Preterm and term labour in multiple pregnancies.

The association between multiple pregnancy and preterm labour is well-established, with >50% of multiple births delivering before 37 weeks. However, there remains limited understanding of the factors predisposing to early delivery of twins. Physiological stimuli to the onset of parturition, including stretch, placental corticotrophin-releasing hormone and lung maturity factors, may be stronger in multiple pregnancies due to the increased fetal and placental mass. Pathological processes including infection and cervical insufficiency also have a role. Treatments that prevent preterm birth in singleton pregnancies, such as progesterone and cervical cerclage appear to be ineffective in multiple pregnancies. This article reviews aspects of preterm birth in twins and higher order multiples including epidemiology, prediction and prevention of preterm labour and potential mechanisms controlling onset of parturition. Evidence relating to the management of labour in preterm and term multiples is also discussed.

Twinning in the offspring of parents with chronic radiation exposure from nuclear testing in Kazakhstan.

The population of the Semipalatinsk region of Kazakhstan was chronically exposed to radioactive fallout from above-ground nuclear tests conducted during 1949-1956 by the Soviet Union. We investigated the effect of radiation exposure and other factors on risks of twinning overall and of same- and different-sex twinning and hence estimated dizygotic and monozygotic twinning rates in 11,605 deliveries around Semipalatinsk, 141 of which were twin, to 3992 mothers exposed to fallout during 1949-1956. Overall, the same-sex twinning rate was 7.85 [95% confidence interval (CI): 6.24, 9.47] per 1000 and the opposite-sex twinning rate was 4.45 (95% CI: 3.23, 5.67). Twinning rates did not differ significantly between radiation exposure categories, parental age at main radiation exposure, or year of birth. Different-sex, but not same-sex, twinning increased with maternal age (P(trend) = 0.04) but not with other demographic factors and was increased soon after radiation exposure [OR = 4.08 (95% CI: 1.11, 15.07)] for births occurring within 5 years compared with more than 20 years after exposure; this effect was similar in villages with low and high radiation exposure, however, so interpretation is uncertain.

Preliminary evidence that estradiol moderates genetic influences on disordered eating attitudes and behaviors during puberty.

BACKGROUND: Puberty moderates genetic influences on disordered eating attitudes and behaviors, with little genetic influence before puberty but large (50%) genetic effects during and after puberty. To date, however, nothing is known about the mechanisms that underlie these effects. Estradiol is a particularly promising candidate, as estrogens become elevated at puberty and regulate gene transcription within neurotransmitter systems important for eating-related phenotypes. The aim of this pilot study was to examine whether estradiol levels moderate genetic influences on disordered eating during puberty. METHOD: Participants included 198 female twins (ages 10-15 years) from the Michigan State University Twin Registry. Disordered eating attitudes and behaviors were assessed with the total score, weight preoccupation, body dissatisfaction and binge eating/compensatory behavior subscales of the Minnesota Eating Behavior Survey (MEBS). Afternoon saliva samples were assayed for estradiol levels. Moderation of genetic effects was examined by comparing twin correlations in low versus high estradiol groups. RESULTS: In the low estradiol group, monozygotic (MZ) and dizygotic (DZ) twin correlations for all MEBS scales were similar, suggesting little genetic influence. In the high estradiol group, the MZ twin correlation was more than double the DZ twin correlation, indicating the presence of genetic effects. Findings could not be accounted for by age, body mass index or the physical changes of puberty. CONCLUSIONS: Estradiol may be one important moderator of genetic effects on disordered eating during puberty. Larger twin studies are needed to replicate this pilot work and quantify the extent of genetic moderation.

An outcome-based approach for the creation of fetal growth standards: do singletons and twins need separate standards?

Contemporary fetal growth standards are created by using theoretical properties (percentiles) of birth weight (for gestational age) distributions. The authors used a clinically relevant, outcome-based methodology to determine if separate fetal growth standards are required for singletons and twins. All singleton and twin livebirths between 36 and 42 weeks' gestation in the United States (1995-2002) were included, after exclusions for missing information and other factors (n = 17,811,922). A birth weight range was identified, at each gestational age, over which serious neonatal morbidity and neonatal mortality rates were lowest. Among singleton males at 40 weeks, serious neonatal morbidity/mortality rates were lowest between 3,012 g (95% confidence interval (CI): 3,008, 3,018) and 3,978 g (95% CI: 3,976, 3,980). The low end of this optimal birth weight range for females was 37 g (95% CI: 21, 53) less. The low optimal birth weight was 152 g (95% CI: 121, 183) less for twins compared with singletons. No differences were observed in low optimal birth weight by period (1999-2002 vs. 1995-1998), but small differences were observed for maternal education, race, parity, age, and smoking status. Patterns of birth weight-specific serious neonatal morbidity/neonatal mortality support the need for plurality-specific fetal growth standards.

