Follow-up of twins: health, behaviour, speech, language outcomes and implications for parents.

The introduction of assisted reproduction has resulted in a growing number of multiple births. These infants and their parents experience increased, and sometimes unique, medical and psychological risks when compared to singletons. Rates of maternal morbidity, fetal and infant mortality are increased in multiple pregnancies. Twins have a death rate four times higher than singletons and this figure is six times higher for triplets. The main reason is preterm and very preterm birth in multiples, resulting in low and very low birth weight children. Perinatal mortality and morbidity are also more elevated in monozygotic (MZ) twins as compared to dizygotic (DZ) twins. In addition to an increased risk of mortality, multiples have higher rates of morbidity, specifically cerebral palsy and mental subnormality. Language and speech delays are more pronounced in multiples, as are cognitive delays, motor development, behavioural problems and difficulties in parent-child interactions. Depression among parents of multiples is reported to be higher than those of singletons. This paper aims to critically appraise the literature regarding the aforementioned topics, including a comparison between the outcomes for iatrogenic and spontaneously conceived twins and to suggest areas for further research.