Repercusión en los resultados neonatales del intervalo de tiempo de nacimiento entre gemelos / Effect of twin-to-twin delivery time interval on neonatal outcome

Objetivo. Evaluar los factores que pueden influir sobre el intervalo de tiempo de nacimiento entre gemelos y sobre el resultado neonatal a corto plazo del segundo gemelo. Material y métodos. Se realizó un estudio descriptivo retrospectivo a través de la base de datos informatizada y la revisión de las historias clínicas de las pacientes atendidas en el Hospital Universitario Miguel Servet desde enero de 2005 hasta diciembre de 2007. Se ha realizado un análisis estadístico para determinar los factores que potencialmente pueden afectar el intervalo de tiempo de nacimiento entre gemelos incluyendo: características maternas, edad gestacional, tipo de parto, discordancia de pesos fetales, pH de arteria umbilical y puntuaciones en el test de Apgar. Resultados. De los 13.340 partos registrados durante el periodo de estudio, 206 gestaciones gemelares se ajustaron a los criterios de inclusión. La mayoría de los segundos gemelos (79,6%) nacieron en los 5 min siguientes al parto del primer gemelo. Las características maternas como la edad, la paridad, la obesidad y el tabaquismo no se relacionaron con el incremento del intervalo al nacimiento. Un mayor intervalo se asoció a un aumento de riesgo de puntuaciones bajas en el test de Apgar y a un descenso de los valores de pH de arteria umbilical. El parto instrumental se asoció a un incremento del intervalo de tiempo. Conclusión. Basándonos en nuestros datos y los reflejados por estudios previos podemos decir que el intervalo de tiempo al nacimiento entre gemelos parece ser un factor de riesgo independiente para un resultado neonatal adverso (AU)

Objective. To evaluate the factors influencing twin-to-twin delivery time interval and the short-term outcome of the second twin. Material and methods. We performed a retrospective, descriptive study by reviewing a computerized database and the medical records of pregnant women attending the Miguel Servet University Hospital from January 2005 to December 2007. A statistical analysis was performed to determine the factors potentially affecting twin-to-twin delivery time interval, including maternal characteristics, gestational age, mode of delivery, fetal weight discordance, umbilical artery pH and Apgar score. Results. Of the 13,430 deliveries registered during the study period, 206 twin pregnancies met the inclusion criteria. Most (79.6%) of the second twins were born within 5min of delivery of the first twin. Maternal characteristics such as age, parity, obesity and smoking were not related to twin-to-twin delivery time interval. A longer time interval was associated with an increased risk of low Apgar scores and a decline in umbilical artery pH in the second twin. Vaginal operative delivery was associated with an increased time interval. Conclusion. Based on our data and the results of previous studies, twin-to-twin delivery time interval seems to be an independent risk factor for adverse neonatal outcome (AU)

EEG polysomnographic study of maturational differences between twins.

The purpose of this pilot study is to asses the effects of multiple pregnancies on the maturation of the developing brain using the polysomnographic EEG recordings. Data from prospectively recorded 10 twin sets, born prematurely (mean 36 gestational week; range 33 - 38 GW) in the Split University Hospital Center, were analysed. We compared sleep architecture parameters in the twins at 37h and 44th postmenstrual age (PMA) with parameters that were expected at that PMA. The same parameters were compared within each twin pair using the Man Whitne test. At first measurement indeterminate sleep (IS) proportion was greater in the first twin than in the second one. The IS sleep proportion was 1.6 fold greater in the first twin (p=0.028), and 1,8 fold less percentage of quite sleep (QS) than the second twin (p=0.054). The length of sleep stages among the twins was similar at the second measurement. Measures of sleep architecture were not significantly different within the twins in second recording. The results of this study obtained on a relatively small number of twins (longer IS and shorter QS in the first twin at the 38th week recordings), showed that the maturational differences among twins exist in utero and shortly after birth, and then disappear until the end of the first month of the postnatal life.

Definition of intertwin birth weight discordance.

