SUMMARY ANSWER The available high- quality evidence indicates that specific treatments may give rise to different effects on cognitive development , with certain treatments , including ICSI , associated with cognitive impairment .
STUDY QUESTION Does  fertility treatment  influence cognitive ability in school aged children , and does the impact vary with the type of treatment ?
WHAT IS KNOWN ALREADY Previous review s of the literature concerning cognitive outcomes among children conceived with medical assistance have concluded that study findings are generally ' reassuring ' , but limited attention has been paid to the quality of this research .
In addition , no review has separately assessed the range of treatment modalities available , which vary in invasiveness , and thus , potentially , in their effects on developmental outcomes .
Language assessment of non-handicapped twins at 5 years of age.
BACKGROUND The aim of the present study was to determine language levels in twins and singletons born after at least 34 weeks gestation and without identifiable neurological abnormality and to evaluate whether in vitro fertilization ( IVF ) affects language development in twin pregnancies . METHODS A prospect i ve study of a large cohort of all children born between 1 January 2001 and 31 December 2003 was carried out at Gazi University Hospital . All live-born twin pairs in which both twins survived were identified , and a comparable sample of families with pairs of singletons were chosen . The  Stanford-Binet Intelligence Scale Form and the translated Turkish form of the Peabody Picture Vocabulary Test  were completed at 60 months . RESULTS Even after excluding the most premature twins and those with diagnosable neurological damage , twins performed worse than singletons on language development tests . Twin girls had better scores than twin boys . A statistically significant difference was found between the scores of term and preterm twins . No significant difference was noted when compared according to birth order . Appropriate for gestational age ( AGA ) twins did better than small for gestational age ( SGA ) twins in the test scores . All twin girls did not differ from singleton girls , but all twin boys performed worse than singleton boys . Term twins had similar results with term singletons , but preterm twins had lower scores than preterm singletons . SGA singletons had better scores than SGA twins , while AGA twins and singletons did not differ . When the children were compared with regard to method of conception , IVF children had significantly lower scores on the tests than those in the spontaneous conception group . CONCLUSION It is hoped that the present findings could lead to a more precise assessment of children for speech impairment and , above all , to more efficient preventive intervention . Whatever mechanisms are involved , the present results indicate that twins born as a result of IVF , are at a disadvantage in terms of language development in comparison with spontaneously conceived twins
SUMMARY ANSWER The available high- quality evidence indicates that specific treatments may give rise to different effects on cognitive development , with certain treatments , including ICSI , associated with cognitive impairment .
STUDY QUESTION Does  fertility treatment  influence cognitive ability in school aged children , and does the impact vary with the type of treatment ?
WHAT IS KNOWN ALREADY Previous review s of the literature concerning cognitive outcomes among children conceived with medical assistance have concluded that study findings are generally ' reassuring ' , but limited attention has been paid to the quality of this research .
In addition , no review has separately assessed the range of treatment modalities available , which vary in invasiveness , and thus , potentially , in their effects on developmental outcomes .