No abstract available.
Humans ; Multiple Birth Offspring ; Twins*

PURPOSE: To determine the secular trend of the multiple birth rate in Korea from 1981 to 2017. METHODS: This study used birth certificate data covering the years 1981–2017 (20,948,901 births), provided by Statistics Korea. The impact of assisted reproductive technologies (ART) on multiple birth was analyzed by examining data prior to and after the introduction of ART and the national support program for infertile couples in South Korea. The odds ratio (OR) and 95% confidence intervals were calculated to describe the secular trend in the multiple birth rate per 100 births. RESULTS: During this period, the multiple birth rate per 100 births increased by 277 percent from 1.031 to 3.891, the twin birth rate increased from 1.013 to 3.807 (275%), and the triplet birth rate increased from 0.018 to 0.084 (363%). The secular trend of the multiple birth rate remained in the 1.000 level during 1981–1991, but has been rising steadily since 1992. The average increment of the multiple birth rate was 3.9% annually from 1981 through 2017 (peaking at more than 10 percent during 2006–2007). Prior to the introduction of ART in Korea (1981–1984), the multiple birth rate was 1.007, but after its introduction, the multiple birth rate was 1.005 in 1985–1989 (OR, 0.998; 95% confidence interval, 0.982–1.014), 1.084 in 1990–1994 (1.007; 1.060–1.094), 1.891 in 2000–2004 (1.894; 1.866–1.922), 3.127 in 2010–2014 (3.173; 3.129–3.217), and 3.811 in 2015–2017 (3.893; 3.835–3.952). CONCLUSION: Over the past three decades, multiple births have risen dramatically in Korea, primarily due to the increasingly widespread use of fertility therapies, and the delayed age of childbearing. There is a need for more research to understand the factors contributing to multiple births, and the national birth registration systems ought to be reformed to monitor whether multiple births originated spontaneously or from assisted-conception.
Birth Certificates ; Birth Rate ; Family Characteristics ; Fertility ; Humans ; Korea ; Multiple Birth Offspring ; Odds Ratio ; Parturition ; Reproductive Techniques, Assisted ; Triplets ; Twins

Over the past 30 years, there has been an increase in the incidence of multifetal pregna-ncies, primarily because of the introduction of ovarian stimulants for ovulation induction and assisted reproductive technology ( ART ) in infertile patients. It is well established that multifetal pregnancies are associated with an increased frequency of the maternal complications and gre-ater perinatal morbidity and mortyality. The adverse outcome of multifetal pregnancies is dire-ctly proportional to the number of fetuses, primarily as an consequence of prterm delivery. Re-duction in the number of fetuses in multifetal pregnancies has been proposed as a way to impr-ove the perinatal outcome in this situation. Therefore, selective fetal reduction ( SFR ) is sugges-ted as a therapeutic option for continuation of pregnancy with fetuses mature enough to survi-ve. In this paper, we report our infertility clinic experiences with 6 patients who carried mult- ifetal pregnancies including 1 quintuplet, 1 quadruplet, and 4 triplets. from January, 1991 to May, 1996, transabdominal SFR was accomplished by fetal intrathoracic KCl injection at 9~10 weeks of gestation. After the prcedure, 4 patients remained as twin pregnancies, and 2 patients as single pregnancy. There have been 3 sets of twin deliveries and the 2 sets of single delivery. One case was aborted. Two patients were delivered after 37 weeks of gestation, 2 patients were at 35 weeks, and 1 patient at 24 weeks. All babies have been healthy after birth in patients after 35 weeks gestation. There was no fetal anomaly related to the procedure in the 6 cases. We concluded that transabdominal SFR is a rather safe and useful procedure that may improve the outcome of multifetal pregnancies.
Fetus ; Humans ; Incidence ; Infertility ; Ovulation Induction ; Parturition ; Pregnancy Reduction, Multifetal* ; Pregnancy* ; Pregnancy, Twin ; Quadruplets ; Quintuplets ; Reproductive Techniques, Assisted ; Triplets ; Twins

OBJECTIVE: The purpose of this study was to investigate the influence of heritability on the craniofacial soft tissue cephalometric characteristics of monozygotic (MZ) twins, dizygotic (DZ) twins, and their siblings (SIB). METHODS: The samples comprised Korean adult twins and their siblings (mean age, 39.8 years; MZ group, n = 36 pairs; DZ group, n = 13 pairs of the same gender; and SIB group, n = 26 pairs of the same gender). Thirty cephalometric variables were measured to characterize facial profile, facial height, soft-tissue thickness, and projection of nose and lip. Falconer's method was used to calculate heritability (low heritability, h2 < 0.2; high heritability, h2 > 0.9). After principal components analysis (PCA) was performed to extract the models, we calculated the intraclass correlation coefficient (ICC) value and heritability of each component. RESULTS: The MZ group exhibited higher ICC values for all cephalometric variables than DZ and SIB groups. Among cephalometric variables, the highest h2 (MZ-DZ) and h2 (MZ-SIB) values were observed for the nasolabial angle (NLA, 1.544 and 2.036), chin angle (1.342 and 1.112), soft tissue chin thickness (2.872 and 1.226), and upper lip thickness ratio (1.592 and 1.026). PCA derived eight components with 84.5% of a cumulative explanation. The components that exhibited higher values of h2 (MZ-DZ) and h2 (MZ-SIB) were PCA2, which includes facial convexity, NLA, and nose projection (1.026 and 0.972), and PCA7, which includes chin angle and soft tissue chin thickness (2.107 and 1.169). CONCLUSIONS: The nose and soft tissue chin were more influenced by genetic factors than other soft tissues.
Adult ; Chin ; Humans ; Lip ; Methods* ; Nose ; Passive Cutaneous Anaphylaxis ; Siblings* ; Twins ; Twins, Dizygotic* ; Twins, Monozygotic*

