1,720,957 research outputs found
P19.18: Polyhydramnios in the sac of the parasitic twin: atypical manifestation of twin-reversed arterial perfusion sequence
No full textOutcome of monochorionic diamniotic twin pregnancies followed at a single center
No full textOBJECTIVE:
We aim to evaluate the outcome of a cohort of monochorionic diamniotic twin pregnancies followed from the first trimester onwards at a single center.
METHOD:
This was a retrospective analysis of prospectively collected data from a series of 300 monochorionic diamniotic twin pregnancies referred to our twin clinic between 2001 and 2012. Pregnancies were followed from the first trimester and fortnightly after 16 weeks of gestation. Data on pregnancy and neonatal outcome were analyzed.
RESULTS:
There were two surviving infants in 259/300 (86.4%) pregnancies, one survivor in 22/300 (7.3%) and no survivors in 19/300 (6.3%) with an overall mortality of 60/600 (10%). Twin-twin transfusion syndrome was diagnosed in 33 cases (11%), isolated intertwin weight discordance ≥ 25% in 35 (11.6%) and major congenital structural anomalies in ten (3.3%). After 32 weeks, the prospective risk of spontaneous fetal intrauterine death was one in 248 (0.4%) per pregnancy.
CONCLUSIONS:
Despite specific prenatal fetal monitoring and management, monochorionic diamniotic twin pregnancies have still to be considered at high risk of mortality, although the prospective risk of intrauterine death after 32 weeks is low. Twin-twin transfusion syndrome and congenital anomalies were the main risk factors for mortalit
Uterine artery Doppler in the management of dichorionic twin pregnancies discordant for intrauterine growth restriction
No full textObjectives
To evaluate the role of uterine artery Doppler in the expectant management of dichorionic twin pregnancies discordant for intrauterine growth restriction (IUGR).
Methods
Retrospective study. We retrieved from our database (2002–2012) data on dichorionic twin pregnancies complicated by IUGR of one twin, defined as abdominal circumference 95th percentile, with no structural or chromosomal abnormalities. Perinatal and pediatric records were examined. In all cases gestational age and chorionicity were determined by ultrasound in the first trimester. Chorionicity was confirmed by placental pathology.
Results
We identified 31 dichorionic twin pregnancies discordant for IUGR. The median gestation at presentation was 26+3 weeks (interquartile range (IQR) 24+0-30+4 weeks). Pre-eclampsia (PE) complicated 8/31 cases. Uterine artery Doppler was evaluated in 28/31 cases, and mean PI was > 95th percentile in 10/28, of which half (5/10) subsequently developed PE, requiring delivery before 32 weeks in 3/5 of cases All pregnancies were offered expectant managed for fetal conditions until 32 weeks. In 5/31 (16%) cases delivery was carried out before 32 weeks because of severe PE (n = 4) or placental abruption (n = 1). There were 7 perinatal deaths. The IUGR twin died in 6/31 pregnancies (19%); in 5 cases intrauterine death occurred before 32 weeks. In one pregnancy both twins died in the neonatal period after a Caesarean section performed at 27+0 weeks because of severe PE. Among the 55 survivors there were 4 infants with disability. The relative risk of developing pre-eclampsia with abnormal uterine artery Doppler waveform in our cohort was 4.5 (1.05-19.11, 95% confidence interval; p = 0.04).
Conclusions
Uterine artery Doppler might be useful to identify cases at higher risk of pre-eclampsia that warrant increased maternal surveillance during expectant management
The natural history of monoamniotic twin pregnancies: a case series and systematic review of the literature.
No full textTo describe the natural history of monoamniotic twin pregnancies in contemporary practice.Cohort study of monochorionic monoamniotic twin pregnancies with two live fetuses diagnosed at less than 16 weeks and prospectively followed up between 2004 and 2013. A systematic review of the literature using Medline, Embase and Scopus, to determine the perinatal mortality rate after 24 weeks gestation in monoamniotic twins was also performed.Twenty pregnancies were analyzed. Four were terminated (in three cases due to fetal abnormalities). Another six miscarried spontaneously. Among ten pregnancies reaching viability, there was double intrauterine death in one, and both fetuses were alive at delivery in the other nine. There were no neonatal deaths. Overall survival for fetuses alive at the initial scan was 18/40 (45\%; 95\% CI 29 to 62\%). At meta-analysis of 13 studies (including the current series), the perinatal mortality rate after 24 weeks was 4.5\% (95\% CI 3.3 to 5.8\%).Despite early diagnosis and intensive monitoring, of those fetuses alive before 16 weeks less than half survive until the neonatal period. Most losses are attributable to fetal abnormalities and spontaneous miscarriage, and are therefore unlikely to be reduced by further improvements in fetal assessment and monitoring. © 2014 John Wiley & Sons, Ltd
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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