Association of AKT1 with verbal learning, verbal memory, and regional cortical gray matter density in twins.

AKT1, encoding the protein kinase B, has been associated with the genetic etiology of schizophrenia and bipolar disorder. However, minuscule data exist on the role of different alleles of AKT1 in measurable quantitative endophenotypes, such as cognitive abilities and neuroanatomical features, showing deviations in schizophrenia and bipolar disorder. We evaluated the contribution of AKT1 to quantitative cognitive traits and 3D high-resolution neuroanatomical images in a Finnish twin sample consisting of 298 twins: 61 pairs with schizophrenia (8 concordant), 31 pairs with bipolar disorder (5 concordant) and 65 control pairs matched for age, sex and demographics. An AKT1 allele defined by the SNP rs1130214 located in the UTR of the gene revealed association with cognitive traits related to verbal learning and memory (P = 0.0005 for a composite index). This association was further fortified by a higher degree of resemblance of verbal memory capacity in pairs sharing the rs1130214 genotype compared to pairs not sharing the genotype. Furthermore, the same allele was also associated with decreased gray matter density in medial and dorsolateral prefrontal cortex (P < 0.05). Our findings support the role of AKT1 in the genetic background of cognitive and anatomical features, known to be affected by psychotic disorders. The established association of the same allelic variant of AKT1 with both cognitive and neuroanatomical aberrations could suggest that AKT1 exerts its effect on verbal learning and memory via neural networks involving prefrontal cortex.

Prevalência de nascimentos gemelares em Pelotas, Rio Grande do Sul, Brasil / Prevalence of twin births in Pelotas, in the State of Rio Grande do Sul, Brazil

OBJETIVOS: avaliar a prevalência de nascimentos gemelares em Pelotas, RS, em três períodos da última década e a influência de alguns fatores sobre este processo. MÉTODOS: estudo de corte transversal (série temporal), baseado no banco de dados do Programa de Monitorização de Defeitos Congênitos, onde se encontram registrados todos os nascimentos ocorridos nos cinco hospitais da cidade de Pelotas, nos anos de 1993, 1997 e 2003. RESULTADOS: a taxa média de gêmeos por mil nascimentos foi de 8,95ë (monozigóticos=2,20ë e dizigóticos=6,76ë ). A taxa de triplos ficou em 0,07ë . A taxa total de nascimentos gemelares, assim como de gêmeos monozigóticos e dizigóticos sofreu elevação no período. A média de idade (27,53 anos) e da ordem gestacional (2,35) das mães de gêmeos foi significativamente mais elevada do que das mães de únicos (26,03 anos e 2,14) respectivamente. Verificaram-se números aproximados de partos gemelares e únicos nos diferentes grupos de renda materna analisados. CONCLUSÕES: as mães com idade maior ou igual a 30 anos foram responsáveis pelo aumento da taxa de gêmeos em Pelotas. A média mais elevada de ordem gestacional em mães de gemelares descartou o uso significativo de técnicas de reprodução assistida.

OBJECTIVES: to evaluate the prevalence of twin births in Pelotas, Rio Grande do Sul, Brazil, during three periods, and the influence of a number of factors on this occurrence. METHODS: a cross-cutting (multiple time series) study was carried out, using the database of the Congenital Defect Monitoring Program, which registers all of the births occurring in the five hospitals of the city of Pelotas, for the years 1993, 1997 and 2003. RESULTS: the mean prevalence of twin births per thousand births (ë )t was 8.95ë (monozygotic=2.20ë and dizygotic=6.76ë ). The prevalence of triplets was 0.07ë . The total prevalence for twin births, in the case of both monozygotic and dizygotic twins rose over the period studied. The mean age of the mother (27.53 years) and the order in the series of gestations (2.35) were significantly higher in cases of twin births than in cases of the birth of a single infant (26.03 years and 2.14 respectively). CONCLUSIONS: mothers aged >30 years were responsible for the increase in the prevalence of twin births in Pelotas. The higher mean position in a sequence of gestations among mothers of twins ruled out the significance of the use of fertility treatment techniques.

Intelligence in early adulthood and life span up to 65 years later in male elderly twins.

BACKGROUND: Previous research has reported that greater intelligence in early life is associated with longer lifespan. Whether this relationship is mediated by genetic factors or environmental factors, some of which could be modified by an individual, is unclear. OBJECTIVE: We examined the association between intelligence test scores, obtained during the 1940s, and age at death in a group of 492 male twin pairs, members of the National Academy of Sciences--National Research Council Twins Registry of WWII veterans. DESIGN: Using self-report information collected in th 1960s, we examined whether modifiable risk factors for mortality, such as use of tobacco and alcohol, cardiovascular disease, and body mass index altered the association between intelligence and longevity. RESULTS: When each member of a twin pair was treated as an independent observation, higher intelligence test scores were associated with longer life span (P = 0.0002). Modifiable risk factors were associated with life span as expected. However, in co-twin control analyses in which one twin served as the control for the other twin, neither intelligence nor any modifiable risk factors showed a significant association with life span. CONCLUSION: Our findings suggest that genetics and early life environmental factors contribute heavily to lifespan and when one controls for these factors using twins, the effect of intelligence on longevity is diminished.

