***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective : To determine , in a community-based sample of slow-to-talk toddlers , the extent to which specific maternal responsive behaviors at 24 months predict child language at 24 and 36 months . Methods : Mother-child dyads were recruited for this prospect i ve longitudinal study from 3 local government areas spanning low , middle , and high socioeconomic status in Melbourne , Australia . At child age 18 months , 1138 parents completed a 100-word expressive vocabulary checklist ; the 251 ( 22.1 % ) children scoring ⩽20th percentile were then followed up to comprise this study . Predictors : Six maternal responsive behaviors ( imitations , interpretations , labels , expansions , supportive directives and responsive questions )  were derived from mother-child free-play videos collected at 24 months of age and coded using the Observer XT system . Outcomes : Expressive and receptive language measured at 24 and 36 months of age ( Preschool Language Scale-4 ) , blind to maternal responsiveness ratings . Results : Two hundred and twenty-six of the 251 ( 90.0 % ) mother-child dyads were followed up at 36 months . In confounder-adjusted linear regression analyses , expansions , imitations , and responsive questions were strongly associated with better receptive and expressive language at 24 and 36 months . Labels unexpectedly predicted poorer expressive language at 36 months . Expansions were the only maternal behavior that predicted improvement in language between 24 and 36 months . Conclusions : Maternal responsive behaviors , particularly expansions , offer promise in enhancing early language learning in slow-to-talk toddlers . Parent-child interactions characterized by frequent use of maternal labels at 24 months could also be a predictive marker of those slow-to-talk toddlers at greater risk of persistent language problems PURPOSE The aim of this study was to investigate the language outcomes of 7-year-old children with and without a history of late language emergence at 24 months . METHOD One hundred twenty-eight children with a history of late language emergence ( LLE ) at 24 months and 109 children with a history of normal language emergence ( NLE ) at 24 months participated in direct behavioral assessment of multiple dimensions of language at 7 years . The children were recruited from a prospect i ve cohort study of 1,766 epidemiologically ascertained 24-month-old singleton children . RESULTS The group mean for the LLE children was within the typical range on an omnibus measure of general language ability and measures of specific dimensions of language . However , a greater percentage of LLE children , relative to NLE children , performed below normative expectations on a measure of general language ability ( 20 % versus 11 % ) , speech ( 7 % versus 2 % ) , syntax ( 18 % versus 8 % ) , and morphosyntax ( 9%-23 % versus 2%-14 % ) , but not vocabulary or semantics . CONCLUSION The results provide support for growth models of language impairment that predict that late onset of language foretells a protracted growth difference for some LLE children relative to NLE children , particularly for syntax and morphosyntax OBJECTIVE To examine psychosocial and obstetric outcomes at 1 year postpartum in first-time mothers who conceived after IVF .  DESIGN Prospect i ve cohort study . SETTING University medical center in the United Kingdom . PATIENT(S ) One hundred twenty-nine mothers with a single naturally conceived birth , 95 mothers with a single IVF birth , and 36 mothers with a twin or triplet IVF birth . MAIN OUTCOME MEASURE(S ) General Health Question naire and Parenting Stress Index . RESULT ( S ) Twenty-two percent of mothers of multiples had Parenting Stress Index scores indicating severe parenting stress , compared with 5 % of mothers of IVF singletons ( odds ratio , 5.14 [ 95 % confidence interval ( CI ) , 1.55 - 16.99 ] ) and 9 % of mothers of naturally conceived singletons ( odds ratio , 2.76 [ 95 % CI , 1.03 - 7.4 ] ) . Mothers of multiple children conceived by IVF did not have poorer mental health but were less likely to be in paid employment at follow-up than were mothers of singletons conceived by IVF ( odds ratio , 0.3 [ 95 % CI , 0.13 - 0.67 ] ) or naturally ( odds ratio , 0.27 [ 95 % CI , 0.12 - 0.59 ] ) . Multiple births were more premature , had lower birth weights , and had more medical complications . They were more likely to have been admitted to special care than were singletons conceived by IVF ( odds ratio , 14.6 [ 95 % CI , 5.1 - 42.0 ) ] or those conceived naturally ( odds ratio , 10.59 [ 95 % CI , 3.67 - 30.57 ] ) CONCLUSION ( S ) Clinicians should ensure that couples making decisions about embryo transfer have considered the potential psychosocial burden of a multiple birth 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 OBJECTIVE To establish the nature and extent of difficulties in parenting and child development in families with twins conceived by assisted reproduction . DESIGN Comparisons were carried out between a representative sample of 344 families with 2- to 5-year-old twins conceived by IVF/intracytoplasmic sperm injection ( ICSI ) and a matched comparison group of 344 families with singletons from IVF/ICSI .  One twin was r and omly selected for data analysis to avoid the bias associated with nonindependence of measures . SETTING A general population sample of IVF/ICSI families . PATIENT(S ) Mothers and children . INTERVENTION(S ) Mothers completed a question naire booklet . MAIN OUTCOME MEASURE(S ) St and ardized measures of the mother 's psychological well-being ( parenting stress , depression , and quality of marriage ) and st and ardized measures of the child 's psychological development ( emotional/behavioral problems and cognitive development ) . RESULT ( S ) Mothers of twins showed significantly higher levels of parenting stress and depression than mothers of singletons and were significantly more likely to find parenting difficult and significantly less likely to obtain pleasure from their child . Regarding the children , there was no difference in the level of emotional or behavioral problems between twins and singletons . However , twins showed significantly lower levels of cognitive functioning . CONCLUSION ( S ) Greater difficulties in parenting and child development were experienced by IVF/ICSI families with twins than by IVF/ICSI families with singletons 
    Output:
    
Results : To our knowledge , this is the first systematic review focused on the comparison of twins ' and singletons ' linguistic environments .
Differences between the groups were found in all of the included studies .
Data against twins were generally identified regarding all the considered linguistic environment 's features .
Conclusion : The disadvantaged linguistic environment of twins is likely due to limited parental re sources and dem and s associated with the management of two children of the same age .
However , the limited and conflicting data found did not allow for a firm conclusion to be drawn on the differences in the twins ' and singletons ' linguistic environments .