Trial construction of birthweight and birth length references for multiple birth neonates in Japan.

在日本，出生、死亡和死产证明目前存储在磁带上的数据文件中。这些证书在市卫生部门存档，并在日本卫生、劳动和福利省转换为计算机档案。这个数据库包含性别、出生体重、胎龄、胎次、父亲和母亲的年龄。通过出生地、父母年龄、胎龄、出生年月日对多胞胎进行识别；多胎母亲生的双胞胎出生体重大于初产母亲生的双胞胎。本研究结果可用于日本多胞胎出生体重的评估。按胎龄划分的出生体长中位数以双胞胎最大，三胞胎最小，四胞胎最小，双胞胎出生体长短于单胎，但与单胎的出生体重差异较小。多胎新生儿发育不对称。围产期死亡率按出生体重和胎龄分类进行比较，双胞胎和三胞胎与单胎，并在每个多胎中以相对危险度±95% ci的最低比率与所有其他比率进行比较。当出生体重和胎龄达到特定多胎理想范围时，围产期死亡率可降低90%以上。为了确定不一致双胞胎的分界点，并澄清围产期死亡是由不一致还是低出生体重本身引起的，对双胞胎数据进行了分析。围产儿死亡率比不协调组高不到20%。出生体重不一致和出生体重过低对日本双胞胎围产期死亡有显著影响。

In Japan, birth, death, and stillbirth certificates are currently stored in data files on magnetic tapes. These certificates are filed in the city health department and changed into computerized files in Ministry of Health, Labour and Welfare of Japan. This database contains sex, birthweight, gestational age, parity, ages of father and mother.Pairs of multiple births were identified by birthplace, the ages of the parents, gestational age, and the year and month of birth; The birthweight of twins from multiparous mothers was greater than those from primiparous mothers. Our results can be used for assessment of birthweight of multiple births in Japan.The median birth length according to gestational age was found to be the greatest in twins, lower in triplets and the lowest in quadruplets, Birth length of twins was shorter than singletons, but difference was smaller than that of birthweight between twins and singletons. Multiple birth neonates showed asymmetrical growth.Perinatal mortality was compared by categories of bithweight and gestational age, for twins and triplets versus singletons, and within each plurality by the lowest rate compared to all other rates as relative risks ±95% CIs. Perinatal death rates can be reduced by more than 90% with attainment of birthweight and gestational age a within a plurality-specific ideal range.To determine cut-off point for discordant twins, and to clarify whether perinatal deaths are caused by discordancy or low birth weight itself, twin dataset was analized. Perinatal mortality rate was higher than that among discordancy less than 20%.Perinatal death of Japanese twins was significantly affected by both discordancy and low birth weight.