PubMed Health⌕ Search

Biomedical subjects

S W Wen

Publications and source records attributed to S W Wen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Recent trends in fetal and infant outcomes following post-term pregnancies.

All births and infant deaths in 1985 87 and 1992 94 in Canada, except in Ontario and Newfoundland, were analyzed to assess the potential impact of the recent increased use of elective labour induction for post-term pregnancies. Probabilistic linkage was carried out of infant death records (Canadian Mortality Database) and respective birth registrations (Canadian Birth Database) for the periods 1985 87 and 1992 94. The combined fetal and infant mortality declined by 20 30% between 1985 87 and 1992 94 at each gestational week beginning at 37 weeks, with no increased reduction among post-term pregnancies. Asphyxia-related fetal and infant deaths, the most likely cause of death being preventable by labour induction for post-term pregnancies, did not decrease among post-term pregnancies. In contrary, a substantial decrease of asphyxia-related deaths was observed at 37 and 38 weeks over the same periods of time. Because fetal and infant deaths are rare events and because the number of pregnancies passing 42 weeks of gestation decreased dramatically during 1992 94, statistically unstable results may be inevitable in the comparison of mortality in this group of pregnancies.

Canada↗
PubMed2000

Impact of prenatal glucose screening on the diagnosis of gestational diabetes and on pregnancy outcomes.

The authors examined the impact of universal screening on the diagnosis of gestational diabetes and its complications. All mothers and newborns registered by the Canadian Institute for Health Information from 1984 to 1996 (even-numbered fiscal years only) were included in the analysis. Over this time period, the proportion of women with gestational diabetes increased ninefold (from 0.3% to 2.7%) while the proportion with prepregnancy diabetes fell from 0.7% to 0.4%. As rates of gestational diabetes increased, a corresponding reduction in the risks of complications (polyhydramnios, amniotic cavity infection, cesarean delivery, and preeclampsia) occurred for women with gestational diabetes. The incidence of gestational diabetes fell in Metro-Hamilton (where screening was discontinued in 1989) but remained high in the rest of Ontario (where screening continued in most areas). No related temporal trends for fetal macrosomia, cesarean delivery, or other diabetes-related complications were observed, regardless of screening policy. The authors concluded that the substantial increase in gestational diabetes in Canada is an artifact caused by universal screening, with no evidence of beneficial effects on pregnancy outcomes.

Blood Glucose↗
PubMed2000

Patterns of infant mortality caused by major congenital anomalies.

BACKGROUND: We assessed the impact of recent advances in perinatal care on infant mortality due to congenital anomaly. METHODS: Analysis of trends in congenital anomaly-attributed infant mortality, using the 1981-1995 Statistics Canada's birth and death records, with a total of 2,878,826 live births, 21,883 infant deaths, and 6, 908 infant deaths due to congenital anomalies. RESULTS: Infant mortality due to major congenital anomaly decreased from 3.11 per 1, 000 live births in 1981 to 1.89 per 1,000 live births in 1995. Cause-specific infant mortality rates for anencephaly, spina bifida, other central nervous system anomalies, cardiovascular system anomalies, respiratory system anomalies, digestive system anomalies, certain musculoskeleton anomalies, urinary system anomalies, chromosomal anomalies, and multiple congenital anomalies were 0.20, 0.23, 0.27, 1.04, 0.24, 0.08, 0.22, 0.16, 0.22, and 0.13 per 1,000 live births, respectively, in 1981-1983, whereas corresponding rates were 0.07, 0.07, 0.18, 0.73, 0.25, 0.03, 0.12, 0.12, 0.26, and 0.06 per 1,000 live births, respectively, in 1993-1995. CONCLUSIONS: Recent Canadian data show that infant deaths caused by major congenital anomalies have decreased significantly, but reductions varied substantially according to specific forms of anomalies.

Canada↗
PubMed2000

Placenta praevia and male sex at birth: results from a population-based study.

