Background
Methods
Study population and data
Definitions of the exposures and outcomes
Outcomes
Explanatory variables
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Maternal place of birth: Based on maternal native country (as recommended [36]), immigrant mothers were distinguished from those of Belgian origin. This variable was grouped into 5 categories according to maternal region of birth: Belgium, European Union outside of Belgium (EU), Maghreb, Sub-Saharan Africa, and other countries. The proposed categorisation takes into account the mapping of the various parts of the world, the distribution of births in Brussels and the results of previous studies on perinatal health in Brussels [20, 21]. Maghreb is the North African region excluding Egypt. In Belgium, North African immigration comes mainly from the Maghreb. So, the interpretation of the results will refer to North Africa. The ‘other countries’ category is very heterogeneous, so it is not reported in the results.
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Household income covers earned income and replacement incomes collected yearly. Real estate and movable incomes are not considered. It is the annual taxable gross income (after deduction of social security contributions). To be able to compare households, the household income is established by factoring in the size of the household (household equivalent income) according to the OECD-modified scale [37]. In the database, we have the equivalent income for households, by deciles. These deciles are based on the distribution of income for all the Belgian households. They have been categorized by quintile. We can therefore know in which quintile (or decile) a household living in brussels is, compared to all the Belgian households, but not the exact amount of the income. To identify the households with an equivalent income below the risk-of-poverty threshold, we have compared the equivalent risk-of-poverty threshold (60% of the median income) to the threshold of the income quintiles. The threshold of the poorest quintile (Q5) is close to the risk-of-poverty threshold. This is why we approximate that households with incomes in the lowest quintile are “at risk of poverty”. Based on income quintiles, three categories of households were identified: households at risk of poverty (Q5), median income households (Q4 and Q3), and high-income households (Q1 and Q2).
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The mother’s employment status is based on the nomenclature of the socioeconomic position of the DWH (Datawarehouse) [38]. It relates to the situation during the last trimester before birth. This situation broadly represents the mothers’ activity during pregnancy [27]. The variable distinguishes: a) mothers who had a job during this trimester, b) those who received social assistance of last resort (any financial aid from a public social welfare centre), c) other situations of off-duty status (unemployment, transition after studies, career interruption, work incapacity...); (d) an ‘other’ category, which includes people who do not contribute to a social security scheme in Belgium (e.g. officials and international diplomats, housewives). This category is rather large in Brussels. The last two categories are very heterogeneous. The comparison and interpretation of the results will mainly focus on the first two categories: mothers who have held a job versus those who benefited from social welfare. Social welfare recipients are a particularly vulnerable group who experiences increased poverty and an important risk of social precariousness. The negative impact of these conditions on health can be important [39, 40].
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Maternal education was categorised into four groups, as in previous studies [21]: superior (university or higher education), upper secondary (completed secondary school), lower secondary or less (up to the third completed year of secondary), completed primary or less, and other. This last category mainly concerns mothers for whom educational level is unknown.
Statistical analysis
Results
Maternal characteristics
N | All births | Belgium | EU27 | North Africa | SS Africa |
---|---|---|---|---|---|
97,844* | 39,591 | 14,195 | 18,797 | 6812 | |
% of births | 100 | 40.5 | 14.5 | 19.2 | 7.0 |
Household income (n) | 88,655 | 38,638 | 11,132 | 18,286 | 5756 |
