Twin studies are important to investigate genetic influences on variation in human brain morphology in health and disease. However, the twin method has been criticized for its alleged non-generalizability due to differences in the intrauterine and family environment of twins, compared with singletons. To test whether twin-singleton differences complicate interpretation of genetic contributions ...

This study analyses the formant dynamics of Mandarin and Shanghainese /ua/ in bilingual identical twins. The results show that despite the same organic structure and similar language environment, differences can be found in their formant dynamics. A comparison between the subjects’ dominant and non-dominant language shows that the twins are more similar in their dominant language. The data also...

A total of 476 infants (386 singletons and 90 twins) born before 32 weeks' gestation were studied to compare long term growth and development in twins and singletons. At 18 months, after adjusting for confounding social, obstetric, and neonatal factors, twins were not disadvantaged in their neurodevelopmental status, but were 1.6 cm shorter than singletons and had thicker triceps and subscapula...

It has long been common knowledge that certain twins resemble one another in a remarkable way. The fact that many more like sexed twins are born than the theoretical ratio 1: 2: 1 would demand constitutes evidence in favour of the belief that such twins are monozygotic, for the actual figures of twin births can be adequately explained on the assumption that about one half the pairs of like sexe...

Ultrasound has revolutioned the care of women carring twins. First trimester evaluation is the best time to determine chorioniocity and amnioniocity in multiple gestations. First trimester diagnosis is based on the number of gestational sacs, amnions and yolk sacs. Growth rate in multiple multiple gestations during the fist and early second trimesters parallels the growth rate of singleton preg...

An evaluation of natuml twinning in beef cattle revealed that cows birthing twins had shorter (P c .Ol) gestation lengths, more (P e .Ol) retained placentas, more (P < .01) dystocia, more (P e .01) days to e m s , lower (P e .01) conception rates and more (P < .01) days to pregnancy than cows birthing singles. Days to estrus, conception rate and days to pregnancy were not affected by number of ...

To compare perinatal outcome of singleton versus twin pregnancies a matched cohort study was performed in Flanders, Belgium. All twins delivered in the region of Flanders during 1998-1999 were compared to singletons, matched for gestational age, fetal sex and maternal parity, resulting in 4384 infants in each group. Above 32 weeks of gestation, birthweight was significantly lower in twins (2095...

Twin studies typically indicate shared environmental influence for cognitive abilities, especially in early childhood. However, across studies, DZ twin correlations tend to be greater than non-twin sibling correlations, suggesting that twin estimates of shared environment are to some extent specific to twins. We tested this hypothesis in a sample of more than 1800 MZ and 1800 same-sex DZ pairs ...

Low birth weight is associated with postnatal physiological changes, including impaired glucose tolerance and increased cortisol secretion, that may predispose to disease in adulthood. Twins are born lighter than singletons, but there are conflicting data regarding the association between birth weight and postnatal physiology in twins. We studied glucose tolerance and ACTH and cortisol response...

We studied the short- and long-term effects of classroom separation in twins on behavior problems and academic performance. Short-term effects were studied at age 7 in twins separated at age 5 and long-term effects at age 12 in twins who had been separated or together most of the time at school. Behavior problems were rated by mothers (Child Behavior Checklist at ages 3, 7 and 12) and teachers ...