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EFORT Open Reviews May 2022Idiopathic scoliosis is the most common spinal deformity and affects 1-3% of children and adolescents. Idiopathic scoliosis may run in families and the purpose of this... (Review)
Review
PURPOSE
Idiopathic scoliosis is the most common spinal deformity and affects 1-3% of children and adolescents. Idiopathic scoliosis may run in families and the purpose of this systematic review was to describe the degree of heritability.
METHODS
We searched Medline, Web of Science and EMBASE for family and twin studies reporting heritability estimates for idiopathic scoliosis, or studies from which heritability estimates could be calculated. Reference lists were screened for additional papers. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The protocol was registered at PROSPERO (registration number: CRD42022307329).
RESULTS
The literature search identified 1134 reports. After full-text screening, nine eligible reports were included for data extraction. Seven were twin studies containing between 5 and 526 pairs, and two were family studies with 1149 and 2732 individuals, respectively. Quality was 'good' in four studies and 'fair' in five studies. In general, studies with radiograph-confirmed diagnosis reported higher heritability estimates than studies with self-reported diagnosis. Population-based twin studies reported lower heritability estimates than clinic-based twin studies. Family-based studies reported higher heritability estimates than twin studies. Pairwise concordance for scoliosis ranged from 0.11 to 1.00 in monozygotic twins and from 0 to 1.0 in dizygotic twins. A meta-analysis of three studies resulted in a narrow sense heritability estimate of 0.57 (95% CI: 0.29-0.86).
CONCLUSION
Twin and family studies indicate a hereditary component in idiopathic scoliosis, but study heterogeneity is large, and the degree of the heritability is uncertain. Nevertheless, known genetic variants associated with idiopathic scoliosis can still only explain a minor part of heritability.
PubMed: 35638601
DOI: 10.1530/EOR-22-0026 -
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 -
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 -
BJOG : An International Journal of... Apr 2021The perinatal mortality and morbidity among twins vary by chorionicity. Although it is considered that monochorionicity is associated with an increased risk of preterm...
BACKGROUND
The perinatal mortality and morbidity among twins vary by chorionicity. Although it is considered that monochorionicity is associated with an increased risk of preterm birth in twin pregnancies, no systematic review exists evaluating this association.
OBJECTIVES
This systematic review was undertaken to assess the association between preterm birth and chorionicity in twin pregnancies.
SEARCH STRATEGY
We searched the electronic databases from January 1990 to July 2019 without language restrictions.
SELECTION CRITERIA
All studies on twin pregnancies where chorionicity and preterm birth were evaluated were included.
DATA COLLECTION AND ANALYSIS
Findings are reported as odds ratios with 95% confidence intervals. The estimates are pooled using random-effects meta-analysis.
MAIN RESULTS
From 13 156 citations, we included 39 studies (29 864 pregnancies). Monochorionicity was significantly associated with increased risk of preterm birth at ≤28, ≤32, ≤34 and <37 weeks in women asymptomatic and symptomatic for preterm labour (odds ratio [OR] 2.14, 95% CI 1.52-3.02, I = 46%, OR 1.55, 95% CI 1.27-1.89 I = 68%, OR 1.47, 95% CI 1.27-1.69, I = 60%, OR 1.66, 95% CI 1.43-1.93, I = 65%, respectively). Among those asymptomatic for preterm labour, significantly increased odds of preterm birth were seen for monochorionicity at gestations ≤34 weeks (OR 1.85, 95% CI 1.42-2.40, I = 25%) and <37 weeks (OR 1.75, 95% CI 1.22-2.53, I = 61%). Sensitivity analysis showed significantly increased odds of spontaneous preterm birth at ≤34 and <37 weeks for monochorionicity (OR 1.25, 95% CI 1.01-1.55, I = 0% and OR 1.41, 95% CI 1.13-1.78, I = 0%).
CONCLUSIONS
Monochorionicity is significantly associated with preterm birth at all gestations.
