).
- Itching / irritation (less with newer formulations).
- Headache (~5-10%).
- Breast tenderness.
- Nausea.
- Mood changes.
- Drowsiness (progesterone is sedating — bedtime use helps).
Don’t stop without consulting team — sudden withdrawal can trigger labour.
Alternatives
- Cervical cerclage — stitch; surgical.
- Arabin pessary — silicone ring; mixed evidence.
- No intervention + monitoring.
17-OHPC injections WITHDRAWN by FDA 2023 (PROLONG trial showed no benefit) — vaginal progesterone preferred.
Sex with progesterone
Depends on individual risk. Short cervix / threatened preterm: sex often avoided (semen prostaglandins; orgasm contractions).
Discuss with specialist. Progesterone pessary: leave 1-2h after insertion before sex; otherwise may dislodge.
If progesterone doesn’t work
If cervix continues shortening / preterm labour starts despite progesterone:
- Rescue cerclage (emergency stitch).
- Hospitalisation + steroids.
- Tocolysis (atosiban, nifedipine) to delay labour 48h.
- Magnesium sulphate for neuroprotection.
Different scenarios — progesterone
Scenario 1: 20-wk anomaly scan reveals cervix 18 mm
Start vaginal progesterone nightly. Serial cervical scans every 1-2 weeks. Watch for preterm labour signs.
Scenario 2: Previous 32-week delivery, now 16 weeks
Start progesterone 16-18 wk. Consider history-indicated cerclage 12-14 wk. Specialist preterm clinic.
Scenario 3: 24 weeks, cervix 8 mm despite progesterone
Rescue cerclage discussed. Hospital admission. Steroids 24-28 wk. Magnesium if labour imminent.
Scenario 4: Twin pregnancy + short cervix
Progesterone not evidence-based for twins. Cerclage decisions individualised. Multi-fetal medicine team.
Scenario 5: Previous progesterone failure, this pregnancy 16 weeks
Continue progesterone but also history-indicated cerclage; intensive monitoring; preterm clinic.
Care guidance — vaginal progesterone
- Start 16-22 weeks when indication identified.
- Continue until 34-36 weeks.
- Bedtime insertion; lie 10-15 min.
- Pantyliner next day.
- Don’t stop suddenly.
- Serial cervical length scans.
- Sex restrictions often alongside.
- Avoid bed rest; gentle exercise OK.
- Cerclage if cervix shortens further.
- Steroids 24-34 wk if preterm imminent.
- Tommy’s for preterm birth support.
- Mental health support — anxiety common.
Sources
- NICE NG25. Preterm labour and birth.
- Romero R, et al. Vaginal progesterone for preventing preterm birth in singletons with short cervix: meta-analysis. UOG 2018.
- EPPPIC Collaboration. Evaluating progestogens for preventing preterm birth: individual patient data meta-analysis. Lancet 2021.
- RCOG Green-top Guideline 60. Cervical cerclage.
- Tommy’s. Preterm birth support.
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Frequently asked questions
Who benefits from vaginal progesterone?
Two evidence-based indications for SINGLETON pregnancies: (1) SHORT CERVIX on mid-trimester ultrasound (TVUS cervical length ≤25 mm at 18-24 weeks) — even without previous preterm birth; (2) PREVIOUS spontaneous preterm birth <34 weeks. PROGESTERONE reduces preterm birth before 34 weeks by ~30-35% (Romero meta-analysis 2018). TWIN pregnancies: NO benefit (EPPPIC 2021 — not effective in multiples). CERCLAGE + PROGESTERONE often combined in highest-risk.
What is vaginal progesterone?
MICRONISED PROGESTERONE (natural form) as pessary or gel inserted vaginally. BRANDS: CYCLOGEST (pessary 400 mg), CRINONE (gel), UTROGESTAN (capsule taken vaginally). DOSE: most studies used 200 mg DAILY at night. CYCLOGEST 400 mg twice daily (200 mg morning + 200 mg evening, total 400 mg) sometimes prescribed. INSERTED at bedtime usually — lay flat 10-15 min after for absorption. ABSORBS through vaginal lining → directly to uterus + cervix. SAFE for baby; minimal systemic absorption.
How does progesterone reduce preterm birth?
MULTIPLE mechanisms: (1) STABILISES the cervix (prevents shortening / opening); (2) REDUCES uterine muscle contractility (anti-contraction effect); (3) ANTI-INFLAMMATORY at the placental interface; (4) IMMUNE modulation reduces inflammation. NATURAL progesterone made by your body throughout pregnancy — supplemental progesterone reinforces protective effect in vulnerable cervices. EVIDENCE: Romero 2018 meta-analysis (974 women, individual patient data) — reduced preterm birth <33 weeks by ~30%; reduced neonatal mortality + composite morbidity.
When do I start progesterone?
FROM 16-22 WEEKS (when indication identified) until 34-36 weeks (cervical maturation, low PTB risk in last weeks). SHORT CERVIX on routine 20-week anomaly scan: start within days of finding. KNOWN PREVIOUS PTB <34 weeks: start at 16-18 weeks usually. EARLIEST 12 weeks if very high risk. CONTINUE until 34-37 weeks depending on protocol. STOPPING after 34 weeks: birth likely after this point won't significantly affect outcomes if it happens.
Will progesterone affect baby?
EXTENSIVELY studied — appears SAFE. NO INCREASE in: birth defects; miscarriage; growth restriction; long-term neurodevelopmental issues (Romero 2018 long-term follow-up). NATURAL progesterone form (not synthetic progestin); mimics body's own hormone. SOME minor neonatal effects possible from late-pregnancy progesterone — usually transient and clinically insignificant. SAFER than UNTREATED short cervix risk of preterm birth.
