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 2004Winnipeg, Manitoba, 2-5 June 2004

Data sources

• Live births 1981-2000

• Infant deaths 1981-2001

• Stillbirths 1981-2000

• 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 (28-364 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

Wilkins-bwtChart-p41.pdf

MortGrid622.pdf

Neonatal mortality (%) by birth weight and gestational age

% Neonatal mortality + av bwtby gest-age + bwt risk group

Risk group N*1000 Neo bwt(g)

Very low 360 0.1 3638

Low 182 0.2 3015

Mod high 35 0.8 2442

High 11 3.7 1807

Very high 3 17.2 1048

Extremely high 1 68.0 645

Rates by gestational age

Weeks Inf Neo Post Stil LBW

20-27 10.8 5.8 5.0 39.5 100.0

28-36 6.9 5.3 1.6 3.0 53.0

37-41 3.1 1.2 1.9 1.9 1.9

42-44 3.6 1.7 1.9 0.2 0.4

– 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

1981-84 8.6 5.3 3.3 7.2 5.1 6.7

1985-88 8.0 4.7 3.3 6.8 4.9 5.9

1988-92 6.7 4.1 2.5 6.3 5.0 6.1

1993-96 5.3 3.5 1.8 5.5 5.1 6.3

1997-00 4.0 2.8 1.2 5.5 5.1 6.6

RR 2.2 1.9 2.8 1.3 1.0 1.0

RD 4.6 2.5 2.1 1.7 0.0 0.1– rates per 1000 except LBW & Pre per 100

Rates by income quintileQ Inf Neo Post Stil LBW Pre SGA

1 6.8 4.1 2.7 6.1 5.7 6.9 10.9

2 5.8 3.7 2.0 5.9 5.2 6.2 10.5

3 5.5 3.5 1.9 5.8 4.9 6.0 9.6

4 5.4 3.6 1.8 5.4 4.7 6.0 9.0

5 5.2 3.2 2.0 5.5 4.4 5.8 8.3

RR 1.3 1.3 1.4 1.1 1.3 1.2 1.3

RD 1.6 0.9 0.7 0.6 1.3 1.1 2.6– 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 3.2 2.3 1.0 3.1 4.7 5.6

South Asian 4.7 3.5 1.2 4.4 7.1 7.4

European 4.1 3.0 1.1 4.3 4.1 5.8

BC total 6.5 4.1 2.4 6.2 5.0 6.3

First Nations 13.0 5.3 7.6 7.5 5.9 9.6

– 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 2004

www.vs.gov.bc.ca/stats/features/index.htm

(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)