OBJECTIVE: To establish the level of birth weight discordance at which perinatal morbidity increases in monochorionic and dichorionic twin pregnancy. METHODS: This prospective multicenter cohort study included 1,028 unselected twin pairs recruited over a 2-year period. Participants underwent two weekly ultrasonographic surveillance from 24 weeks of gestation with surveillance of monochorionic twins two-weekly from 16 weeks. Analysis using Cox proportional hazards compared a composite measure of perinatal morbidity (including any of the following: mortality, respiratory distress syndrome, hypoxic-ischemic encephalopathy, periventricular leukomalacia, necrotizing enterocolitis, or sepsis) at different degrees of birth weight discordance with adjustment for chorionicity, gestational age, twin-twin transfusion syndrome, birth order, gender, and growth restriction. RESULTS: Perinatal outcome data were recorded for 977 patients (100%) who continued the study with both fetuses alive beyond 24 weeks, including 14 cases of twin-twin transfusion syndrome. Adjusting for gestation at delivery, twin order, gender, and growth restriction, perinatal mortality, individual morbidity, and composite perinatal morbidity were all seen to increase with birth weight discordance exceeding 18% for dichorionic pairs (hazard ratio 2.2, 95% confidence interval [CI] 1.6-2.9, P<.001) and 18% for monochorionic twins without twin-twin transfusion syndrome (hazard ratio 2.6, 95% CI 1.6-4.3, P<.001). A minimum twofold increase in risk of perinatal morbidity persisted even when both twin birth weights were appropriate for gestational age. CONCLUSION: : The threshold for birth weight discordance established by this prospective study is 18% both for dichorionic twin pairs and for monochorionic twins without twin-twin transfusion syndrome. This threshold is considerably lower than that defined by many retrospective series as pathologic. We suggest that an anticipated difference of 18% in birth weight should prompt more intensive fetal monitoring.

Are twins growth restricted?

It is now well established that IUGR is associated with an increased risk of a range of adult onset diseases, including cardiovascular disease, obesity, and type 2 diabetes. Infants from twin pregnancies are generally born smaller than singletons; therefore, it has been suggested that twins represent a naturally occurring model of IUGR. Although twin gestations contribute significantly to the population burden of preterm birth and small size at birth, whether twins have the same long-term health consequences as IUGR singletons remains unclear. The purpose of this review is to consider what is currently known about the clinical implications of twinning, the differences that exist between the growth and developmental profiles of singleton and twin fetuses, and to use this as a basis for exploring the question of whether fetuses conceived as twins are analogous to IUGR singletons of similar birthweight and gestation. This question is increasingly important in both the clinical and research settings, because the incidence of twinning is increasing and the long-term implications of reduced size at birth are mostly investigated in species which bear multiple offspring.

Curiouser and curiouser: genetic disorders of cortical specialization.

The processes by which cortical areas become specialized for high-level cognitive functions may be revealed by the study of familial developmental disorders such as dyslexia, dyscalculia, prosopagnosia, color agnosia and amusia. These disorders are characterised by the inability to integrate information across multiple areas and the consequent failure to develop representations of the knowledge of some category based on its associated attributes. In contrast, synesthesia may be seen as a hyper-associative condition, possibly due to a failure to properly segregate areas into distinct networks. Here, I consider recent advances in our understanding of the genetic and neurobiological bases of these conditions and the developmental mechanisms underlying the specialization of cortical areas and networks.

Added value measures in education show genetic as well as environmental influence.

Does achievement independent of ability or previous attainment provide a purer measure of the added value of school? In a study of 4000 pairs of 12-year-old twins in the UK, we measured achievement with year-long teacher assessments as well as tests. Raw achievement shows moderate heritability (about 50%) and modest shared environmental influences (25%). Unexpectedly, we show that for indices of the added value of school, genetic influences remain moderate (around 50%), and the shared (school) environment is less important (about 12%). The pervasiveness of genetic influence in how and how much children learn is compatible with an active view of learning in which children create their own educational experiences in part on the basis of their genetic propensities.