This study examined the relationship between male sex at birth and placenta praevia in 433031 mother/infant dyads (linked by a common institutional code and hospital admission number) in the Canadian province of Quebec, during the fiscal years of 1991/92-1995/96. The male-to-female ratio among pregnancies with and without placenta praevia was calculated and compared. The male-to-female ratio at birth was higher in pregnancies complicated by a placenta praevia (1.19) than in those without it (1.04; P < 0.02). This increased ratio persisted after accounting separately for the potential confounding and/or modifying effects of maternal age, infant birthweight and gestational age by stratified and multiple logistic regression analyses. We conclude that pregnant women with male babies carry a higher risk of placenta praevia.

Birth Weight↗
PubMed2000

Gestational age- and birthweight-specific declines in infant mortality in Canada, 1985-94. Fetal and Infant Health Study Group of the Canadian Perinatal Surveillance System.

We studied infant mortality rates in Canada within specific gestational age and birthweight categories after using probabilistic techniques to link information in Statistics Canada's live births data base (1985-94) with that in the death data base (1985-95). Gestational age- and birthweight-specific mortality rates in 1992-94 were contrasted with those in 1985-87 with changes expressed in terms of relative risks with 95% confidence intervals [CI]. Statistically significant reductions in infant mortality were observed beginning at 24-25 weeks of gestation and extended across the gestational age range to post-term births. Crude infant mortality rates, infant mortality rates among those > or = 500 g and among those > or = 1000 g decreased by 22%, 25% and 26%, respectively, from 1985-87 to 1992-94. The magnitude of the reductions in infant mortality rates ranged from 14% [95% CI 7, 21%] at 24-25 weeks of gestation to 40% [95% CI 31, 47%] at 28-31 weeks. Almost all reductions in gestational age- and birthweight-specific infant mortality between 1985-87 and 1992-94 were due to approximately equal reductions in neonatal and post-neonatal mortality. Live births > or = 42 weeks of gestation did not follow this rule; post-neonatal mortality rates among such live births decreased significantly by 51% [95% CI 26, 68%], although neonatal mortality rates showed no significant change. The mortality reductions observed across the gestational age and birthweight range are probably a consequence of specific clinical interventions complementing improvements in fetal growth. Temporal changes in the outcome of post-term pregnancies need to be carefully examined, especially in relation to recent changes in the obstetric management of such pregnancies.

Adult↗
PubMed2000

Clues to the aetiological heterogeneity of testicular seminomas and non-seminomas: time trends and age-period-cohort effects.

BACKGROUND: Most previous epidemiological studies have treated testicular cancer as a single entity. However, some investigators suggest that testicular seminomas and non-seminomas may have different risk profiles. We examine the time trends in incidence of the two main histological types separately. METHODS: From 1970 through 1995, 7296 cases of testicular cancer were registered in the Canadian provinces of Ontario, Saskatchewan and British Columbia. In addition to analyses of the secular trends by age group and birth cohort, an age-period-cohort (APC) model with standard Poisson assumptions was fitted to the data to assess the time effects. RESULTS: The age-adjusted incidence rate for seminomas increased by 53%, from 1.5 per 100 000 males in 1970-1971 to 2.3 per 100 000 males in 1994-1995. Non-seminomas increased by 91%, from 1.1 to 2.1 per 100 000 males over the same period. Non-seminomas were more frequent at young ages whereas seminomas dominated in older ages. In contrast to seminomas, non-seminomas occurred predominantly among adolescent men (15-19 years), with a fourfold increase between 1970-1971 and 1994-1995. Age-period-cohort modelling showed that the increase in the risk of both seminomas and non-seminomas followed a birth cohort pattern, but with differences in birth cohorts in addition to significantly distinct age patterns. CONCLUSIONS: Our findings support the hypothesis postulating aetiological heterogeneity in the development of seminomas and non-seminomas. We suggest that epidemiological studies of testicular cancer treat seminomas and non-seminomas separately.

Adolescent↗
PubMed2000

Longest held occupation in a lifetime and risk of disability in activities of daily living.

