Biomedical subjects

Linda Dodds

Publications and source records attributed to Linda Dodds.

At least 19 recordsLinked to original sources

PubMed2006

The association between low level exposures to ambient air pollution and term low birth weight: a retrospective cohort study.

BACKGROUND: Studies in areas with relatively high levels of air pollution have found some positive associations between exposures to ambient levels of air pollution and several birth outcomes including low birth weight (LBW). The purpose of this study was to examine the association between LBW among term infants and ambient air pollution, by trimester of exposure, in a region of lower level exposures. METHODS: The relationship between LBW and ambient levels of particulate matter up to 10 um in diameter (PM10), sulfur dioxide (SO2) and ground-level ozone (O3) was evaluated using the Nova Scotia Atlee Perinatal Database and ambient air monitoring data from the Environment Canada National Air Pollution Surveillance Network and the Nova Scotia Department of Environment. The cohort consisted of live singleton births (> or =37 weeks of gestation) between January 1, 1988 and December 31, 2000. Maternal exposures to air pollution were assigned to women living within 25 km of a monitoring station at the time of birth. Air pollution was evaluated as a continuous and categorical variable (using quartile exposures) for each trimester and relative risks were estimated from logistic regression, adjusted for confounding variables. RESULTS: There were 74,284 women with a term, singleton birth during the study period and with exposure data. In the analyses unadjusted for year of birth, first trimester exposures in the highest quartile for SO2 and PM10 suggested an increased risk of delivering a LBW infant (relative risk = 1.36, 95% confidence interval = 1.04 to 1.78 for SO2 exposure and relative risk = 1.33, 95% confidence interval = 1.02 to 1.74 for PM10). After adjustment for birth year, the relative risks were attenuated somewhat and not statistically significant. A dose-response relationship for SO2 was noted with increasing levels of exposure. No statistically significant effects were noted for ozone. CONCLUSION: Our results suggest that exposure during the first trimester to relatively low levels of some air pollutants may be associated with a reduction in birth weight in term-born infants. These findings have implications for the development of effective risk management strategies to minimize the public health impacts for pregnant women.

Adult↗

PubMed2006

Stillbirth risk factors according to timing of exposure.

PURPOSE: The purpose of the present study is to identify risk factors for stillbirth and explore hypotheses about the cause of stillbirth based on the time in gestation when exposures occur. METHODS: Relationships between lifestyle factors, pregnancy conditions, medication use, and occupation on risk for stillbirth were examined within a population-based case-control study. Women who had a stillbirth and a random sample of women who had a live birth between 1999 and 2001 were identified through perinatal databases in Nova Scotia and Eastern Ontario, Canada. Exposure data were collected for each month of pregnancy and analyzed within trimesters. Case-control data were converted to case-cohort data, and hazard ratios (HRs) and 95% confidence intervals (CIs) were determined from Cox proportional hazards models. RESULTS: This study included 105 stillbirth cases and 389 live-birth controls. Fertility treatment in the present pregnancy was associated with increased risk for stillbirth (adjusted HR, 4.0; 95% CI, 1.4-11.6). Smoking during the first trimester also was associated with increased risk for stillbirth (adjusted HR, 2.4; 95% CI, 1.2-4.9). Other risk factors included antiemetic use during the first trimester, second-trimester antibiotic use, low family income, and age older than 35 years. CONCLUSIONS: Risk factors identified in this study concur with findings of previous studies and support the importance of early pregnancy exposures on stillbirth risk.

Adult↗

PubMed2006

Determinants of survival in children with congenital abnormalities: a long-term population-based cohort study.

