Features
Early pregnancy: uterus too large for dates; hyperemesis. Later there may be polyhydramnios. The signs are that >2 poles may be felt; there is a multiplicity of fetal parts; 2 fetal heart rates may be heard (reliable if heart rates differ by >10 beats/min). Ultrasound confirms diagnosis (and at 10-14 weeks, can distinguish monochorionic from dichorionic twins).1
Complications during pregnancy
Polyhydramnios; pre-eclampsia is more common (10% in singleton pregnancies; 30% in twins); anaemia is more common (iron and folate requirements are increased). There is an increased incidence of APH (6% for twins, vs 4.7% for singletons) due to both abruption and placenta praevia (large placenta).
Fetal complications
Perinatal mortality for twins is 36.7/1000 (8/1000 if single; 73/1000 for triplets; and 204 for higher multiples). The main problem is prematurity. Mean gestation for twins is 37 weeks, for triplets 33 weeks. Growth restricted babies (p 52) are more common (growth the same as singletons up to 24 weeks but may be slower thereafter). Malformation rates are increased 2-4 times, especially in monozygotic twins. Severe disability rate 1.5% for singletons, 3.4% for twins. Ultrasound is the main diagnostic test. Selective fetocide (eg with intracardiac potassium chloride) is best used before 20 weeks if indicated. With monozygotic twins, intermingling blood supply may result in disparate twin size and one being born plethoric (hence jaundiced later), the other anaemic. If one fetus dies in utero it may become a fetus papyraceous which may be aborted later or delivered prematurely.
Complications of labour
PPH is more common (4-6% in singletons, 10% in twins). Malpresentation is common (cephalic/cephalic 40%, cephalic/breech 40%, breech/breech 10%, cephalic/transverse (Tv) 5%, breech/Tv 4%, Tv/Tv 1%). Rupturing of vasa praevia, increased rates of cord prolapse (0.6% singleton, 2.3% twins), premature separation of the placenta and cord entanglement (especially monozygous) may all present difficulties at labour. Despite modern technology some twins remain undiagnosed, staff are unprepared, and syntometrine may be used inappropriately, so delaying delivery of the second twin. Epidural anaesthesia is helpful for versions.
Management
- Ensure adequate rest (need not entail admission).
- Use ultrasound for diagnosis and monthly checks on fetal growth.
- Give additional iron and folate to the mother during pregnancy.
- More antenatal visits, eg weekly from 30 weeks (risk of eclampsia↑).
- Tell the mother how to identify preterm labour, and what to do.
- Consider induction at 40 weeks. Have an IVI running in labour and an anaesthetist available at delivery. Paediatricians (preferably one for each baby) should be present at delivery for resuscitation should this be necessary (second twins have a higher risk of asphyxia).
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