The twinning rates by zygosity in Japan, 1975-1994.
The twinning rates by zygosity in Japan, 1975-1994.
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1975 年至 1994 年日本按接合性划分的孪生率。
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
K. Nonaka
中科院分区：
文献类型：
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作者：
Y. Imaizumi;K. Nonaka
日本的同卵（MZ）双胞胎率从1975年（3.74‰）到1994年（4.23‰）基本保持不变，而异卵（DZ）双胞胎率从1975年（1.86‰）到1986年（2.27‰）基本保持不变，并逐渐上升到1994年（3.89‰）。自1987年以来，DZ双胞胎率较高的原因是接受促排卵激素治疗的母亲比例较高，部分原因是日本的体外受精。至于产妇年龄，除了最年轻和最年长年龄组外，各产妇年龄组的MZ双胞胎率几乎保持不变。另一方面，DZ孪生率在35-39岁年龄组呈上升趋势，此后呈下降趋势。1994年，在30-34岁和35-39岁的产妇年龄组中，DZ双胞胎的双胞胎率高于MZ双胞胎。至于孪生率的地域差异，在1986年至1994年期间，47个县中有31个县的DZ率逐年显著增加。1994年，在47个县中，有21个县的双胞胎率高于MZ率，其中两个县的DZ率与MZ率相等。1994年与1955-1959年和1974年相比，双胞胎合子率的地理变异发生了巨大变化。
The monozygotic (MZ) twinning rate in Japan had remained nearly constant from 1975 (3.74 per 1,000 births) to 1994 (4.23), whereas the dizygotic (DZ) twinning rate had remained nearly constant from 1975 (1.86) to 1986 (2.27), and had gradually increased up to 1994 (3.89). The higher DZ twinning rate since 1987 has been attributed to the higher proportion of mothers treated with ovulation-inducing hormones and partially attributed to in-vitro fertilisation in Japan. As for maternal age, MZ twinning rates have remained nearly constant for maternal age groups except the youngest and the oldest age groups. On the other hand, DZ twinning rates increased up to the 35-39 years of age group and decrease thereafter. In 1994, the twinning rate was higher in DZ twins than in MZ twins for maternal age groups of 30-34 years and of 35-39 years. As for geographical variations in twinning rates, DZ rates statistically significantly increased with the year during the period from 1986 to 1994 in 31 out of 47 prefectures. In 1994, twinning rates in 21 out of 47 prefectures were higher in the DZ than the MZ rate, and the DZ rate is equal to the MZ rate in two prefectures. Geographical variations in twinning rates by zygosity in 1994 drastically changed from those during the period from 1955-1959 and in 1974.