[Associations between mothers' economic insecurity and mood and thoughts on life with children at infants' 3-month check-ups: A cross-sectional study using data from infant health check-ups].

Objectives　We aimed to clarify the relationship between economic insecurity and the psychological profiles of mothers raising infants by analyzing data from three-month health check-ups in relation to the birth population in order to generate basic data that can be used to consider support for families facing economic insecurity.Methods　The study area was a neighborhood in a major Japanese city. The survey focused on 1013 mothers who had received health check-ups for children aged 18 months between November 2017 and October 2019. The data included in the analysis were data from the children's three-month health check-ups and survey data from 908 mothers who responded to the questionnaire and consented to the use of their health check-up data. After excluding data from potential participants who were not mothers or had multiple births, data from 847 participants were analyzed (valid response rate: 93.3%).　The objective variables were mothers' mood and thoughts about life with their children at the time of the three-month check-up as the mothers' psychological profiles. The explanatory variable was the presence or absence of maternal economic insecurity, and logistic regression analysis was conducted, adjusted for the children's sex and birth order, presence or absence of maternal counselors, and the mothers' educational attainment.Results　A total of 60 (7.1%) mothers were economically insecure. Of the mothers' moods, 122 (14.4%) reported feeling anxious, followed by 36 (4.3%) who reported feeling lonely. Of their thoughts on life with their children, 776 (91.6%) mothers reported that they enjoyed it, and 567 (66.9%) reported that they were happy to be parents. On the other hand, 157 (18.5%) reported feeling frustrated, and 75 (8.9%) reported that the lack of time for themselves was painful. Economically insecure mothers had an odds ratio of 5.59 (95% confidence interval, 2.49-12.55) for feeling lonely, 4.77 (2.67-8.54) for feeling anxious, and 2.70 (1.50-4.86) for feeling frustrated, all significantly higher than in mothers not facing economic insecurity.Conclusion　Economic insecurity among mothers at the time of the three-month check-up was associated with the psychological states of loneliness, anxiety, and frustration about living with their children. It was suggested that to solve economically insecure mothers' problems, they need support, including connecting them with social welfare services, so that they will be able to raise their children in a more stable environment.

Changing genetic architecture of body mass index from infancy to early adulthood: an individual based pooled analysis of 25 twin cohorts.

BACKGROUND: Body mass index (BMI) shows strong continuity over childhood and adolescence and high childhood BMI is the strongest predictor of adult obesity. Genetic factors strongly contribute to this continuity, but it is still poorly known how their contribution changes over childhood and adolescence. Thus, we used the genetic twin design to estimate the genetic correlations of BMI from infancy to adulthood and compared them to the genetic correlations of height. METHODS: We pooled individual level data from 25 longitudinal twin cohorts including 38,530 complete twin pairs and having 283,766 longitudinal height and weight measures. The data were analyzed using Cholesky decomposition offering genetic and environmental correlations of BMI and height between all age combinations from 1 to 19 years of age. RESULTS: The genetic correlations of BMI and height were stronger than the trait correlations. For BMI, we found that genetic correlations decreased as the age between the assessments increased, a trend that was especially visible from early to middle childhood. In contrast, for height, the genetic correlations were strong between all ages. Age-to-age correlations between environmental factors shared by co-twins were found for BMI in early childhood but disappeared altogether by middle childhood. For height, shared environmental correlations persisted from infancy to adulthood. CONCLUSIONS: Our results suggest that the genes affecting BMI change over childhood and adolescence leading to decreasing age-to-age genetic correlations. This change is especially visible from early to middle childhood indicating that new genetic factors start to affect BMI in middle childhood. Identifying mediating pathways of these genetic factors can open possibilities for interventions, especially for those children with high genetic predisposition to adult obesity.

[Perceptual changes among public health nurses brought on through a newly adopted system for providing continuous support in the municipality: Modelled at its core on Finnish practice for maternity and child health clinics (Neuvola)].