Monochorionic diamniotic twin gestations discordant for markedly enlarged nuchal translucency.

OBJECTIVE: To assess karyotypes and outcomes of monochorionic diamniotic (MCDA) twin pregnancies discordant for markedly enlarged nuchal translucency (NT) in the first trimester. METHOD: Brigham and Women's Hospital's ultrasound database was queried to identify all MCDA gestations in which one twin had NT ≥ 3.5 mm and the co-twin had normal NT. Cytogenetic results, ultrasound findings, and pregnancy outcomes were reviewed. RESULTS: Of 162 MCDA twin pairs, 11 were discordant for NT ≥ 3.5. Chromosomal abnormalities were present in three cases: one twin pair was concordant for trisomy 18; one pair discordant for mosaic trisomy 2; and one pair discordant for confined placental mosaicism (CPM) (high frequency tetraploidy). Adverse outcomes for twins with euploid or unknown karyotypes included twin reverse arterial perfusion (TRAP) sequence, growth discordance, and esophageal atresia with tracheoesophageal fistula. CONCLUSION: Postfertilization nondisjunction leading to mosaicism in one fetus, discordant phenotypes yet concordant karyotypes, and discordance for CPM were documented phenomena, supporting karyotyping of both twins. In this case series, discordant NT was a marker for chromosome abnormalities, as well as for complications specific to monochorionic gestations, including TRAP sequence, amniotic fluid discordance, and structural anomalies. Nonetheless, normal fetal anatomy and karyotype were the most common outcomes.

Associations between sports participation, cardiorespiratory fitness, and adiposity in young adult twins.

Exercise behavior, cardiorespiratory fitness, and obesity are strongly influenced by genetic factors. By studying young adult twins, we examined to what extent these interrelated traits have shared genetic and environmental etiologies. We studied 304 twin individuals selected from the population-based FinnTwin16 study. Physical activity was assessed with the Baecke questionnaire, yielding three indexes: sport index, leisure-time index, and work index. In this study, we focused on sport index, which describes sports participation. Body composition was determined using dual-energy X-ray absorptiometry and cardiorespiratory fitness using a bicycle ergometer exercise test with gas exchange analysis. The Baecke sport index was associated with high maximal oxygen uptake adjusted for lean body mass (Vo(2max)[adj]) (r = 0.40), with low body fat percentage (BF%) (r = -0.44) and low waist circumference (WC) (r = -0.29). Heritability estimates for the key traits were as follows: 56% for sport index, 71% for Vo(2max)[adj], 77% for body mass index, 66% for WC, and 68% for BF%. The association between sport index and Vo(2max) was mostly explained by genetic factors (70%), as were both the association between sport index and BF% (71%) and that between sport index and WC (59%). Our results suggest that genetic factors explain a considerable part of the associations between sports participation, cardiorespiratory fitness, and obesity.

Abdominal circumference ratio for the diagnosis of intertwin birth weight discordance.

OBJECTIVES: We assessed the accuracy of predicting severe twin birth weight discordance (>25%) using the estimated fetal weights (EFW) and abdominal circumference (AC) ratio. METHOD: A cohort of twin gestations underwent ultrasound examinations within two weeks from birth. We focused on the accuracy of EFW and on the diagnosis of severe birth weight discordance by the difference in EFWs and the AC ratio. RESULTS: The 661 eligible twin pairs included 51 (7.7%) severely discordant pairs. The accuracy of an EFW to predict the actual birth weight was quite poor, with an acceptable specificity (96.4%), but low sensitivity (28.6-40.5%), to detect severely discordant pairs, whereas an AC ratio of 1.3 detected these discordant pairs with sensitivity and specificity of 97.3-100% and 99.6-99.7%, respectively. CONCLUSION: By comparing EFWs, 59.5-71.4% of discordant pairs >25% are missed, whereas an AC ratio >1.3 would identify almost all cases.

Intra-uterine exposure to dual fetal programming sequences among surviving co-twins.

