Late Pregnancy · Preterm
Antenatal Steroids — Preterm Lung Maturation
Steroid injections given to mum when preterm birth is likely — speed up baby's lung maturation. 31% reduction in neonatal death; 34% reduction in respiratory distress. Single most effective intervention in modern obstetrics. NICE NG25 / Cochrane.
Last reviewed 2 June 2026
Antenatal corticosteroids — eligibility
Should I have antenatal steroids?
wk
d
Enter gestational age and answer the questions to see eligibility.
Educational tool only — not medical advice. Antenatal corticosteroids are the single most effective intervention in modern obstetrics for improving preterm outcomes — they reduce neonatal mortality by ~31 %, RDS by ~34 %, IVH by ~45 %, NEC by ~50 %, and need for respiratory support (Roberts 2017 Cochrane meta-analysis, 30 trials, 7,774 women). The decision is made by your obstetric team based on the specific clinical situation.
What does this mean?
One of the highest-impact interventions in all of medicine. Liggins & Howie’s 1972 sheep-to-clinic translation remains the standard of care 50+ years later. Two doses of betamethasone 12 mg IM 24 h apart (or dexamethasone 6 mg IM × 4 doses 12 h apart) accelerates fetal lung surfactant production and reduces every major preterm complication. The benefit window is 2–7 days after the first dose; ideally courses are completed before delivery but a single dose is still useful. 23–33+6 weeks: routine if delivery within 7 days. 34–36+6 weeks (late preterm): ALPS trial (NEJM 2016) — give if no prior course and singleton. ≥ 37 weeks or already treated: not indicated. Rescue (single) course considered if first course > 14 d ago and a new acute risk emerges; serial courses are NOT recommended due to growth-restriction risk.
Why steroids for preterm birth?
Betamethasone or dexamethasone injections cross the placenta and speed up baby’s lung maturation.
Cochrane 2017 meta-analysis (30 trials, 7,774 women):
- 31% reduction in baby death.
- 34% reduction in respiratory distress.
- 45% reduction in brain bleeding.
- 50% reduction in necrotising enterocolitis.
- Less need for ventilator.
Single most effective intervention in modern obstetrics.
When are they offered?
- Women at risk of preterm birth between 24+0 to 33+6 weeks.
- Consider 23+0-23+6 with specific clinical factors.
- Consider 34+0-36+6 in selected cases (ALPS trial).
- Delivery expected within 7 days for max benefit.
Indications:
- Established preterm labour.
- PPROM.
- Planned preterm delivery (severe PE, IUGR).
- Cervical insufficiency / short cervix.
The course
- Betamethasone 12 mg IM × 2 doses, 24h apart (most common UK).
- Dexamethasone 6 mg IM every 12h × 4 doses (equivalent).
Maximum effect 24-48h after second dose. Optimal effect window: 24h-7 days after course.
If you don’t deliver within 7 days
Rescue course may be considered if >7 days since original AND still <34 weeks AND preterm birth now imminent within 7 days.
Single rescue course only — multiple courses not routinely given (concerns about cumulative effects).
Are steroids safe?
Overwhelmingly yes — benefits far outweigh risks.
Maternal:
- Transient blood sugar rise (24-72h).
- Brief sleep disturbance.
- Sometimes mild malaise.
For baby:
- Transient reduction in fetal movements (24-48h).
- Long-term follow-up studies show NO concerning developmental, cardiometabolic, or psychological effects from single course.
Steroids with diabetes
Yes, but glucose monitoring intensified. Steroids cause transient hyperglycaemia for 24-72h. Effects more pronounced if you have GDM/T1DM/T2DM.
Extra glucose monitoring (4-6 hourly); insulin doses often increase for 2-3 days; sometimes admit for management.
Late preterm (34-37 weeks)?
ALPS trial (NEJM 2016): betamethasone at 34-36+6 reduces respiratory complications. Recommended in selected cases: planned C-section <39 wk; preterm labour 34-36+6; PPROM in this window.
Drawback: transient neonatal hypoglycaemia — monitored.
Different scenarios — steroids
Scenario 1: 28 weeks, established preterm labour
Betamethasone 12 mg now + 24h later. Magnesium sulphate for neuroprotection. Try to delay labour 24-48h if possible.
Scenario 2: 32 weeks, PPROM today
Betamethasone course. Antibiotics. Watch for chorioamnionitis. Aim to maintain pregnancy to 34-37 weeks unless infection.
Scenario 3: 25 weeks, severe PE, delivery planned in 48h
Steroids urgent. Magnesium. BP control. NICU prep. Plan delivery after second steroid dose if maternal/fetal condition allows.
Scenario 4: 38 weeks, elective C-section booked
Consider betamethasone 24h before per ASTECs trial. Reduces respiratory issues. NICE supports selectively.
Scenario 5: 30 weeks, given steroids 10 days ago, now in preterm labour
Rescue course warranted — second course of 2 doses. Last course before delivery.