Objectives　This study targeted public health nurses in a Japanese municipality that had newly adopted the core components of the Finnish system to provide continuous support to families with children until preschool. It sought to analyze changes in their perceptions for activities in maternal and child health care before and after the adoption.Methods　Relevant data were collected through semi-structured focus group interviews, following an interview guide, conducted from September to October 2020. The study protocol was approved by the Ethics Committee of Osaka City University in Japan.Results　A total of 12 public health nurses participated. Prior to the adoption of the system modelled on Finnish practice, these nurses were dedicated to addressing the risks regarding families with children (especially those at high risk) through continuous engagement. However, they were hesitant to proactively engage with families at lower risk as non-continuous, one-off engagements resulted in a patchwork response. After the system was adopted, the nurses became aware of the trust cultivated with families under their care, which included those at lower risk, that enabled them to respond to the changing needs flexibly. The nurses recognized that they had acquired the capability to notice the subtle signs of changes, engage more proactively with the families under their care, and deliver the necessary preventive interventions at an early stage. They also demonstrated joy and satisfaction derived from the growth of children and mothers under their care, as well as keen awareness of the need to improve their professional skills, even though they were busy.Conclusion　These findings indicate that the continuous support system modelled on the core components from Finland enables public health nurses to proactively engage with families at lower risk and deliver preventive interventions at an early stage. The system also motivated Japanese public health nurses who found greater pleasure in their work.

Triplets, birthweight, and handedness.

The mechanisms behind handedness formation in humans are still poorly understood. Very low birthweight is associated with higher odds of left-handedness, but whether this is due to low birthweight itself or premature birth is unknown. Handedness has also been linked to development, but the role of birthweight behind this association is unclear. Knowing that birthweight is lower in multiple births, triplets being about 1.5 kg lighter in comparison with singletons, and that multiples have a higher prevalence of left-handedness than singletons, we studied the association between birthweight and handedness in two large samples consisting exclusively of triplets from Japan (n = 1,305) and the Netherlands (n = 947). In both samples, left-handers had significantly lower birthweight (Japanese mean = 1,599 g [95% confidence interval (CI): 1,526-1,672 g]; Dutch mean = 1,794 g [95% CI: 1,709-1,879 g]) compared with right-handers (Japanese mean = 1,727 g [95% CI: 1,699-1,755 g]; Dutch mean = 1,903 g [95% CI: 1,867-1,938 g]). Within-family and between-family analyses both suggested that left-handedness is associated with lower birthweight, also when fully controlling for gestational age. Left-handers also had significantly delayed motor development and smaller infant head circumference compared with right-handers, but these associations diluted and became nonsignificant when controlling for birthweight. Our study in triplets provides evidence for the link between low birthweight and left-handedness. Our results also suggest that developmental differences between left- and right-handers are due to a shared etiology associated with low birthweight.

[Relationship between economic disparity and eating habits of 3-year-old children].

Objectives　This study aimed to clarify the relationship between economic disparity and eating habits of young children to explore the support that should be provided to families with young children.Methods　We conducted an anonymous self-administered questionnaire survey of parents who brought their children to the 3-year-old health checkup in four wards in City A. Questionnaire items examined the children's eating habits and the childrearing environment, such as the parents' socioeconomic status. Of 1,150 parents asked to participate in the survey, 616 responded (response rate: 53.6%). Invalid questionnaires (e.g., with missing answers) were eliminated. The remaining 498 parents (effective response rate: 80.8%) were classified into two groups to examine the association of household financial status with their 3-year-old eating habits: the relative poverty group and the non-relative poverty group. The groups were divided according to the poverty line of the Comprehensive Survey of Living Conditions. Statistical analysis was performed using Fisher's exact test and the Mann-Whitney U test. Eating habits that were identified to be associated with relative poverty were further tested using logistic regression analysis.Results　Analysis of the children's eating habits in the two groups revealed that, compared with the non-relative poverty group, there was a higher proportion of 3-year-olds who ate vegetables less than 6 days a week (P=0.003) and who consumed snacks 6 days or more per week (P=0.034) in the relative poverty group. The associations of relative poverty with vegetable intake less than 6 days a week and snack consumption 6 days or more a week remained significant after adjusting for parents' age, highest educational attainment, and subjective views on the everyday economic situation. Regarding the childrearing environment, the relative poverty group had a higher proportion of parents who were younger than 30 years of age (P<0.001) and in single-parent households (P=0.007). The relative poverty group had a higher proportion of parents whose highest education level was high school (P<0.001). Furthermore, the subjective view of the everyday economic situation was more negative in the relative poverty group (P<0.001).Conclusion　Economic disparity was related to the eating habits of 3-year-old children. The study results indicate that identifying families with financial difficulties during pregnancy and childbirth is necessary to support them early on so that young children can acquire healthy eating habits.

