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KMID : 1138720200460010079
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Korean Public Health Research
2020 Volume.46 No. 1 p.79 ~ p.85
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Secondary Sex Ratio of Twin Birth in Korea, 2000-2018
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Park Sang-Hwa
Lee Jae-Hyung
Lim Dar-Oh
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Abstract
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Objective: To determine the secondary sex ratio of the twin and singleton births. in Korea from 2000 to 2018.
Methods: This study used birth certificate data (twin: 115,656 pairs, total birth: 8,763,140 births) covering the years 2000-18 provided by Statistics Korea. The secondary sex ratio (male/female x 100) of twin and singleton births was analyzed by examining data on the sex composition of twin pairs (same-sex twin and opposite-sex twin). The odds ratio (OR) and 95% confidence intervals were calculated to describe the trend of the sex ratio at birth in twin and singleton births.
Results: During this period, the proportion of opposite-sex twin increased from 28.4 percent to 38.4 percent. The average increment of the opposite-sex twin was 0.6 percent annually. The proportion of same-sex twin decreased from 71.6 percent to 61.6 percnet during the period. The mean sex ratio of singleton was higher (106.9±1.7) than that of twin (102.9±2.4). The proportion of same-sex twin was 37.6 percent in 2015-18 (odds ratio: 1.28, 95% confidence interval: 1.24-1.31), compared with the proportion of same-sex twin in 2000-04 (29.4 percent). the odds ratio of sex ratio in singleton birth was 1.06 in 2000-04, 1.03 in 2005-09, 1.04 in 2010-14, and 1.02 in 2015-18, as compare to five-year term of the sex ratio in twin.
Conclusion: The secondary sex ratio of singleton was higher than that of twin. The incidence of opposite-sex twin increased by 0.6 percent annually, and proportion of same-sex twin decreased during the period. More research is required to understand the contributing factors to the sex ratio of twin and singleton births.
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KEYWORD
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sex ratio, twin, singleton
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