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BMJ (Clinical Research Ed.) Sep 2016To determine the risks of stillbirth and neonatal complications by gestational age in uncomplicated monochorionic and dichorionic twin pregnancies. (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
To determine the risks of stillbirth and neonatal complications by gestational age in uncomplicated monochorionic and dichorionic twin pregnancies.
DESIGN
Systematic review and meta-analysis.
DATA SOURCES
Medline, Embase, and Cochrane databases (until December 2015).
REVIEW METHODS
Databases were searched without language restrictions for studies of women with uncomplicated twin pregnancies that reported rates of stillbirth and neonatal outcomes at various gestational ages. Pregnancies with unclear chorionicity, monoamnionicity, and twin to twin transfusion syndrome were excluded. Meta-analyses of observational studies and cohorts nested within randomised studies were undertaken. Prospective risk of stillbirth was computed for each study at a given week of gestation and compared with the risk of neonatal death among deliveries in the same week. Gestational age specific differences in risk were estimated for stillbirths and neonatal deaths in monochorionic and dichorionic twin pregnancies after 34 weeks' gestation.
RESULTS
32 studies (29 685 dichorionic, 5486 monochorionic pregnancies) were included. In dichorionic twin pregnancies beyond 34 weeks (15 studies, 17 830 pregnancies), the prospective weekly risk of stillbirths from expectant management and the risk of neonatal death from delivery were balanced at 37 weeks' gestation (risk difference 1.2/1000, 95% confidence interval -1.3 to 3.6; I(2)=0%). Delay in delivery by a week (to 38 weeks) led to an additional 8.8 perinatal deaths per 1000 pregnancies (95% confidence interval 3.6 to 14.0/1000; I(2)=0%) compared with the previous week. In monochorionic pregnancies beyond 34 weeks (13 studies, 2149 pregnancies), there was a trend towards an increase in stillbirths compared with neonatal deaths after 36 weeks, with an additional 2.5 per 1000 perinatal deaths, which was not significant (-12.4 to 17.4/1000; I(2)=0%). The rates of neonatal morbidity showed a consistent reduction with increasing gestational age in monochorionic and dichorionic pregnancies, and admission to the neonatal intensive care unit was the commonest neonatal complication. The actual risk of stillbirth near term might be higher than reported estimates because of the policy of planned delivery in twin pregnancies.
CONCLUSIONS
To minimise perinatal deaths, in uncomplicated dichorionic twin pregnancies delivery should be considered at 37 weeks' gestation; in monochorionic pregnancies delivery should be considered at 36 weeks.
SYSTEMATIC REVIEW REGISTRATION
PROSPERO CRD42014007538.
Topics: Female; Gestational Age; Humans; Infant, Newborn; Infant, Newborn, Diseases; Intensive Care, Neonatal; Perinatal Death; Pregnancy; Pregnancy, Twin; Prospective Studies; Risk Factors; Stillbirth; Twins, Dizygotic; Twins, Monozygotic
PubMed: 27599496
DOI: 10.1136/bmj.i4353 -
Journal of Child Psychology and... May 2016The etiology of Autism Spectrum Disorder (ASD) has been recently debated due to emerging findings on the importance of shared environmental influences. However, two... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
The etiology of Autism Spectrum Disorder (ASD) has been recently debated due to emerging findings on the importance of shared environmental influences. However, two recent twin studies do not support this and instead re-affirm strong genetic effects on the liability to ASD, a finding consistent with previous reports. This study conducts a systematic review and meta-analysis of all twin studies of ASD published to date and explores the etiology along the continuum of a quantitative measure of ASD.
METHODS
A PubMed Central, Science Direct, Google Scholar, Web of Knowledge structured search conducted online, to identify all twin studies on ASD published to date. Thirteen primary twin studies were identified, seven were included in the meta-analysis by meeting Systematic Recruitment criterion; correction for selection and ascertainment strategies, and applied prevalences were assessed for these studies. In addition, a quantile DF extremes analysis was carried out on Childhood Autism Spectrum Test scores measured in a population sample of 6,413 twin pairs including affected twins.
RESULTS
The meta-analysis correlations for monozygotic twins (MZ) were almost perfect at .98 (95% Confidence Interval, .96-.99). The dizygotic (DZ) correlation, however, was .53 (95% CI .44-.60) when ASD prevalence rate was set at 5% (in line with the Broad Phenotype of ASD) and increased to .67 (95% CI .61-.72) when applying a prevalence rate of 1%. The meta-analytic heritability estimates were substantial: 64-91%. Shared environmental effects became significant as the prevalence rate decreased from 5-1%: 07-35%. The DF analyses show that for the most part, there is no departure from linearity in heritability.
