title: Analysis of multiple birth rates in Japan. III. Secular trend, maternal age effect and geographical variation in triplet rates.
mesh_terms: D000328:Adult; D001723:Birth Rate; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008423:Maternal Age; D011247:Pregnancy; D012744:Sex Ratio; D014310:Triplets; D015053:Zygote