From November 16–19, 2014, twin researchers of the world will descend on the lovely city of Budapest, Hungary for the 3rd World Congress on Twin Pregnancy, held in conjunction with the 15th Congress of the International Society of Twin Studies (ISTS). It is the first time a Central and Eastern European country will host the congress. On this occasion, we were honored by the request from the editor of Twin Research and Human Genetics, Nick Martin, to put together a special issue highlighting twin research conducted in Central and Eastern Europe (CEE).

Since 1876, statistical data on twin and multiple (TAM) births and deliveries have been registered in Hungary. Although there were some years during this 138-year period when twin births and deliveries were left out of the statistics, the trends can be followed, except for the period of World War II. The trends of twinning over the past four decades are summarized in this article, relying on official statistical data since 1970. Notably, the TAM birth rate rose following the Act CLIV of 1997 on Health. The Act provided state support for assisted reproductive treatments (ART), which spectacularly increased the ratio of twins — and especially of triplets — among live births. The trend has turned around since 2009–2010, and a decreasing era of TAM births seems to have begun. This article discusses some of the main and most interesting findings connected with TAM births, including twinning rates associated with different age groups, educational level, and actual place of residence by mothers, and the number of previous pregnancies of the mother. Ratios of live born males compared with live born females, lengths and weights at birth both among twins and singletons, and infant mortality rates have been calculated from the data. Twinning rates are higher in the western counties, the capital and its suburbs, and lower in the eastern counties.

The study aimed at investigating the impact of late prematurity (LPT) on neonatal outcome in twins and neonatal morbidity and mortality within LPT with regard to the completed weeks of gestation. The study was conducted in six tertiary obstetric departments from different provinces of Poland (Warsaw, Lublin, Poznan, Wroclaw, Bytom). It included 465 twin deliveries in the above centers in 2012. A comparative analysis of maternal factors, the course of pregnancy and delivery and neonatal outcome between LPT (34 + 0–36 + 6 weeks of gestation) and term groups (completed 37 weeks) was performed. The neonatal outcome included short-term morbidities. The analysis of neonatal complication rates according to completed gestational weeks was carried out. Out of 465 twin deliveries 213 (44.8%) were LPT and 156 (33.55%) were term. There were no neonatal deaths among LPT and term twins. One-third of LPT newborns suffered from respiratory disorders or required antibiotics, 40% had jaundice requiring phototherapy, and 30% were admitted to NICU. The analysis of neonatal morbidity with regard to each gestational week at delivery showed that most analyzed complications occurred less frequently with the advancing gestational age, especially respiratory disorders and NICU admissions. The only two factors with significant influence on neonatal morbidity rate were neonatal birth weight (OR = 0.43, 95% CI = 0.2–0.9, p = .02) and gestational age at delivery (OR = 0.62, 95% CI = 0.5–0.8, p < .01). LPT have a higher risk of neonatal morbidity than term twins. Gestational age and neonatal birth weight seem to play a crucial role in neonatal outcome in twins.

Aiming to perform the first sociological survey of Hungarian twins, our main question was whether being a twin has positive consequences on one's life. Adult twins completed our questionnaire at three Hungarian summer twin festivals, in hospitals during medical twin studies, and on some websites online. Data represent 140 twin pairs (mean age: 38.2 ± 14.6 years). We employed some indices for measuring the resource nature of twinship. Three main types of benefits were distinguished: profit of attraction, as ‘material capital’; the easier obtainability of cultural goods when twins take part in it, as ‘cultural capital’; and positive aspects of an a priori existing dyadic relation, as ‘relational capital’. We were interested in the difference among types of twins regarding advantages. We paid special attention to the five groups of twins derived from gender and zygosity (i.e., monozygotic females, monozygotic males, dizygotic females, dizygotic males, opposite-sex pairs). Our analysis showed that Hungarian twins involved in our research basically enjoy their twinship; during their lives they used and still make use of different benefits given by it. In our twin samples, women had more advantages from being a twin than men. Significant differences could be observed on all indicators between monozygotic and dizygotic twins.

Valvular heart disease is a multifactorial disorder. Twin studies may help to better understand both genetic and environmental determinants contributing to the development of valve lesions. We describe the case of a 45-year-old female asymptomatic triplet with multiple valvular heart lesions, with a somewhat different pattern between the dizygotic twin pairs compared with the monozygotic twin pair. After thorough assessment of medical history and physical examination, the triplet underwent two- and three-dimensional transthoracic and transesophageal echocardiographic examinations to assess the pathomechanism and severity of their heart valve lesions. The monozygotic twin pair (second-born twin B and third-born twin C) showed the same pattern of valvular lesions: mild mitral, tricuspidal, and aortic regurgitation of the same pathomechanism (posterior mitral valve cleft and aortosclerosis). Interestingly, the examination of first-born twin (twin A), who was dizygotic to twins B and C, revealed mild protosystolic mitral and mild tricuspidal regurgitation, but neither aortic insufficiency nor mitral cleft or indentation could be detected. Beyond the genetic effect, we presume that the intrauterine twinning process might also play a role in the development of congenital valvular heart disease. In order to verify this, further investigation should be performed on larger twin populations. Nevertheless, when one twin is affected, the other asymptomatic twin should also be examined for valvular heart disease.

