PURPOSE: To determine the secular trend of the multiple birth rate in Korea from 1981 to 2017. METHODS: This study used birth certificate data covering the years 1981–2017 (20,948,901 births), provided by Statistics Korea. The impact of assisted reproductive technologies (ART) on multiple birth was analyzed by examining data prior to and after the introduction of ART and the national support program for infertile couples in South Korea. The odds ratio (OR) and 95% confidence intervals were calculated to describe the secular trend in the multiple birth rate per 100 births. RESULTS: During this period, the multiple birth rate per 100 births increased by 277 percent from 1.031 to 3.891, the twin birth rate increased from 1.013 to 3.807 (275%), and the triplet birth rate increased from 0.018 to 0.084 (363%). The secular trend of the multiple birth rate remained in the 1.000 level during 1981–1991, but has been rising steadily since 1992. The average increment of the multiple birth rate was 3.9% annually from 1981 through 2017 (peaking at more than 10 percent during 2006–2007). Prior to the introduction of ART in Korea (1981–1984), the multiple birth rate was 1.007, but after its introduction, the multiple birth rate was 1.005 in 1985–1989 (OR, 0.998; 95% confidence interval, 0.982–1.014), 1.084 in 1990–1994 (1.007; 1.060–1.094), 1.891 in 2000–2004 (1.894; 1.866–1.922), 3.127 in 2010–2014 (3.173; 3.129–3.217), and 3.811 in 2015–2017 (3.893; 3.835–3.952). CONCLUSION: Over the past three decades, multiple births have risen dramatically in Korea, primarily due to the increasingly widespread use of fertility therapies, and the delayed age of childbearing. There is a need for more research to understand the factors contributing to multiple births, and the national birth registration systems ought to be reformed to monitor whether multiple births originated spontaneously or from assisted-conception.
Birth Certificates ; Birth Rate ; Family Characteristics ; Fertility ; Humans ; Korea ; Multiple Birth Offspring ; Odds Ratio ; Parturition ; Reproductive Techniques, Assisted ; Triplets ; Twins

BACKGROUND: As the aging society progresses, the average age of mothers is also increasing. Advanced maternal age has been known to be associated with perinatal outcomes, as well as birth weight (BW). In this study, we aimed to investigate the perinatal factors associated with low birth weight infants (LBWIs) using birth statistics of the Korean population. METHODS: Birth statistics between 1993 and 2016 from the Korean Statistical Information Service were reviewed. We investigated 12,856,614 data points, which included the number of births, BWs, percentage of preterm births and LBWIs, multiple pregnancies, and maternal age. RESULTS: The proportion of LBWIs delivered by mothers of advanced maternal age has gradually increased since 1993. In addition, the proportion of older mothers (≥ 35 years old) giving birth to LBWIs has increased over the years. Average BW has a negative correlation with the ratio of preterm births, LBW, multiple births, and advanced maternal age. The mean BW also has a negative correlation with maternal age. CONCLUSION: This study shows that the average BW continues to decline, and the incidence of LBWIs is increasing in Korea since 1993. This study also revealed that several perinatal factors, including percentage of preterm births, LBWIs, multiple births, and maternal age influence the mean BW. Although this study did not investigate the effects of decreasing mean BW on perinatal health, future research is worth discussing.
Aging ; Birth Weight* ; Female ; Humans ; Incidence* ; Infant ; Infant, Low Birth Weight* ; Infant, Newborn ; Information Services ; Korea* ; Maternal Age* ; Mothers ; Multiple Birth Offspring ; Parturition* ; Pregnancy ; Pregnancy, Multiple ; Premature Birth

OBJECTIVES: The aim of this study was to evaluate the impact of shifts in maternal age and parity on the increasing trends in the low birth weight (LBW) and very low birth weight (VLBW) rates from 2005 to 2015 in South Korea. METHODS: Data from 4 993 041 live births registered with Statistics Korea during the period between 2005 and 2015 were analyzed. Applying a modified standardization method, we partitioned the total increment in the LBW and VLBW rates into (1) the increase in the LBW and VLBW rates due to changes in the maternal age and parity distribution (AP-dis) and (2) the increase due to changes in the age-specific and parity-specific rates (AP-spe) of LBW and VLBW for singleton and multiple births, respectively. RESULTS: During the study period, the total increment in the LBW and VLBW rates was 1.43%p and 0.25%p, respectively. Among singleton births, changes in the AP-dis accounted for 79% (0.34%p) and 50% (0.06%p) of the total increment in the LBW and VLBW rates, respectively. Meanwhile, among multiple births, changes in the AP-dis did not contribute to the increase in the LBW and VLBW rates, with 100% of the increase in the LBW (1.00%p) and VLBW (0.13%p) rates being attributed to changes in the AP-spe. CONCLUSIONS: This study demonstrated that shifts in maternal age and parity were prominent contributors to the increase in the LBW and VLBW rates among singleton births between 2005 and 2015 in South Korea.
Female ; Humans ; Infant ; Infant, Low Birth Weight ; Infant, Newborn ; Infant, Very Low Birth Weight ; Korea ; Live Birth ; Maternal Age ; Methods ; Multiple Birth Offspring ; Parity ; Parturition