The New West Japan Twins and Higher Order Multiple Births Registry.

The new West Japan Twins and Higher Order Multiple Births Registry was established by recruiting young twins and multiple births and by referrals from public health centers in the 1990s. The participants included in the survey comprised over 7800 twins and 4241 higher order multiples, and their families. Specifically, the present registry contains one of the largest triplet samples in the world. For these twins and multiples, data on year of delivery, mode of delivery, gestational age, intrapartum complications, longitudinal physical measures, motor milestones, cerebral palsy and feeding methods were obtained from records in the Maternal and Child Health Handbooks and schools. Participating mothers were asked to indicate family structure, parental educational history, maternal sleeping time, maternal health condition, maternal and paternal age at multiple delivery, complications during pregnancy, handedness of multiples and age at menarche of multiples. However, the zygosity differed among the various collaborating public health centers according to factors such as the time of investigation. Follow-up questionnaires have been mailed out every 3-4 years for longitudinal studies. This article describes the goals of this registry, recruitment of multiples and the focus of the study. The goals of this registry are not only to conduct research on human genetics and maternal and child health, but also to contribute to providing appropriate information for families with multiples.

[Childcare burdens perceived by mothers with an inter-pregnancy interval less than 12 months].

Objectives　The aims of this study were to investigate perceived childcare burdens among mothers with an inter-pregnancy interval of less than 12 months, and to identify the factors associated with those perceptions.Methods　Anonymous, self-administered questionnaires on inter-pregnancy intervals, the Edinburgh postnatal depression scale (EPDS), and the childcare emotion scale were distributed to mothers who visited one of three health and welfare centers in City A for three-month well-baby checkups. Six hundred eighty-five subjects were classified into four groups according to their inter-pregnancy interval (<12 months apart; ≥12 months but <24 months apart; ≥24 months apart; and a group with no siblings), and they was used to analyze associations between the timing of pregnancy and the mothers' perceptions of their childcare burdens. Chi-squared tests, a one-way analysis of variance, the Kruskal-Wallis test, and linear regression analyses were used for analysis.Results　The inter-pregnancy interval was <12 months in 35 of the 685 respondents, ≥12 months but <24 months in 114 respondents, and ≥24 months in 194 respondents. There were 342 respondents in the no-siblings group. Linear regression analyses disclosed some factors associated with the subordinate items of the childcare emotion scale. "Feeling restricted by childcare duties" is significantly correlated to inter-pregnancy interval (P=.032), family composition (P=.014), time of sleeping (P=.010), and night wake-up time (P=.001). "Feeling of burden because of the child's attitude and behavior" was significantly related to inter-pregnancy interval (P<.001), mother's age (P=.003), time of sleeping (P=.009), and night wake-up time (P=.002). "Anxiety about the child's growth" was significantly related to inter-pregnancy interval (P<.001), mother's age (P=.016), and gestational age (P<.001). In addition, the group with gestation intervals of less than 12 months had significantly higher numbers of women in single-parent households (P=.005), who were unmarried (P=.007), had only a junior high school education (P=.0027), and were 24 years old or younger (P<.001).Conclusion　The pregnancy interval is significantly related to the "Feeling restricted by childcare duties," "Feeling of burden because of the child's attitude and behavior," and "Anxiety about the child's growth," even after adjusting the influence of other factors. In addition, the results of this study demonstrated that mothers in the <12 months group were more likely to be in a single-parent household, unmarried, with low educational attainment, and were 24 years old or younger. The results suggest that greater support is needed for these mothers.

Maternal subjective well-being and preventive health care system in Japan and Finland.

