Cognitive and verbal development of discordant twins without neurological morbidity

Abstract

The aims of this longitudinal study are to investigate the cognitive and verbal development of discordant twins without neurological morbidity. Twenty pairs (40 infants) of discordant twins (discordance range 15-41%) were examined. A follow-up study was carried out of 11 selected pairs (22 infants), with biological and cognitive measures at birth, at 1 year, at 2 years and at 4 years. Results show that biological growth differences (weight, height and head circumference) tended to disappear after the age of 2 years. Significant differences were found in cognitive and verbal skills between the larger and smaller co-twins at all ages. When the twins were small for gestational age, and were close to very low birth weight, together with severe discordance, their cognitive and verbal scores were consistently below the range of normality. In conclusion, the differences between the larger and smaller co-twins appear to persist up to 4 years of age, with respect to cognitive and verbal skills. A possible additive effect of biological risk factors that accumulated in the severe discordances was observed, which appeared to increase the probability of smaller co-twins suffering delayed cognitive and verbal development.

Cognitive outcome in childhood of birth weight discordant monochorionic twins: the long-term effects of fetal growth restriction

“…Our study results are similar to those of Torche et al ,28 Edmonds et al ,29 Bellido-Gonzalez et al 30 and Goyen et al 31 but are in contrast to the studies by Reolan et al 32 and Stauffer et al 33. Torche et al 28 showed IUGR has effect on children’s cognitive development, as measured by test scores in primary school.…”

“…Edmonds et al 29 found birth weight discordance affects verbal IQ. Bellido-Gonzalez et al 30 showed cognitive and verbal domain differences persist consistently throughout the ages 1, 2 and 4 years. They had a small sample size with only nine pairs.…”

Early environmental risk factors for neurodevelopmental disorders – a systematic review of twin and sibling studies

“…Two twin studies of high quality ( N = 248) and a case control study ( N = 1,464) with higher risk of bias showed no statistical within-pair association with a diagnosis of ID (Chatterji et al, 2014; Monset-Couchard et al, 2004; Steingass et al, 2013). For IQ, on the other hand, two twin studies ( N = 144) and one sibling cohort study ( N = 50) found associations (Bellido-González et al, 2007; Churchill, 1965; Kilbride et al, 2004). Suicide attempts with Tardyl during pregnancy was associated with ID and IQ in one sibling study, one large population-based sibling case control study suggested an increased risk for ID linked to nonoptimal gestational duration, and one large population-based sibling cohort study reported increased risk for ID linked to orofacial clefts.…”

Evaluation of Birth Weight and Neurodevelopmental Conditions Among Monozygotic and Dizygotic Twins

“…13 Additionally, previous studies have reported no associations between lower birth weight and ID, 17 while associations have been reported for lower IQ. 18,19 A recent study found that in pairs with birth weight discordance of 18% or greater, the lowerweighted twin had a higher likelihood of presenting with traits of autism and ADHD than their co-twin. 20 However, that study only included monozygotic twins and was limited to few discordant pairs and a categorical measure of birth weight discordance.…”