Taiwan Birth Registry Research Articles

Socio-economic inequalities in low-birth weight, full-term babies from singleton pregnancies in Taiwan

This study investigated the chronological trend of low-birth weight in full-term babies (TLBW) in Taiwan in the 1980s and 1990s when the nation experienced a rapid economic advancement, and assessed the association between TLBW and parental education and marital status. Data from liveborn singletons from Taiwan's birth registry, born between 1978 and 1997, were used to calculate overall and socio-economic factor-specific rates of TLBW for every 2-year interval in this 20-year period. Logistic regression models were used to assess the trend of TLBW rates, and the interaction between secular time, selected demographic factors and other predictors. Among 6,159,070 full-term, liveborn singletons, 208,729 were TLBW. The average annual rate of TLBW was 3.39% in the study period. The period-specific TLBW declined monotonically from 4.41% in 1978-1979 to 2.49% in 1996-1997, representing a 43% deduction. Multiple logistic regression demonstrated persistent declining trends irrespective of the educational level or marital status of the parents. However, the decline was slower for populations of lower socio-economic status, such as less-educated parents and unmarried mothers, which enhanced the inequalities of TLBW risk across populations. The TLBW risk ratios of the least-educated mothers to the most-educated mothers increased from 1.43 in 1978-1979 to 2.05 in 1996-1997. Unmarried status was an independent predictor of elevated risk of TLBW. The association between socio-economic inequality and the risk of TLBW infants was sustained over the 1980s and 1990s in Taiwan. Interventions are necessary to promote antenatal care and educational attainment, particularly for lower socio-economic and socially deprived populations in Taiwan.

Risks and causes of mortality among low‐birthweight infants in childhood and adolescence

The purpose of the study was to estimate the risks of mortality among infants with low birthweight (LBW, <2500 g) during their childhood and adolescence using a prospective cohort design. A total of 341 249 livebirths were registered in the 1985 Taiwan Birth Registry. We identified the 11 701 LBW singletons and randomly selected the same number of normal-birthweight (NBW) singletons. Study subjects of both LBW and NBW groups were linked, through the individual's unique personal identification number, to the Taiwan Death Registry to identify those who died between 1985 and 2003. Using the life-table method, we calculated the age-specific and cumulative survival rate for both LBW and NBW groups. We used Cox's proportional hazard model with adjustment for potential confounders to estimate the age-specific hazard ratio (HR) of mortality. Age-specific causes of mortality were presented for both groups. The result showed that the cumulative survival rate over an 18-year period for the LBW and NBW subjects was estimated at 95.83% and 99.37%, respectively. Significantly increased adjusted HR of mortality associated with LBW was limited to ages <1 year (boys: 8.99; girls: 8.29) and 1-4 years (boys: 2.19; girls: 2.25). Conditions originating in the perinatal period and congenital anomalies were the most prevalent cause of death among LBW and NBW, respectively. Between ages 1 and 18 years, injury and poisoning became the top ranked causes of death irrespective of birthweight and gender. Although there were small numbers of congenital anomalies, they were still a leading cause of death for LBW subjects, but not for NBW subjects, at ages 5-18 years. The LBW subjects were also likely to suffer from respiratory causes at 5-18 years. This study suggested, therefore, that LBW infants tended to have significantly elevated mortality rates under the age of 5 years, and were vulnerable to more non-injury deaths in their childhood and adolescence.

The differential effect of foreign‐born status on preterm birth: a Taiwan population‐based birth registry study

Whether foreign-born status confers a protective effect on preterm birth in Taiwan was investigated using singleton live birth data from the 2004 Taiwan Birth Registry (n = 211,946). Newborns of foreign-born mothers (FBMs) comprised 13.7% of the population. The preterm birth rate of newborns of FBMs (5.9%) was significantly lower than that of newborns of Taiwan-born mothers (TBMs) (8.0%) (P < 0.0001). After having adjusted for predisposing maternal factors or adverse pregnancy conditions, newborns of FBMs still had a lower risk in preterm birth than that of TBMs, with an odds ratio of 0.74 and 95% confidence interval between 0.71 and 0.79. Selection was hypothesised to explain the low preterm birth rate in FBMs.