BACKGROUND: Today more children with birth defects survive early childhood because of improved medical care; however, little information is available about patterns of long-term mortality and survival in this population. In particular, it is not clear whether other birth characteristics, apart from birth defects, have any role in their mortality. METHODS: Two large cohorts of children with and without birth defects were followed for up to 17 years. More than 45,000 children with birth defects, and 45,000 matched children without birth defects born in Ontario between 1979 and 1986 were followed. Throughout the study period long-term survival rates and the risk of death were compared between the 2 cohorts. Birth characteristics were also examined to determine their effect on the risk of death. RESULTS: During the study the deaths of 3620 and 301 children with and without birth defects, respectively, were recorded, indicating that those with birth defects had a 13 times higher rate of mortality (relative risk [RR], 12.9, 95% confidence interval [CI], 12.1-13.7). Mortality rates in the birth-defects cohort remained higher even after 10-15 years. In both groups children of low gestational age and low birth weight had a higher risk of death. There was a strong dose-response relationship between the number of defects and the risk of death. CONCLUSIONS: Children born with abnormalities face many challenges throughout their lifetimes. If they survive the high mortality risk of the first year of life, they still have to face the considerably higher risk of death in the years to come. In addition to birth defects, other birth characteristics play an independent role in their mortality. These indicators could be used to identify high-risk children.

Adolescent↗

PubMed2006

Risk factors for hyperemesis gravidarum requiring hospital admission during pregnancy.

OBJECTIVE: To identify risk factors for hyperemesis requiring hospital admission during pregnancy. METHODS: Data from a population-based cohort of all deliveries in Nova Scotia, Canada between 1988 and 2002 were obtained from the Nova Scotia Atlee Perinatal Database. Women with 1 or more antepartum admissions for hyperemesis were compared with women with no admissions for hyperemesis. Relative risks (RRs) and 95% confidence intervals (CIs) were estimated using logistic regression and used to determine a set of independent risk factors for hyperemesis. RESULTS: The overall rate of admission for hyperemesis was 0.8% (n = 1,301) among 157,922 deliveries. In the adjusted analysis, hyperthyroid disorders (RR 4.5, 95% CI 1.8-11.1), psychiatric illness (RR 4.1, 95% CI 3.0-5.7), previous molar pregnancy (RR 3.3, 95% CI 1.6-6.8), preexisting diabetes (RR 2.6, 95% CI 1.5-4.7), gastrointestinal disorders (RR 2.5, 95% CI 1.8-3.6), and asthma (RR 1.5, 95% CI 1.2-1.9) were all statistically significant risk factors for hyperemesis, whereas maternal smoking and maternal age older than 30 were associated with decreased risk. Compared with singleton male pregnancies, singleton female pregnancies, pregnancies with multiple male fetuses, and male and female combinations were associated with statistically significant increased risk of hyperemesis. CONCLUSION: Although hospitalization for hyperemesis occurs in less than 1% of pregnant women, this translates to a large number of hospital admissions. The factors associated with hyperemesis are primarily medical and fetal factors that are not easily modifiable, but identification of these factors may be useful in determining those women at high risk for developing hyperemesis. LEVEL OF EVIDENCE: II-2.

Adult↗

PubMed2006

Outcomes of pregnancies complicated by hyperemesis gravidarum.

OBJECTIVE: To evaluate maternal and neonatal outcomes among women with hyperemesis during pregnancy. METHODS: A population-based retrospective cohort study was conducted among women with singleton deliveries between 1988 and 2002. Hyperemetic pregnancies were defined as those requiring one or more antepartum admissions for hyperemesis before 24 weeks of gestation. Severity of hyperemesis was evaluated according to the number of antenatal hospital admissions (1 or 2 versus 3 or more) and according to weight gain during pregnancy (< 7 kg [15.4 lb] versus > or = 7 kg). Maternal outcomes evaluated included weight gain during pregnancy, gestational diabetes, gestational hypertension, labor induction, and cesarean delivery. Neonatal outcomes included 5-minute Apgar score of less than 7, low birth weight, small for gestational age, preterm delivery, and perinatal death. Logistic regression was used to generate adjusted odds ratios for all outcomes, and the odds ratios were converted to relative risks. RESULTS: Of the 156,091 singleton pregnancies, 1,270 had an admission for hyperemesis. Compared to women without hyperemesis, infants born to women with hyperemesis and with low pregnancy weight gain (< 7 kg [15.4 lb]) were more likely to be low birth weight, small for gestational age (SGA), born before 37 weeks of gestation, and have a 5-minute Apgar score of less than 7. Compared with infants born to women without hyperemesis, rates of low birth weight and preterm delivery were substantially higher among infants born to women with hyperemesis and low pregnancy weight gain (4.2% versus 12.5% and 4.9% versus 13.9%, respectively). The outcomes among infants born to women with hyperemesis with pregnancy weight gain of 7 kg (15.4 lb) or more were not different from the outcomes among women without hyperemesis. CONCLUSION: The results of this study suggest that the adverse infant outcomes associated with hyperemesis are a consequence of, and mostly limited to, women with poor maternal weight gain. LEVEL OF EVIDENCE: II-2.