Behavioral genetic research has been conducted at the University of Warsaw for the past 20 years. The work done at the University focuses primarily on the origins of individual differences in temperament and other personality traits. In particular, research is directed toward the traits postulated in the Regulative Theory of Temperament. We also focused on the heritability of socio-political attitudes, risk factors for human health, and post-traumatic stress disorder. The majority of the research that has been carried out is grounded in twin and family studies, although recent work based on molecular techniques has also been developed. This article reviews the most important directions and findings of behavioral genetics research at the University of Warsaw.

Background: Few, and inconsistent, studies have showed high heritability of some parameters of the anterior segment of the eye; however, no heritability of anterior chamber volume (ACV) has been reported, and no study has been performed to investigate the correlation between the ACV and central corneal thickness (CCT). Methods: Anterior segment measurements (Pentacam, Oculus) were obtained from 220 eyes of 110 adult Hungarian twins (41 monozygotic and 14 same-sex dizygotic pairs; 80% women; age 48.6 ± 15.5 years) obtained from the Hungarian Twin Registry. Results: Age- and sex-adjusted heritability of ACV was 85% (bootstrapped 95% confidence interval; CI: 69% to 93%), and 88% for CCT (CI: 79% to 95%). Common environmental effects had no influence, and unshared environmental factors were responsible for 12% and 15% of the variance, respectively. The correlation between ACV and CCT was negative and significant (rph = −0.35, p < .05), and genetic factors accounted for the covariance significantly (0.934; CI: 0.418, 1.061) based on the bivariate Cholesky decomposition model. Conclusion: These findings support the high heritability of ACV and central corneal thickness, and a strong genetic covariance between them, which underscores the importance of identification of the specific genetic factors and the family risk-based screening of disorders related to these variables, such as open-angle and also angle closure glaucoma and corneal endothelial alterations.

Chromosome 17q21.31 microdeletion syndrome is a genomic disorder caused by a recurrent 600 kb long deletion. The deletion affects the region of a common inversion present in about 20% of Europeans. The inversion is associated with the H2 haplotype carrying additional low-copy repeats susceptible to non-allelic homologous recombination, and this haplotype is prone to deletion. No instances of 17q21.31 deletions inherited from an affected parent have been reported, and the deletions always affected a parental chromosome with the H2 haplotype. The syndrome is characterized clinically by intellectual disability, hypotonia, friendly behavior and specific facial dysmorphism with long face, large tubular or pear-shaped nose and bulbous nasal tip. We present monozygotic twin sisters showing the typical clinical picture of the syndrome. The phenotype of the sisters was very similar, with a slightly more severe presentation in Twin B. The 17q21.31 microdeletion was confirmed in both patients but in neither of their parents. Potential copy number differences between the genomes of the twins were subsequently searched using high-resolution single nucleotide polymorphism (SNP) and comparative genome hybridisation (CGH) arrays. However, these analyses identified no additional aberrations or genomic differences that could potentially be responsible for the subtle phenotypic differences. These could possibly be related to the more severe perinatal history of Twin B, or to the variable expressivity of the disorder. In accord with the expectations, one of the parents (the mother) was shown to carry the H2 haplotype, and the maternal allele of chromosome 17q21.31 was missing in the twins.

The International Society for Twin Studies has lost a valued friend and colleague. Dr Louis Keith, Emeritus Professor of Obstetrics and Gynecology at Northwestern University, in Chicago, passed away on Sunday, July 6, 2014. His life and work with twins will be acknowledged at the November 2014 International Twin Congress in Budapest, Hungary. Next, twin research reports on the severity of asthma symptoms, a case of chimerism, and factors affecting DNA breakage and repair mechanisms are reviewed. Media reports cover twins born apart, elevated twin frequencies, a celebrity father of twins, and a family's decision to keep conjoined twins together.

The world of twin research and the medical specialty of Obstetrics and Gynecology have lost a giant. Dr Louis G. Keith passed away on July 6, 2014 at the age of 79. Always full of optimism and energy, and considered indefatigable by friends and family, Dr Louis Keith returned from one of his many world lecture tours in June of this year and after two days of feeling tired received a surprise diagnosis of an occult Stage 4 kidney cancer. He died comfortably at home 2 weeks later surrounded by family and friends. His practical and elegant charm was intact to the end, as he counseled those close to him not to be sad, saying, ‘We should all celebrate that I have been fortunate to have the most amazing life imaginable.’