Increased vascular endothelial growth factor and pregnancy-associated glycoproteins, but not insulin-like growth factor-I, in maternal blood of cows gestating twin fetuses.

Differences in placental mass and vascularity exist between cows gestating single vs. multiple fetuses. Therefore, the association between fetal number and placental development or function was assessed by comparing concentrations of vascular endothelial growth factor (VEGF), pregnancy-associated glycoproteins (PAG), IGF-I, and progesterone in the maternal blood of cattle selected for twin births and gestating 1 (n = 23) vs. 2 (n = 17) fetuses. Samples of jugular venous blood were collected serially at a mean of 57, 121, 192, and 234 d (range within groups was 20 d) after AI. Plasma concentrations of VEGF, IGF-I, and progesterone were measured by double-antibody RIA, and of PAG by an indirect sandwich ELISA. Concentrations of VEGF and progesterone were greater (P < 0.05) in dams with twin vs. single fetuses. Maternal VEGF concentrations did not differ among collection times, but progesterone concentrations increased (P < 0.01) between d 192 and 234. Conversely, PAG concentrations were low at d 57 and 121 and did not differ between dams carrying singles or twins. However, the subsequent increase (P < 0.01) in PAG was greater in dams with twins, resulting in greater (P < 0.01) PAG concentrations for dams with twins at d 192 and 234 (type of birth x time; P < 0.01). Maternal IGF-I concentrations were unaffected by fetal number. Because corpora lutea persisted for the duration of the evaluation period, maternal progesterone concentrations were likely related to the number of corpora lutea rather than the number of fetuses. It is postulated that the greater PAG and VEGF concentrations in the blood of dams gestating twins are the result of a larger uteroplacental mass, including increased numbers of binucleate cells and increased angiogenesis and vasculogenesis associated with a twin pregnancy. Although PAG and VEGF were elevated in dams gestating twins, variability within and among birth groups limits the use of PAG or VEGF measurements for the diagnosis of twins.

[An attempt to determine the variability of thermal phenotypes in monozygotic twins]. / Fenotypy termiczne blizniat monozygotycznych--próba oceny ich zróznicowania.

INTRODUCTION: All solid bodies emit electromagnetic radiation at temperatures above absolute zero. The radiation spectrum depends, among other factors, on temperature. Thermovision is a method in which an infrared camera is used to record infrared radiation (IR) emitted by human skin. It is widely used in medicine, for instance to diagnose inflammation of the skin, some types of neoplasms, collagenosis, and peripheral vascular disease. The literature, however, lacks reports on the variability in thermal emission by the skin of healthy individuals or twins. Interpretation of the results is based on simply analysing the subject individually or comparing symmetrical body sides. Hence, there is a need to study thermal emission using monozygotic twins as a model. MATERIAL AND METHODS: An attempt was made in the present study to determine the variability of thermal phenotypes of faces, backs, and hands in monozygotic twins (MZ), compare thermal emission in MZ and dizygotic twins (DZ), and establish the thermal norm. Using the ThermaCAM SC500 camera, 44 pairs of MZ and 15 pairs of DZ were studied. Descriptive statistics are given as means, standard deviation, and max. and min. values. The following tests were used for statistical analysis: Shapiro-Wilk's, Snedecor's, Brown-Forsythe's, Mann-Whitney's U, and Kruskal-Wallis. Data from the digital image analyser were tested using the cluster analysis methods, especially the k-means method. CONCLUSIONS: The following conclusions were drawn: 1. Full genetic identity does not produce a thermal consistency within the range of isotherms tested, whether in relation to their values or distribution. 2. Differences in the thermal image may have their source in ontogenetic development during intra-uterine and postnatal stages and may be related to individual differences in adaptation to the environment. 3. These results are potentially useful to compare physiological states between individuals and to differentiate pathological changes. 4. The results of this study do not allow for any conclusions regarding the thermal norm. However, a basis has been created for further research in larger samples of the population.

Identical triplets and twins developed from isolated blastomeres of 8- and 16-cell mouse embryos supported with tetraploid blastomeres.