How do I insert vaginal progesterone?
(1) WASH hands. (2) LIE on back / side with knees bent. (3) UNWRAP pessary (rounded end may be easier to insert; comes out as smooth bullet shape). (4) PUSH gently with finger as high as comfortable (about 2-3 inches). (5) STAY LYING DOWN for 10-15 minutes for absorption — set timer; read; relax. (6) MAY LEAK some next day — wear pantyliner. INSERTION at BEDTIME most convenient. APPLICATOR sometimes provided (Crinone gel). DON'T panic about depth — anywhere in upper vagina works.
What are the side effects?
USUALLY MINIMAL. POSSIBLE: (1) VAGINAL discharge (often mild waxy/creamy); (2) ITCHING / irritation (less common with newer formulations); (3) HEADACHE (~5-10%); (4) BREAST tenderness; (5) NAUSEA; (6) MOOD changes; (7) FATIGUE; (8) DROWSINESS (progesterone is sedating — bedtime use helps). MORE COMMON with oral progesterone vs vaginal; vaginal route maximises local effect + minimises systemic. NEVER STOP without consulting team — sudden withdrawal can trigger labour.
What if I have spotting / bleeding while on progesterone?
ASSESS as you would without progesterone — light spotting common in pregnancy; HEAVY bleeding warrants urgent assessment. CONTINUE progesterone unless told otherwise (sudden stopping can destabilise). HOSPITAL evaluation: ultrasound + cervix check + fetal monitoring. SOMETIMES progesterone INCREASED if cervix shortening continues despite treatment. ANY BLEEDING in 2nd trimester of high-risk pregnancy: get checked same day.
What's the alternative to vaginal progesterone?
(1) CERVICAL CERCLAGE (stitch) — surgical; for short cervix + previous preterm; or rescue cerclage if dilated. (2) ARABIN PESSARY (silicone ring around cervix) — mixed evidence. (3) NO INTERVENTION + monitoring — if low-moderate risk. (4) 17-OHPC (17-hydroxyprogesterone caproate) INJECTIONS — WITHDRAWN by FDA in 2023 (PROLONG trial showed no benefit); ONCE standard US therapy; no longer recommended. VAGINAL progesterone now preferred over 17-OHPC. PROGESTERONE + CERCLAGE often combined in highest-risk.
Will I have cervical length scans alongside?
YES — usually. SHORT CERVIX known: scans every 1-2 weeks until 24 weeks; less frequent after. PROGRESS: cervix may stabilise / improve with progesterone; some shorten further despite (cerclage discussed). DOPPLERS (uterine artery + umbilical artery) may also be assessed. MONITORING for fetal growth, amniotic fluid, signs of preterm labour. INTENSIVE antenatal care; multidisciplinary team (consultant obstetrician + fetal medicine + maternal-fetal specialist).
Can I have sex while on progesterone?
USUALLY YES — but DEPENDS on individual risk. IF short cervix / threatened preterm: SEX often AVOIDED (semen has prostaglandins; orgasm causes contractions; physical irritation of cervix). DISCUSS with your specialist. PROGESTERONE PESSARY: leave 1-2 hours after insertion before considering; otherwise may dislodge. CERVICAL CERCLAGE in place: usually sex restricted. INFORMED choice. NOT a 'forever' restriction — usually until cervix lengthens or after stitch placed.
Can I exercise on progesterone?
USUALLY YES, with modifications for underlying preterm risk. AVOID: high-impact, jumping, contact sports, heavy lifting (>5 kg routinely), prolonged standing. RECOMMENDED: walking, swimming, prenatal yoga, gentle stretching. EXERCISE doesn't dislodge progesterone or shorten cervix — but RESTRICTIONS often imposed alongside progesterone for high-risk women. DISCUSS individual plan with team. BED REST historically prescribed but NO LONGER recommended (no benefit; may cause harm).
Will progesterone hurt or be uncomfortable?
USUALLY NO. SOME WOMEN find first few days uncomfortable; resolves. INSERTION feels mildly intrusive initially; technique improves with practice. DISCHARGE next day common — wear pantyliner. RARELY: vaginal irritation, allergic reaction (different brand sometimes helps). STAY LYING DOWN 10-15 min after insertion = reduces leakage + improves absorption. PARTNER not affected by progesterone.
What if progesterone doesn't work?
IF CERVIX continues shortening / preterm labour starts despite progesterone: ESCALATION options: (1) CERCLAGE (rescue stitch) — emergency procedure; (2) HOSPITALISATION for monitoring + steroids; (3) TOCOLYSIS (atosiban, nifedipine) to delay labour 48h for steroids; (4) MAGNESIUM SULPHATE for neuroprotection if delivery imminent. NOT a failure — biological reality. NEONATAL team prepared for early delivery. EVERY WEEK GAINED in womb improves outcomes.
Will I need progesterone next pregnancy?
DEPENDS on outcome + indications. PREVIOUS PROGESTERONE for short cervix without preterm birth: serial cervical length scans next time + progesterone if short again. PREVIOUS PRETERM BIRTH despite progesterone: progesterone again from earlier; consider history-indicated cerclage at 12-14 weeks; intensive specialist care. PRECONCEPTION consultation valuable. NOT guaranteed but evidence supports continuing use in subsequent pregnancies.
How does this relate to other calculators on BumpBites?
Companion: /calculators/cervical-length for diagnosis; /calculators/quipp-app for risk assessment; /calculators/fetal-fibronectin; /calculators/antenatal-steroids if preterm imminent; /calculators/magnesium-sulphate for neuroprotection; /calculators/contraction-timer; /calculators/pregnancy-week.