Adult↗

PubMed2006

Socioeconomic status and receipt of obstetric services in Canada.

OBJECTIVE: To examine differences in labor induction and cesarean delivery rates by socioeconomic status in Nova Scotia, Canada. METHODS: We studied all women in Nova Scotia who delivered between 1988 and 1995 after a singleton pregnancy. Information was obtained from the Nova Scotia Atlee Perinatal Database and the federal income tax (T1) Family Files maintained by the Small Area and Administrative Data Division of Statistics Canada (n = 76,440). Labor induction and cesarean delivery rates were contrasted by family income and other indices, with adjustment for risk factors carried out using logistic models. RESULTS: Maternal characteristics and other factors varied by socioeconomic status; in the lowest income group 4.4% of women were aged 35 years or older, and 49.4% were nonsmokers, whereas in the highest income group 17.7% were aged 35 years or older, and 88.7% were nonsmokers. Crude induction rates were similar across income groups (17.7% compared with 18.1% in the lowest compared with highest income groups), but there were significant differences in crude cesarean (17.7% compared with 21.2%) and crude primary cesarean rates (12.5% compared with 17.0%). Controlling for differences in risk factors altered these relationships. Adjusted rate ratios, 95% confidence intervals (CIs) and P values contrasting the lowest compared with highest income groups were labor induction 1.09 (95% CI 1.00-1.19), P = .05; overall cesarean delivery 1.12 (95% CI 1.03-1.23), P = .01; primary cesarean delivery 1.09 (95% CI 0.98-1.21), P = .12. CONCLUSION: Affluent women in Canada are not more likely to have labor induction or cesarean delivery compared with less affluent women. LEVEL OF EVIDENCE: II-2.

Adult↗

PubMed2006

Relation of pregnancy and neonatal factors to subsequent development of childhood epilepsy: a population-based cohort study.

OBJECTIVE: We examined the effect of pregnancy and neonatal factors on the subsequent development of childhood epilepsy in a population-based cohort study. PATIENTS AND METHODS: Children born between January 1986 and December 2000 in Nova Scotia, Canada were followed up to December 2001. Data on pregnancy and neonatal events and on diagnoses of childhood epilepsy were obtained through record linkage of 2 population-based databases: the Nova Scotia Atlee Perinatal Database and the Canadian Epilepsy Database and Registry. Factors analyzed included events during the prenatal, labor and delivery, and neonatal time periods. Cox proportional hazards regression models were used to estimate relative risks and 95% confidence intervals. RESULTS: There were 648 new cases of epilepsy diagnosed among 124,207 live births, for an overall rate of 63 per 100,000 person-years. Incidence rates were highest among children <1 year of age. In adjusted analyses, factors significantly associated with an increased risk of epilepsy included eclampsia, neonatal seizures, central nervous system (CNS) anomalies, placental abruption, major non-CNS anomalies, neonatal metabolic disorders, neonatal CNS diseases, previous low birth weight infant, infection in pregnancy, small for gestational age, unmarried, and not breastfeeding infant at the time of discharge from hospital. CONCLUSIONS: Our study supports the concept that prenatal factors contribute to the occurrence of subsequent childhood epilepsy.

Breast Feeding↗

PubMed2005

A population-based study to determine the performance of the Cognitive Adaptive Test/Clinical Linguistic and Auditory Milestone Scale to Predict the Mental Developmental Index at 18 Months on the Bayley Scales of Infant Development-II in very preterm infants.

