Infant mortality in Alberta and all of Canada.
Explore the source record for details and available documents.
Alberta↗
Biomedical subjects
Alexander C Allen
Publications and source records attributed to Alexander C Allen.
Fetal and neonatal mortality among twin gestations in a Canadian population: the effect of intrapair birthweight discordance.
The purpose of this study was to examine the association between intrapair birthweight discordance and fetal and neonatal mortality. This was a historical cohort study, using the Statistics Canada linked birth-infant death file. Twin births in Canada (excluding Ontario) for the period 1986-1997 were studied. Outcome measures were fetal and neonatal mortality. Among 59,034 twin births, 53% had 0 to 9% birthweight difference; 30% had 10 to 19% discordance; 11% had 20 to 29% discordance; and 6% had > or = 30% discordance. Maternal age, parity, sex discordance, and gestational age were important factors affecting birth weight discordance. Fetal death rates were 0.95, 1.26, 3.14, and 11.10%, respectively, in infants with a birthweight discordance of 0 to 9, 10 to 19, 20 to 29, and > or = 30%. Corresponding figures for neonatal death rates were 1.90, 2.32, 3.05, and 8.86%, respectively. Adjustment for important confounding variables including the actual birthweight and gestational age substantially reduced the birthweight discordance-related risk of fetal and neonatal mortality, but the results remained statistically significant and clinically important. The birthweight discordance-related risk of fetal and neonatal mortality was higher in smaller twins than in larger twins and higher in infants with gestational age > or = 37 weeks than those < 37 weeks. Birthweight discordance is an important risk factor for fetal and neonatal mortality, and the birthweight discordance-related risk of fetal and neonatal mortality is higher in smaller twins than in larger twins and higher in term twins than in preterm twins.
Adult↗
The perinatal effects of delayed childbearing.
OBJECTIVE: To determine if the rates of pregnancy complications, preterm birth, small for gestational age, perinatal mortality, and serious neonatal morbidity are higher among mothers aged 35-39 years or 40 years or older, compared with mothers 20-24 years. METHODS: We performed a population-based study of all women in Nova Scotia, Canada, who delivered a singleton fetus between 1988 and 2002 (N = 157,445). Family income of women who delivered between 1988 and 1995 was obtained through a confidential linkage with tax records (n = 76,300). The primary outcome was perinatal death (excluding congenital anomalies) or serious neonatal morbidity. Analysis was based on logistic models. RESULTS: Older women were more likely to be married, affluent, weigh 70 kg or more, attend prenatal classes, and have a bad obstetric history but less likely to be nulliparous and to smoke. They were more likely to have hypertension, diabetes mellitus, placental abruption, or placenta previa. Preterm birth and small-for-gestational age rates were also higher; compared with women aged 20-24 years, adjusted rate ratios for preterm birth among women aged 35-39 years and 40 years or older were 1.61 (95% confidence interval [CI] 1.42-1.82; P < .001) and 1.80 (95% CI 1.37-2.36; P < .001), respectively. Adjusted rate ratios for perinatal mortality/morbidity were 1.46 (95% CI 1.11-1.92; P = .007) among women 35-39 years and 1.95 (95% CI 1.13-3.35; P = .02) among women 40 years or older. Perinatal mortality rates were low at all ages, especially in recent years. CONCLUSION: Older maternal age is associated with relatively higher risks of perinatal mortality/morbidity, although the absolute rate of such outcomes is low.
Adult↗
The influence of hospital closures in Nova Scotia on perinatal outcomes.