Objective: To explore the gene-lifestyle interaction on coronary heart disease (CHD) in adult twins of China. Methods: Participants were selected from twin pairs registered in the Chinese National Twin Registry (CNTR). Univariate interaction model was used to estimate the interaction, via exploring the moderation effect of lifestyle on the genetic variance of CHD. Results: A total of 20 477 same-sex twin pairs aged ≥25 years were recruited, including 395 CHD cases, and 66 twin pairs both had CHD. After adjustment for age and sex, no moderation effects of lifestyles, including current smoking, current drinking, physical activity, intake of vegetable and fruit, on the genetic variance of CHD were found (P>0.05), suggesting no significant interactions. Conclusion: There was no evidence suggesting statistically significant gene-lifestyle interaction on CHD in adult twins of China.
Adult ; China/epidemiology* ; Coronary Disease/genetics* ; Diseases in Twins/genetics* ; Humans ; Life Style ; Twins/genetics* ; Twins, Dizygotic ; Twins, Monozygotic

Objective: To describe the distribution characteristics of tea consumption in adult twins recruited in the Chinese National Twin Registry (CNTR) and provide clues to genetic and environmental influences on tea consumption. Methods: Enrolled in CNTR during 2010-2018, 25 264 twin pairs aged 18 years and above were included in subsequent analysis. Random effect models were used to estimate tea consumption in the population and regional distribution characteristics. The concordance rate of the behavior and difference in consumption volume of tea within pairs were also described. Results: The mean age of all subjects was (35.38±12.45) years old. The weekly tea consumers accounted for 17.0%, with an average tea consumption of (3.36±2.44) cups per day. The proportion of weekly tea consumers was higher among males, 50-59 years old, southern, urban, educated, and the first-born in the twin pair (P<0.05), and lower among unmarried individuals (P<0.001). Within-pair analysis showed that the concordance rate of tea consumption of monozygotic (MZ) twins was higher than that of dizygotic (DZ) twins and the overall heritability of tea consumption was 13.45% (11.38%-15.51%). Stratified by the characteristics mentioned above, only in males, the concordance rate of MZ showed a tendency to be greater than that of DZ (all P<0.05). The differences in consumption volume of tea within twin pairs were minor in MZ among males (P<0.05), while the differences were not significant in female twins. Conclusion: There were discrepancies in the distribution of tea consumption among twins of different demographic and regional characteristics. Tea consumption was mainly influenced by environmental factors and slightly influenced by genetic factors. The size of genetic factors varied with gender, age, and region, and gender was a potential modified factor.
Adult ; China ; Diet ; Female ; Humans ; Male ; Middle Aged ; Tea ; Twins, Dizygotic ; Twins, Monozygotic ; Young Adult

PURPOSE: To evaluate the genetic factor in development of comitant strabismus. METHODS: We retrospectively reviewed 48 patients of 24 twins classified into monozygotic or dizygotic twin and analyzed gestational period and birth weight, refraction, phenotype and age of onset, amount of deviation, surgical history, and associated systemic or other ocular anomaly except strabismus. RESULTS: Seventeen of the 24 twins (70.8%) showed phenotypic concordance. The concordance was significantly higher in monozygotic twins (15 of the 18 pairs, 83.3%) than in dizygotic twins (2 of the 6 pairs, 33.3%) (p=0.038). Out of 15 twins with monozygosity who showed concordance, the predominant phenotype was intermittent exotropia (9 pairs, 60.0%). Concordance rate according to phenotype was high in refractive or nonrefractive accommodative esotropia (3 of the 3 pairs, 100.0%) and intermittent exotropia (9 of the 10 pairs, 90.0%). Most of concordant pairs showed similarity in age of onset and amount of deviation between first and second child. CONCLUSIONS: The concordance rate in monozygotic twin was high, especially in refractive or nonrefractive accommodative esotropia and intermittent exotropia, and therefore genetic factor can be responsible for the development of these types of strabismus.
Age of Onset ; Birth Weight ; Child ; Esotropia ; Exotropia ; Humans ; Phenotype ; Retrospective Studies ; Strabismus* ; Twins* ; Twins, Dizygotic ; Twins, Monozygotic

OBJECTIVETo assess the genetic and environmental influences on the somatotype of children and adolescents, and the effects of sex and age.