Care guidance — antenatal steroids
- 2 doses 24h apart, IM.
- Maximum effect 24-48h after 2nd dose.
- Window 7 days for full benefit.
- Rescue course if >7 days + still <34 wk + new preterm risk.
- Glucose monitoring if diabetic.
- Magnesium sulphate alongside if <32 wk.
- Reduced fetal movements 24-48h normal.
- Safe long-term — single course.
- Late preterm (34-37) considered selectively.
- NICU briefing for preterm babies.
Sources
- NICE NG25. Preterm labour and birth.
- Roberts D, et al. Antenatal corticosteroids for accelerating fetal lung maturation. Cochrane Database Syst Rev 2017.
- Gyamfi-Bannerman C, et al. Antenatal Betamethasone for Women at Risk for Late Preterm Delivery (ALPS). NEJM 2016.
- Crowther CA, et al. Repeat doses of antenatal corticosteroids: meta-analysis. Lancet 2015.
- RCOG Scientific Impact Paper 64. Antenatal corticosteroids.
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Frequently asked questions
Why are steroids given for preterm birth?
ANTENATAL CORTICOSTEROIDS (ACS) — betamethasone or dexamethasone injections given to mum when preterm delivery is likely. CROSS the placenta + speed up baby's LUNG MATURATION. The 2017 Cochrane meta-analysis (30 trials, 7,774 women) found: 31% reduction in baby death; 34% reduction in respiratory distress syndrome (lung not developed enough); 45% reduction in brain bleeding; 50% reduction in necrotising enterocolitis (gut condition); reduced need for ventilator. SINGLE MOST EFFECTIVE intervention in modern obstetrics. SAFE for mum + baby.
When are steroids offered?
RCOG / NICE NG25 / ACOG: WOMEN AT RISK OF PRETERM BIRTH between 24+0 AND 33+6 WEEKS. CONSIDER 23+0-23+6 if specific clinical factors. CONSIDER 34+0-36+6 in selected cases (e.g. planned C-section before 39 weeks, ALPS trial supported). DELIVERY EXPECTED within 7 days for maximum benefit. INDICATIONS: established preterm labour; preterm pre-labour rupture of membranes (PPROM); planned preterm delivery (severe PE, IUGR, etc.); cervical insufficiency / short cervix imminent labour.
What's the steroid course?
STANDARD: TWO DOSES 24 HOURS APART, INTRAMUSCULAR INJECTION (in thigh or buttock). OPTIONS: (1) BETAMETHASONE 12 mg IM × 2 doses, 24h apart (most common UK); (2) DEXAMETHASONE 6 mg IM every 12h × 4 doses (equivalent). MAXIMUM EFFECT: 24-48 HOURS after SECOND dose; benefit BEGINS within hours. WINDOW: optimal effect 24h-7 days after course. If delivery delayed >7 days from course, RESCUE STEROIDS may be considered if still <34 weeks.
What if I don't deliver within 7 days?
EFFECT GRADUALLY DIMINISHES from 7 days post-course. NICE NG25 / RCOG 2022: RESCUE COURSE may be considered if: original course was >7 DAYS AGO; still <34 WEEKS; preterm birth NOW imminent within next 7 days. SINGLE RESCUE COURSE only — NOT routinely repeated multiple times (concerns about long-term cognitive/behavioural outcomes with multiple courses). DOSE: same as original (2 doses 24h apart). EVIDENCE: Crowther 2011 ASTEROID trial supported single rescue.
Are steroids safe for baby?
OVERWHELMINGLY YES — benefits far outweigh risks. SHORT-TERM: minimal maternal side effects (transient blood sugar rise — issue if diabetic; sleep disturbance; sometimes brief malaise). FOR BABY: TRANSIENT reduction in fetal movements (24-48h); rarely small effect on cord blood pressure. LONG-TERM: extensive follow-up studies (Roberts 2017 Cochrane) show NO concerning developmental, cardiometabolic, or psychological adverse effects from single course. MULTIPLE COURSES: more research — possible small effect on growth + behaviour; therefore single rescue course only.
Can I have steroids if I have diabetes?
YES — but glucose monitoring intensified. BETAMETHASONE/DEXAMETHASONE cause transient maternal HYPERGLYCAEMIA (high blood sugar) for 24-72 hours. EFFECTS most pronounced if you have GDM/T1DM/T2DM. MANAGEMENT: extra glucose monitoring (4-6 hourly); INSULIN dose adjustments — often needs increasing or initiated for 2-3 days; admit for management usually. BENEFITS still outweigh risks. AFTER 72 HOURS: glucose returns to normal.
What about steroids for late preterm (34-37 weeks)?