OBJECTIVE: To evaluate the effect of hospital closures on critical obstetrical interventions and perinatal outcomes in rural communities in Nova Scotia, Canada. METHODS: A population-based cohort study was carried out for the years 1988 to 2002, using data extracted from the Nova Scotia Atlee Perinatal Database. Regions of maternal residence were defined geographically and administratively as Eastern, Northern,Western, and Central. The time periods of 1988 to 1993 and 1996 to 2002 were chosen based on the timing of hospital closures. Changes in rates of several perinatal outcomes were examined by region in relation to the extent of hospital closures experienced by that region. RESULTS: The majority of hospital closures occurred in 1994 to 1995 with the establishment of new health regions, and affected the Western region most profoundly. In comparison with the Central region (relative risk [RR], 0.56; 95% confidence interval [CI], 0.53-0.59), the temporal reduction in the rate of forceps-assisted vaginal delivery was smaller in the Western region (RR, 0.83; 95% CI, 0.76-0.91; P < .001), but greater in the Northern (RR, 0.36; 95% CI, 0.32-0.41; P < .001) and Eastern (RR, 0.26; 95% CI, 0.23-0.30; P < .001) regions. The temporal increase in the rate of breastfeeding at discharge from hospital was smaller in the Northern region (RR, 1.36; 95% CI, 1.29-1.45; P < .001) compared to that in the Central region (RR, 1.55; 95% CI, 1.49-1.61). The decrease in the rate of fetal growth restriction was smaller in the Western (RR, 0.95; 95% CI, 0.87-1.02; P = .002) and Eastern (RR, 0.90; 95% CI, 0.82-0.98; P = .002) regions of residence compared to the Central region (RR, 0.75; 95% CI, 0.71-0.79). There were no significant regional differences in temporal patterns of preterm induction and/or preterm Caesarean delivery, or perinatal mortality. CONCLUSION: Although trends over time demonstrated some regional differences in obstetrical interventions and perinatal outcomes, our retrospective evaluation did not reveal a consistent relationship between reductions in maternity services associated with hospital closures and systematic, population-level adverse perinatal consequences in Nova Scotia.
Adult↗
Exposure assessment in epidemiologic studies of adverse pregnancy outcomes and disinfection byproducts.
A major challenge in studies that examine the association between disinfection byproducts in drinking water and pregnancy outcomes is the accurate representation of a subject's exposure. We used household water samples and questionnaire information on water-use behavior to examine several aspects of exposure assessment: (i) the distribution and correlation of specific disinfection byproducts, (ii) spatial distribution system and temporal variation in byproduct levels, and (iii) the contribution of individual water-use behavior. The level of specific trihalomethanes (THMs) and haloacetic acids (HAAs) was determined for 360 household water samples in Eastern Ontario and Nova Scotia. Subjects were interviewed regarding tap water ingestion and showering and bathing practices. In both provinces, total THMs correlated highly with chloroform (correlation coefficient (r) >0.95) and less so with total HAAs (r = 0.74 in Nova Scotia and r = 0.52 in Ontario). The correlation between total THMs and bromodichloromethane was high in Nova Scotia (r = 0.63), but low in Ontario (r = 0.26). The correlation was between THM level in individual household samples, and the mean THM level during the same time period from several distribution system samples was 0.63, while a higher correlation in THM level was observed for samples taken at the same location 1 year apart (r = 0.87). A correlation of 0.73 was found between household THM level and a total exposure measure incorporating ingestion, showering, and bathing behaviors. These results point to the importance of: measurement of different classes of byproducts; household rather than distribution system sampling; and, incorporation of subject behaviors in exposure assessment in epidemiologic studies of disinfection byproducts and adverse pregnancy outcomes.
Acetates↗
Trihalomethanes in public water supplies and risk of stillbirth.
BACKGROUND: The chlorine used to disinfect public drinking water supplies reacts with naturally occurring organic matter to form a number of chemical byproducts. Recent studies have implicated exposure to chlorination byproducts in drinking water, trihalomethanes (THMs), in particular, with intrauterine death. METHODS: We conducted a population-based case-control study in Nova Scotia and Eastern Ontario, Canada, to examine the effect of exposure to THMs on stillbirth risk. Cases were women who had a stillborn infant, and controls were a random sample of women with live births. Subjects were interviewed, and women with a public water source provided a residential water sample. Risks were examined according to residential THM level in tap water and to a total exposure metric incorporating tap water ingestion, showering, and bathing. RESULTS: We enrolled 112 stillbirth cases and 398 live birth controls. Women with a residential total THM level of 80 or more microg/L had twice the risk of a stillbirth compared with women with no exposure to THMs (adjusted odds ratio [OR] = 2.2; 95% confidence interval [CI] = 1.1-4.4). The highest quintile of total THM exposure using the total exposure metric was associated with an adjusted odds ratio of 2.4 (95% CI = 1.2-4.6) compared with women not exposed to THMs. Similar results were seen for specific THM compounds. A monotonic dose-response relationship was not seen. CONCLUSIONS: Our results provide evidence for an increased risk of stillbirth associated with exposure to chlorination byproducts through ingestion and showering and bathing, although there was not a clear dose-response relationship.