Background: Maternal well-being is an important issue not only for mothers but also for their offspring and whole families. This study aims to clarify differences in subjective well-being for mothers with infants and associated factors by comparing Japanese and Finnish mothers. Methods: In Finland, 101 mothers with infants who received health check-ups at child's age 4 months participated in the study. In Japan, 505 mothers with infants who should receive health check-ups at child's age 4 months and, whose age, age of the infant and number of children matched with the Finnish mothers were selected. The factors associated with maternal subjective well-being were explored by the linear regression analysis. All Finnish mothers had individual infant health check-ups by nurses in Child Health Clinics nearly monthly. The same nurse was responsible for following up the family throughout the years. All Japanese participants received group health check-up once at child's age 3 to 4 months, and a nurse did not cover same child and their mother. Results: Finnish mothers showed significantly better subjective well-being compared with Japanese mothers. Whereas 85% of Finnish mothers responded that they had obtained childcare information from public health nurses, significantly fewer Japanese mothers indicated the same response (8%). Linear regression analyses disclosed that mothers' subjective well-being was associated with country, mothers' stress and age. Conclusion: Finnish mothers had better subjective well-being than Japanese mothers. Our results may indicate that the Finnish health care system supports mothers better than the Japanese health care system does.

Education in Twins and Their Parents Across Birth Cohorts Over 100 years: An Individual-Level Pooled Analysis of 42-Twin Cohorts.

Whether monozygotic (MZ) and dizygotic (DZ) twins differ from each other in a variety of phenotypes is important for genetic twin modeling and for inferences made from twin studies in general. We analyzed whether there were differences in individual, maternal and paternal education between MZ and DZ twins in a large pooled dataset. Information was gathered on individual education for 218,362 adult twins from 27 twin cohorts (53% females; 39% MZ twins), and on maternal and paternal education for 147,315 and 143,056 twins respectively, from 28 twin cohorts (52% females; 38% MZ twins). Together, we had information on individual or parental education from 42 twin cohorts representing 19 countries. The original education classifications were transformed to education years and analyzed using linear regression models. Overall, MZ males had 0.26 (95% CI [0.21, 0.31]) years and MZ females 0.17 (95% CI [0.12, 0.21]) years longer education than DZ twins. The zygosity difference became smaller in more recent birth cohorts for both males and females. Parental education was somewhat longer for fathers of DZ twins in cohorts born in 1990-1999 (0.16 years, 95% CI [0.08, 0.25]) and 2000 or later (0.11 years, 95% CI [0.00, 0.22]), compared with fathers of MZ twins. The results show that the years of both individual and parental education are largely similar in MZ and DZ twins. We suggest that the socio-economic differences between MZ and DZ twins are so small that inferences based upon genetic modeling of twin data are not affected.

Characteristics of stepfamilies and maternal mental health compared with non-stepfamilies in Japan.

BACKGROUND: Stepfamilies remain poorly understood in Japanese society, and the support needs of stepfamily mothers are unclear. This study aimed to identify characteristics of stepfamilies and maternal mental health as compared with non-stepfamilies in Japan to utilize as a primary resource for providing effective support through community-based health care for stepfamilies. METHODS: From December 2011 to July 2012, we conducted this questionnaire survey with mothers at 3- and 4-month checkups for infants. The response rate was 75.1%. The sample for analysis included responses of 2246 mothers, excluding single mothers. RESULTS: Respondents comprised 47 (2.1%) stepfamilies and 2199 (97.9%) non-stepfamilies. There were significantly higher rates of parents with not more than a high school education and ≥3 children among stepfamilies compared with non-stepfamilies. Stepfamily mothers had significantly higher rates of feeling a lack of economic resources, absence of participation in childbirth education classes, smoking during pregnancy, and unplanned pregnancy. Furthermore, they also had significantly higher rates of depression and a lack of confidence in the parent role. Maternal depression was associated with factors such as maternal age, self-perceived health, stress level, confidence in breastfeeding, confidence in the parent role, and number of children. CONCLUSIONS: These findings suggest that stepfamilies exhibit many characteristics related to social disadvantage and problems with community-based health care in Japan. Healthcare providers should be aware of stepfamily mothers' support needs and should put in place a support system for stepfamilies. Moreover, compared with non-stepfamily mothers, stepfamily mothers have a significantly higher prevalence of depression. However, stepfamily composition does not necessarily increase the risk of maternal depression. Therefore, healthcare providers should put in place a system for obtaining more thorough information about stepfamilies and conduct an early assessment to identify their support needs.

Erratum to: Characteristics of stepfamilies and maternal mental health compared with non-stepfamilies in Japan.

[This corrects the article DOI: 10.1186/s12199-017-0658-z.].

Twin's Birth-Order Differences in Height and Body Mass Index From Birth to Old Age: A Pooled Study of 26 Twin Cohorts Participating in the CODATwins Project.