METHODSThe components of somatotype were calculated by using Heather-Cater method in a total of 376 twin pairs of Han nationality, including 245 monozygotic (MZ) and 131 like-sex dizygotic (DZ) twin pairs aged 6 to 18 years. Model-fitting method by Mx package was performed to evaluate the proportion of variance components and to analyze the effects of sex and age on each component of somatotype using the adjusted data for other two somatotype components. The heritability of each component in different development periods divided by growth spurt was also evaluated.

RESULTSThe estimated heritabilities of endomorphic, mesomorphic and ectomorphic components were 0.45, 0.80, 0.44 in boys, 0.82, 0.79 and 0.81 in girls respectively after adjusting age. In boys, the heritability of endomorphic component during late puberty was significantly higher than that during pre-puberty (t = 4.99, P < 0.01) and puberty (t = 6.16, P < 0.01), while the heritability of ectomorphic component during late puberty was significantly lower than that during pre-puberty (t = 3.35, P < 0.01) and puberty (t = 4.12, P < 0.01). In girls, the heritability of endomorphic (t = 2.77, P < 0.01) or mesomorphic (t = 2.08, P < 0.05) component during pre-puberty was significantly higher than that in early puberty.

CONCLUSIONThe genetic influence on somatotype of girls should be much more than that of boys, especially on the endomorphic and ectomorphic components. For boys, the mesomorphic component is mainly determined by genetic factors, but the other components are mainly affected by environmental ones. The effects of the development periods on the heritability of somatotype should be paid much attention to.

Adolescent ; Asian Continental Ancestry Group ; Child ; China ; Female ; Humans ; Male ; Somatotypes ; genetics ; Twins ; genetics ; Twins, Dizygotic ; genetics ; Twins, Monozygotic ; genetics

Objective: To describe the distribution characteristics of coronary heart disease in adult twins recruited from Chinese Twin Registry (CNTR), and provide clues and evidence for the effect of genetic and environmental influences on coronary heart disease. Methods: By using the data of CNTR during 2010-2018, a total of 34 583 twin pairs aged ≥18 years who completed questionnaire survey and had related information were included in the current study to analyze the population and area distribution characteristics of coronary heart disease. Random effect models were used to compare the differences between groups. The concordane rate of coronary heart disease were calculated respectively in monozygotic (MZ) twin pairs and dizygotic (DZ) twin pairs to estimate the heritability. Results: The twin pairs included in this analysis were aged (34.2±12.4) years. The overall prevalence rate of coronary heart disease in twin pairs was 0.7%. Twin pairs who were women, older, obese and lived in northern China had higher prevalence of coronary heart disease (P<0.05). Intra-pair analysis in the same-sex twin pairs found that the concordane rate of coronary heart disease was higher in MZ twin pairs (25.3%) than in DZ twins (7.4%), and the difference was statistically significant (P<0.001). The overall heritability of coronary heart disease was 19.3% (95%CI: 11.8%-26.8%). Stratified by gender, age and area, the concordane rate was still higher in MZ twin pairs than in DZ pairs. Participants who were women, aged 18-30 years or ≥60 years and lived in northern China had a higher heritability of coronary heart disease. Conclusion: The distribution of coronary heart disease in twin pairs differed in populations and areas. The prevalence of coronary heart disease was affected by genetic factors, but the effect varied with age, gender and area.
Adolescent ; Adult ; China/epidemiology* ; Coronary Disease/genetics* ; Diseases in Twins/genetics* ; Female ; Humans ; Male ; Twins, Dizygotic ; Twins, Monozygotic/genetics*

Objective: To describe the distribution characteristics of hypertension among adult twins in the Chinese National Twin Registry (CNTR) and to provide clues for exploring the role of genetic and environmental factors on hypertension. Methods: A total of 69 220 (34 610 pairs) of twins aged 18 and above with hypertension information were selected from CNTR registered from 2010 to 2018. Random effect models were used to describe the population and regional distribution of hypertension in twins. To estimate the heritability, the concordance rates of hypertension were calculated and compared between monozygotic twins (MZ) and dizygotic twins (DZ). Results: The age of all participants was (34.1±12.4) years. The overall self-reported prevalence of hypertension was 3.8%(2 610/69 220). Twin pairs who were older, living in urban areas, married, overweight or obese, current smokers or ex-smokers, and current drinkers or abstainers had a higher self-reported prevalence of hypertension (P<0.05). Analysis within the same-sex twin pairs found that the concordance rate of hypertension was 43.2% in MZ and 27.0% in DZ, and the difference was statistically significant (P<0.001). The heritability of hypertension was 22.1% (95%CI: 16.3%- 28.0%). Stratified by gender, age, and region, the concordance rate of hypertension in MZ was still higher than that in DZ. The heritability of hypertension was higher in female participants. Conclusions: There were differences in the distribution of hypertension among twins with different demographic and regional characteristics. It is indicated that genetic factors play a crucial role in hypertension in different genders, ages, and regions, while the magnitude of genetic effects may vary.
Adult ; Female ; Humans ; Male ; Alcohol Drinking ; Diseases in Twins/genetics* ; Hypertension/genetics* ; Twins, Dizygotic/genetics* ; Twins, Monozygotic/genetics*