ALPS TRIAL (Gyamfi-Bannerman NEJM 2016) showed: betamethasone at 34-36+6 weeks for women at risk of late preterm delivery REDUCED respiratory complications in babies. NOW recommended in SELECTED cases at 34-37 weeks: e.g. PLANNED C-SECTION before 39 wk; preterm labour 34-36+6 wk; PPROM in this window. NOT universal — discussed case-by-case. DRAWBACK: transient neonatal hypoglycaemia — needs monitoring. NICE NG25: consider if delivery within 24-48 hours likely.
Why do I need an INJECTION? Can't I take a tablet?
INJECTION (intramuscular) gives reliable, predictable blood levels. ORAL STEROIDS less reliable for this purpose (variable absorption). MAGAZINE injection in big muscle (gluteal / thigh). NOT painful long-term — brief sting, may leave bruise. SECOND DOSE in different site. NURSE / midwife / doctor administers. RECOVERY immediate; you can drive / continue normal activity. SOME WOMEN have slight tenderness 1-2 days.
Will my baby be ok if I'm only 24-26 weeks?
VERY PRETERM (24-28 weeks) babies: STEROIDS ESPECIALLY important — biggest survival impact. WITHOUT steroids: ~60-70% survival 24 weeks, ~75-85% 26 wk, ~85-95% 28 wk. WITH steroids: survival improves substantially — many of these statistics include treated babies now. ALSO REDUCES major morbidity (brain bleeds, lung disease, gut issues). MAGNESIUM SULPHATE ALSO GIVEN before 32 wk delivery — additional neuroprotection. NEONATAL CARE has advanced enormously — many former 'micropreemie' babies now thrive.
What about steroids for term babies / planned C-section?
TERM C-SECTION (37+ weeks): not routinely given. ELECTIVE C-SECTION BEFORE 39 WEEKS (37-38+6): ASTEcS trial showed benefit — fewer respiratory issues. NICE NG192 / RCOG: consider for elective C-section 37-38+6 weeks. SINGLE COURSE 24h before surgery. SOME UK trusts routine; others case-by-case. PLANNED C-SECTION at 39+ weeks: usually not needed. EMERGENCY C-SECTION at term: not appropriate (too late + not indicated).
What's the difference between betamethasone and dexamethasone?
BOTH effective; minor differences. BETAMETHASONE: 2 doses 12 mg IM, 24h apart. Most common UK. DEXAMETHASONE: 4 doses 6 mg IM, 12h apart. SLIGHTLY cheaper; same total dose. NEUROLOGICAL OUTCOMES: some studies suggest dexamethasone associated with slightly lower brain bleed rate; others equivocal. CHOICE: hospital protocol-dependent; either acceptable. BOTH CROSS PLACENTA efficiently. EQUIVALENT for clinical purposes.
Will steroids affect my pregnancy after I receive them?
MINIMAL impact. MATERNAL effects: 24-72h transient blood sugar rise; brief sleep disturbance; sometimes light malaise. NO impact on continuing pregnancy if delivery doesn't happen. CAN CONTINUE pregnancy normally — pregnancy not destabilised by steroid administration. SOME women have steroids and continue pregnancy weeks more — fine. BABY may show transiently reduced movements 24-48h; resumes normal pattern.
What about steroids without confirmed preterm risk?
NOT GIVEN routinely. NEEDS CLINICAL INDICATION: established preterm labour; PPROM; planned early delivery; threatened preterm with cervical changes; emergency conditions threatening preterm. EVIDENCE-BASED indications matter — steroids have risks (especially with multiple courses); not for every twinge. CLINICIAN judgment: balance risk of preterm birth vs unnecessary exposure. PRIVATE practice sometimes gives more readily than NHS.
Can I refuse steroids?
YES — informed choice. WHY SOMEONE MIGHT REFUSE: unconvinced of evidence (evidence very strong); religious reasons; concerns about long-term effects (very low risk in singletons with single course). BUT: declining steroids in confirmed preterm birth significantly increases baby's risk of death + serious morbidity. DISCUSSION WITH consultant + neonatologist before declining. WRITTEN documentation. RESPECTED — but informed consent important to understand consequences.
What about magnesium sulphate alongside?
DIFFERENT but COMPLEMENTARY. MAGNESIUM SULPHATE (MgSO4) — given before delivery <32 weeks: reduces cerebral palsy by ~30% in surviving babies. NEUROPROTECTIVE. NICE / RCOG / ACOG recommend if delivery within 24h expected. SEPARATE from steroids — given via IV (4g loading + 1g/hr for 24h). MAY BE given in same time period as steroids. NOT cause confusion with magnesium for seizure prevention in PE — same drug different indications.
How does this relate to other calculators on BumpBites?
Companion: /calculators/cervical-length for preterm risk; /calculators/vaginal-progesterone-ptb for prevention; /calculators/fetal-fibronectin / /calculators/quipp-app for risk stratification; /calculators/magnesium-sulphate for neuroprotection; /calculators/preeclampsia-diagnosis; /calculators/hellp-classifier (may need steroids if PTB imminent); /calculators/eos-sepsis.