We analyzed birth order differences in means and variances of height and body mass index (BMI) in monozygotic (MZ) and dizygotic (DZ) twins from infancy to old age. The data were derived from the international CODATwins database. The total number of height and BMI measures from 0.5 to 79.5 years of age was 397,466. As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood. After adjusting the results for birth weight, the birth order differences decreased and were no longer statistically significant. First-born twins had greater BMI than the second-born twins over childhood and adolescence. After adjusting the results for birth weight, birth order was still associated with BMI until 12 years of age. No interaction effect between birth order and zygosity was found. Only limited evidence was found that birth order influenced variances of height or BMI. The results were similar among boys and girls and also in MZ and DZ twins. Overall, the differences in height and BMI between first- and second-born twins were modest even in early childhood, while adjustment for birth weight reduced the birth order differences but did not remove them for BMI.

Child Maltreatment Among Singletons and Multiple Births in Japan: A Population-Based Study.

BACKGROUND: The occurrence of multiple births has been recognized as a risk factor for child maltreatment. However, few population-based studies have examined the relationship between multiple births and child maltreatment. This study aimed to evaluate the degree of risk of child maltreatment among singletons and multiple births in Japan and to identify factors associated with increased risk. METHODS: Using population-based data, we analyzed the database of records on child maltreatment and medical checkups for infants aged 1.5 years filed at Nishinomiya City Public Health Center between April 2007 and March 2011. To protect personal information, the data were transferred to anonymized electronic files for analysis. RESULTS: After adjusting by logistic regression for each associated factor and gestation number, multiples themselves were not associated with the risk of child maltreatment. However, compared with singletons, multiples had a significantly higher rate of risk factors for child maltreatment, including low birth weight and neural abnormality. Moreover, compared with mothers of singleton, mothers of twins had a significantly higher rate of poor health, which is a risk factor of child maltreatment. CONCLUSION: Multiples were not associated with the risk of child maltreatment. However, compared with singletons, multiples and their mothers had a significantly higher rate of risk factors of child maltreatment.

Zygosity Differences in Height and Body Mass Index of Twins From Infancy to Old Age: A Study of the CODATwins Project.

A trend toward greater body size in dizygotic (DZ) than in monozygotic (MZ) twins has been suggested by some but not all studies, and this difference may also vary by age. We analyzed zygosity differences in mean values and variances of height and body mass index (BMI) among male and female twins from infancy to old age. Data were derived from an international database of 54 twin cohorts participating in the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins), and included 842,951 height and BMI measurements from twins aged 1 to 102 years. The results showed that DZ twins were consistently taller than MZ twins, with differences of up to 2.0 cm in childhood and adolescence and up to 0.9 cm in adulthood. Similarly, a greater mean BMI of up to 0.3 kg/m2 in childhood and adolescence and up to 0.2 kg/m2 in adulthood was observed in DZ twins, although the pattern was less consistent. DZ twins presented up to 1.7% greater height and 1.9% greater BMI than MZ twins; these percentage differences were largest in middle and late childhood and decreased with age in both sexes. The variance of height was similar in MZ and DZ twins at most ages. In contrast, the variance of BMI was significantly higher in DZ than in MZ twins, particularly in childhood. In conclusion, DZ twins were generally taller and had greater BMI than MZ twins, but the differences decreased with age in both sexes.

The CODATwins Project: The Cohort Description of Collaborative Project of Development of Anthropometrical Measures in Twins to Study Macro-Environmental Variation in Genetic and Environmental Effects on Anthropometric Traits.

For over 100 years, the genetics of human anthropometric traits has attracted scientific interest. In particular, height and body mass index (BMI, calculated as kg/m2) have been under intensive genetic research. However, it is still largely unknown whether and how heritability estimates vary between human populations. Opportunities to address this question have increased recently because of the establishment of many new twin cohorts and the increasing accumulation of data in established twin cohorts. We started a new research project to analyze systematically (1) the variation of heritability estimates of height, BMI and their trajectories over the life course between birth cohorts, ethnicities and countries, and (2) to study the effects of birth-related factors, education and smoking on these anthropometric traits and whether these effects vary between twin cohorts. We identified 67 twin projects, including both monozygotic (MZ) and dizygotic (DZ) twins, using various sources. We asked for individual level data on height and weight including repeated measurements, birth related traits, background variables, education and smoking. By the end of 2014, 48 projects participated. Together, we have 893,458 height and weight measures (52% females) from 434,723 twin individuals, including 201,192 complete twin pairs (40% monozygotic, 40% same-sex dizygotic and 20% opposite-sex dizygotic) representing 22 countries. This project demonstrates that large-scale international twin studies are feasible and can promote the use of existing data for novel research purposes.