TWEETABLE ABSTRACT
In twin pregnancies, monochorionicity is associated with an increased risk of preterm birth at all gestations.
Topics: Adult; Chorion; Female; Humans; Pregnancy; Pregnancy, Twin; Premature Birth; Risk Factors; Twins, Dizygotic; Twins, Monozygotic
PubMed: 32888235
DOI: 10.1111/1471-0528.16479 -
Journal of Perinatal Medicine Sep 2020Objectives To compare the fetal and maternal outcomes in surviving singletons of vanishing twin, with singletons or twins, in pregnancies following assisted reproductive... (Meta-Analysis)
Meta-Analysis
Objectives To compare the fetal and maternal outcomes in surviving singletons of vanishing twin, with singletons or twins, in pregnancies following assisted reproductive technology (ART). Content We searched the PubMed, Embase, Web of Science and Cochrane databases from the time of conception of the database until Dec 2019 to identify relevant published studies. Perinatal outcomes were synthesized with random effects meta-analysis using RevMan 5.3. Summary and Outlook Fifteen studies were included. Dichorionic twin pregnancies conceived by ART wherein the vanishing twin phenomenon occurred had a risk of fetal malformation similar to that of ART singleton pregnancies (OR=1.25; 95% CI 0.87-1.79) and a higher risk of fetal malformation compared with ART twin pregnancies (OR=1.82; 95% CI 1.23-2.70). Moreover, the remaining fetus in ART vanishing twin pregnancy was at a significantly higher risk of preterm birth (<37 weeks) compared to fetuses in ART singleton pregnancies (OR=2.41; 95% CI 1.46-3.99) and a markedly lower risk of preterm birth (<37 weeks) compared to the fetuses in ART twin pregnancies (OR=0.19; 95% CI 0.16-0.22). Meanwhile, the risk of delivery of infants who were small for gestational age (SGA) was significantly higher in ART vanishing twin pregnancies compared to that in ART singleton pregnancies (OR=2.70; 95% CI 1.39-5.24) and similar to that in ART twin pregnancies (OR=0.67; 95% CI 0.27-1.65). The risks of preterm birth and of the infant being SGA is higher for the remaining fetus in an ART vanishing twin pregnancy compared to those for the fetuses in ART singleton pregnancies; the risk of fetal malformation is also higher in such cases compared with ART twin pregnancies.
Topics: Congenital Abnormalities; Female; Fetal Death; Humans; Infant, Newborn; Infant, Small for Gestational Age; Pregnancy; Pregnancy, Twin; Premature Birth; Reproductive Techniques, Assisted; Risk Assessment; Twins, Dizygotic
PubMed: 32697761
DOI: 10.1515/jpm-2020-0088 -
Medicine Jun 2020Published findings on perinatal outcomes of multifetal pregnancy reduction (MPR) of dichorionic diamniotic (DCDA) twin pregnancy to singleton are controversial. We... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Published findings on perinatal outcomes of multifetal pregnancy reduction (MPR) of dichorionic diamniotic (DCDA) twin pregnancy to singleton are controversial. We performed a meta-analysis to appraise the effects of MPR of DCDA twin pregnancy versus expectant management on perinatal outcomes.
METHODS
Four electronic databases were searched from their inception to June 15, 2019, to identify publications that appraised MPR before 15 weeks of gestation. Studies reporting perinatal outcomes of both MPR of DCDA twin pregnancy to singleton and expectant management were considered. The relative risks (RRs) and mean differences with 95% confidence intervals (CIs) were pooled using a random-effects model.
RESULTS
Six studies involving 7398 participants showed that MPR of DCDA twin pregnancy to singleton was associated with a lower risk of preterm birth (5 studies with 7297 participants; RR: 0.30, 95% CI: 0.22-0.40; P < .001) and higher birth weight (4 studies with 5763 participants; mean differences: 548.10 g, 95% CI: 424.04-672.15; P < .001) than expectant management; there was no difference in the occurrence of miscarriages (5 studies with 7355 participants; RR: 1.57, 95% CI: 0.90-2.75; P = .11). Sensitivity analysis showed that all the results were stable and reliable, with the omission of 2 studies with serious risk of bias.
