Twin Types: Variations and Common Themes/Twin Research Reviews: Birth Weight and Brain Development; Twinning and Vocabulary Knowledge; Fetal Loss in Twin Pregnancy; Twin-Family Olympic Medal Winners/Human Interest: Young Twin Soldiers; Twin-Run Laundry; Male-Female Pair and Politics; Twin-Based Graphic Novel; Twin Sisters’ Deliveries

Modern reproductive technology and revisions of conventional family structures have yielded a curious array of twin-like sibships. Many of these pairings pose the same rearing questions and educational issues for parents and teachers as do ordinary monozygotic and dizygotic twins. This article considers how we classify these sibships, given the important implications for the pair members, their families, their friends and the professionals who care for them. Next, reviews of research on twins’ birth weight and brain development, twinning and vocabulary knowledge, fetal loss in twin pregnancy and twin-family Olympic medal winners are presented. The final topic covers recent media attention to young twin soldiers, a twin-run laundry, a male-female pair’s political differences, a twin-based graphic novel and twin sisters’ deliveries.

The Swedish Twin Registry in the Third Millennium: An Update

The Swedish Twin Registry was first established in the late 1950s. Today it includes more than 170,000 twins — in principle all twins born in Sweden since 1886. In this article we describe some ongoing and recently completed projects based on the registry. In particular, we describe recent efforts to screen all twins born between 1959 and 1985, and young twin pairs when they turn 9 and 12 years of age. For these studies, we present initial frequencies of common conditions and exposures.

Effect of weaning age on growth rates of lambs infected by gastrointestinal parasites

Gastrointestinal parasitism is one of the most important challenges facing low chemical or organic livestock production systems but also conventional farmers as resistance to anthelmintics becomes more widespread. Young twin-born and reared lambs were challenged for 5 days (Experiment 1) or trickle infected with parasites (Experiment 2) and not weaned (Expt. 1. only) or early (8 and 7 weeks) or late weaned (16 and 14 weeks; Expt. 1 & 2 respectively). Liveweight gain was measured until lambs were 19 weeks of age (Expt. 1) or 25 weeks of age (Expt. 2). Early weaning (7-8 weeks) reduced liveweight gain by at least 25% in both years and lambs remained 5 kg lighter at the completion of the experiments. Parasite infection had modest effects on lamb performance and there was no interaction between weaning age and parasite infection in either year. Infected lambs generally grew well, gaining at least 90 g/d possibly due to the relatively young age of the lambs limiting their ability to mount an immune response. Keywords: gastrointestinal parasites, low chemical, organic livestock production, sheep, growth rates

Evaluation of Zygosity Diagnosis in Twin Pairs Below Age Seven by Means of a Mailed Questionnaire

The mothers of a consecutive series of 125 same sexed pairs of twins aged 6 months to 6 1/2 years completed a mailed questionnaire concerning the physical similarity of the twin partners. Zygosity diagnoses were first determined blindly on the basis of the answers given by the mothers, who did not know the result of the blood group test when fullfilling the questionnaire. Next, the results were compared with the zygosity determination based on examination of erythrocyteserum- and enzyme-groups. It turned out that a few simple questions distinguished well enough between MZ and DZ pairs, with a frequency of misclassification of 4%, leaving 5% as unclassifiable. It is concluded that twin zygosity can be estimated by a simple questionnaire with sufficient accuracy even in very young twin pairs. This has relevant implications for more extensive twin studies where the use of a wide spectrum of serological characters would imply too high expenses.