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.

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

Studies from several countries report increases in rates of gestational diabetes mellitus (GDM) over recent decades. Exposure to environmental chemicals could contribute to this trend. To determine the associations between plasticisers and metals measured in early pregnancy with impaired glucose tolerance (IGT) and GDM in a Canadian pregnancy cohort. Women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) Study were included if they had a singleton delivery and did not have pre-existing diabetes. Eleven phthalate metabolites and total bisphenol A (BPA) were measured in first-trimester urine samples, and four metals (lead, cadmium, mercury and arsenic) were measured in first-trimester blood samples. IGT and GDM were assessed in accordance with standard guidelines by chart review. Chemical concentrations were grouped by quartiles, and associations with outcomes were examined using logistic regression with adjustment for maternal age, race, pre-pregnancy BMI, and education. Restricted cubic spline analysis was performed to help assess linearity and nature of any dose-response relationships. Of 2001 women recruited into the MIREC cohort, 1274 met the inclusion criteria and had outcome data and biomonitoring data measured for at least one of the chemicals we examined. Elevated odds of GDM were observed in the highest quartile of arsenic exposure (OR = 3.7, 95% CI = 1.4-9.6) in the adjusted analyses. A significant dose-response relationship was observed in a cubic spline model between arsenic and odds of GDM (p < 0.01). No statistically significant associations were observed between phthalates or BPA or other metals with IGT or GDM. Our findings add to the growing body of evidence supporting the role of maternal arsenic exposure as a risk factor for gestational diabetes.