CONCLUSION
Compared to expectant management, MPR of DCDA twin pregnancy to singleton prevents preterm birth and low birth weight, without increasing the risk of miscarriages. Regarding perinatal morbidity related to preterm birth, MPR can be reserved as a remediation measure to improve the perinatal outcomes of DCDA twin pregnancies.
Topics: Adult; Amnion; Chorion; Female; Humans; Pregnancy; Pregnancy Outcome; Pregnancy Reduction, Multifetal; Pregnancy, Twin; Twinning, Dizygotic; Twins, Dizygotic; Watchful Waiting
PubMed: 32569212
DOI: 10.1097/MD.0000000000020730 -
Pediatric Surgery International Aug 2020Biliary atresia (BA) in twins is extremely rare reported in the literature, but twin studies are useful methods of examining the associated factors of a complex disease.... (Meta-Analysis)
Meta-Analysis
PURPOSE
Biliary atresia (BA) in twins is extremely rare reported in the literature, but twin studies are useful methods of examining the associated factors of a complex disease. The objective of this study was to analyze the characteristics and patterns of biliary atresia in twins from reviewing available articles.
METHODS
PubMed and EMBASE databases were reviewed for related articles using the keywords ''biliary atresia'', ''twins'', ''monozygotic (MZ)'', and ''dizygotic (DZ)'', including relevant papers in the reference lists.
RESULTS
This analysis was extracted from 12 articles, with a total of 35 twin pairs included. BA was found in 36 out of 70 twin subjects (51.4%), of which had an even gender split. 97.1% twins were discordant, among 55.9% of which were monozygotic twin sets, indicating that BA may be related to genetic phenotype or penetrance. Isolated BA was the largest group with 27 (75%) affected twins. Only one pair of dizygotic twins (2.9%) demonstrate concordance for BA, and have one affected family member.
CONCLUSION
BA was found in nearly half of twin subjects with an even gender split. Isolated BA was the largest group, in which the number of monozygotic twins was similar with dizygotic twins, so the onset of the disease may not associate with the zygosity of twins. Most of twin sets had discordant disease presentation, especially monozygotic twins therein, emphasizing the role of epigenetic factor in the pathogenesis of BA. Future studies should take genetic testing among any twin sets in BA, especially the disease-associated mutations, thus be useful to investigate the etiology of disease.
Topics: Adult; Biliary Atresia; Diseases in Twins; Female; Humans; Male; Twins
PubMed: 32504124
DOI: 10.1007/s00383-020-04690-4 -
American Journal of Medical Genetics.... Mar 2019Twins, particularly monochorionic (MC) pairs, are at increased risk for fetal death. Whereas previous work has sought to understand the mechanisms for this increased...
Twins, particularly monochorionic (MC) pairs, are at increased risk for fetal death. Whereas previous work has sought to understand the mechanisms for this increased mortality, most studies analyze viable twin pregnancies or liveborn twin cohorts. In the Wisconsin Stillbirth Service Program cohort of 3,137 stillbirths and second trimester miscarriages, we identified 175 twin pregnancies for a twinning rate of 56/1,000, which is approximately double the general population. The excess of twins among miscarriages and stillbirths was attributable to MC pairs as the incidence of dizygotic (DZ) twinning was not increased compared to livebirth data. The leading causes of fetal demise among twins were twin-twin transfusion, acardia, and twin-twin disruption. Maternal causes of death, primarily premature rupture of membranes, were moderately increased in both MC and DZ twins relative to singletons. Although deceased twins were smaller than expected for viable twins at comparable gestational ages, placenta weights of deceased MC pairs were large compared to combined fetal weight, which indicates placental inefficiency likely due to vascular shunting. Co-twin survival was much lower for MC than for DZ pairs. Therefore, earlier diagnosis and treatment of MC twinning complications may decrease prenatal mortality.