CONCLUSIONS
We demonstrate that: (a) ASD is due to strong genetic effects; (b) shared environmental effects become significant as a function of lower prevalence rate; (c) previously reported significant shared environmental influences are likely a statistical artefact of overinclusion of concordant DZ twins.
Topics: Autism Spectrum Disorder; Diseases in Twins; Genetic Predisposition to Disease; Humans
PubMed: 26709141
DOI: 10.1111/jcpp.12499 -
JCPP Advances Jul 2021Non-shared environment (NSE) effects account for around one-third of the etiology of autism spectrum disorder (ASD). However, the knowledge of mechanisms and phenotypic...
BACKGROUND
Non-shared environment (NSE) effects account for around one-third of the etiology of autism spectrum disorder (ASD). However, the knowledge of mechanisms and phenotypic profiles associated with NSE in ASD is scarce.
METHODS
A systematic search was conducted using Embase, MEDLINE, and PsycINFO for studies published in English between 1990 and August 2020 using co-twin control design to compare behavioral and biological phenotypes among monozygotic (MZ) twin pairs concordant/discordant for ASD, clinical autism symptoms, or autistic traits. Risk of bias was assessed through a modified Newcastle-Ottawa Scale.
RESULTS
Twenty six articles were included. Differential DNA methylation and gene expression were found among ASD discordant twins; however, genetic results were inconsistent. Neurological disorders and early medical events were associated with ASD and autistic traits, while no within pair differences were found for minor physical anomalies or head circumference. Structural and functional brain imaging studies and research on social and other cognitive/behavioral functions were inconclusive. Risk of bias assessment found that all studies used the same exposure (or outcome) measures to collect data for participants and most used either secure health-related records or structured interviews for ascertainment of exposure; however, only a handful of studies representative of the population from which they were drawn. Formal assessment of risk of publication bias (i.e., funnel plot) was not possible.
CONCLUSIONS
Our results suggest that NSE in ASD could be associated with heterogeneous postzygotic genetic mechanisms and manifest as a range of biological and behavioral phenotypes. Extant findings were limited by relatively few studies, small sample sizes, and methodological diversity. More research is needed on co-occurring biological and behavioral phenotypes using a consistent format for designing, analyzing, and reporting MZ ASD discordant twin studies in order to further examine the role of NSE in the etiology of ASD.
PubMed: 37431470
DOI: 10.1111/jcv2.12017 -
Journal of Perinatology : Official... Feb 2023Through a systematic review and meta-analyses, we aimed to analyze the impact of chorionicity on neurodevelopment outcomes. (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
Through a systematic review and meta-analyses, we aimed to analyze the impact of chorionicity on neurodevelopment outcomes.
STUDY DESIGN
We conducted a comprehensive search strategy through Medline, Embase, Web of Science, and reference lists of the retrieved studies until August 2022. Studies that examined the association between chorionicity and children's neurodevelopment outcomes were included.
RESULTS
Twelve studies were included. Monochorionic (MC) twins increased the odds of neurodevelopment impairment, cerebral palsy compared to dichorionic (DC) twins. The differences in neurodevelopmental impairment and cerebral palsy between the two groups disappeared after excluding infants with twin-twin transfusion (TTTS). After fetoscopic laser surgery (FLS) for MC twins, there were no differences too.
CONCLUSIONS
Compared to DC twins, MC twins were associated with an increased risk of neurodevelopment impairment. MC twins complicated by TTTS were at high risk of neurologic disability, and FLS was an acceptable treatment modality for them.
Topics: Pregnancy; Infant; Female; Child; Humans; Pregnancy, Twin; Cerebral Palsy; Fetofetal Transfusion; Twins, Dizygotic; Twins, Monozygotic; Pregnancy Outcome
PubMed: 36333420
DOI: 10.1038/s41372-022-01534-y -
BMC Psychology Jan 2022In the general population, 10.6% of people favor their left hand over the right for motor tasks. Previous research suggests higher prevalence of atypical (left-, mixed-,... (Meta-Analysis)
Meta-Analysis
BACKGROUND
In the general population, 10.6% of people favor their left hand over the right for motor tasks. Previous research suggests higher prevalence of atypical (left-, mixed-, or non-right-) handedness in (i) twins compared to singletons, and in (ii) monozygotic compared to dizygotic twins. Moreover, (iii) studies have shown a higher rate of handedness concordance in monozygotic compared to dizygotic twins, in line with genetic factors playing a role for handedness.