The freemartinism syndrome affects almost all female calves born as co-twins to male calves, whereas little is known about this phenomenon in female sheep. Within this context, 1,185 ewe-lambs from the Ripollesa sheep breed were genotyped for the presence of oY1 polymorphism (a non-autosomal region of the Y chromosome). Neither ewe-lambs from single births (856) nor ewe-lambs from all-female multiple births (170) were revealed as freemartins, whereas five of 159 ewe-lambs from multiple births with male co-twins were freemartins (3.15 ± 1.38%). All freemartin ewe-lambs were confirmed by physical examination of external genitalia. The results confirm a low incidence of freemartinism from heterosexual twin pregnancies in Ripollesa sheep.
Animals ; Cattle ; Female ; Freemartinism ; Genitalia ; Heterosexuality ; Humans ; Incidence ; Male ; Multiple Birth Offspring ; Parturition ; Physical Examination ; Pregnancy, Twin ; Sheep

Fetal death is an important indicator of national health care. In Korea, the fetal mortality rate is likely to increase due to advanced maternal age and multiple births, but there is limited research in this field. The authors investigated the characteristics of fetal deaths, the annual changes in the fetal mortality rate and the perinatal mortality rate in Korea, and compared them with those in Japan and the United States. Fetal deaths were restricted to those that occurred at 20 weeks of gestation or more. From 2009 to 2014, the overall mean fetal mortality rate was 8.5 per 1,000 live births and fetal deaths in Korea, 7.1 in Japan and 6.0 in the United States. While the birth rate in Korea declined by 2.1% between 2009 and 2014, the decrease in the number of fetal deaths was 34.5%. The fetal mortality rate in Korea declined by 32.9%, from 11.0 in 2009 to 7.4 in 2014, the largest decline among the 3 countries. In addition, rates for receiving prenatal care increased from 53.9% in 2009 to 75.0% in 2014. Perinatal mortality rate I and II were the lowest in Japan, followed by Korea and the United States, and Korea showed the greatest decrease in rate of perinatal mortality rate II. In this study, we identified that the indices of fetal deaths in Korea are improving rapidly. In order to maintain this trend, improvement of perinatal care level and stronger national medical support policies should be maintained continuously.
Birth Rate ; Delivery of Health Care ; Fetal Death ; Fetal Mortality ; Humans ; Infant ; Infant Mortality ; Infant, Newborn ; Japan* ; Korea* ; Live Birth ; Maternal Age ; Multiple Birth Offspring ; Perinatal Care ; Perinatal Mortality* ; Pregnancy ; Prenatal Care ; Stillbirth ; United States*

PURPOSE: To figure out the contribution of maternal age distribution to the preterm birth (PTB) rate of multiple births between 1997~98 and 2014~15. METHODS: Multiple birth certificate data of Korea Statistics were used for this analysis. There were 18,557 births in 1997~98 and 30,992 births in 2014~15. Kitagawa's decomposition method was used to examine the contribution of age-specific PTB rate and maternal age distribution of multiple births to overall increment of PTB rate in multiple births between 1997~98 and 2014~15. RESULTS: PTB rate of multiple births increased from 32.40 percent to 58.22 percent (odds ratio: 1.80, 95% confidence interval: 1.76~1.84) during 1997-2015. PTB rate of multiple births greatly increased for women aged 25~29 years (odds ratio: 2.09) during the same period. The rates increased 1.88 times for women aged ≤24 years, followed by women aged 30~34 years (OR: 1.65), women aged 35~39 years (1.54), and women aged ≥ 40 years (1.36). Most (78.7%) of the overall increment in PTB rate of multiple births was attributable to the increase in the dimension of women aged 30~34 years, and 49.9 percent for women aged 35~39 years. CONCLUSION: The total increment in the PTB rate of multiple births was explained by increase the proportion and the PTB rate of women aged 30~39 years. More research is needed to comprehend the contributing age factors to PTB rate of multiple births.
Age Factors ; Female ; Humans ; Incidence* ; Korea ; Maternal Age* ; Methods ; Multiple Birth Offspring* ; Parturition ; Premature Birth*

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.
Female ; Humans ; Incidence* ; Korea* ; Logistic Models ; Maternal Age* ; Multiple Birth Offspring ; Odds Ratio ; Parity ; Parturition* ; Premature Birth*