OBJECTIVES: To determine optimal ages to perform the Cognitive Adaptive Test/Clinical Linguistic and Auditory Milestone Scale (CAT/CLAMS) and optimal "cutoff" score of the CAT/CLAMS to screen very preterm infants (<31 weeks) for severe cognitive-adaptive delay and to ascertain the sensitivity, specificity and likelihood ratios using optimal cutoff scores compared with the Mental Developmental Index (MDI) of the Bayley Scales of Infant Development II. METHODS: A population-based cohort of very preterm infants who were born to mothers who resided in Nova Scotia or Prince Edward Island were evaluated at 4, 8, 12, and 18 months' corrected gestational age, which included a CAT/CLAMS by a physician. At 18 months' corrected gestational age, each child was assessed using the Bayley Scales of Infant Development II, the "gold standard" for developmental delay in young infants. The results of each CAT/CLAMS was compared with the 18-month MDI to identify significant developmental delay (MDI <70). RESULTS: Optimal scores on the CAT/CLAMS to identify correctly MDI <70 were determined by using the kappa statistic for chance independent agreement. Sensitivities and specificities for optimal cutoff scores were as follows: 4-month score <109 (88% and 37%), 8-month score <98 (75% and 82%), 12-month score <81 (63% and 99%), and 18-month score <83 (88% and 98%). CONCLUSION: Sensitivity and specificity of the CAT/CLAMS are high in very preterm infants at identifying major developmental delay at 12 and 18 months. For follow-up programs without psychology services, the CAT/CLAMS at 12 and 18 months is a reasonable screening tool to determine which children need expedited psychology referral for cognitive delay.

Child Development↗

PubMed2005

Congenital abnormalities and childhood cancer.

BACKGROUND: The examination of specific characteristics of neoplasms diagnosed in children have suggested that a significant proportion can be attributed to a genetic mutation or genetic predisposition. Although the study of a genetic predisposition to cancer in children remains in the early stages, congenital abnormalities could provide essential information for mapping predisposing lesions in children with cancer. METHODS: In the current study, 2 large cohorts of children with and without congenital abnormalities were followed for the occurrence of cancer and death up to 18 years. Through this study, the risk of developing cancer by age at diagnosis, effects of birth characteristics on cancer risk, and possible associations between specific anomalies and tumor types were examined. RESULTS: Based on the follow-up of 90,400 children, the risk of developing cancer during the first year of life was found to be nearly 6 times higher in children with anomalies (rate ratio [RR] of 5.8; 95% confidence interval [95% CI], 3.7-9.1). Children with birth defects were found to be at a higher risk for developing leukemia (RR of 2.7; 95% CI, 2.1-3.6), tumors of the central nervous system (RR of 2.5; 95% CI, 1.8-3.4), sympathetic nervous system tumors (RR of 2.2; 95% CI, 1.4-3.4), and soft tissue sarcomas (RR of 1.9; 95% CI, 1.0-3.5). Among children with birth defects, children with Down syndrome, nervous system anomalies, and anomalies of the urinary system had the highest incidence rates of cancer. In the presence of birth defects, other factors such as birth weight, gestational age, age of the mother, and birth order were not found to be associated significantly with the risk of cancer. CONCLUSIONS: The significant relative risks found in the current study provided evidence of links between the presence of abnormalities and the development of cancer. Some "cancer-prone" abnormalities were identified in the current study. Such anomalies may be markers of other exposures or processes that increase the risk of developing cancer.

Adult↗

PubMed2005

Customized birth weight for gestational age standards: Perinatal mortality patterns are consistent with separate standards for males and females but not for blacks and whites.

BACKGROUND: Some currently available birth weight for gestational age standards are customized but others are not. We carried out a study to provide empirical justification for customizing such standards by sex and for whites and blacks in the United States. METHODS: We studied all male and female singleton live births and stillbirths (22 or more weeks of gestation; 500 g birth weight or over) in the United States in 1997 and 1998. White and black singleton live births and stillbirths were also examined. Qualitative congruence between gestational age-specific growth restriction and perinatal mortality rates was used as the criterion for identifying the preferred standard. RESULTS: The fetuses at risk approach showed that males had higher perinatal mortality rates at all gestational ages compared with females. Gestational age-specific growth restriction rates based on a sex-specific standard were qualitatively consistent with gestational age-specific perinatal mortality rates among males and females. However, growth restriction patterns among males and females based on a unisex standard could not be reconciled with perinatal mortality patterns. Use of a single standard for whites and blacks resulted in gestational age-specific growth restriction rates that were qualitatively congruent with patterns of perinatal mortality, while use of separate race-specific standards led to growth restriction patterns that were incompatible with patterns of perinatal mortality. CONCLUSION: Qualitative congruence between growth restriction and perinatal mortality patterns provides an outcome-based justification for sex-specific birth weight for gestational age standards but not for the available race-specific standards for blacks and whites in the United States.