Adult↗
Does the risk of cerebral palsy increase or decrease with increasing gestational age?
BACKGROUND: It is generally accepted that the risk of cerebral palsy decreases with increasing gestational age of live born infants. However, recent studies have shown that cerebral palsy often has prenatal antecedents including congenital malformations, vascular insults and maternal infection. Cerebral palsy is therefore better viewed as occurring among fetuses, rather than among infants. We explored the epidemiologic implications of this change in perspective. METHODS: We used recently published data from Shiga Prefecture, Japan and from North-East England to examine the pattern of gestational age-specific rates of cerebral palsy under these alternative perspectives. We first calculated gestational age-specific rates of cerebral palsy as per convention, by dividing the number of cases of cerebral palsy identified among live births within any gestational age category by the number of live births in that gestational age category. Under the alternative formulation, we calculated gestational age-specific rates of cerebral palsy by dividing the number of cases of cerebral palsy identified among live births within any gestational age category by the number of fetuses who were at risk of being born at that gestation and being afflicted with cerebral palsy. RESULTS: Under the conventional formulation, cerebral palsy rates decreased with increasing gestational age from 63.9 per 1,000 live births at <28 weeks gestation to 0.9 per 1,000 live births at 37 or more weeks gestation. When fetuses were viewed as potential candidates for cerebral palsy, cerebral palsy rates increased with increasing gestational age from 0.08 per 1,000 fetuses at risk at <28 weeks gestation to 0.9 per 1,000 fetuses at risk at 37 or more weeks gestation. CONCLUSIONS: The fetuses-at-risk approach is the appropriate epidemiologic formulation for calculating the gestational age-specific rate of cerebral palsy from a causal perspective. It shows that the risk of cerebral palsy increases as gestational duration increases. This compelling view of cerebral palsy risk may help refocus research aimed at understanding and preventing cerebral palsy.
Journal Article↗
A parsimonious explanation for intersecting perinatal mortality curves: understanding the effect of plurality and of parity.
BACKGROUND: Birth weight- and gestational age-specific perinatal mortality curves intersect when compared across categories of maternal smoking, plurality, race and other factors. No simple explanation exists for this paradoxical observation. METHODS: We used data on all live births, stillbirths and infant deaths in Canada (1991-1997) to compare perinatal mortality rates among singleton and twin births, and among singleton births to nulliparous and parous women. Birth weight- and gestational age-specific perinatal mortality rates were first calculated by dividing the number of perinatal deaths at any given birth weight or gestational age by the number of total births at that birth weight or gestational age (conventional calculation). Gestational age-specific perinatal mortality rates were also calculated using the number of fetuses at risk of perinatal death at any given gestational age. RESULTS: Conventional perinatal mortality rates among twin births were lower than those among singletons at lower birth weights and earlier gestation ages, while the reverse was true at higher birth weights and later gestational ages. When perinatal mortality rates were based on fetuses at risk, however, twin births had consistently higher mortality rates than singletons at all gestational ages. A similar pattern emerged in contrasts of gestational age-specific perinatal mortality among singleton births to nulliparous and parous women. Increases in gestational age-specific rates of growth-restriction with advancing gestational age presaged rising rates of gestational age-specific perinatal mortality in both contrasts. CONCLUSIONS: The proper conceptualization of perinatal risk eliminates the mortality crossover paradox and provides new insights into perinatal health issues.