OBJECTIVES: To examine the association between the longest held occupation in a lifetime and risk of disability in activities of daily living (ADL) among elderly people (65 years and older) in northern Taiwan. METHODS: A case-control design was used nested within two cohorts of a total of 2198 elderly people who had been followed up either between 1993 and 1997 or between 1996 and 1997. Cases were 360 elderly people with ADL disability within the study period. For each case, two sex matched controls were randomly sampled from the pool of elderly people free from ADL disability. Occupational data were collected through interviews conducted in 1997. Performed job contents were classified into occupational categories and occupation based social classes. Unconditional logistic regression techniques were used to estimate relative risk and 95% confidence intervals (95% CIs) of ADL disability. RESULTS: Compared with people who were former legislators, government administrators, or business executives and managers, workers in agriculture, animal husbandry, forestry, or fishing (odds ratio (OR) 1.9, 95% CI 1.1 to 3.5) and workers in craft and related trades (OR 1.9, 95% CI 1.1 to 3.4) had significantly increased risks of subsequent ADL disability. Differential risks of ADL disability were found across social classes, with a significant dose-response trend in which unskilled blue collar workers had an 1.8 times higher risk of ADL disability than higher social classes of white collar workers. CONCLUSIONS: After adjustment for education, there was still an inverse relation between risk of ADL disability and social class. Although total control for all the known risk factors for ADL disability among elderly people was impossible, the results tend to suggest a potential for an effect of longest held occupation in a lifetime on risk of ADL disability.

Activities of Daily Living↗
PubMed2000

An assessment of the validity of a computer system for probabilistic record linkage of birth and infant death records in Canada. The Fetal and Infant Health Study Group.

Studies on the validity of probabilistic record linkage are sparse. We performed a probabilistic linkage to link the 1984-1994 birth records (obtained from the Canadian Birth Data Base) with 1984-1995 infant death records (from the Canadian Mortality Data Base) in Canada. We extracted the linked birth-death records for Nova Scotia and Alberta (from January 1990 to December 1991) obtained from Statistics Canada's vital registration data and compared them with corresponding records from provincial data (primarily hospital records). The results showed that over 99% of infant deaths (153/155) in the Nova Scotia provincial data were successfully located in the linked Statistics Canada file; the corresponding figure for Alberta neonatal deaths was also 99% (365/367). The distributions of gestational age and birth weight in matched cases demonstrated high agreement between the two data sources. We conclude that the computer system for probabilistic linkage developed by Statistics Canada using the available personal identifying variables in the Canadian Birth Data Base and the Canadian Mortality Data Base is valid.

Alberta↗
PubMed2000

Infant mortality by gestational age and birth weight in Canadian provinces and territories, 1990-1994 births.

We compared gestational age-specific and birth weight-specific infant mortality in the Canadian provinces (excluding Ontario) and territories using the linked birth and death records for 1990-1994 births. Compared with Quebec, early neonatal mortality rates were higher in Saskatchewan, Alberta and Newfoundland among extremely small and preterm infants and among infants with no information on gestational age and birth weight on their records. Post- neonatal mortality rates were higher in Prince Edward Island, Manitoba, Saskatchewan, Alberta, British Columbia and the Northwest Territories among preterm (and low birth weight) and term (and normal birth weight) infants. We suggest that differences in registration practices probably explain the substantial interprovincial variations in early neonatal mortality rates among extremely small and preterm infants, whereas differences in demographic profile and the quality of obstetric, neonatal and infant care probably explain interprovincial variations in infant mortality rates among less extremely small and preterm infants.

Adolescent↗
PubMed2000

[Application of capillary chromatography in benzene boiling range analysis].

The experimental data were analyzed by regression analytical method and the relation between the quantity of impurities and the boiling range of benzene was demonstrated. It was proved that when the quantity of hydrocarbon impurities was within certain limits, the quality of benzene fractions can be determined by analyzing the hydrocarbon impurities in it. So the distillation method for analyzing benzene boiling range may be replaced by capillary chromatography for analyzing the hydrocarbon impurities. The practical applications support the above suggestion.

English Abstract↗
PubMed1999

Uses of ecologic studies in the assessment of intended treatment effects.

