Imaizumi Y
Institute of Population Problems, Ministry of Health and Welfare, Tokyo, Japan.
Acta Genet Med Gemellol (Roma). 1990;39(3):295-306. doi: 10.1017/s0001566000005201.
Multiple birth rates in entire Japan were analyzed using vital statistics for 1951 to 1988. The triplet rate was nearly constant from 1951 to 1974, where the rate per million births was 58, then increased with the year up to 1982 (104), and decreased up to 1984, and suddenly increased thereafter (109 in 1987). The average rate of quadruplets per million births from 1951 to 1968 was 0.93, then increased with the year up to 1975 (7.5), and decreased until 1984 and suddenly increased thereafter (10.6 in 1987). The rate of quintuplets was 0.77 per million births during the period from 1975 to 1987. The higher multiple birth rate since 1975 was attributed to the higher proportion of mothers treated with ovulation-inducing hormones in Japan. Since 1985, higher multiple birth rates might be partially attributed to in vitro fertilization. The stillbirth rates for male triplets gradually decreased from 1960 to 1978 and thereafter remained constant at a little higher level except in 1988, whereas the rates for females gradually decreased with the year. The overall stillbirth rates decreased to 1/4 for triplets and to 1/5 for quadruplets during the 37-year period from 1951. The overall stillbirth rate of quintuplets was 0.60 (51/85) during the period 1975-1987.
利用1951年至1988年的人口动态统计数据，对全日本的多胞胎出生率进行了分析。三胞胎出生率在1951年至1974年间几乎保持恒定，每百万例出生中三胞胎的发生率为58例，随后逐年上升，至1982年达到104例，1984年下降，此后又突然上升（1987年为109例）。1951年至1968年，每百万例出生中四胞胎的平均发生率为0.93例，随后逐年上升，至1975年达到7.5例，1984年下降，此后又突然上升（1987年为10.6例）。1975年至1987年期间，五胞胎出生率为每百万例出生0.77例。1975年以来较高的多胞胎出生率归因于日本接受促排卵激素治疗的母亲比例较高。自1985年以来，较高的多胞胎出生率可能部分归因于体外受精。男性三胞胎的死产率从1960年至1978年逐渐下降，此后除1988年外，一直保持在略高的水平，而女性三胞胎的死产率则逐年下降。从1951年起的37年期间，三胞胎的总体死产率降至四分之一，四胞胎降至五分之一。1975年至1987年期间，五胞胎的总体死产率为0.60（51/85）。
