Stillbirth epidemiology, diabetes, and other risk factors among all pregnancies in Alberta from 2000 to 2009


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Canadian National Perinatal Research Meeting, Bannf (Alberta), Feb 12-15, 2014

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Stillbirth epidemiology, diabetes, and other risk factors among all pregnancies in Alberta from 2000 to 2009

  1. 1. Stillbirth epidemiology, diabetes, and other risk factors among all pregnancies in Alberta from 2000 to 2009 Richard T. Oster and Ellen L. Toth INTRODUCTION Despite the first comprehensive set of worldwide estimates suggesting that 2.6 million stillbirths occurred in 2009 (1), previously stillbirths have been given little recognition compared to other pregnancy complications or causes of maternal and neonatal deaths. The tragedy and impact of stillbirth is however receiving new warranted attention clinically and academically, as highlighted in a recent special series of the Lancet (2). In Canada, women of First Nations descent have been shown to be at an elevated risk of numerous adverse pregnancy outcomes, including stillbirths which are 68% more likely among pregnant First Nations women according to a systematic review and meta-analysis (3). This has sparked new research into stillbirth rates and risk factors among First Nations women, with Auger et al (4) pointing toward diabetes (driven by obesity) as a major cause. However, the epidemiology of First Nations stillbirths is still poorly understood as stillbirth type (antepartum or intrapartum) has not been considered, longitudinal changes have not been rigorously explored, and data on risk factors (including diabetes in pregnancy type) is limited. The purpose of this study was to gain a better understanding of extent of the problem of stillbirths and the relationship between stillbirth and other potential pregnancy-related factors may yield knowledge to better inform intervention type and timing, with the goal of lowering risk of stillbirth in First Nations pregnancies. We used provincial administrative data to: 1) determine and compare the age-adjusted annual prevalence rates of stillbirth longitudinally by First Nations and non-First Nations ethnicity; and 2) examine the relationship between pre-existing diabetes and gestational diabetes mellitus (GDM), stillbirths, and other possible underlying factors amongst First Nations and non-First Nations pregnancies. Department of Medicine, University of Alberta (antepartum and intrapartum) for the entire province by ethnicity were calculated and compared. Rates were age-standardized to the maternal age distribution of the total number of pregnancies in 2005 from the Canadian Vital Statistics by the direct method. Crude prevalence rates were also calculated to make comparisons with previous studies. For longitudinal analyses, the Average Annual Percent Change (AAPC) in stillbirth prevalence over time was computed and compared between ethnicities. Tests of parallelism were performed to determine if trends over time differed by ethnicity. Statistical modeling (purposeful) using logistic regression was used to evaluate the relationships between stillbirth (antepartum and intrapartum), diabetes in pregnancy, and other potential explanatory variables. RESULTS Between 2000-2009 there were 433,445 pregnancies in Alberta. Only records with gestational age ≥ 20 weeks were included in the analysis. Records with missing stillbirth data were not included. A total 426,945 pregnancy records were explored, of which 28,296 (6.63%) were First Nations women. The overall age-adjusted rates of antepartum and intrapartum stillbirth were significantly (p < 0.05) higher in the First Nations group (1.30% and 0.39% respectively) compared to non-First Nations (0.46% and 0.22% respectively). The rate ratios (First Nations to non-First Nations) for age-adjusted antepartum and intrapartum stillbirth prevalence were and 2.86 and 1.80 respectively. Non-First Nations P-value for Comparison Antepartum Stillbirths 1.63 (-6.79-10.81) 0.47 (-1.11-2.07) 0.475 Intrapartum Stillbirths 0.37 (-8.33-9.90) -1.13 (-5.15-3.05) 0.649 In multivariate analysis, First Nations ethnicity was an independent predictor of antepartum stillbirth (OR 1.70, 95% CI 1.47-1.97) and intrapartum stillbirth (OR 1.62, 95% CI 1.29-2.03) (Table 2). Age ≥ 35, history of abortion, history of stillbirth, and pregestational diabetes were significant risk factors for both