Multiple pregnancies have come under intense scrutiny because they are associated with prematurity and growth restriction. In developed countries, high rates of multiple pregnancies following assisted reproductive technology have been cited as a reason why preterm delivery rates remain stubbornly high and perinatal statistics have plateaued.
Long-term outcomes of twins take decades to be determined and it is described that twins born in developed countries half a century ago had lower IQs and academic performances than singletons. However, recent figures from Scandinavian studies show no differences between singletons and twins as measured by all cause mortality and academic achievement (Christensen & McGue BMJ 2008;337:a651:245-6). Perhaps modern antenatal care and catch-up interventions have nullified the discrepancies, but there is strong evidence that disadvantage no longer applies in these sophisticated environments.
It is of interest that a Taiwanese study of twins born in the mid-1980s shows that the subjects had lower academic achievements than singletons and had a lesser probability of attending college (Tsou et al pp 277-80). Is it possible that developing socio-economic factors play a role still, while these factors have been eradicated in developed countries?