Journal Article↗
Changes in maternal characteristics and obstetric practice and recent increases in primary cesarean delivery.
OBJECTIVE: To estimate the contribution of changes in maternal characteristics (namely, age, parity, prepregnancy weight, weight gain in pregnancy, smoking status) and obstetric practice (namely, labor induction, epidural anesthesia, delivery by an obstetrician, midpelvic forceps delivery) to recent increases in primary cesarean delivery rates. METHODS: We studied all deliveries in Nova Scotia, Canada, between 1988 and 2000 after excluding women who had a previous cesarean delivery (n = 127,564). Logistic regression was used to study the effect of changes in maternal characteristics and obstetric practice on primary cesarean delivery rates. The effect of changes in midpelvic forceps delivery was examined through ecologic Poisson regression. RESULTS: Primary cesarean delivery rates increased from 13.4% of deliveries in 1988 to 17.5% in 2000. This was due to increases in cesarean deliveries for dystocia (14% increase), breech (24% increase), suspected fetal distress (21% increase), hypertension (47% increase), and miscellaneous indications (73% increase). Adjustment for maternal characteristics reduced the temporal increase in primary cesarean delivery rates between 1988-1991 and 1998-2000 from 21% (95% confidence interval [CI] 16%, 25%) to 2% (95% CI -2%, 7%). Additional adjustment for obstetric practice factors further reduced period effects. Midpelvic forceps delivery was significantly and negatively associated with primary cesarean delivery (P =.001). CONCLUSION: Recent increases in primary cesarean delivery rates are a consequence of changes in maternal characteristics. Obstetric practice, which has altered due to changes in maternal characteristics and concerns related to fetal and maternal safety, has also contributed to increases in primary cesarean delivery.
Adult↗
Relationship of prenatal diagnosis and pregnancy termination to overall infant mortality in Canada.
CONTEXT: Prenatal diagnosis and termination of affected pregnancies can prevent infant deaths due to congenital anomalies, but an effect at the population level has not been shown. OBJECTIVE: To examine the impact of recent changes in congenital anomaly-related fetal and infant deaths on overall population-based infant mortality. DESIGN, SETTING, AND SUBJECTS: Birth cohort-based study of all live births, stillbirths, and infant deaths in Canada (excluding Ontario) for 1991-1998. MAIN OUTCOME MEASURES: Cause-specific infant mortality rates and gestational age-specific fetal death rates. RESULTS: The birth cohort-based infant mortality rate fluctuated between 6.4 and 6.1 per 1000 live births between 1991 and 1995, then dropped to 5.4 per 1000 in 1996 and 5.5 per 1000 in 1997. The rate of infant death from congenital anomalies was stable between 1991 and 1995 but declined by 21% (95% confidence interval, 19%-32%) from 1.86 per 1000 in 1995 to 1.47 per 1000 in 1996 and 1997. Fetal deaths due to pregnancy termination at 20 to 23 weeks' gestation increased dramatically in 1994, while fetal deaths due to congenital anomalies at 20 to 21 weeks increased in 1995 and subsequently. Provinces/territories with high rates of fetal death due to pregnancy termination/congenital anomalies at 20 to 23 weeks had fewer infant deaths due to congenital anomalies. CONCLUSION: A large decrease in infant deaths due to congenital anomalies was associated with the most recent decline in infant mortality in Canada, suggesting that increases in prenatal diagnosis and pregnancy termination for congenital anomalies are related to decreases in overall infant mortality at the population level.
Abortion, Induced↗
Preterm birth, stillbirth and infant mortality among triplet births in Canada, 1985-96.
