Imaizumi Y, Inouye E
Acta Genet Med Gemellol (Roma). 1984;33(1):107-14. doi: 10.1017/s0001566000007571.
The rates of MZ and DZ twin births and of triplet births slightly decreased in Japan in 1955-1967 and 1974, whereas that of trizygotic triplets tripled. The rates of triplet and quadruplet births were comparable to those of Caucasians. Although the sample size is small, Japan seems to be characterized by higher rates of triplets and quadruplets of polyembryonal origin and lower rates of those of polyovulational origin as compared to Caucasian populations. Stillbirth rates in both MZ and DZ twins gradually decreased in 1960-1967 and 1974. The rate was higher in MZ than DZ twins, and higher in males than females. The secular trends of stillbirth rates in like-sexed triplets was similar to that in twins, whereas the rate in unlike-sexed triplets remained almost constant for the entire period. The rate was higher in like-sexed than unlike-sexed triplets.
1955年至1967年以及1974年期间，日本单卵双胞胎（MZ）和双卵双胞胎（DZ）的出生率以及三胞胎出生率略有下降，而三卵性三胞胎的出生率增长了两倍。三胞胎和四胞胎的出生率与白种人相当。尽管样本量较小，但与白种人群体相比，日本似乎具有多胚胎来源的三胞胎和四胞胎出生率较高、多排卵来源的三胞胎和四胞胎出生率较低的特点。1960年至1967年以及1974年期间，MZ和DZ双胞胎的死产率均逐渐下降。MZ双胞胎的死产率高于DZ双胞胎，男性的死产率高于女性。同性三胞胎死产率的长期趋势与双胞胎相似，而异性三胞胎的死产率在整个时期几乎保持不变。同性三胞胎的死产率高于异性三胞胎。