OBJECTIVE: The dynamics of fetal programming following in utero demise of a co-twin are poorly understood. METHODS: The authors examined fetal programming using a unique application of the change-point analysis method, and identified two types of fetal programming that occurred when a viable twin sibling died in utero, while the co-twin survived. RESULTS: In one type, the initial twin fetal programming trajectory was maintained while in a subset of surviving co-twins a "switch" from a twin to a singleton fetal program (dual fetal programming exposure) was observed. The results suggest that the timing in utero of conversion from a twin to a singleton programming pattern occurred slightly earlier among opposite-sex than in same-sex surviving co-twins. CONCLUSION: For the conversion from a twin to a singleton program to happen, the surviving co-twin must have attained a "critical mass" when the twin sibling died. Whereas, for same-sex surviving co-twins the critical mass for conversion was the 80th percentile of gestational-age specific birth weight, opposite-sex surviving co-twins converted at a lower critical mass (70th percentile). These novel findings warrant further study to confirm the new hithertofore unknown phenomenon of dual fetal programming sequence, and to determine the implications in terms of subsequent morbidity or mortality during infancy, childhood and adult life.

Network analysis of resting state EEG in the developing young brain: structure comes with maturation.

During childhood, brain structure and function changes substantially. Recently, graph theory has been introduced to model connectivity in the brain. Small-world networks, such as the brain, combine optimal properties of both ordered and random networks, i.e., high clustering and short path lengths. We used graph theoretical concepts to examine changes in functional brain networks during normal development in young children. Resting-state eyes-closed electroencephalography (EEG) was recorded (14 channels) from 227 children twice at 5 and 7 years of age. Synchronization likelihood (SL) was calculated in three different frequency bands and between each pair of electrodes to obtain SL-weighted graphs. Mean normalized clustering index, average path length and weight dispersion were calculated to characterize network organization. Repeated measures analysis of variance tested for time and gender effects. For all frequency bands mean SL decreased from 5 to 7 years. Clustering coefficient increased in the alpha band. Path length increased in all frequency bands. Mean normalized weight dispersion decreased in beta band. Girls showed higher synchronization for all frequency bands and a higher mean clustering in alpha and beta bands. The overall decrease in functional connectivity (SL) might reflect pruning of unused synapses and preservation of strong connections resulting in more cost-effective networks. Accordingly, we found increases in average clustering and path length and decreased weight dispersion indicating that normal brain maturation is characterized by a shift from random to more organized small-world functional networks. This developmental process is influenced by gender differences early in development.

Twinning frequency of Japanese Macaques (Macaca fuscata) at Takasakiyama.

In a wild-living, artificially provisioned population of Japanese macaques at Takasakiyama in southern Japan, nine sets of twins were recorded from 12,392 known deliveries over a 56-year study period. Recorded twinning frequency was 0.073%. During the first 28-year period, artificial food was given until macaques were satiated and population size increased rapidly. In the second 28-year period, provisioned food was restricted to about half of the former period's calorific content. Seven sets of twins were born in the first period and two sets in the second. Twining frequency in the two periods was 0.137 and 0.027%, respectively. In comparing studies of other Catarrhine primate samples, we hypothesize that twinning frequency is influenced by living conditions, and we suggest that living conditions should be carefully evaluated in studies of twinning frequency.

Birth weight discordance of twin pairs and their subsequent growth patterns.

BACKGROUND: Few studies have compared the growth of a twin with its co-twin and particularly in relation to birth weight discordance. AIM: The study investigated how the degree of birth weight discordance affected subsequent growth. METHODS: Birth weight discordance of 762 twin pairs was determined. Subsequent weight, height and occipital-frontal head circumference (OFC) measurements were obtained between the ages of 2-9 years. Corresponding standard deviations scores (SDS) were analysed according to birth weight discordance, sex and zygosity. Weight status was taken into account by assigning twins into sub-groups according to whether they were the heavier twin at birth and remained heavier, became the lighter of the twin pair or had the same weight, for subsequent measurements. RESULTS AND CONCLUSIONS: The degree of birth weight discordance had little effect on subsequent growth except in monozygotic (MZ) twins with >20% discordance. Severe low birth weight ( < 1.95 kg) is more significant in suppressing subsequent growth than the degree of discordance per se. A surprisingly high proportion of twins reversed their weight status when reviewed at an older age.