METHODS
By means of a systematic review, we identified 59 studies from previous literature and performed three sets of random effects meta-analyses on (i) twin-to-singleton Odds Ratios (21 studies, n = 189,422 individuals) and (ii) monozygotic-to-dizygotic twin Odds Ratios (48 studies, n = 63,295 individuals), both times for prevalence of left-, mixed-, and non-right-handedness. For monozygotic and dizygotic twin pairs we compared (iii) handedness concordance Odds Ratios (44 studies, n = 36,217 twin pairs). We also tested for potential effects of moderating variables, such as sex, age, the method used to assess handedness, and the twins' zygosity.
RESULTS
We found (i) evidence for higher prevalence of left- (Odds Ratio = 1.40, 95% Confidence Interval = [1.26, 1.57]) and non-right- (Odds Ratio = 1.36, 95% Confidence Interval = [1.22, 1.52]), but not mixed-handedness (Odds Ratio = 1.08, 95% Confidence Interval = [0.52, 2.27]) among twins compared to singletons. We further showed a decrease in Odds Ratios in more recent studies (post-1975: Odds Ratio = 1.30, 95% Confidence Interval = [1.17, 1.45]) compared to earlier studies (pre-1975: Odds Ratio = 1.90, 95% Confidence Interval = [1.59-2.27]). While there was (ii) no difference between monozygotic and dizygotic twins regarding prevalence of left- (Odds Ratio = 0.98, 95% Confidence Interval = [0.89, 1.07]), mixed- (Odds Ratio = 0.96, 95% Confidence Interval = [0.46, 1.99]), or non-right-handedness (Odds Ratio = 1.01, 95% Confidence Interval = [0.91, 1.12]), we found that (iii) handedness concordance was elevated among monozygotic compared to dizygotic twin pairs (Odds Ratio = 1.11, 95% Confidence Interval = [1.06, 1.18]). By means of moderator analyses, we did not find evidence for effects of potentially confounding variables.
CONCLUSION
We provide the largest and most comprehensive meta-analysis on handedness in twins. Although a raw, unadjusted analysis found a higher prevalence of left- and non-right-, but not mixed-handedness among twins compared to singletons, left-handedness was substantially more prevalent in earlier than in more recent studies. The single large, recent study which included birth weight, Apgar score and gestational age as covariates found no twin-singleton difference in handedness rate, but these covariates could not be included in the present meta-analysis. Together, the secular shift and the influence of covariates probably make it unsafe to conclude that twinning has a genuine relationship to handedness.
Topics: Birth Weight; Functional Laterality; Humans; Prevalence; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35033205
DOI: 10.1186/s40359-021-00695-3 -
American Journal of Perinatology Feb 2022This study was aimed to report the incidence of neonatal morbidity in monochorionic monoamniotic (MCMA) twin pregnancies according to gestational age at birth and type... (Meta-Analysis)
Meta-Analysis
OBJECTIVE
This study was aimed to report the incidence of neonatal morbidity in monochorionic monoamniotic (MCMA) twin pregnancies according to gestational age at birth and type of management adopted (inpatient or outpatient).
STUDY DESIGN
Medline and Embase databases were searched. Inclusion criteria were nonanomalous MCMA twins. The primary outcome was a composite score of neonatal morbidity, defined as the occurrence of at least one of the following outcomes: respiratory morbidity, overall neurological morbidity, severe neurological morbidity, and infectious morbidity, necrotizing enterocolitis at different gestational age windows (24-30, 31-32, 33-34, and 35-36 weeks). Secondary outcomes were the individual components of the primary outcome and admission to neonatal intensive care unit (NICU). Subanalysis according to the type of surveillance strategy (inpatient compared with outpatient) was also performed. Random effect meta-analyses were used to analyze the data.
RESULTS
A total of 14 studies including 685 MCMA twin pregnancies without fetal anomalies were included. At 24 to 30, 31 to 32, 33 to 34, and 35 to 36 weeks of gestation, the rate of composite morbidity was 75.4, 65.5, 37.6, and 18.5%, respectively, the rate of respiratory morbidity was 74.2, 59.1, 35.5, and 12.2%, respectively, while overall neurological morbidity occurred in 15.3, 10.2, 4.3, and 0% of the cases, respectively. Infectious morbidity complicated 13, 4.2, 3.1, and 0% of newborns while 92.1, 81.6, 58.7, and 0% of cases required admission to NICU. Morbidity in pregnancies delivered between 35 and 36 weeks of gestation was affected by the very small sample size of cases included. When comparing the occurrence of overall morbidity according to the type of management (inpatient or outpatient), there was no difference between the two surveillance strategies ( = 0.114).
