Multiple Pregnancy

Multiple Pregnancy Incidence – 1/80 twins (more common in africa) 1/3 identical (monozygitic), 2/3 non identical (dizygotic) Recent increase in dizygotic due to IVF & other fertility treatments Dizygotic – each has own chorion, amnion & placenta = dichroionic, diamniotic Monozygotic – split before 3 days à dichorionic, diamniotic, – splitting at blastocyst stage (day 4-7) à monochorionic, diamniotic, – splitting day 7-14 à monochorionic and monoamniotic, – splitting beyond day 14 à risk of conjoint twins Diagnosis USS – all twins have separate amnion sacs(inner), identical share a chorion (outer) Can look for lambda sign on US if early enough. Left = identical. Right = non identical. NB – all twins look like left from 20 weeks onwards. Maternal Complications Anaemia – due to increased demand. May justify folate & Fe supplement Antepartum haemorrhage – placenta praevia is more common with multiple preg (cos larger area) Pre-eclampsia – 3-4x risk of singleton pregnancy Fetal Complications Structural defects – higher risk if monochorionic (hydrocephalus, gastro atresia, cardiac defects). Usually only one child affected. Selective termination of one fetus using KCl is only possible with dichorionic. Chromosomal abnormalities – usually discordant in dizygotic and concordant with monozygotic. Double amnio is gold standard for genetic testing (not possible to ensure samples from placenta are unique to one fetus) Increased liquor – due to 2 babies producing fluid, can cause preterm labour Pre-term delivery – approx 36 weeks, mono earlier than di. Often electively delivered early to prevent complications of spontaneous labour Growth restriction – due to mothers limited resources. More common in mono (see TTTS below) Congenital anomaly – partly nutritional (is there sufficient folate for 2 babies), also because if mono then genes are same (if one has defect, both will) Antenatal problems specific to multiple pregnancy Twin-Twin Transfusion Syndrome(TTTS) – upto 35% of monochorionic twins affected. Net flow from one to other twin (via anastomosis in placenta) à donor has FGR & oligohydramnios while recipient thrives and has polyhydramnios (with risk of high output cardiac failure). Monitor by assessing AFI for each twin regularly. Treatment options include aspiration of amniotic fluid from the recipent sac and laser division of the placenta. If donor dies necrotic tissue will flow to recipient twin --> brain infarcts (“porencephalic cyst”) Twins with one fetal death In 1st trimester usually does not affect the survivor. In late 2nd or 3rd usually à labour If monochorionic risk of cerebral injury and hypotension in survivor. Twin reversed arterial perfusion sequence (acardia) If the heart of one twin stops, it may be partially perfused by other twins circulation à cardiac failure of survivor Management of twin delivery 40% cephalic – cephalic 40% cephalic – breech 10% breech – cephalic 10% others inc transverse Common to induce labour at 38 weeks, or C-section at 38 weeks if indicated (eg TTTS) Ensure both are monitored through labour) not one monitored twice! Syntocinon infusion on standby incase uterine contractions cease after 1st delivery