Early pregnancy growth and pregnancy outcome in twin pregnancies.

OBJECTIVES: The objective of this study was to determine the association of crown-rump length (CRL) discrepancy in monochorionic and dichorionic twins with subsequent pregnancy outcomes. METHOD: A retrospective analytical study was performed among 660 twin pregnancies over 12 years in one fetal medicine tertiary referral center in the United Kingdom. A literature search was performed to identify all reports in the English language literature in this topic between 1998 and 2009. RESULTS: Five hundred and six dichorionic and 154 monochorionic twin pregnancies were studied. Median percentage CRL discordance in monochorionic and dichorionic pregnancies was not different (3.9 +/- 8.34, range 0-59 and 3.2 +/- 5.65 range 0-37.5, respectively, p = 0.225). Single or double fetal loss was higher in monochorionic twins than the dichorionic twins. Loss rate was 17.53% (27) and 3.95% (20) respectively (p = < .0001). CRL disparity and birth weight discordancy showed statistically significant correlation (Spearman's rho, p = 0.040). Statistically significant correlation was seen between percentage CRL disparity and pregnancy loss rate (p = 0.008). However, the sensitivity of this CRL discrepancy to detect subsequent fetal loss or birth weight discordance is poor. INTERPRETATION: CRL discrepancy is independent of chorionicity in twins. CRL discrepancy is correlated to subsequent pregnancy loss and birth weight discordance, but the clinical utility of this observation is limited. The difference in twin CRL at 11-14 weeks is likely to represent physiological variation in a majority of cases.

Primary tooth emergence in Australian children: timing, sequence and patterns of asymmetry.

BACKGROUND: Information on the timing and sequence of human tooth emergence is valuable when analysing human growth and development, predicting the age of individuals, and for understanding the effects of genetic and environmental influences on growth processes. This paper provides updated data on the timing and sequence of primary tooth emergence in Australian children for both clinicians and researchers. METHODS: Twins were recruited from around Australia with data collected through parental recording of twins' primary tooth emergence. One twin from each pair was then randomly selected to enable the calculation of descriptive statistics for timing, sequence and asymmetry in tooth emergence. RESULTS: The first and last primary teeth emerged, on average, at 8.6 months and 27.9 months, respectively, with teeth emerging in the order: central incisor, lateral incisor, first molar, canine, second molar. Left-side antimeric teeth were more likely to emerge before their right-side counterparts but this was not statistically significant. At least 35% of all antimeric pairs had emerged within two weeks of each other, serving as a useful guideline for assessing symmetrical versus asymmetrical development. CONCLUSIONS: Primary tooth emergence in Australian twins is occurring later than reported previously for Australian singletons but is consistent with findings for singletons in other ethnic groups. The most common sequence of primary tooth emergence appears to be consistent in twins and singletons and has not changed over time.

Multidimensional assessment of health status in a dependent sample: an exploratory analysis for adult twins in China.

Health is a multidimensional and continual concept. Traditional latent analytic approaches have inherent deficits in capturing the complex nature of the concept; however, the Grade of Membership (GoM) model is well suited for this problem. We applied the GoM method to a set of 31 indicators to construct ideal profiles of health status based on physical, mental and social support items among 848 adult twins from Qingdao, China. Four profiles were identified: healthy individuals (pure type I), individuals with personality disorders (pure type II), individuals with mental impairments (pure type III) and individuals with physical impairments (pure type IV). The most frequently occurring combination in this population was profiles I, II, IV (14.74%), followed by profiles I, II, III, IV (13.44%), and then type I (11.08%). Only 13.56% of subjects fell completely into one single pure type, most individuals exhibited some of the characteristics of two or more pure types. Our results indicated that, compared to conventional statistical methods, the GoM model was more suited to capture the complex concept of health, reflecting its multidimensionality and continuity, while also exhibiting preferable reliability. This study also made an important contribution to research on GoM application in non-independent samples.