Association between physical and motor development in childhood: a longitudinal study of Japanese twins.

Length and weight in infancy are associated with neurodevelopment, but less is known about growth in other anthropometric measures. In this study we analyzed how the development in length, weight, head circumference, and chest circumference over infancy is associated with motor development in early childhood, using a twin study design. Information on physical development over infancy and the age at achievement of eight developmental milestones over early childhood was collected for 370 Japanese twin pairs. Linear mixed models were used to analyze how physical development is associated with motor development between individual twins, as well as within twin pairs, adjusting the results for shared maternal and postnatal environmental factors. Delayed motor development was associated with smaller body size over infancy, and we also found some suggestive evidence that it was associated with catch-up growth as well. When studying the associations within twin pairs discordant for motor development, similar associations were found. However, chest circumference showed the most robust association within discordant twin pairs. Smaller body size and rapid catch-up growth are associated with delayed motor development. When studying these associations within twin pairs and thus adjusting the results for gestational age as well as many other maternal and postnatal environmental factors, chest circumference showed the most robust association. Chest circumference, rarely used in developed countries, can offer additional information on prenatal conditions relevant for further motor development not achieved by more traditional anthropometric measures.

Activities and health status of dispatched public health nurses after the great East Japan earthquake.

OBJECTIVE: This study aimed to elucidate the actual activities conducted by public health nurses during their dispatch and their health status during and after dispatch to the three prefectures most severely affected by the Great East Japan Earthquake. SAMPLE: A survey request was sent to a total of 2,237 facilities. Of these, 778 facilities returned questionnaires from dispatched public health nurses. RESULTS: The participants of this study were 1,570 dispatched health nurses who participated in activities mostly at evacuation centers, followed by evacuees' homes. After dispatch, an earlier postdisaster phase at the start of dispatch was independently associated with poor subjective well-being, low mood, worsened sleep state, and intense fatigue. Work hours per day were associated with poor subjective well-being and intense fatigue after dispatch. CONCLUSION: Results suggest that the factor that most strongly affected the postdispatch health of the nurses was the phase that they began their dispatch.

Social modifications of the multiple birth effect on IQ and body size: a population-based study of young adult males.

BACKGROUND: Twins and triplets fall behind singletons in cognitive and physical development. We analysed whether these differences are modified by family social position. METHODS: IQ, height, body mass index (BMI) and elbow flexion, handgrip and knee extension strength were measured in Swedish men born between 1951 and 1976 during the conscription examination at 17 to 20 years of age. Information from Swedish registers on all siblings and parental socio-economic position were linked to these measures. Together, the measures were available for 1,140,329 singletons, 19,55 twins and 207 triplets. The data were analysed using regression analyses and fixed-effect models which compare twins and triplets with their singleton brothers. RESULTS: Twins and triplets had slightly lower IQ, height, BMI and muscle strength than did singletons both at the population level as well as when compared with their singleton brothers. Although the differences between twins and triplets were small, they were largest in families with lower socio-economic position. We also found larger differences in IQ among the sons of mothers born before 1940. CONCLUSIONS: Twins and triplets fall slightly behind singletons in cognitive and physical development, even in early adulthood, but twins and triplets show no major differences. These differences are largest in families in a low socio-economic position. Our results underscore the importance of the postnatal environment in the development of twins and triplets and suggest that their parents, especially those in a low socio-economic position, need special support.

The West Japan Twins and Higher Order Multiple Births Registry.

The West Japan Twins and Higher Order Multiple Births Registry was established in the 1990s by recruiting young twins and multiples and through referrals from public health centers. To date, over 7,000 twins and 4,300 higher order multiple births and their families have been registered in the survey, and it includes one of the largest triplet samples in the world. Follow-up questionnaires are also mailed every 2 to 3 years as part of longitudinal survey studies. This article describes the goals of the registry, the recruitment of multiples, and the overall focus of the study. The goals of the registry are not only to provide data for research on human genetics and maternal and child health, but also to provide appropriate information for families with multiples.