CONCLUSION
MCMA pregnancies are at high risk of composite neonatal morbidity, mainly respiratory morbidity that gradually decreases with increasing gestational age at delivery with a significant reduction for pregnancies delivered between 33 and 34 weeks. We found no difference in the occurrence of neonatal morbidity between pregnancies managed as inpatient or outpatient.
KEY POINTS
· MCMA pregnancies are at high risk of composite neonatal morbidity, mainly respiratory morbidity.. · Neonatal morbidity gradually decreases with increasing GA at delivery, mostly between 33 and 34 weeks.. · There is no difference in the occurrence of neonatal morbidity between in- or outpatient management..
Topics: Female; Gestational Age; Humans; Incidence; Infant, Newborn; Infant, Newborn, Diseases; Pregnancy; Pregnancy, Twin; Respiration Disorders; Twin Studies as Topic; Twins, Monozygotic
PubMed: 32722824
DOI: 10.1055/s-0040-1714420 -
Twin Research and Human Genetics : the... Jun 2016The natural history of stage 1 Twin-to-twin transfusion syndrome (TTTS) remains unclear and its optimal management is yet to be established. The main aims of this... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVES
The natural history of stage 1 Twin-to-twin transfusion syndrome (TTTS) remains unclear and its optimal management is yet to be established. The main aims of this meta-analysis were to quantify the incidence of progression in stage 1 TTTS and to ascertain survival in these pregnancies.
METHODS
MEDLINE, EMBASE, and The Cochrane Library were searched. Reference lists within each article were hand-searched for additional reports. The outcomes included incidence of progression and survival in stage 1 TTTS. Randomized controlled trials, cohort and case-control studies were included. Case reports, studies including three or fewer cases of stage 1 TTTS, and editorials were excluded. Proportion meta-analysis was used for analysis (Registration number: CRD42016036190).
RESULTS
The search yielded 3,085 citations; 18 studies were included in the review (172 pregnancies to assess progression and 433 pregnancies to assess the survival). The pooled incidence of progression in stage 1 TTTS was 27% [95% CI 16-39%]. The pooled overall survival, double survival and at least one survival in the pregnancies managed expectantly were 79% [95% CI 62-92%], 70% [95% CI 54-84%] and 87% [95% CI 69-98%], respectively. In those undergoing amnioreduction, the corresponding figures were 77% [95% CI 68-85%], 67% [95% CI 57-76%] and 86% [95% CI 76-94%], respectively. The survival rates were 68% [95% CI 54-81%], 54% [95% CI 36-72%], and 81% [95% CI 69-90%], when laser surgery was performed.
CONCLUSIONS
The optimal initial management of stage 1 TTTS remains in equipoise. The ongoing randomized trial comparing immediate laser surgery versus conservative management should provide a definitive answer.
Topics: Adult; Arteriovenous Anastomosis; Female; Fetofetal Transfusion; Humans; Placenta; Pregnancy; Pregnancy, Twin; Survival Rate; Twins, Monozygotic
PubMed: 27137946
DOI: 10.1017/thg.2016.33 -
Sleep Medicine Reviews Aug 2021Twin studies have consistently found that genetic factors explain a substantial proportion of the variance for insomnia. However, studies vary widely in their... (Meta-Analysis)
Meta-Analysis Review
Twin studies have consistently found that genetic factors explain a substantial proportion of the variance for insomnia. However, studies vary widely in their heritability estimates. Therefore, this meta-analysis aimed to: 1) Estimate the mean heritability of insomnia; 2) Assess heterogeneity among twin studies of insomnia; and 3) Search and analyse characteristics of the studies (moderator variables) that may explain heterogeneity among estimates. For this purpose, separate meta-analyses were carried out for MZ and DZ correlations and for heritability estimates by assuming random-effects models. Thirteen independent samples were included in this meta-analysis. The heterogeneity index for heritability estimates was significant in both best fitting models (I = 98.77, P < .0001) and full models (I = 97.80, P < .0001). MZ correlations were higher (0.37; 95%CI: 0.31,.43) than DZ correlations (0.15; 95%CI: 0.12,.18). A mean heritability of 0.39 (95%CI: 0.32,.44) was found for insomnia. These results highlight the role of genetic factors in explaining differences among the population on insomnia and Emphasize heterogeneity among studies. Further research is needed to identify variables that could explain this heterogeneity.
