Deshayne B. Fell

Impact of influenza exposure on rates of hospital admissions and physician visits because of respiratory illness among pregnant women

Background: Excess deaths have occurred among pregnant women during influenza pandemics, but the impact of influenza during nonpandemic years is unclear. We evaluated the impact of exposure during nonpandemic influenza seasons on the rates of hospital admissions and physician visits because of respiratory illness among pregnant women. Methods: We conducted a 13-year (1990–2002) population-based cohort study involving pregnant women in Nova Scotia. We compared rates of hospital admissions and physician office visits because of respiratory illness during the influenza season in each trimester of pregnancy with rates during the influenza season in the year before pregnancy and with rates in non-influenza seasons. Poisson regression analyses were performed to estimate rate ratios and 95% confidence intervals (CIs). Results: Of 134 188 pregnant women in the study cohort, 510 (0.4%) were admitted to hospital because of a respiratory illness during pregnancy and 33 775 (25.2%) visited their physician for the same reason during pregnancy. During the influenza seasons, the rate ratio of hospital admissions in the third trimester compared with admissions in the year before pregnancy was 7.9 (95% CI 5.0–12.5) among women with comorbidities and 5.1 (95% CI 3.6–7.3) among those without comorbidities. The rate of hospital admissions in the third trimester among women without comorbidities was 7.4 per 10 000 woman-months during the influenza season, compared with 5.4 and 3.1 per 10 000 woman-months during the peri-and non-influenza seasons respectively. Corresponding rates among women with comorbidities were 44.9, 9.3 and 18.9 per 10 000 woman-months. Only 6.7% of women with comorbidities had received influenza immunization. Interpretation: Our data support the recommendation that pregnant women with comorbidities should receive influenza vaccination regardless of their stage of pregnancy during the influenza season. Since hospital admissions because of respiratory illness during the influenza season were also increased among pregnant women without comorbidities, all pregnant women are likely to benefit from influenza vaccination.

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 ≥ 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

The role of prenatal, obstetric and neonatal factors in the development of autism.

We conducted a linked database cohort study of infants born between 1990 and 2002 in Nova Scotia, Canada. Diagnoses of autism were identified from administrative databases with relevant diagnostic information to 2005. A factor representing genetic susceptibility was defined as having an affected sibling or a mother with a history of a psychiatric or neurologic condition. Among 129,733 children, there were 924 children with an autism diagnosis. The results suggest that among those with low genetic susceptibility, some maternal and obstetric factors may have an independent role in autism etiology whereas among genetically susceptible children, these factors appear to play a lesser role. The role of pre-pregnancy obesity and excessive weight gain during pregnancy on autism risk require further investigation.

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

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 μg/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.

Effect of respiratory hospitalization during pregnancy on infant outcomes

The purpose of this study was to determine whether maternal hospitalization for a respiratory-related condition during influenza season results in an increased risk of neonatal morbidity. With the use of a 13-year population-based cohort study of all singleton live births in Nova Scotia (1990-2002), neonatal outcomes were compared between women with and without hospital admission for respiratory illness during influenza season at any time in pregnancy. Logistic regression analyses were performed to examine infant outcomes and to estimate relative risks and 95% confidence intervals. Infants who were born to mothers who had been hospitalized for respiratory illness during influenza season at any time during pregnancy were more likely to be small for gestational age (15.3% vs 9.7%; adjusted relative risk, 1.66; 95% confidence interval, 1.11-2.49) and to have lower mean birthweight (3348.5 ± 498.2 g vs 3531.3 ± 504.1 g; β score, -86.67; P < .009) than were infants who were born to women without an influenza-season respiratory hospitalization during pregnancy. Our findings in a cohort of singleton infants who were born in a high-resource setting support the findings that were described in Bangladesh that demonstrated an increased number of small-for-gestational-age infants and a lower mean birthweight among babies who were born to mothers who were not protected by influenza vaccine.

