Breast-feeding rates and related maternal and infants' obstetric factors in Japanese twins

<p><b>OBJECTIVES</b>The aims of the present study are to describe the secular trend of breast-feeding rates in Japanese twins in comparison with the general population, and then to clarify the maternal and infants' obstetric factors associated with breast-feeding in twins.</p><p><b>METHODS</b>Breast-feeding rates from 0 to 6 full months and related maternal and infant obstetric factors were analyzed using 4,023 Japanese twins, consisting of two different volunteer-based twin samples, age 1-15 years, whose birth year ranged from 1968 to 2003. Data were collected through mailed or hand-delivered questionnaires. Obstetric factors that affect full and partial breast-feeding of twins were confirmed using logistic analyses according to birth order in twin pairs, adjusted by birth year.</p><p><b>RESULTS</b>The full breast-feeding rates of twins were lower than those of the general population. On the other hand, the combined rates of full and partial breast-feeding were close to those of general population, except for the period 1968-1974. The percentage of concordance pares was around 95% for all months. The most influential factor that negatively correlated with breast-feeding from 0 to 6 months was gestational weeks. Higher maternal age at twin birth and the use of an incubator also prevented breast-feeding in the neonatal period.</p><p><b>CONCLUSIONS</b>The results of the present study for the first time indicated that full breast-feeding of twins has risen recently in Japan, although the rates are still lower than those of the general population. The importance of the gestational weeks for breast-feeding rates was also shown.</p>

Nongenetic Factors Associated with Human Handedness and Footedness in Japanese Twin Children

Objective: The aim of this study is to clarify the factors related to the handedness and footedness of twins using two of the largest databases on Japanese twins available. Methods: The first group consisted of 1,131 twin pairs, all school children either 11 or 12 years old (S group), and the second group consisted of 951 twin pairs of different ages (1–15 years) in several maternal associations (M group). All data were gathered using a questionnaire. Factors associated with the handedness or footedness of twin individuals were analyzed by univariate and multivariate logistic analyses. Results: Multivariate logistic analysis showed that for handedness, birth year (OR=1.02) and neonatal asphyxia (OR=1.62) were selected in the S group, and sex (OR=1.34), the age of twins (OR=1.56), parity (OR=1.31), gestational age (OR=1.58), and family history (OR=1.82) were selected in the M group. For footedness, birth complications (OR=1.37) were selected in the S group, and sex (OR=1.33), the age of twins (OR=1.69), gestational age (OR=1.83), and family history (OR=2.49) were selected in the M group. Factors associated with handedness and footedness specific to twins, such as zygosity, placentation, birth order within twin pairs and the sex of the cotwin, were not found, although being a twin might have some effects. Conclusion: It was concluded that factors that affect handedness or footedness in general, such as sex, birth year, age, parity, neonatal asphyxia, gestational age, birth complications, and family history, seem to have stronger effects on handedness and footedness than being a twin.

Motor Development of Japanese Twins in Childhood as Reported by Mothers

Objective: Twins tend to lag behind singletons in their motor development, though the causes of this appear to be complicated and are not yet fully understood. The present study was performed to clarify the factors associated with the motor development of twins. Methods: The twins in the first group consisted of school applicants, including 1131 twin pairs, and the second group consisted of children of members of several maternal associations, and included 951 pairs. All data were gathered by questionnaire survey, and six gross-motor development milestones were analyzed in individuals or pairs. Results: Relative to general population norms in Japan, twins tended to be delayed in reaching several motor development milestones. Stepwise regression analysis showed that of all the variables measured, gestational age was the most influential on all six milestones. Birthweight was also influential on most milestones. Other factors affecting motor development milestones were parity for ‘sitting without support,’ ‘pulling up to a standing position,’ and ‘walking without support,’ and zygosity for ‘walking without support.’ In these cases, longer gestational age, heavier birthweight, primiparity, and dizygosity showed a tendency toward earlier attainment of development. Motor development within pairs was more similar in monozygotic pairs compared with dizygotic pairs regarding each item, suggesting genetic contributions. Conclusion: The results of the present study showed specific and nonspecific factors that affect motor development of twins. These findings should prove useful in understanding the motor development of twin children and help clinicians to refine maternal and child health care for multiple-birth children.

Motor development of Japanese twins in childhood as reported by mothers

<p><b>OBJECTIVE</b>Twins tend to lag behind singletons in their motor development, though the causes of this appear to be complicated and are not yet fully understood. The present study was performed to clarify the factors associated with the motor development of twins.</p><p><b>METHODS</b>The twins in the first group consisted of school applicants, including 1131 twin pairs, and the second group consisted of children of members of several maternal associations, and included 951 pairs. All data were gathered by questionnaire survey, and six gross-motor development milestones were analyzed in individuals or pairs.</p><p><b>RESULTS</b>Relative to general population norms in Japan, twins tended to be delayed in reaching several motor development milestones. Stepwise regression analysis showed that of all the variables measured, gestational age was the most influential on all six milestones. Birthweight was also influential on most milestones. Other factors affecting motor development milestones were parity for 'sitting without support,' 'pulling up to a standing position,' and 'walking without support,' and zygosity for 'walking without support.' In these cases, longer gestational age, heavier birthweighf, primiparity, and dizygosity showed a tendency toward earlier attainment of development. Motor development within pairs was more similar in monozygotic pairs compared with dizygotic pairs regarding each item, suggesting genetic contributions.</p><p><b>CONCLUSION</b>The results of the present study showed specific and nonspecific factors that affect motor development of twins. These findings should prove useful in understanding the motor development of twin children and help clinicians to refine maternal and child health care for multiple-birth children.</p>

Nongenetic factors associated with human handedness and footedness in Japanese twin children

<p><b>OBJECTIVE</b>The aim of this study is to clarify the factors related to the handedness and footedness of twins using two of the largest databases on Japanese twins available.</p><p><b>METHODS</b>The first group consisted of 1,131 twin pairs, all school children either 11 or 12 years old (S group), and the second group consisted of 951 twin pairs of different ages (1-15 years) in several maternal associations (M group). All data were gathered using a questionnaire. Factors associated with the handedness or footedness of twin individuals were analyzed by univariate and multivariate logistic analyses.</p><p><b>RESULTS</b>Multivariate logistic analysis showed that for handedness, birth year (OR=1.02) and neonatal asphyxia (OR=1.62) were selected in the S group, and sex (OR=1.34), the age of twins (OR=1.56), parity (OR=1.31), gestational age (OR=1.58), and family history (OR=1.82) were selected in the M group. for footedness, birth complications (OR=1.37) were selected in the S group, and sex (OR=1.33), the age of twins (OR=1.69), gestational age (OR=1.83), and family history (OR=2.49) were selected in the M group. Factors associated with handedness and footedness specific to twins, such as zygosity, placentation, birth order within twin pairs and the sex of the cotwin, were not found, although being a twin might have some effects.</p><p><b>CONCLUSION</b>It was concluded that factors that affect handedness or footedness in general, such as sex, birth year, age, parity, neonatal asphyxia, gestational age, birth complications, and family history, seem to have stronger effects on handedness and footedness than being a twin.</p>