Topics: Humans; Sleep Initiation and Maintenance Disorders; Twins, Dizygotic; Twins, Monozygotic
PubMed: 33556853
DOI: 10.1016/j.smrv.2021.101437 -
Ultrasound in Obstetrics & Gynecology :... Aug 2014The aim of this systematic review was to explore the relationship between crown-rump length (CRL) discordance detected at 11-14 weeks of gestation and adverse outcome in... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
The aim of this systematic review was to explore the relationship between crown-rump length (CRL) discordance detected at 11-14 weeks of gestation and adverse outcome in twin pregnancy and to assess its predictive accuracy.
METHODS
A protocol designed a priori following MOOSE guidelines and recommended for systematic review and meta-analysis was used. The outcomes observed were: total fetal and perinatal loss, fetal loss at <24 weeks, fetal loss at ≥ 24 weeks, birth-weight (BW) discordance, preterm delivery (PTD) at < 34 weeks and fetal anomalies. The analysis was performed for all twins and for dichorionic (DC) and monochorionic (MC) twins separately.
RESULTS
A total of 2008 articles were identified and 17 studies were included in the systematic review. Twin pregnancies with CRL discordance ≥ 10% were at significantly higher risk of perinatal loss (RR, 2.80; 95% CI, 1.25-6.27; P = 0.012), fetal loss at ≥ 24 weeks (RR, 4.07; 95% CI, 1.47-11.23; P = 0.006), BW discordance (RR, 2.24; 95% CI, 1.89-2.64; P < 0.001) and PTD at < 34 weeks (RR, 1.49; 95% CI, 1.23-1.80; P < 0.001) but not of fetal loss at < 24 weeks (P = 0.130). A meta-analysis of fetal anomalies was not possible because fewer than two studies explored this outcome. However, when used alone to screen for adverse pregnancy outcome, the predictive accuracy of CRL discordance was low for each of the outcomes explored.
CONCLUSION
CRL discordance is associated with an increased risk of adverse pregnancy outcome. However, the accuracy of CRL discordance in predicting adverse outcome is poor and thus limits its routine use in clinical practice.
Topics: Birth Weight; Crown-Rump Length; Female; Fetus; Humans; Infant, Newborn; Pregnancy; Pregnancy Outcome; Pregnancy, Twin; Twins, Dizygotic; Twins, Monozygotic; Ultrasonography, Prenatal
PubMed: 24585501
DOI: 10.1002/uog.13335 -
Obstetrics and Gynecology Jun 2013To estimate the risk of stillbirth in apparently uncomplicated monochorionic-diamniotic twin pregnancies by systematic review and meta-analysis and compare it with that... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
To estimate the risk of stillbirth in apparently uncomplicated monochorionic-diamniotic twin pregnancies by systematic review and meta-analysis and compare it with that in uncomplicated dichorionic pregnancies.
DATA SOURCES
We performed an electronic search (January 1985 to April 2012) of Medline, PubMed, Embase, and ClinicalTrials.gov databases.
METHODS OF STUDY SELECTION
Studies detailing gestational-age specific stillbirth rates after 24 weeks of gestation in monochorionic-diamniotic twin pregnancies uncomplicated by twin-twin transfusion syndrome, growth restriction, or major anomalies. The rate and risk of stillbirth were calculated in 2-week gestational age blocks and compared in controlled studies with dichorionic pregnancies.
TABULATION, INTEGRATION, AND RESULTS
We evaluated 361 studies to include nine informative studies, four after additional data from the investigators. The rate of stillbirth per 1,000 uncomplicated monochorionic-diamniotic pregnancies at 32-33, 34-35, and 36-37 weeks of gestation was 5.1, 6.8, and 6.2, respectively. The risk of stillbirth per pregnancy at 32, 34, and 36 weeks of gestation was 1.6%, 1.3% and 0.9%, respectively. Compared with uncomplicated dichorionic pregnancies, the odds ratio for stillbirth per pregnancy at 32, 34, and 36 weeks of gestation was 4.2 (95% confidence interval [CI] 1.4-12.6), 3.7 (CI 1.1-12.0), and 8.5 (CI 1.6-44.7), respectively.
CONCLUSION
Uncomplicated monochorionic twin pregnancies are at substantial risk of stillbirth throughout the third trimester, which is severalfold higher than in dichorionic twin pregnancies. Given the risk of fetal death to the cotwin, these data should inform decisions around timing of delivery in seemingly normal monochorionic twin pregnancies.
Topics: Female; Humans; Pregnancy; Pregnancy, Twin; Stillbirth; Twins, Monozygotic
PubMed: 23812469
DOI: 10.1097/AOG.0b013e318292766b