The world of twins: an update.

In last years, owing to the widespread availability of assisted-reproduction technology, multiple pregnancy rates in Western countries have increased. In twin pregnancies, an increased rate of gestational complications, intrauterine growth restriction (IUGR), preterm birth and severe perinatal conditions is present. These complications are more frequent in monozygotic twins compared to dizygotic twins as well as an increased relative risk of chromosomal abnormalities and congenital malformation. Monochorionic twins are at higher risk for complications, since they share a common placenta where an imbalance in unidirectional arteriovenous anastomoses can lead to twin–twin transfusion syndrome. This extremely dangerous condition, if not early identified, can determine severe fetal complications with mortality rates that, in case of no treatment, reaches 90%. Laser photocoagulation is the treatment of choice in severe twin-to-twin transfusion syndrome with high survival rate. IUGR occurs more frequently in MC twins and along with prematurity and perinatal pathology is considered an important determinant of developmental delay.

The source of error in the estimation of intertwin birth weight discordance.

OBJECTIVE: to assess the accuracy of paired estimated fetal weights (EFWs) to predict three levels of twin birth weight discordance (>15%, >20% and >25%). METHOD: a cohort of twin pairs underwent ultrasound examinations within 2 weeks from birth. We calculated the frequency of under- and overestimation of the actual birth weight (< or >10%, respectively) in the entire cohort as well in the subset of mono- and dichorionic pairs. RESULTS: discordance was largely underestimated (observed 10.4 ± 0.8% compared to actual 19.2 ± 1.1%, P=0.001) because the larger twin was more frequently underestimated [30.6 vs. 17.7%, odds ratio (OR) 2.0, 95% confidence interval (CI) 1.1, 3.9 in the entire cohort, and 34.2 vs. 13.1%, OR 3.4, 95% CI 1.4, 8.4 in the dichorionic pairs]. Overall, the specificity for detecting the three levels of discordance was adequate (91.5-94.2%) but the sensitivity was poor (11.1-17.8%) and tended to decrease with increasing discordance level. CONCLUSION: the poor ability of paired EFWs to diagnose birth weight discordance results from underestimation of the larger twin.

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.

Twin birth weight discordance: associated factors and outcome.

OBJECTIVE: To determine the frequency of twin birth weight discordance and compare the maternal characteristics and neonatal outcome in discordant and concordant twin gestations. STUDY DESIGN: Cross-sectional comparative study. PLACE AND DURATION OF STUDY: MCH Centre, Unit-II, Pakistan Institute of Medical Sciences, Islamabad, from January 2005 to December 2007. METHODOLOGY: All twin gestations delivered at > 28 weeks gestation were included. Birth weight discordance was defined as > 20% twin birth weight difference and two groups were developed accordingly. Prenatal complications, gestational age at delivery, mode of delivery and neonatal outcome were compared using chi-square and Fischer exact test with significance at p < 0.05. RESULTS: Two hundred and fifty three pairs of twins were delivered during the three years. The frequency of birth weight discordance was 19% (48 verses 205 concordant twin pairs). Preterm delivery (68% vs. 25%), pre-labour rupture of membranes (33% vs. 9%) and pregnancy induced hypertension (22% vs. 12%) were significantly more frequent in birth weight discordant compared to concordant gestations. The cesarean section rate was 29% and 21% respectively. Twelve (12%) discordant and 29 (7%) concordant infants required NICU admission. There were 10 intrauterine deaths (10%) and one (1%) neonatal death among the discordant twins while 18 (4%) intrauterine deaths and 10 (2.4%) neonatal deaths occurred in concordant twins, resulting in uncorrected PNMR of 114.5 and 43.9 per 1000 births respectively. CONCLUSION: Twin pregnancies with birth weight discordance are at higher risk of prenatal complications and have less favourable perinatal outcome. Their timely antenatal detection is, therefore, important for closer surveillance and timely delivery.