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KMID : 0892720160200030221
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Journal of the Korean Society of Maternal and Child Health
2016 Volume.20 No. 3 p.221 ~ p.227
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Contribution of Maternal Age Distribution to Incidence of Preterm Birth ; 1997~99 and 2012~14 Singleton Birth Certificated Data of Korea
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Park Sang-Hwa
Kim Hoon
Lim Dar-Oh
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Abstract
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Purpose: The objective of the study was to compare contribution of maternal age to preterm birth (PTB) rates between 1997~99 and 2012~14.
Methods: We used 1997~99 (1,872,720 births) and 2012~14 (1,280,348 births) singleton birth certificated data of Korea Statistics excluding multiple birth and extra-marital birth cases. We decomposed the contributions of age-specific PTB rates and maternal age distribution (Kitagawa’s decomposition method) to overall PTB rates during the period. Odds ratio (OR) and 95% confidence intervals were calculated from logistic regression to describe the secular trend of PTB rate by birth year and maternal age.
Results: The incidence of PTB increased 1.5 times, from 3.0 percent to 4.6 percent, during 1997~2014. After adjustment by logistic regression for infantile sex, parity and maternal age, the odds ratio of PTB in birth year of 2012~14 was 1.38 (95% confidence interval: 1.36~1.39), compared with incidence of PTB in 1997~99. During the period, PTB rates increased 1.79 times in women aged 20~24 years and 25~29 years (OR: 1.56), whereas rates remained stable in women aged 35 years and older (OR: range from 1.08 to 1.13). 87.5% of the overall increase in the PTB rates was attributable to the increase in the proportion of women aged 30~34 years, but these age group accounted for only a small portion of the increase in PTB rates (OR: 1.27).
Conclusion: The remainder of the total increment in the PTB rates during the period was explained by increase the proportion of women aged 30~34 years. There was a need to close attention in this area to understand the contributing factors to the secular trend of PTB rates.
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KEYWORD
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singleton preterm birth, maternal age, contribution of preterm
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