antepartum and intrapartum stillbirth regardless of ethnicity. Gestational diabetes was not a risk factor for stillbirths. Table 2. Multivariate predictors of antepartum and intrapartum stillbirth among Albertan women by ethnicity. Values are ORs (95% CI). All women (n = 426 945) First Nations women (n = 28 296) OR for antepartum OR for intrapartum OR for antepartum OR for intrapartum stillbirth stillbirth stillbirth stillbirth x 1.6 Prevalence 1 1.37 (1.24-1.51) 1.27 (1.10-1.46) 1.47 (1.07-2.04) - Parity (≤ 3)† 1.40 (1.22-1.62) 0.65 (0.50-0.86) 1.50 (1.10-2.04) - Multiple gestation 2.84 (2.44-3.31) 1.80 (1.37-2.35) - - Ethnicity 1.70 (1.47-1.97) 1.62 (1.29-2.03) NA NA Pregestational hypertension 2.46 (1.83-3.29) 1.95 (1.16-3.27) - - - 0.32 (0.18-0.57) - - Pregestational diabetes 2.11 (1.48-3.00) 2.38 (1.42-3.99) 2.13 (1.07-4.63) 3.20 (1.14-8.97) Pregestational weight ≥ 91kg - 0.62 (0.47-0.82) - - Anemia 1.84 (1.29-2.64) 2.26 (1.35-3.78) - - Drug dependant 2.04 (1.59-2.62) - 2.12 (1.463.07) - 1.29 (1.16-1.44) - - - 1.52(1.30-1.78) 2.35 (1.92-2.88) 1.71 (1.19-2.46) 2.90 (1.73-4.87) 1.74 (1.20-2.52) - 2.84 (1.47-5.53) - 3.85 (3.10-4.78) 3.83 (2.68-5.46) 3.06 (1.88-4.98) 2.89 (1.30-6.41) - 0.62 (0.48-0.80) - - 1.80 (1.27-2.54) 2.84 (1.82-4.44) - - 0.58 (0.34-0.98) - - - Gestational diabetes 0.8 0.6 IMPLICATIONS 0.4 0.2 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Year First Nations B Non-First Nations 0.6 x Parity (0)† History of C-section 1.4 Stillbirth rates have remained stable in Alberta over 10 years, but are higher in First Nations pregnancies compared to non-First Nations. This may be at least in-part due to the higher incidence and prevalence of type 2 diabetes amongst young First Nations women. Increased awareness of pregestational diabetes could lead to better recognition and management and decreased numbers of stillbirths. 0.5 REFERENCES 0.4 Prevalence 1.78 (1.03-3.24) History of LGA Non-First Nations 1.67 (1.15-2.42) History of fetal anomaly First Nations 1.37 (1.16-1.63) History of stillbirth A 1.58 (1.42-1.76) History of neonatal death Figure 1. Age-adjusted prevalence of stillbirth over time in Alberta by ethnicity. A = antepartum stillbirth ; B = intrapartum stillbirth. Age ≥ 35 History of abortion x 0.3 0.2 0.1 0 2000 2001 2002 2003 2004 2005 Year All analyses were conducted using STATA statistical software (version 11) and Joinpoint (version 3.5.1). Annual age-adjusted rates of stillbirth First Nations Smoker Between 2000 and 2009, age-adjusted prevalence rates of both antepartum and intrapartum stillbirth remained stable in both groups (Figure 1, Figure 2, Table 1). No longitudinal between group differences (parallelism) were noted. 1.2 Ethical approval was obtained from the Human Research Ethics Board of the University of Alberta. We conducted a secondary analysis of data previously obtained (5). Briefly, anonymized data from all provincial delivery records for the years 2000-2009 was requested from the Alberta Perinatal Health Program, which compiles perinatal data from hospital births and registered midwife attended home births. Specifics on how the APHP collects and characterizes data can be found elsewhere (5). Importantly, prior to our acquisition, the data was sent to Alberta Health for First Nations ethnicity ascertainment. Three unique and distinct populations of Canadian Aboriginal people are recognized by the federal government: First Nations, Métis (mixed blood) and Inuit. De-identified complete data was returned by AHW in STATA format. The data were matched using the Personal Health Number and First Nations individuals were classified as any Alberta resident registered under the Indian Act of Canada and entitled to Treaty status with the federal Government. Women delivering in Alberta with a First Nations identifier (First Nations or Inuit) were considered “First Nations” whereas all other women (including First Nations individuals without Treaty status and Métis individuals) were considered “non-First Nations”. Table 1. Ethnicity comparisons of antepartum and intrapartume stillbirth prevalence over time in Alberta, 2000-2009. Values are AAPC (95% CI) in age-adjusted rates. x 1.8 METHODS x 2006 2007 2008 2009 1. Cousens S et al. The Lancet. 2011;377(9774):1319-30. 2. The Lancet. 2011;377 (9774). 3. Shah PS et al. Women’s Health Issues. 2011;21(1):28-39. 4. Auger N et al. Canadian Medical Association Journal. 2013. Epub. 5. Oster RT. Dissertation. University of Alberta. 2013