Because of the potential for confounding by indication (disease severity) in individual-level observational studies of intended treatment effects, a treatment designed to prevent an adverse event may appear to cause it. We use a hypothetical example to show that despite substantial variation in the frequency of treatment among patients residing in different geographic areas, a constant area-specific mortality rate can be observed, indicating the absence of confounding by indication at the ecologic level. The advantage of ecologic over individual-level observational studies in the assessment of intended treatment effects holds even if variations in disease severity, socioeconomic status, and other unmeasured factors are taken into account, as long as treatment utilization is influenced by practice style in the local medical community independently of disease severity. Ecologic studies can suggest the need for changes in practice, help resolve ethical issues, and indicate priorities for randomized trials.

Bias↗
PubMed1998

Secular trends in preterm birth: a hospital-based cohort study.

CONTEXT: Canada and the United States have reported a recent increase in the incidence of preterm birth, but the reasons for this increase are unknown. OBJECTIVE: To assess secular trends in preterm birth and its potential determinants. DESIGN: Hospital-based cohort study. SETTING: Canadian tertiary care university teaching hospital, 1978-1996. PARTICIPANTS: A total of 65574 nonreferred live births and stillbirths. MAIN OUTCOME MEASURES: Changes in occurrence of preterm birth, before and after adjustment for changes in method of gestational age assessment, obstetric intervention, registration of births weighing less than 500 g, and sociodemographic, behavioral, and clinical determinants. RESULTS: A crude secular increase in preterm births was seen for births less than 37, 34, and 32 completed weeks using 3 alternative gestational age estimation methods. Based on an algorithm incorporating both menstrual and early ultrasound gestational age estimates, rates increased from 6.6% to 9.8% for births at less than 37 weeks' gestation, 1.7% to 2.3% at less than 34 weeks, and 1.0% to 1.2% at less than 32 weeks. Exclusion of births weighing less than 500 g and those with induction or preterm cesarean delivery without labor before each of the corresponding gestational age cutoffs eliminated the secular trends for births before 34 and 32 weeks and attenuated the trend for births before 37 weeks. Nearly half of the remaining trend for births before 37 weeks was accounted for by the increasing use of early ultrasound dating. The residual trend was eliminated after controlling for secular increases in unmarried status and the proportion of women aged 35 years or older. These factors, combined with a decrease in alcohol consumption and increases in histological chorioamnionitis and cocaine use, appear to have counteracted a reduction in preterm birth since the mid-1980s that otherwise would have been observed. CONCLUSIONS: This hospital's increase in preterm births since 1978 parallels increases reported in population-based national studies from the United States and Canada. This trend appears largely attributable to the increasing use of early ultrasound dating, preterm induction and preterm cesarean delivery without labor, and changes in sociodemographic and behavioral factors.

Canada↗
PubMed1998

Determinants of preterm birth rates in Canada from 1981 through 1983 and from 1992 through 1994.

BACKGROUND: The rates of preterm birth have increased in many countries, including Canada, over the past 20 years. However, the factors underlying the increase are poorly understood. METHODS: We used data from the Statistics Canada live-birth and stillbirth data bases to determine the effects of changes in the frequency of multiple births, registration of births occurring very early in gestation, patterns of obstetrical intervention, and use of ultrasonographic dating of gestational age on the rates of preterm birth in Canada from 1981 through 1983 and from 1992 through 1994. All births in 9 of the 12 provinces and territories of Canada were included. Logistic-regression analysis and Poisson regression analysis were used to estimate changes between the two three-year periods, after adjustment for the above-mentioned determinants of the likelihood of preterm births. RESULTS: Preterm births increased from 6.3 percent of live births in 1981 through 1983 to 6.8 percent in 1992 through 1994, a relative increase of 9 percent (95 percent confidence interval, 7 to 10 percent). Among singleton births, preterm births increased by 5 percent (95 percent confidence interval, 3 to 6 percent). Multiple births increased from 1.9 percent to 2.1 percent of all live births; the rates of preterm birth among live births resulting from multiple gestations increased by 25 percent (95 percent confidence interval, 21 to 28 percent). Adjustment for the determinants of the likelihood of preterm birth reduced the increase in the rate of preterm birth to 3 percent among all live births and 1 percent among singleton births. CONCLUSIONS: The recent increase in preterm births in Canada is largely attributable to changes in the frequency of multiple births, obstetrical intervention, and the use of ultrasound-based estimates of gestational age.

