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Analysis of multiple birth rates in Japan

IV. Secular trend, effect of maternal age and gestational age in stillbirth rates of triplets

Summary

Over-all stillbirth rate of triplets in Japan was slightly increased from 1951 to 1961 and markedly decreased thereafter up to 1968 and 1974. The stillbirth rate of triplets remained two to three times as high as that of twins and five to seven times as high as that of the general population during the period from 1951 to 1968 and in 1974.

Secular change of the stillbirth rate of like-sexed triplets indicated a similar tendency to over-all rate whereas the rate of unlike-sexed triplets remained almost constant for the entire period. For the entire period from 1955 to 1967 and in 1974, the difference between stillbirth rates of like- and unlike-sexed triplets is statistically significant at the 0.1% level, the rate being higher in like-sexed triplets than in unlike-sexed triplets, but sex of each triplet did not affect the stillbirth rate. The stillbirth rate in 1974 was the lowest in the first-born children (0.328), followed by the second (0.353) and the third (0.378), but the differences are not significant at the 5% level.

In like-sexed triplets the stillbirth rate decreased from the youngest maternal age group to maternal age group of 30–34 years, then markedly increased thereafter. The pattern is similar but more marked in unlike-sexed triplets.

The mean gestational age was the shortest in triplet sets all stillborn (23.3 weeks), whereas those of other categories of survival state were between 34.8 to 35.2 weeks.

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Imaizumi, Y., Inouye, E. Analysis of multiple birth rates in Japan. Jap J Human Genet 25, 219–227 (1980). https://doi.org/10.1007/BF01997699

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Keywords

  • General Population
  • Birth Rate
  • Cancer Research
  • Entire Period
  • Similar Tendency

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