We studied the developmental potential of single blastomeres from early cleavage mouse embryos. Eight- and sixteen-cell diploid mouse embryos were disaggregated and single blastomeres from eight-cell embryos or pairs of sister blastomeres from sixteen-cell embryos were aggregated with 4, 5 or 6 tetraploid blastomeres from 4-cell embryos. Each diploid donor embryo gave eight sister aggregates, which later were manipulated together as one group (set). The aggregates were cultured in vitro until the blastocyst stage, when they were transferred (in sets) to the oviducts of pseudopregnant recipients. Eighteen live foetuses or pups were obtained from the transfer (11.0% of transferred blastocysts) and out of those, eleven developed into fertile adults (one triplet, one pair of twins and four singletons). In all surviving adults, pups and living foetuses, only diploid cells were detected in their organs and tissues as shown by analysis of coat pigmentation and distribution of glucose phosphate isomerase isoforms. In order to explain the observed high rate of mortality of transferred blastocysts, in an accompanying experiment, the diploid and tetraploid blastomeres were labelled with different fluorochromes and then aggregated. These experiments showed the diploid cells to be present not only in the inner cell mass (ICM) but also in the trophectoderm. The low number of diploid cells and the predominance of tetraploid cells in the ICM of chimaeric blastocysts might have been responsible for high postimplantation mortality of our experimental embryos.

Gender mix in twins and fetal growth, length of gestation and adult cancer risk.

This study evaluated the effect of gender mix (the gender combinations of twin pairs) on fetal growth and length of gestation, and reviewed the literature on the long-term effects of this altered fetal milieu on cancer risk. In singletons, it is well established that females weigh less than males at all gestations, averaging 125-135 g less at full term. This gender difference is generally believed to be the result of the effect of androgens on fetal growth. The gender difference in fetal growth is greater before the third trimester and less towards term, with males growing not only more, but also earlier than females. Plurality is a known risk factor for reduced fetal growth and birthweight. Compared with singletons, the mean birthweight percentiles of twins fall substantially (by 10% or more) below the singleton 10th percentile by 28 weeks, below the singleton 50th percentile by 30 weeks, and below the singleton 90th percentile by 34 weeks. In unlike-gender twin pairs, it has been reported that the female prolongs gestation for her brother, resulting in a higher birthweight for the male twin than that of like-gender male twins. Other researchers have demonstrated that females in unlike-gender pairs had higher birthweights than females in like-gender pairs. Analyses from our consortium on 2491 twin pregnancies with known chorionicity showed longer gestations and faster rates of fetal growth in both males and females in unlike-gender pairs compared with like-gender male or female pairs, although these differences were not statistically significant. The post-natal effects for females growing in an androgenic-anabolic environment include increased sensation-seeking behaviour and aggression, lowered visual acuity, more masculine attitudes and masculinising effects of the auditory system and craniofacial growth. In contrast, there is no evidence to suggest that there might be a similar feminising effect on males from unlike-gender pairs. This hormonal exposure in utero may influence adult body size and susceptability to breast cancer.

Fetal phenotypes and neonatal and early childhood outcomes in twins.

OBJECTIVES: The purpose of this study was to evaluate factors associated with, and postnatal consequences of, altered patterns of fetal growth in twins. STUDY DESIGN: Fetal growth was measured at 28 weeks' gestation on 218 twins, including head circumference, abdominal circumference, and femur length, and characterized as > or < or =10th %ile; children were followed up until the age of three years. Logistic regression was used to generate odds ratios of perinatal factors associated with reduced fetal growth. RESULTS: Maternal height <62 inches was associated with reductions in femur length (adjusted odds ratio [AOR] 3.88, 95% CI 1.42-10.57) and abdominal circumference (AOR 8.63, 95% CI 2.41-30.94), while primiparity had a protective effect on both of these fetal measurements (AOR 0.28, 95% CI 0.13-0.64, and AOR 0.18, 95% CI 0.06-0.60, respectively), as well as head circumference (AOR 0.32, 95% CI 0.15-0.69). Smoking adversely affected femur and head growth (AOR 24.10, 95% CI 3.69-157.57, and AOR 10.82, 95% CI 1.73-67.79, respectively). Fetal reduction adversely affected femur and abdomen growth (AOR 5.85, 95% CI 1.52-22.51 and AOR 4.90, 95% CI 1.01-23.86, respectively), and monochorionicity and maternal weight gain <0.65 lb/wk before 20 weeks adversely affected femur growth (AOR 5.47, 95% CI 1.65-18.10, and AOR 3.39, 95% CI 1.34-8.59, respectively). At age 3 years, all categories of twins with reduced growth by 28 weeks' gestation were significantly shorter in height, and those with reduced abdominal circumference or head circumference at 28 weeks were also significantly lighter in weight compared with twins with adequate fetal growth by 28 weeks' gestation. CONCLUSION: These data identify short maternal height, smoking, monochorionicity, fetal reduction, and inadequate weight gain before 20 weeks as risk factors associated with reduced twin fetal growth by 28 weeks' gestation and significant residual reductions in height and weight through 3 years of age.