PURPOSE: To identify the effects of modified parenteral nutrition (PN) and enteral nutrition (EN) regimens on the growth of very low birth weight (VLBW) infants. METHODS: The study included VLBW infants weighing <1,500 g, admitted to Chungnam National University Hospital between October 2010 and April 2014, who were alive at the time of discharge. Subjects were divided according to 3 periods: period 1 (n=37); prior to the PN and EN regimen being modified, period 2 (n=50); following the PN-only regimen modification, period 3 (n=37); following both PN and EN regimen modification. The modified PN regimen provided 3 g/kg/day of protein and 1 g/kg/day of lipid on the first day of life. The modified EN regimen provided 3.5-4.5 g/kg/day of protein and 150 kcal/kg/day of energy. We investigated growth rate, anthropometric measurements at 40 weeks postconceptional age (PCA) and the incidence of extrauterine growth restriction (EUGR) at 40 weeks PCA. RESULTS: Across the 3 periods, clinical characteristics, including gestational age, anthropometric measurements at birth, multiple births, sex, Apgar score, surfactant use and PDA treatment, were similar. Growth rates for weight and height, from time of full enteral feeding to 40 weeks PCA, were higher in period 3. Anthropometric measurements at 40 weeks PCA were greatest in period 3. Incidence of weight, height and head circumference EUGR at 40 weeks PCA decreased in period 3. CONCLUSION: Beginning PN earlier, with a greater supply of protein and energy during PN and EN, is advantageous for postnatal growth in VLBW infants.
Apgar Score ; Chungcheongnam-do ; Enteral Nutrition ; Gestational Age ; Head ; Humans ; Incidence ; Infant* ; Infant, Very Low Birth Weight* ; Multiple Birth Offspring ; Parenteral Nutrition ; Parturition ; Passive Cutaneous Anaphylaxis

OBJECTIVETo analyze the trends of multiple births rates and their perinatal outcomes in Zhejiang province from 2008 to 2013.

METHODSData were obtained from hospital-based perinatal mortality surveillance system in Zhejiang, including all the hospitals in 30 monitoring counties (districts). All births (28 or more weeks of gestation) born in the monitoring hospitals were included in our study within 7 days after delivery from 2008 to 2013. Chi-square test was performed for statistical analyses for comparisons between regions. Trends in the incidence of multiple births and causes of perinatal death were analyzed using chi-square test for trend.

RESULTSFrom 2008 to 2013, the multiple births rate in Zhejiang province was increased and the rates were 2.32% (5 551/239 636), 2.49% (6 053/243 452), 2.61% (6 549/250 594), 2.82% (7 758/275 105), 2.91% (8 803/302 447) and 3.06% (9 051/295 709), respectively. And the perinatal mortality rates for multiple births were 4.32% (240/5 551), 3.45% (209/6 053), 3.76% (246/6 549), 2.86% (222/7 758), 2.77% (244/8 803) and 2.11% (191/9 051), respectively. A significant drop in the perinatal mortality rates for multiple births was observed between 2008 and 2013 (χ(2) trend = 66.52, P < 0.001). There was a significantly greater risk for perinatal death to multiple births when compared with single birth (OR = 3.62, 95% CI: 3.42-3.83). The three leading causes of perinatal death for multiple births were birth defect, premature and/or low birth weight, and twin-twin transfusion syndrome.

CONCLUSIONThe multiple births rates in Zhejiang province showed an increasing trend. The perinatal mortality rates for multiple births were decreased annually, however, it was still higher than those in developed countries.

China ; Congenital Abnormalities ; Female ; Fetofetal Transfusion ; Humans ; Incidence ; Infant ; Infant, Low Birth Weight ; Infant, Newborn ; Multiple Birth Offspring ; Perinatal Mortality ; Pregnancy ; Pregnancy, Multiple ; Premature Birth

PURPOSE: The statistical birth data related to maternity and newborns over the past 15 years in Korea was analyzed in order to review the changing patterns of maternity and newborns in Korea. METHODS: Statistical data after 1995 in Korea were obtained from the Statistics Korea. Birth data related to maternity (distribution of birth rate, maternal age, advanced maternal age group, rank of birth, and time of pregnancy) and newborn (distribution of number of births, birth weight, ratio of sex, and multiple births) were analyzed. RESULTS: The average age of maternity is increasing while births in an advanced age has also increased from 4.7% in 1995 to 15.5% in 2009. There was a decrease in the total number of births, total birth rate and average birth weight. The rate of premature births in an advanced age occupied more than 6% of this study. The ratio of sex from the third born child and beyond has been relieved. The rate of multiple births has increased. The birth rate within two years of cohabitation before giving birth to a couple's first child has decreased. CONCLUSIONS: The rates of newborns requiring perinatal care such as births of prematurity, low birth weight infants, multiple pregnancies, etc are increasing. This is in relation to the increase in age of maternity and number of pregnancies in an advanced age. Therefore, there is an increase demand for strategies in order to decrease the age of maternity and the rate of pregnancies in an advanced age.
Birth Rate ; Birth Weight ; Child ; Female ; Humans ; Infant ; Infant, Low Birth Weight ; Infant, Newborn ; Korea ; Maternal Age ; Multiple Birth Offspring ; Parturition ; Perinatal Care ; Pregnancy ; Pregnancy, Multiple ; Premature Birth ; Sex Ratio