Topics: Abortion, Spontaneous; Cause of Death; Databases, Factual; Female; Fetal Death; Health Surveys; Humans; Pregnancy; Pregnancy Trimester, Second; Pregnancy, Twin; Prevalence; Stillbirth; Twins, Dizygotic; Twins, Monozygotic; Wisconsin
PubMed: 30663217
DOI: 10.1002/ajmg.a.61014 -
Pediatric Surgery International Aug 2017Hirschsprung's disease (HSCR) is known to occur in families. The reported overall incidence of familial cases is 7.6%, with a higher incidence of 15-21% in total colonic... (Meta-Analysis)
Meta-Analysis Review
AIM OF THE STUDY
Hirschsprung's disease (HSCR) is known to occur in families. The reported overall incidence of familial cases is 7.6%, with a higher incidence of 15-21% in total colonic aganglionosis and 50% in the rare total intestinal aganglionosis. HSCR is extremely rare in twins. The aim of this study was to systematically analyse the patterns of HSCR in twins published in the literature.
METHODS
Electronic databases Pubmed and Medline were screened for relevant articles using the keywords "Hirschsprung's disease", "aganglionosis", "twins", "monozygotic", and "dizygotic". Examining reference lists identified further relevant papers.
MAIN RESULTS
Twelve studies with a total of 18 twin pairs were included in this analysis. 67% twins were discordant. HSCR was found in 24 out of 36 twin subjects (67%), of which 83% affected were male. Rectosigmoid type was reported in 71% of patients, long-segment disease in 21, and 8% presented with a total aganglionosis. Three twin pairs had at least one family member affected with HSCR.
CONCLUSION
HSCR was found in two-thirds of twin subjects with a male predominance. Rectosigmoid aganglionosis was the most common variant. Disease discordance was identified, where environmental insults were postulated to be predisposing factors to disease expression. Future studies investigating the disease-associated mutations in the already identified HSCR genes should provide insights into the genetic basis of HSCR in twins.
Topics: Diseases in Twins; Female; Hirschsprung Disease; Humans; Incidence; Male; Twins
PubMed: 28601901
DOI: 10.1007/s00383-017-4110-7 -
Twin Research and Human Genetics : the... Apr 2017Traditionally, it is understood that dizygotic (DZ) twins always have a dichorionic placenta. However, with 8% blood chimerism in DZ twins, placental sharing is probably... (Review)
Review
Traditionally, it is understood that dizygotic (DZ) twins always have a dichorionic placenta. However, with 8% blood chimerism in DZ twins, placental sharing is probably more common than previously has been recognized. In this article, we will review all available cases of monochorionic dizygotic (MCDZ) twins. A total of 31 twins have been described in literature. A monochorionic diamniotic placenta is reported in all cases. Assisted reproductive technology is responsible for the origin of the pregnancy in 82.1% of the cases. In 15.4% of the sex-discordant twins, a genital anomaly was reported in one of the twins. Chimerism is demonstrable in 90.3% of the twins, leading to various diagnostic difficulties. As this review shows that most MCDZ twins are discovered by accident, it can be argued that it is far more common than has been assumed until now. However, the prevalence is still unclear. Awareness of MCDZ twinning is important, with subsequently correct medical strategies. Similarly, the resulting (blood) chimerism is essential to consider in diagnostic procedures, pre- and postnatally. More research on the effect of placental transfusion between sex-discordant twins is required.
Topics: Chimerism; Chorion; Female; Humans; Male; Placenta; Pregnancy; Pregnancy, Twin; Reproductive Techniques, Assisted; Twins, Dizygotic; Ultrasonography, Prenatal
PubMed: 28236812
DOI: 10.1017/thg.2017.4