Birth Rate↗
PubMed1998

Trends and variations in length of hospital stay for childbirth in Canada.

BACKGROUND: Early discharge after childbirth is widely reported. In this study the authors examined trends in maternal length of hospital stay in Canada from fiscal year 1984-85 through fiscal year 1994-95. They also examined variations in length of stay in 1994-95 in most of the Canadian provinces and the territories. METHODS: Epidemiologic analyses of the temporal and geographic variations in maternal length of hospital stay in Canada from 1984-85 to 1994-95 (even years only), based on hospital discharge data collected by the Canadian Institute for Health Information, with a total of 1,456,800 women for the 6 study years. RESULTS: Mean length of hospital stay decreased during the decade, from 5.3 days in 1984-85 to 3.0 days in 1994-95, with similar trends for both cesarean and vaginal delivery. The decrease resulted from both increasing rates of short stay (less than 2 days) and decreasing rates of long stay (more than 4 days). Substantial temporal and interprovincial variations in several medical and obstetric complications were also observed but did not explain the corresponding variations in length of stay. The reduction in length of hospital stay was not restricted to uncomplicated cases: there was an equivalent decrease in cases with complications. In 1994-95 the average length of hospital stay in Alberta was 2.6 days, 0.3 to 1.7 days shorter than in the other provinces and the territories. INTERPRETATION: Length of hospital stay for childbirth has decreased substantially in Canada in recent years, but there remain important interprovincial variations. These trends and variations are not likely due to changes or differences in patient-specific factors.

Canada↗
PubMed1998

Ultrasonographic examination of intrauterine growth for multiple fetal dimensions in a Chinese population. Central-South China Fetal Growth Study Group.

OBJECTIVE: We sought to construct an ultrasonography-based growth curve in a Chinese population. STUDY DESIGN: Routine ultrasonographic examination was performed in 5496 normal pregnancies (>95% first births) in five obstetric ultrasonography laboratories in Central-South China from January 1, 1992, to December 31, 1993. RESULTS: All the fetal growth measures increased with gestational age, whereas the ratios either decreased or remained constant across gestation. Biparietal diameter and cerebral hemispheric width were higher at early gestational ages, whereas femur length, thoracic circumference, and abdominal circumference were lower at later gestational ages in our study than in previous studies. The ratio of lateral ventricular width/cerebral hemispheric width was lower at an early gestational age but higher in later gestational ages in our study. CONCLUSIONS: A different standard of ultrasonography-based fetal growth is needed for different populations. The ultrasonography-based growth curve constructed in this large Chinese population provides an additional tool for the evaluation of fetal growth and development.

Abdomen↗
PubMed1998

Normal amniotic fluid index by gestational week in a Chinese population. Central-South China Fetal Growth Study Group.

OBJECTIVE: To construct an ultrasonography-based gestation-specific amniotic fluid index (AFI) curve in a Chinese population. METHODS: Routine obstetric ultrasonography examinations were performed in 5496 normal pregnancies (more than 95% first births) in five obstetric ultrasound laboratories in Central-South China from January 1, 1992, to December 31, 1993. A gestation-specific AFI curve was constructed and compared with previous studies. RESULTS: The gestational ages of the patients included in this study ranged from 16 to 40 weeks. The gestation-specific AFI showed patterns similar to those observed previously, with the median being 72 mm at 16 weeks, increasing to 119 mm at 26 weeks, and then gradually declining to a median of 91 mm at 40 weeks. However, the absolute value of AFI in this Chinese population was consistently and substantially lower than values reported in previous studies in populations with mixed parities. CONCLUSION: Different standards of AFI are needed for different populations.

Amniotic Fluid↗