Presentation
Good morning, sir. Mrs J is a 31-year-old trader, para 2+0 with two living children, at 32 weeks by a 12-week scan, which showed a dichorionic diamniotic twin pregnancy. She conceived spontaneously; her mother had twins. She has had worsening back pain, breathlessness and heartburn, and pedal swelling for 2 weeks, with no headache or visual symptoms. Fetal movements are normal. She has had no bleeding, leaking or contractions. Her packed cell volume at 28 weeks was 29%. Both previous deliveries were spontaneous vaginal deliveries at term without complications. On examination she is mildly pale, with bilateral pedal oedema to the ankles. Her blood pressure is 130/84 mmHg. The abdomen is markedly distended with a symphysis–fundal height of 38 cm, larger than dates. Multiple fetal parts are palpable, with two fetal poles: the leading twin is longitudinal and cephalic, 5/5 palpable, and the second is longitudinal with the breech in the upper uterus. Two fetal hearts are heard at 140 and 152 per minute, more than 10 beats apart. Urinalysis shows no protein.
Diagnosis
Dichorionic diamniotic twin pregnancy at 32 weeks — twin 1 cephalic, twin 2 breech — with mild anaemia, in a multipara with a family history of twins.
Differential diagnoses
Of a uterus large for dates with multiple fetal parts:
- Polyhydramnios with a singleton — tense, one fetal pole and heart, fluid thrill
- Macrosomic singleton — diabetes, one fetal heart
- Singleton with fibroids — firm irregular masses separate from the fetus
- Higher-order multiple pregnancy — more than two poles, assisted conception
- Wrong dates
Investigations
| Test | What you expect or look for |
|---|---|
| First-trimester ultrasound | Lambda (twin peak) sign in dichorionic twins; T sign in monochorionic diamniotic twins; no dividing membrane in monoamniotic twins |
| Serial growth scans | Every 4 weeks from 20 weeks in dichorionic twins; every 2 weeks from 16 weeks in monochorionic twins |
| Growth discordance | Estimated weight difference of 25% or more (20% in some guidance) needs specialist review |
| Deepest vertical pool of liquor | TTTS: 8 cm or more in the recipient and below 2 cm in the donor |
| Umbilical artery Doppler | Growth restriction in either twin |
| Middle cerebral artery peak velocity | Twin anaemia–polycythaemia sequence in monochorionic twins |
| Anomaly scan | Higher rate of structural anomalies, especially cardiac |
| Haemoglobin | At booking, 20–24 and 28 weeks — higher iron and folate needs |
| Blood pressure and urine protein | Every visit — pre-eclampsia is 2–3 times more common |
| Glucose tolerance test | Higher risk of gestational diabetes |
| Presentation scan at 36 weeks or in labour | Plan the mode of delivery |
Quintero staging of twin–twin transfusion syndrome
| Stage | Findings |
|---|---|
| I | Polyhydramnios in the recipient, oligohydramnios in the donor; donor bladder visible |
| II | Donor bladder not visible |
| III | Critically abnormal Doppler in either twin |
| IV | Hydrops in either twin |
| V | Death of one or both twins |
Management
Care is in a consultant-led multiple pregnancy clinic with midwives, a fetal medicine specialist for monochorionic twins, and the neonatologist. I would explain that twin pregnancies carry higher risks of preterm birth, anaemia, pre-eclampsia and bleeding after delivery, and that most go well with closer monitoring.
Non-pharmacological
- More frequent antenatal visits and serial scans as above
- Nutrition advice; more rest; stop heavy work
- Education on symptoms of preterm labour and pre-eclampsia
- Birth plan in a hospital with a neonatal unit and blood available
Pharmacological
- Iron 60–120 mg elemental and folic acid daily — IV iron if not responding
- Low-dose aspirin 75–150 mg from 12 weeks if she has another moderate risk factor for pre-eclampsia
- Antenatal corticosteroids if preterm birth is expected before 34 weeks
- Cervical cerclage, progesterone and bed rest do not prevent preterm birth in unselected twin pregnancies
Surgical and interventional
- Timing of delivery (NICE): uncomplicated dichorionic diamniotic twins from 37+0 weeks; monochorionic diamniotic from 36+0 weeks; monoamniotic twins by caesarean section at 32+0–33+6 weeks
- Mode: vaginal birth is appropriate when the first twin is cephalic, as here, whatever the presentation of the second; caesarean section if the first twin is non-cephalic, for monoamniotic twins, and for the usual obstetric indications
- Intrapartum care: IV access, group and cross-match, continuous monitoring of both twins, epidural encouraged, ultrasound machine in the room, oxytocin ready, neonatal team for each baby
- After twin 1: clamp the cord, palpate the abdomen or scan to confirm the lie of twin 2, stabilise a longitudinal lie, and listen to the heart; rupture membranes once the presenting part enters the pelvis; start oxytocin if contractions do not return within 10 minutes; aim for delivery within 30 minutes
- Twin 2 non-longitudinal: external cephalic version, or internal podalic version and breech extraction by an experienced obstetrician, or caesarean section
- Third stage: active management plus an oxytocin infusion for 4 hours because of the higher risk of PPH
- Twin–twin transfusion syndrome (stage II or more, before 26 weeks): fetoscopic laser ablation of placental anastomoses
Complications and follow-up
- Maternal: hyperemesis, anaemia, pre-eclampsia, gestational diabetes, antepartum haemorrhage, polyhydramnios, preterm labour, operative delivery, postpartum haemorrhage, postnatal depression
- Fetal: preterm birth (the main cause of morbidity), growth restriction and discordance, congenital anomalies, stillbirth, cord entanglement in monoamniotic twins, locked twins, and TTTS, TAPS and co-twin death in monochorionic twins
After delivery, watch for postpartum haemorrhage, support breastfeeding two babies, and discuss contraception.
Examiner questions
References
- Cunningham FG, Leveno KJ, Dashe JS, Hoffman BL, Spong CY, Casey BM, eds. Williams Obstetrics. 26th ed. New York: McGraw Hill; 2022.
- National Institute for Health and Care Excellence. Twin and triplet pregnancy (NG137). London: NICE; 2019.