Section I Biology: Zygocity and chorionicity OR Biology and genetics of dizygotic and monozygotic twinning -- The vanishing twin -- Genomic studies of complex traits: the value of twins -- Placentation in multiple pregnancy -- 'Omic' twin studies -- Section I Epidemiology: Epidemiology of twins and multiple pregnancy -- Assisted conception and multiple pregnancy -- Emerging methods in twin research -- Section III Antenatal Care in twins and multiple pregnancy: Dating of the pregnancy (determining the gestational age) -- Determining chorionicity and amnionicity -- Twin labelling, timing, frequency and content of ultrasound assessment -- Prenatal screening for and diagnosis of aneuploidy -- Screening for structural abnormalities -- Assessment of fetal growth in twins and multiple pregnancy -- Section IV Prenatal complications in multiple pregnancy: Twin pregnancies discordant for fetal anomaly -- Fetal reduction/selective termination in uncomplicated twins and multiple pregnancy -- Preterm birth in twins and multiple pregnancy -- Fetal growth restriction -- Stillbirth and single inutero death -- Section V Complications unique to monochorionic twin pregnancies: Twin to twin transfusion syndrome -- Twin anaemia polycythaemia sequence -- Twin reversed arterial perfusion sequence -- Monochorionic monoamniotic twin pregnancy -- Diagnosis and management of conjoined twins -- Section VI Peripartum care: Timing of birth in uncomplicated twin pregnancy -- Mode of delivery in twin pregnancy and delivery of the second twin -- Analgesia and anaesthetic consideration -- Postpartum hemorrhage and maternal morbidity in multiple pregnancy -- Section VII Postnatal care: Breast feeding twins and multiples -- Postpartum depression and psychiatric considerations -- Postnatal neonatal assessment in multiple pregnancy -- Support after single loss in twin and multiple pregnancy -- Section VIII Childhood development: Cerebral palsy and neurodevelopmental delay in multiple pregnancy -- Long term follow-up: indications and methodology -- Neuroimaging & the brain; the role of twin studies -- Section IX Research, registries and Parent views: Research studies in twins and multiple pregnancy (Global Twins and Multiples Priority Setting Partnership) -- Twin and multiple pregnancy registries -- Twin and multiple pregnancy: patient voice.