Using linked birth and infant death data to describe disparities in birth outcomes across various demographic groupings in British Columbia from 1981 through 2000 Russell Wilkins (Statistique Canada) William Kierans (BC Vital Statistics Agency) Michael Kramer (McGill University) Canadian Population Society, Congress 2004 Winnipeg, Manitoba, 2-5 June 2004

Data sources Live births Infant deaths Stillbirths Census income data for EAs –1981*, 1986, 1991, 1996 –2001 not available when analysed

Methods: data preparation Link births and deaths (probabilistic) Determine First Nation status of births Generate 1996 EA from postal codes Translate from 1996 EA to: –1981 EA, 1986 EA, 1991 EA, and 2001 DA Calculate family size-adjusted IPPE Define IPPE quintiles for each census year

Methods: analysis Define events and rates of interest: –Low birth weight (LBW), prematurity, SGA –Stillbirth, neonatal, post-neonatal mortality –Birth weight percentiles by gestational age –Neonatal mortality by birth weight + gest age Compile results by groupings of interest: –Sex, plurality, parity, marital status, period –First Nation status, community size, region –Chinese, South Asian, European immigrants –Neighbourhood income quintile

Results 880,283 live births 5,506 stillbirths (20+ weeks or 500+ g) 5,698 infant deaths (< 1 year) 3,565 neonatal deaths (<28 days) 2,107 post-neonatal deaths ( days) 44,407 low birth weight (<2500 g) 55,637 preterm (<37 weeks) 89,423 small for gestational age (<10 p’tile)

Birth weight percentiles by gestational age for the full population

Neonatal mortality (%) by birth weight and gestational age

% Neonatal mortality + av bwt by gest-age + bwt risk group Risk group N*1000 Neobwt(g) Very low Low Mod high High Very high Extremely high

Rates by gestational age Weeks Inf NeoPost Stil LBW –Infant, neonatal and post-neonatal mortality per 1,000 live births –Stillbirth rate per 1,000 total births (live births + stillbirths) –Low birth weight rate per 100 live births

Rates by secular period Inf Neo Post Stil LBW Pre RR RD –rates per 1000 except LBW & Pre per 100

Rates by income quintile Q Inf Neo Post Stil LBW Pre SGA RR RD –rates per 1000 except LBW Pre SGA per 100

Rates for immigrants by origin & for First Nations vs BC total Inf Neo Post Stil LBW Pre Chinese South Asian European BC total First Nations –rates per 1000 except LBW Pre per 100

Discussion Mortality grids have only rarely been calculated for large populations (firsts for Canada and so many sub-populations) Mortality grids and birth weight percentile charts are needed by obstetricians and perinatalogists, as well as by families of premature and/or growth-retarded or macrosomic infants.

Work ahead... Articles for peer-reviewed journals –appropriateness of single vs multiple standards for specific subpopulations such as immigrants and First Nations (physiologic/pathologic?) –trends and differentials in birth outcomes by neighbourhood income (incl causes of death) –body length and head circumference measurements for recent years –urban-rural and regional differences (access?)

Note Conventional denominators were used for this descriptive report The “fetuses-at-risk” (KS Joseph) approach will be used for future analytical studies based on these data

For copies of the report Kierans W et al., Charting birth outcome in British Columbia BC Vital Statistics Agency, Victoria BC April (report plus 2 appendices)

Authors Kierans W, Uh SH, Mohamed J (BCVS) Kramer M (McGill Epidemiol, Pediatrics) Foster L (BC Min Children & Fam Dev) Liston R (UBC Obstetrics) Wilkins R (Statistics Canada, U Ottawa)