Length of First Birth Interval and Incidence of Twin Birth in Korea; 2010~2015

PURPOSE: To compare the incidence of twin births with the length of first birth interval (LFBI: from marriage to first birth) among primiparous women. METHODS: The birth certificated data of Korea Statistics from 2010 to 2015 were used for this analysis. There were 1,356,204 births of primiparous women from total birth cases (2,736,296 births). The data involving multiparous women, teenage birth, extra-marital birth, and triplet birth cases were excluded from all analyses. Odds ratio and 95 percent confidence intervals were calculated from logistic regression to examine the risk of twin birth by LFBI adjusted for year of birth, maternal age, paternal age, age difference between couples, and maternal education and occupation. RESULTS: The frequency of LFBI was 41.5 percent in ≤12 months, 30.7 percent in 13~24 months, 13.1 percent in 25~36 months, and 2.1 percent in LFBI of ≥85 months. The mean LFBI was 21.5 months. The incidence of twin birth increased with prolonged LFBI. The twin birth rates per LFBI were 0.8 percent, 3.1 percent, 7.9 percent, and 11.0 percent in LFBI of ≤12 months, 25~36 months, 49~60 months, and 73~84 months, respectively. Odds ratio of twin births rate by LFBI were 1.510 (95% confidence interval: 1.449~1.574) for the LFBI of 13~24 months, 9.839 (9.390~10.309) for 49~60 months, and 13.244 (12.458~14.080) for ≥73~84 months, each compared with LFBI of ≤12 months. Odds ratio of twin birth rate in LFBI of ≤72 months was higher in women aged 35 and older, as compared to women aged ≤34 years. Odds ratio of twin birth rate by maternal age (≤34 years versus ≥35 years) reversed in LFBI of ≥73 months. CONCLUSION: The risk of twin birth increased significantly with prolonged LFBI. There is a need to understand the factors (fertility therapy and etc.) to increased risk of twin birth in prolonged LFBI.

The Relationship between Maternal Age at Birth and Intertwin Birth Weight Discordance in Korea

PURPOSE: To compare the relationship between intertwin birth weight discordance and maternal age at birth. METHODS: There were 51,726 pairs of twins born from 2007 to 2014 according to the birth certificate data of Korea Statistics (3,701,806 births). The data were excluded due to extra marital births, home births, and teenage births. Birth weight discordance rate (%) was calculated according to the following formula: (larger birth weight - smaller birth weight)/(birth weight of the larger twin) ×100. The odds ratio of intertwin birth weight discordance rate (≥25%) in maternal age at birth was calculated by logistic regression adjusted by the year of birth, gestational age, maternal education, infantile gender and paternal age. RESULTS: The mean birth weight of the heavier twin and that of the lighter twin were 2.536 kg and 2.254 kg, respectively. The mean birth weight difference of intertwins was 0.282 kg. The mean birth weight discordance rate by maternal age was 10.5 percent for maternal ages between 20 and 29 years, 11.0 percent for between 30 and 34 years, and 11.4 percent for 35 years and older. The frequency of birth weight discordance level of ≥25 percent increased as the maternal age increased. The rate of birth weight discordance (≥25%) was 7.7 percent for maternal ages between 20 and 29 years, 8.3 percent for between 30 and 34 years, and 8.7 percent in for 35 years and older. Compared with women from 20 to 29 years of age, the odds ratio of ≥25 percent discordance was 1.094 (95% confidence interval: 1.005~1.190) for 30 to 34 years, and 1.164 (1.401~1.301) for 35 years and older. The odds ratio of ≥25 percent discordance for the different-sexed twins was higher than that of the same-sexed twins in overall maternal age groups of 20 to 29 years, 30 to 34 years, and 35 years and older. CONCLUSION: The risk of birth weight discordance level of ≥25 percent was associated with the older maternal age. More research is required to understand the risk factors of intertwin birth weight discordance for older women.

The Discordance of Intra-twin Birth Weight by Infantile Gender and Birth Order in Korea; 2008-2013 / 대한주산의학회잡지

PURPOSE: To investigate the incidence of intra-twin birth weight discordance and its association with infantile gender and birth order. METHODS: We used the data of birth from 2008 to 2013 of Korea Statistics (38,140 pairs of twins). Adjusted logistic regression analyses were performed to describe the birth weight discordance (> or =25%) according to infantile gender and birth order (twin A: 1st, twin B: 2nd). Birth weight discordance was calculated as 100 x (birth weight difference/birth weight of the heavier twin). RESULTS: Twin A (mean 2.431 kg) was heavier than twin B (mean 2.359 kg), and the weight difference was 0.281 kg on average. Overall incidence of birth weight discordance was 8.3 percent. The incidence of discordance was 8.8 percent among unlike-sexed pairs and 8.0 percent among like-sexed pairs. Twins with birth weight A> or =B (10.2 percent) showed higher incidence of discordance than twins with birth weight A or =B) as compared to like-sexed twins (female-female) with birth weight (A

Survey on fertility of retained placenta and abomasal displacement cows after single or twin births in dairy cows in Korea / 대한수의학회지

Calving records of Holstein dairy cows from 2005 to 2010 comprising Goyang and Paju cities herd with 2,362 calving events representing 240 twin births were used to evaluate the effect of abomasal displacement and retained placenta after single or twin births on fertility. In retained placenta cows, the period of twin pregnancy (mean 270.5 days) was shorter than that of single pregnancy (mean 274.8 days), however first artificial insemination period (twin: mean 107.4 days, single: mean 92.0 days), non-pregnant period (twin: 154.8 days, single: 132.2 days), and number of insemination (twin: mean 2.00 times, single: mean 1.87 times) of twin pregnancy were increased as compared with single pregnancy. In abomasal displacement cows, first artificial insemination period (twin: mean 122.9 days, single: mean 106.0 days), non-pregnant period (twin: 172.4 days, single: 152.0 days), and number of insemination (twin: mean 2.16 times, single: mean 1.89 times) of twin pregnancy were increased as compared with single pregnancy. The prevalence of complication such as retained placenta, abomasal displacement with single or twin births increased first artificial insemination period, non-pregnant period, and number of insemination period.