Recent increases in the frequency of multiple births and simultaneous increases in preterm birth among multiple births have focused attention on such births. However, most previous studies have examined twins rather than higher-order multiples. We carried out a study to examine rates and trends in preterm birth and in gestational age-specific fetal and infant mortality among triplet births in Canada. We used data from the stillbirth, live birth and mortality files of Statistics Canada for the years 1985-97. All births in Canada (excluding those occurring in Ontario and Newfoundland) were included in the study, with two periods (1985-90 vs. 1991-96) being contrasted for assessing temporal change. Changes were estimated using relative risks, 95 confidence intervals [CI] and two-tailed P-values. The rate of preterm birth among triplet live births increased by 6 (95 CI 3, 9) from 90.4 in 1985-90 to 96.0 in 1991-96. Stillbirth rates among triplets did not change significantly and were 30.3 per 1000 total births in 1985-90 and 33.8 per 1000 total births in 1991-96. Infant mortality among triplets declined from 112.7 per 1000 live births in 1985-90 to 73.8 per 1000 live births in 1991-96. In spite of temporal reductions in infant mortality, triplet births continue to be associated with very high rates of preterm birth and fetal and infant mortality. Fetal mortality among triplets has not changed over the last ten years.
Birth Weight↗
The impact of missing birth weight in deceased versus surviving fetuses and infants in the comparison of birth weight-specific feto-infant mortality.
Birth weight-specific is preferred to crude feto-infant mortality in epidemiologic studies comparing rates across jurisdictions, because it can help limit the bias arising from regional differences in the completeness of reporting of vital events and in classification of live versus stillbirth among extremely small and immature infants. The potential impact of missing birth weight information in deceased versus surviving fetuses and infants in the comparison of birth weight-specific feto-infant mortality has been seldom examined, however. The authors investigated this issue, using data collected from two nationwide surveys of all pregnancy outcomes occurring 15 17 May 1989 and 12 16 February 1996, respectively, in Taiwan and the 1989 and 1996 linked birth and infant death records in Canada (excluding Ontario and Newfoundland). The proportions with missing birth weight information in Taiwan in 1989 were 25.0%, 15.4%, 0%, and 0.6%, respectively, for stillbirths, neonatal deaths, post-neonatal deaths, and survivors, and in 1996 were 100%, 5.0%, 0%, and 0.2%. The proportions with missing birth weight information in Canada in 1989 were 5.8%, 2.6%, 1.2%, and 0.6%, respectively, for fetal deaths, neonatal deaths, post-neonatal deaths, and survivors, and in 1996 were 5.0%, 2.4%, 1.1%, and 0.6%. Infant and (especially) fetal death rates were substantially higher in Taiwan than in Canada among births with missing birth weight. The authors concluded that differences in missing birth weight information between deaths and survivors can bias comparisons of birth weight-specific feto-infant mortality.
Bias↗
Changes in maternal characteristics in Nova Scotia, Canada from 1988 to 2001.
BACKGROUND: Maternal characteristics such as age, parity, smoking status, pre-pregnancy weight and pregnancy weight gain have changed in many industrialized countries in recent years. Many of these changes have not been adequately described at a population level. The purpose of this study was to describe recent trends in selected maternal characteristics in Nova Scotia. METHODS: Data from a population-based perinatal database were used to examine changes in maternal age, parity, smoking, pre-pregnancy weight, delivery weight and pregnancy weight gain among all deliveries between 1988 and 2001. RESULTS: The proportion of deliveries to women > or = 35 years increased by 84% over the study period from 7.0% in 1988-1991 to 12.9% in 1998-2000, while deliveries to women > or = 40 years increased by more than 100%. The number of nulliparous women > or = 35 years also increased significantly. The overall prevalence of smoking decreased from 32.7% in 1988-1991 to 25.1% in 1998-2001, however the prevalence of smoking among women <20 years did not change over the study period and was almost 50%. The proportion of women with a pre-pregnancy weight of > or = 90 kilograms (kg) increased by 165% from 4.1% in 1988-1991 to 10.7% in 1998-2001. The proportion of women with pregnancy weight gain of < 7 kg and > or =18 kg increased by 37% and 13%, respectively. CONCLUSION: Dramatic changes have occurred in several important maternal characteristics and there is evidence of ongoing change. Continuation of these trends is likely to impact on future obstetric practice and perinatal health.
Adult↗