Journal Article↗

PubMed2005

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↗

PubMed2004

Influenza vaccine programs and pregnancy: a need for more evidence.

Influenza viruses are the most common cause of seasonal respiratory morbidity in the world. Annual influenza vaccination is recommended for persons at high risk for serious disease. In the United States, in 2004, the Advisory Committee on Immunization Practices added all pregnant women to its high-risk list. In Canada, the National Advisory Committee on Immunization only includes pregnant women who have other underlying risk factors in the high-priority category for influenza immunization. This commentary provides an overview of maternal morbidity in pandemic and nonpandemic influenza seasons as well as a list of research questions whose answers are needed for evidence-based public health policy in this area.

Canada↗

PubMed2004

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↗

PubMed2004

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↗

PubMed2004

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↗

PubMed2004

Residential mobility during pregnancy.

In epidemiological studies of environmental exposures and adverse pregnancy outcomes, maternal residence at delivery is often used to assign an exposure level, based on routinely collected data. In order to examine the potential for exposure misclassification due to residential mobility, we examined maternal mobility according to changes in residence overall, as well as changes in municipality and county. The potential for mobility to be related to pregnancy outcomes was considered by examining the relationship between mobility and risk factors commonly included in investigations of adverse pregnancy outcomes. Previously collected data were studied from 398 population-based control subjects from a case-control study of stillbirths. We compared demographic, lifestyle, medical, pregnancy and environmental factors of women who moved during pregnancy with those who did not. Bivariable and multivariable log binomial regressions were used to identify risk factors that were associated with mobility during pregnancy. Twelve per cent of subjects moved at least once during their pregnancy. Among women who moved, the majority (62%) moved within the same municipality. In bivariable analyses, we found that low family income, lower maternal age, unmarried status and tobacco use were associated with an increased likelihood of moving during pregnancy, whereas women who used folic acid before conception and who had a higher prepregnancy body mass index (BMI) were less likely to move during pregnancy. In multivariable analyses, only family income, age and prepregnancy BMI were independently predictive of mobility. These results indicate that in studies using maternal residence at delivery to assign environmental exposures, mobility during pregnancy is likely to be prevalent enough to introduce exposure misclassification. The potential for differential exposure misclassification should be considered should any of the risk factors for moving identified by this study also be risk factors for the outcome under study.

Adult↗

PubMed2003

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↗

PubMed2003

Impact of participation in the Halifax County Preterm Birth Prevention Project.

OBJECTIVES: (1). To determine if participation in the Halifax County Preterm Birth Prevention Project (HCPBPP) reduced the risk of preterm birth; (2). to evaluate the degree to which specific components of the HCPBPP contributed to preterm-birth risk reduction. METHODS: A nested case-control study was conducted among women residing in Halifax County who gave birth at the IWK Grace Health Centre during the final year of the HCPBPP. Cases, defined as women who delivered preterm (<37 weeks), and controls, defined as women who delivered at full term, were recruited to complete interviewer-administered questionnaires. Three controls per case were sequentially selected. The exposures of interest were overall participation and compliance with specific components of the program. Univariate and multivariate statistical methods were employed to evaluate the effect of exposure to the preterm-birth prevention program. RESULTS: Seventy cases and 210 controls were enrolled in the study. Although 82% of subjects participated in some aspect of the HCPBPP, only 8% of high-risk and 6% of low-risk women complied fully with program recommendations. Exposure to project educational strategies or pelvic examinations provided no protective benefit for preterm birth in low-risk or high-risk women. However, compliance with prenatal care providers recommendations to restrict activity or monitor for uterine contractions by self-palpation was associated with a marked reduction in the risk of preterm birth among low-risk women (odds ratio, 0.20; 95% confidence interval, 0.08 0.50). CONCLUSION: Although full participation in the HCPBPP protocol was limited, the findings of this case-control study suggest that activity restriction and uterine activity monitoring by self-palpation may reduce the likelihood of preterm birth in women with no identifiable risk factors for prematurity.

Bed Rest↗