Acta geneticae medicae et gemellologiae: twin research 

About: Acta geneticae medicae et gemellologiae: twin research is an academic journal. The journal publishes majorly in the area(s): Twin Pregnancy & Pregnancy. It has an ISSN identifier of 1120-9623. Over the lifetime, 158 publications have been published receiving 3144 citations.

The Minnesota twin family registry : some initial findings

Abstract: A birth-record based Registry is nearing completion of some 8,000 pairs of twins born in Minnesota from 1936 to 1955, plus some 1,200 pairs of male twins born 1971-81. The middle-aged twins were recruited with graded incentives so that ease of recruitment could be measured; it was found that pairs concordant for ease of recruitment were no more similar than discordant pairs in education, socioeconomic status (SES), or a variety of personality and interest factors, ie, that selection bias may not be a problem in research with adult twins when contacts are only by mail. A 50% decrease in neonatal mortality from 1936-55 to 1971-81 was associated with an increase from 3.5 to 4.0 per thousand in the frequency of viable MZ twin births. The broad heritability of SES, educational attainment, fecundity, and risk for divorce ranges from 0.30 to 0.50, although all 4 variables are plainly multifactorial and the latter 2 both involve variance contributed by a second person. Investigators interested in making use of this research resource are invited to submit proposals.

Swedish early separated twins: identification and characterization.

Abstract: A sample of twins separated early in life has been identified in the Swedish Twin Registry. When the registry was compiled in 1961 (old cohort) and 1973 (young cohort), one or both members of 961 pairs indicated that they were separated by the age of 10. In May 1979, both members of 698 pairs were alive and were sent a questionnaire concerning the circumstances of separation. Items included reasons and timing of separation, biological relatedness of rearing parents, degree of contact after separation (including whether they lived in the same area, attended the same school, or lived together again), rough measures of selective placement, and current frequency of contact. An attempt was then made to categorize the pairs based on degree of separation. A total of 257 pairs met the criteria: rearing parents of one twin biologically unrelated to rearing parents of the cotwin, twins not living together again after separation, and contact after separation a few times a year or less. As much as 50% were separated by their first birthday, and 80% by the age of five. Various data from the twin registry are presented describing the entire sample of early separated twins as compared to a matched sample of twins reared together.

The vanishing twin.

Abstract: In general, it has not been recognized that many twin or multiple gestations are lost in utero early in pregnancy. Until the advent of ultrasound, the ability to document early human fetal loss in multiple gestation was difficult. However, recent reports of serial ultrasound examinations of pregnant women have documented the "disappearance" of at least one of two gestational rings. Furthermore, the number of twins observed at delivery was significantly less than the number of twin conceptions originally identified by ultrasound during the first trimester. These observations led to the concept of the "vanishing twin" [8,10,13,15,17,20,22,35,41]. In order to obtain reference and personal data on this subject, we reviewed the literature and corresponded with members of the International Society for Twin Studies and obstetricians affiliated with Northwestern University Medical School, Chicago, Illinois. The nine studies that have documented this phenomenon cite "disappearance" rates ranging from 0% to 78%, depending on patient population and timing of ultrasonography [8,10,13,15,17,20,22,35,41]. Several explanations are offered: physiological mechanisms of "disappearance" (resorption or formation of a blighted ovum or fetus papyraceus), artifactual error, incomplete scanning technique, and poor quality ultrasound equipment. The only complication thus far associated with "disappearance" of a fetus is slight vaginal bleeding.

Testing Twin Means and Estimating Genetic Variance. Basic Methodology for the Analysis of Quantitative Twin Data

Abstract: Twin methodology for the analysis of continuously distributed traits is presented as a guideline for initial steps in the analysis of twin data. Tests for heterogeneity of twin means and variances are reviewed along with estimates of genetic variance. Analysis of twin data appears on the surface to be a rather simple task, but investigators may well be confused by the wealth of choices available for hypothesis testing. This paper is designed to help the less experienced investigator, with perhaps a modest amount of data, begin analysis with maximum attention to testing all testable assumptions of the twin model, and using recent examples of applications of the methods.