Red Flags
- Monochorionic monoamniotic twins or any monochorionic pregnancy with growth discordance, polyhydramnios/oligohydramnios sequence, or amniotic fluid disparity — twin-to-twin transfusion syndrome; tertiary fetal medicine same-week[1]
- Threatened preterm labour <34 weeks in twins — admit; corticosteroid; magnesium sulfate for neuroprotection if <32 weeks; tocolysis only to complete steroid course[1]
- Discordant fetal anomaly or selective intrauterine growth restriction in monochorionic pair — fetal medicine; selective fetoscopic laser or selective termination per legal/ethical framework[1]
- Severe pre-eclampsia in multifetal pregnancy — admit; deliver as for singleton; multifetal pregnancy increases pre-eclampsia and HELLP risk[1]
First-line treatment
Interventions
- Chorionicity-driven antenatal pathway[1]Dichorionic-diamniotic: scan every 4 weeks from 24, deliver 37–38 weeks. Monochorionic-diamniotic: scan every 2 weeks from 16, deliver 36–37 weeks. Monochorionic-monoamniotic: tertiary surveillance, deliver 32–34 weeks via caesarean
- Cervical length screening for preterm birth prevention[1]Transvaginal cervical length 18–24 weeks; vaginal progesterone 200 mg PO/PV daily for short cervix <25 mm; cerclage selective in twin pregnancies; pessary not routinely indicated
- Nutritional support and supplementation[1]Caloric increase ~300 kcal/day above singleton; calcium 2000–2500 mg/day; iron-folic acid double-dose; vitamin D and B12 per status
- Mode of delivery[1]Vaginal delivery for cephalic-cephalic dichorionic twins with experienced operator; caesarean for non-cephalic first twin, monochorionic-monoamniotic, prior caesarean, or maternal/fetal indication
First-line drug therapy
| Drug | Class | Adult | Paediatric | Notes |
|---|---|---|---|---|
| Antenatal corticosteroids[1] | Glucocorticoid for fetal lung maturation | Betamethasone 12 mg IM × 2 doses 24 h apart, or dexamethasone 6 mg IM × 4 doses 12 h apart | — | All anticipated preterm twin delivery 24+0 to 34+6 weeks; complete course before delivery if possible; rescue course if delivery delayed >7 days |
| Magnesium sulfate (neuroprotection)[1] | Tocolytic / neuroprotective | 4 g IV over 20 min, then 1 g/h IV until delivery or 24 h | — | Anticipated delivery <32 weeks; reduces cerebral palsy risk by ~30% in survivors |
| Vaginal progesterone[1] | Progestogen | 200 mg vaginal pessary or gel daily from 16–22 weeks until 36 weeks for short cervix | — | Preterm birth prevention in singleton with short cervix; in twins limited evidence but considered for short cervix; not for routine multifetal use |
| Aspirin (pre-eclampsia prevention)[1] | Antiplatelet (low-dose) | 150 mg PO at night from 12+0 to 36+0 weeks | — | All twin pregnancies have elevated pre-eclampsia risk and qualify for prophylaxis |
Antenatal corticosteroids[1]
Glucocorticoid for fetal lung maturation
- Adult
- Betamethasone 12 mg IM × 2 doses 24 h apart, or dexamethasone 6 mg IM × 4 doses 12 h apart
- Paediatric
- —
All anticipated preterm twin delivery 24+0 to 34+6 weeks; complete course before delivery if possible; rescue course if delivery delayed >7 days
Magnesium sulfate (neuroprotection)[1]
Tocolytic / neuroprotective
- Adult
- 4 g IV over 20 min, then 1 g/h IV until delivery or 24 h
- Paediatric
- —
Anticipated delivery <32 weeks; reduces cerebral palsy risk by ~30% in survivors
Vaginal progesterone[1]
Progestogen
- Adult
- 200 mg vaginal pessary or gel daily from 16–22 weeks until 36 weeks for short cervix
- Paediatric
- —
Preterm birth prevention in singleton with short cervix; in twins limited evidence but considered for short cervix; not for routine multifetal use
Aspirin (pre-eclampsia prevention)[1]
Antiplatelet (low-dose)
- Adult
- 150 mg PO at night from 12+0 to 36+0 weeks
- Paediatric
- —
All twin pregnancies have elevated pre-eclampsia risk and qualify for prophylaxis
Safety-net
- Reduced fetal movements in either twin at any gestation — same-day maternity assessment unit; this is harder to detect than in singletons[1]
- Sudden weight gain (>2 kg/week), severe leg/face swelling, severe headache or visual change — pre-eclampsia signs warrant same-day review[1]
- Attend every growth scan and Doppler appointment; many complications in monochorionic twins are silent and progress quickly[1]
Referral criteria
- All monochorionic twin pregnanciesTertiary fetal medicine for chorionicity-specific surveillance[1]
- Suspected TTTS, sIUGR, or selective fetal anomalyTertiary fetal medicine same-week for fetoscopic options[1]
- Threatened preterm labour or short cervixObstetric admission for steroid and consideration of progesterone, cerclage, or transfer to neonatal-equipped centre[1]
- Higher-order multiples (triplets+)Tertiary maternal-fetal medicine and consider multifetal reduction counselling per local framework[1]
Clinical summary
Antenatal surveillance, preterm birth prevention, and timing of delivery for twin and higher-order multiple pregnancies stratified by chorionicity.