Are vital Twins prematures?

Abstract

SUMMARYThe Authors have analyzed the data concerning length of gestation and neonatal weigth and length measurements in 2,440 living twin pairs (from the files of the Mendel Institute), in order to verify the frequent assumption that all twins should be considered as prematures and, as such, affected by congenital debility.Comparing their findings with the standard values for prematures, they reach the conclusion that the majority of twins who have survived the perinatal period were not prematures. Furthermore, the less developed among such twins differ from single-born prematures by reason of their subsequent normal auxologic development, whereby the Authors propose that they should rather be considered as “premature-like”.

Lifetime Socioeconomic Position and Twins' Health: An Analysis of 308 Pairs of United States Women Twins

“…Study limitations include (a) the relatively small number of twin pairs (albeit similar to other twin studies [3,11]); (b) lack of data on detailed occupational class position over time and on age at obtaining a college degree, plus prior or current data on income, poverty, wealth, and debt; (c) lack of data on gestational age, birth weight, birth order, and whether the twins had shared or separate chorions and amniotic sacs [2,7,11,40]; (d) lack of data on differences in the twins' childhood experiences and exposures (e.g., differential treatment accorded to first- versus second-born twins, and to monozygotic versus dizygotic twins [6]); and (e) lack of data on male twins; in addition, the small number of women twins who were concordant on adult working class position limits generalizability (but not internal validity) of results. Most studies assessing the impact of childhood socioeconomic position on health, however, have relied on occupational and sometimes educational data [8,9,26,41–46], reflecting difficulties in obtaining income data across the lifecourse [16–18].…”

“…Unlike prior research, however, the present study newly employed a same-gender twin design, affording comparatively tight matching on life circumstances through early adolescence, with monozygotic twins additionally matched on genetic inheritance, thereby circumventing important concerns raised about likely unmeasured confounders affecting results of prior studies dependent upon adult recall of—and limited data on—childhood socioeconomic position. Even so, generalizability of results to nontwins could be hampered if twins differ systematically from nontwins on factors influencing associations between socioeconomic position and adult health, as perhaps related to maternal and zygotic characteristics relevant to risk of monozygotic or dizygotic twinning or to exposures contingent upon being a twin in utero (e.g., down-regulation of growth) [2,4–7,49–52]. …”

“…Far fewer studies have investigated how twins raised together, but who differ in their postadolescent socioeconomic position, compare on adult health status [2,4]. Yet such research could potentially inform current debates over the contribution of lifecourse socioeconomic conditions to adult health [8–11], given twins' shared genetic inheritance and early life socioeconomic plus biological exposures.…”

Genetic and Extragenetic Variance In Motor Performance

“…Studies pertaining to the heritability of anthropometric dimensions (Vandenberg 1962, Gedda et al 1964, Mizuno 1965, Hirata 1966) and motor performance (McNemar 1933, Brody 1937) support the contention that the genetic influence to motor performance and successful athletic participation substantially outweigh the nongenetic influences. Scarr (1966), however, reported only moderate heritability coefficients for activity level and reaction time, whereas Williams and Hearfield (1973) found approximately equal genetic and extragenetic influences to individual differences in the performance of a ladder climb task.…”