Birth Weight Correlates Differently with Cardiovascular Risk Factors in Youth

Childhood obesity has become prevalent, resulting in a greater risk of hypertension, diabetes, and dyslipidemia. However, the relationship between these comorbid conditions and birth weight remains uncertain. We conducted this study to evaluate the relationship between birth weight and cardiovascular risk factors in children and adolescents. In a nationwide survey conducted between 1992 and 2000, all schoolchildren 6 to 18 years old with glucosuria, proteinuria, or microscopic hematuria in repeated urine samples were included and received a physical examination and blood test. Those with gestational age <37 weeks were excluded. We enrolled 81,538 children (51,111 girls and 30,427 boys) and obtained their birth weights from the Taiwan Birth Registry. Obesity and hypertension were defined by age- and sex-specific cut-offs. Diabetes was diagnosed if the fasting glucose was >7 mM. The risk of obesity was higher for those with birth weights > or =4000 grams [odds ratio (OR), 1.65] and 3543 to 3999 grams (OR, 1.28) and lower for those with birth weights 2601 to 2999 grams (OR, 0.90), using 3000 to 3542 grams as the reference group. An increased risk of diabetes was associated with both higher and lower birth weights, indicating a U-shaped relationship (OR, <2600 grams, 1.607; 2601 to 2999 grams, 1.119; 3543 to 3999 grams, 1.112; > or =4000 grams, 1.661). In the 10- to 12-year-old age group, the risk of hypertension was higher in those with birth weights <2600 grams (OR, 1.20). Low birth weight was associated with childhood diabetes. High birth weight was correlated with childhood obesity and diabetes. Our data indicate different relationships between birth weight and the development of obesity, hypertension, and diabetes in childhood.

Birth weight and type 1 diabetes among schoolchildren in Taiwan—A population-based case-controlled study

To explore the relationship between birth weight and type 1 diabetes, data from national birth registry and national surveillance of diabetes in Taiwanese schoolchildren were analyzed. From 1992 to 1997, all schoolchildren aged 6–18 years were screened for diabetes by a mass urine survey program in Taiwan Province. This cohort consisted of 1966 children with diabetes and 1780 of randomly selected subjects with normal fasting glycemia. Questionnaires were designed for telephone interviews with students’ parents or physicians to classify subjects’ types of diabetes. The birth history of each participant was obtained from the Taiwan's Birth Registry. After merging the data, there were 835 subjects, including 277 of type 1 diabetes and 533 of normal fasting glycemia available for the present analyses. The odds ratio (95% CI) for type 1 diabetes, after adjusting age, sex, socioeconomic status, family history of diabetes, birth order, breast-feeding, BMI, and gestational diabetes mellitus was 2.24 (1.11–4.50) for children with low birth weight (<5th percentile, i.e., ≤2600 g) when compared with the referent group of a birth weight of 3000–3542 g (equivalent to the 25–75th percentile). In conclusion, low birth weight was associated with increased risk of type 1 diabetes in Taiwanese schoolchildren.

Birth outcomes of infants born in areas with elevated ambient exposure to incinerator generated PCDD/Fs

The purpose of this study was to determine if elevated ambient exposure to incinerator generated polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) may affect birth outcomes of exposed infants born in Taipei metropolitan areas, Taiwan. The relationships between exposure to elevated PCDD/Fs concentration and various birth outcomes including birth weight, gestational age, and proportion of females were cross-sectionally assessed in 1991 (one year before the incinerator started to operate) and 1997 (five years later), respectively. We used the US EPA Industrial Source Complex Model-Sort Term modeling technique to determine the ambient PCDD/Fs concentrations in the study areas, in which 40 districts with annual averaged PCDD/Fs exposure of ≥ 0.03 pg TEQ/m 3 were considered as the exposed areas and another 40 districts with an estimated concentration of zero were randomly selected as reference areas. Information on birth outcomes was retrieved from the Taiwan's Birth Registry. A total of 6697 and 6282 neonates were included in the analysis for 1991 and 1997, respectively. After controlling for potential confounders, the results showed that the odds ratios (ORs) of low birth weight (< 2500 g) for higher exposures were 0.94 (> 0.05 pg TEQ/m 3) and 091 (0.03–0.05 pg TEQ/m 3) in 1991 and were 1.07 (> 0.05 pg TEQ/m 3) and 1.06 (0.03–0.05 pg TEQ/m 3) in 1997. The corresponding ORs were 1.05/0.86 (1991) and 1.12/1.22 (1997) for preterm (< 37 completed weeks of gestation), as well as 0.95/1.00 (1991) and 0.95/0.90 (1997) for female births. The above ORs were all close to unity and were statistically insignificant. When birth weight was analyzed as a continuous variable, the difference in mean birth weight between exposed group (> 0.03 pg TEQ/m 3) and reference group decreased from 3.02 g in 1991 to − 5.87 g in 1997. Analysis of continuous data also showed that the mean difference in gestational age between exposed and reference areas decreased from 0.05 weeks in 1991 to − 0.09 week ( p < 0.05) in 1997. This study tends to conclude that the incinerator generated dioxin poses little effects on birth weight and female birth, but might pose small effects on gestational age. If the observed adverse effects turn out to be real, the measures now taken for improvement of abatement of waste gases seem to be a wise thing to do.