Comparison of Adolescent, Young Adult, and Adult Women’s Maternity Experiences and Practices

BACKGROUND AND OBJECTIVE: Pregnant adolescents face unique challenges. Understanding the experiences, knowledge, and behaviors of adolescents during the pregnancy and postpartum periods may contribute to improvement of their maternity care. The purpose of this study was to compare the maternity experiences, knowledge, and behaviors of adolescent, young adult, and adult women by using a nationally representative sample. METHODS: This study used data from the Canadian Maternity Experiences Survey (N = 6421). The weighted proportions of each variable were calculated by using survey sample weights. Logistic regression was used to estimate odds ratios. Bootstrapping techniques were used to calculate variance estimates for prevalence and 95% confidence intervals. RESULTS: Adolescents and young adults were more likely to experience physical abuse in the previous 2 years, initiate prenatal care late, not take folic acid before or during pregnancy, have poor prenatal health behaviors, have a lower cesarean delivery rate, have lower breastfeeding initiation and duration rates, experience more stressful life events, experience postpartum depression symptoms, and rate their infant’s health as suboptimal than adult women. Adolescents were more likely to rate their own health as suboptimal. CONCLUSIONS: Adolescents have unique needs during pregnancy and postpartum. Health care professionals should seek to provide care in a manner that acknowledges these needs.

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 subjects 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.

Examining Caesarean Section Rates in Canada Using the Robson Classification System

OBJECTIVE To determine the groups within the obstetric population contributing most substantially to the Caesarean section rate in five Canadian provinces. METHODS Hospital births from five participating provinces were grouped into Robsons 10 mutually exclusive and totally inclusive classification categories. The relative contribution of each group to the overall CS rate, relative size of group, and CS rate were calculated for British Columbia, Alberta, Ontario, Nova Scotia, and Newfoundland and Labrador for the four-year period from 2007-2008 to 2010-2011. RESULTS In all five provinces (accounting for approximately 64% of births in Canada), and for all years examined, the group making the largest relative contribution to the CS rate was women with at least one previous CS and a term, singleton, cephalic-presenting pregnancy (Robson Group 5). The CS rate for this group ranged from 76.1% in Alberta to 89.9% in Newfoundland and Labrador in 2010 to 2011, accounting for 11.3% of all deliveries. The rate of CS for Group 5 decreased slightly over the four years, except in Ontario. The next largest contributing group was nulliparous women with a term, singleton, cephalic-presenting pregnancy. Those with induced labour or Caesarean section before labour (Robson Group 2) had CS rates ranging from 34.4% in Nova Scotia to 44.6% in British Columbia (accounting for 13.1% of all deliveries), and those with spontaneous onset of labour (Robson Group 1) had CS rates of 14.5% to 20.3% in 2010 to 2011 (accounting for 23.6% of all deliveries). CONCLUSION All hospitals and health authorities can use this standardized classification system as part of a quality improvement initiative to monitor Caesarean section rates. This classification system identifies relevant areas for interventions and resources to reduce rates of Caesarean section.

Cesarean and Vaginal Birth in Canadian Women: A Comparison of Experiences

BACKGROUND Many publications have examined the reasons behind the rising cesarean delivery rate around the world. Womens responses to the Maternity Experiences Survey of the Canadian Perinatal Surveillance System were examined to explore correlates of having a cesarean section on other experiences surrounding labor, birth, mother-infant contact, and breastfeeding. METHODS A randomly selected sample of 8,244 estimated eligible women stratified primarily by province and territory was drawn from the May 2006 Canadian Census. Completed responses were obtained from 6,421 women (78%). RESULTS Three-quarters of the women (73.7%) gave birth vaginally and 26.3 percent by cesarean section, including 13.5 percent with a planned cesarean and 12.8 percent with an unplanned cesarean. In addition to more interventions in labor, women who had a cesarean birth after attempting a vaginal birth had less mother-infant contact after birth and less optimal breastfeeding practices. CONCLUSION Findings from the Maternity Experiences Survey indicated that women who have cesarean births experience more interventions during labor and birth and have less optimal birthing and early parenting outcomes.