Higher Incidence of disability in multiples
It is important to recognise not all disabilities in multiples have the same cause. This is only a very brief summary and much more information can be found in medical texts such as Blickstein and Keith (2005). We are concerned here only with potential implications for schooling.
(i) the process of twinning, especially MZ twinning is linked with some congenital abnormalities such as cleft palate and certain cardiac conditions. Some of these may be associated with the split of the mass of developing cells into two or more individuals and some to placentation and the transfusion syndrome.
(ii) the higher risks of being born preterm and of low or very low birthweight. The best known example of such problems is Cerebral Palsy which is more common in twins, unfortunately even more common in higher multiples and especially common when one or more of the multiples has died.
Just imagine what it is like for the child and the family going through school as the disabled survivor of a set of multiples? And will the school even know this?
What has been recognised and emphasised in the last few years is that the babies are having problems before the birth and so the blaming of these difficulties on what happened at delivery is not appropriate in the vast majority of cases.
Another major problem is retinopathy of prematurity, the visual problems that some very preterm babies experience as a consequence of the oxygen-enriched environment needed to help them survive. It is not that this is specifically more common in multiples but rather that more multiples are preterm and therefore more likely to need such intensive intervention.
(iii) a common link between multiple birth and a disorder. For example, both Down Syndrome and DZ twinning become more common as mothers get older, though this is partly counterbalanced by the high miscarriage rate of babies with Down Syndrome. Another condition, Fragile-X is the most common inherited form of Intellectual Disability and there is some evidence that women with this condition are more likely to release multiple eggs and so have more DZ twins.
(iv) growing-up as a multiple. The question of speech and language problems was raised in the preschool section and the related topics of Reading Problems and of ADHD in The School Years section.
Detailed analysis of our extensive Australian data shows little role for influences before or at birth on these behavioural problems, except for a link between twins who are small for gestational age and language problems. Thus the reasons multiples have more problems must have more to do with life in a multiple birth family and the extra demands this brings.
It is important not to extrapolate directly from studies of preterm birth in singleborn children to multiples. Given twins on average are born four or so weeks earlier than singletons (and going as far as 41 weeks may actually carry risks for multiples), then being born at say 35 weeks does not carry the same risk of physical and behavioural problems for multiples as for 35 week singletons.
(v) and MOST IMPORTANT. Many problems have nothing to do with multiple birth. The sad fact is that quite a few singleborn children in our population have behavioural or physical problems. No one can guarantee a baby or babies will be healthy. Every parent wants to know why a difficulty has happened in their child and sometimes the fact the child is a multiple offers the most obvious but not always the correct explanation.
Not only may "multiples as the explanation" be incorrect, it may lead to negative attitudes "If we had not had twins, this would not have happened" and even the idea that the only possible intervention is one specific to multiples. So parents may spend a lot of time trying to find other multiple birth families with the same disability, rather than drawing upon the resources and knowledge of families who have one or more affected singleborn children. It would be ideal for multiple birth families to link together, but this is impractical for rarer disabilities and for people living in less populated areas.
This still leaves many healthy multiples!
But the fact is that problems are more common in multiples, and those working in Special Education need to know the issues we have raised. We have deliberately not talked about how much more common problems are. If families expecting multiples are concerned about this, the best person to provide local information is their own specialist.
Obviously we cannot cover all types of disability and so we focus on the three main areas of reading problems, ADHD and that group of major difficulties that includes Cerebral Palsy, sensory problems and intellectual disability. Many people may think you should not classify something as significant as Cerebral Palsy in the same sentence as ADHD. But one of our Australian studies found mothers who had children with ADHD were much more depressed than mothers who had children with Cerebral Palsy and felt much less certain of their parenting skills. With Cerebral Palsy, people recognise your child or children have a problem and are supportive. ADHD is regarded by many with scepticism and often attributed incorrectly to bad parenting.