Association between maternal exposure to elevated ambient sulfur dioxide during pregnancy and term low birth weight

This retrospective cohort study investigated whether the risk of delivering full term (37–44 completed weeks of gestation) low birth weight (LBW) infants is associated with differences in exposure to air pollutants in different trimesters. Full-term infants (37 completed weeks of gestation) with a birth weight below 2500 g were classified as term LBW infants. The study infants comprised 92,288 full-term live singletons identified from the Taiwan birth registry and born in the city of Taipei or Kaoshiung in Taiwan between 1995 and 1997. Maternal exposures to various air pollutants including CO, SO 2, O 3, NO 2, and PM 10 in each trimester of pregnancy was estimated as the arithmetic means of all daily measurements taken by the air quality monitoring station nearest to the district of residence of the mother at birth. The multivariable logistic regression model with adjustment for potential confounders was used to assess the independent effect of specific air pollutants on the risk of term LBW. This study suggested a 26% increase in term LBW risk given maternal ambient exposure to SO 2 concentration exceeding 11.4 ppb during pregnancy compared to low exposure (<7.1 ppb) (OR=1.26, 95% CI=1.04–1.53). Since the relative risk of term LBW was reassessed according to exposure level in each trimester, mothers exposed to >12.4 ppb of SO 2 in the last trimester showed 20% higher risk (OR=1.20, 95% CI=1.01–1.41) of term LBW delivery than mothers with lower exposure (<6.8 ppb). No significant elevation ORs was observed for other air pollutants.

Validation of the Taiwan Birth Registry using obstetric records.

Birth certificates are a major source of population-based data often used in maternal and child health research, but their value depends upon the level of accuracy of the data. The purpose of this study was to assess the validity of the birth registry data in Taiwan. Obstetric records of a total of 2779 infants born at a municipal hospital in Taipei between 1995 and 1997 were abstracted and linked to the Taiwan Birth Registry (TBR). Concordance was presented by agreement percentages for various birth characteristics including gender, birth order, birth weight, and gestational age. Concordance was further assessed using Cohen's k and sensitivity/specificity for both birth weight and gestational age, with both variables categorized according to their customary definitions. Missing data for specific items in the TBR ranged from 0% (gender) to 1.6% (birth order). The birth registry accurately reported all 4 selected items, with the highest and lowest concordance percentage noted for gender (99.0%) and gestational age (88.3%), respectively. The level of agreement indicated by the Cohen's k statistic ranged from 0.92 to 0.96 for birth weight and gestational age when both variables were treated as categorical variables. The TBR showed a low rate of missing information and high levels of validity for the elements frequently used in maternal and child health research in Taiwan.

Demographic characteristics and trends in the prevalence of low birth weight from singleton pregnancies in Taiwan, 1978-1997.

Low birth weight (LBW) has adverse influences on lifetime health. This study examined trends in LBW in Taiwan between 1978 and 1997, and assessed the risk of LBW associated with gender, birth order of infant, and parental age at delivery. Information on live born singletons for the study period was retrieved from the Taiwan birth registry. We calculated biannual trends for overall LBW rates and for specific demographic factors. Log-linear models with a Poisson assumption were used to assess the linear trend of the LBW rates and the interaction between time and selected demographic factors. Log-linear models were also used to estimate the independent effect of individual demographic factors on the risk of LBW. The LBW prevalence declined from 6.78% (55,694/820,364) in 1978-79 to 4.95% (30,907/623,971) in 1996-97, representing a 27.10% reduction. The prevalence of LBW showed a noticeable reduction between the late 1970s and mid-1980s, and appeared homogeneous after the mid-1980s. This declining trend was evident for almost all of the selected demographic factors. The only exception was in infants born to teenage fathers, which showed a 10.59% increase in prevalence of LBW during the 20-year study period. Infants born to mothers or fathers aged 35 and above had the greatest reduction (47.58% and 41.44%, respectively) in the rate of LBW, whereas teenage mothers had the lowest reduction (11.75%) in the rate of LBW. Parental age at an infant birth has a strong association with reduction of LBW risk. Education programs focusing on the problem of teenage pregnancy may accelerate the reduction of LBW.