high (%) | 24.85 | 38.75 | 31.77 | 4.06 | 8.01 |
median (%) | 33.75 | 34.88 | 31.69 | 36.05 | 29.90 |
low (at risk of poverty) (%) | 41.40 | 26.36 | 36.53 | 59.89 | 62.09 |
Employed (n) | 97,844 | 39,591 | 14,195 | 18,797 | 6812 |
Yes (%) | 40.91 | 60.49 | 42.86 | 17.75 | 22.97 |
No - social recipient (%) | 6.98 | 3.24 | 3.13 | 6.33 | 30.49 |
No - other (%) | 19.60 | 29.18 | 7.93 | 17.10 | 11.44 |
Other (%) | 32.51 | 7.09 | 46.08 | 58.82 | 35.10 |
Maternal education (n) | 97,142 | 39,369 | 14,109 | 18,582 | 6749 |
Superior (%) | 29.29 | 38.28 | 41.89 | 10.09 | 17.44 |
secondary superior (%) | 32.53 | 33.10 | 30.41 | 32.77 | 33.47 |
< = secondary inferior (%) | 30.69 | 22.81 | 22.55 | 45.90 | 40.41 |
Other | 7.49 | 5.80 | 5.16 | 11.24 | 8.68 |
Living alone (n) | 92,975 | 38,909 | 13,417 | 18,414 | 6154 |
No - married (%) | 61.45 | 52.53 | 65.92 | 84.46 | 41.45 |
No - not married (%) | 17.16 | 26.56 | 20.50 | 1.94 | 12.58 |
Yes (%) | 15.78 | 15.70 | 10.66 | 9.70 | 37.16 |
Unknown | 5.61 | 5.21 | 2.92 | 3.90 | 8.81 |
Parity (n) | 97,234 | 39,381 | 14,144 | 18,645 | 6771 |
0 (%) | 47.70 | 52.09 | 53.74 | 36.66 | 44.75 |
1–2 (%) | 43.70 | 41.73 | 42.32 | 47.19 | 44.22 |
3 (%) | 8.60 | 6.18 | 3.94 | 16.14 | 11.03 |
Maternal age (n) | 97,844 | 39,591 | 14,195 | 18,797 | 6812 |
< 20 (%) | 2.39 | 2.39 | 1.74 | 2.01 | 3.27 |
20–40 (%) | 93.29 | 94.68 | 92.74 | 91.24 | 93.09 |
> = 40 (%) | 4.31 | 2.92 | 5.52 | 6.75 | 3.64 |
Infant sex (n) | 97,844 | 39,591 | 14,195 | 18,797 | 6812 |
Female | 48.73 | 48.89 | 48.85 | 48.18 | 48.61 |
LBW (n) | 96,813 | 39,155 | 14,060 | 18,616 | 6742 |
(%) | 4.64 | 5.08 | 3.98 | 3.29 | 5.75 |
Preterm (n) | 95,490 | 38,670 | 13,830 | 18,428 | 6657 |
(%) | 5.22 | 5.48 | 4.95 | 4.09 | 5.65 |
SGA (n) | 94,650 | 38,306 | 13,725 | 18,280 | 6601 |
% | 10.56 | 11.40 | 9.97 | 8.62 | 12.33 |
Relation between the mothers’ characteristics and the adverse pregnancy outcomes
All Births | Belgium | EU27 | North Africa | Sub-Saharan Africa | ||||||
---|---|---|---|---|---|---|---|---|---|---|
% | OR (95% CI) | % | OR (95% CI) | % | OR (95% CI) | % | OR (95% CI) | % | OR (95% CI) | |
LBW | ||||||||||
Household income | ||||||||||
high | 4.13 | 1 | 4.31 | 1 | 3.71 | 1 | 3.67 | 1 | 2.84 | 1 |
median | 4.64 | 1,12 (1,03-1,23)b | 5.06 | 1,18 (1,05-1,32)b | 3.80 | 1,02 (0,80-1,31) | 3.38 | 0,91 (0,61-1,38) | 5.91 | 2,15 (1,19-3,86)a |
low (at risk of poverty) | 4.66 | 1,13 (1,04-1,23)b | 5,59 | 1,31 (1,17-1,47)c | 4.51 | 1,22 (0,97-1,54) | 3.02 | 0,81 (0,54-1,21) | 5.99 | 2,18 (1,23-3,84)b |
Employed | ||||||||||
Yes | 4.61 | 1 | 4.73 | 1 | 3.88 | 1 | 3.79 | 1 | 5.66 | 1 |
No - social recipient | 6.65 | 1,47 (1,32-1,63)c | 9.54 | 2,12 (1,74-2,58)c | 7.82 | 2,09 (1,44-3,05)c | 3.91 | 1,03 (0,73-1,45) | 6.05 | 1,07 (0,81-1,42) |
No - other | 5.16 | 1,12 (1,03-1,21)b | 5.41 | 1,04 (1,04-1,27)b | 5.31 | 1,38 (1,03-1,85)a | 3.29 | 0,86 (0,66-1,45) | 7.13 | 1,28 (0,90-1,81) |
Other | 3.92 | 0,84 (0,78-0,90)c | 4.73 | 0,99 (0,82-1,20) | 3.58 | 0,91 (0,76-1,10) | 3.07 | 0,80 (0,65-0,99) | 5.11 | 0,89 (0,67-1,18) |
Maternal education | ||||||||||
Superior | 4.08 | 1 | 4.10 | 1 | 3.35 | 1 | 3.38 | 1 | 6.01 | 1 |
secondary superior | 4.81 | 1,19 (1,09-1,29)c | 5.23 | 1,28 (1,15-1,44)c | 4.21 | 1,26 (1,03-1,55)a | 3.53 | 1,04 (0,78-1,39) | 5.66 | 0,93 (0,69-1,26) |
< = secondary inferior | 4.80 | 1,18 (1,09-1,28)c | 6.27 | 1,56 (1,39-1,75)c | 4.49 | 1,34 (1,08-1,68)b | 2.99 | 0,88 (0,66-1,16) | 5.39 | 0,88 (0,66-1,19) |
other | 5.34 | 1,32 (1,17-1,49)c | 5.76 | 1,42 (1,17-1,73)c | 5.03 | 1,52 (1,06-2,19)a | 3.89 | 1,16 (0,82-1,62) | 6.91 | 1,15 (0,77-1,73) |
Living alone (n) | ||||||||||
No - married | 3.75 | 1 | 3.97 | 1 | 3.30 | 1 | 3.02 | 1 | 4.85 | 1 |
No - not married | 5.33 | 1,44 (1,32-1,56)c | 5.70 | 1,46 (1,31-1,63)c | 4.45 | 1,36 (1,10-1,69)b | 2.55 | 0,84 (0,43-1,63) | 4.82 | 0,99 (0,68-1,44) |
Yes | 6.19 | 1,69 (1,56-1,83)c | 6.43 | 1,66 (1,46-1,88)c | 6.26 | 1,95 (1,53-2,50)c | 4.81 | 1,62 (1,28-2,05)c | 6.68 | 1,40 (1,09-1,74)b |
Unknown | 5.50 | 1,49 (1,31-1,69)c | 5.96 | 1,53 (1,25-1,87)c | 5.44 | 1,68 (1,07-2,65)a | 3.23 | 0,85 (0,53–135) | 6.00 | 1,25 (0,83-1,87) |
SGA | ||||||||||
Household income (n) | ||||||||||
high (%) | 9.88 | 1 | 10.24 | 1 | 9.60 | 1 | 8.39 | 1 | 9.21 | 1 |
median (%) | 10.68 | 1,09 (1,03-1,15)b | 11.76 | 1,16 (1,08-1,26)c | 10.06 | 1,05 (0,89-1,23) | 8.73 | 1,04 (0,79-1,37) | 11.92 | 1,33 (0,93-1,89) |
low (at risk of poverty) (%) | 10.71 | 1,09 (1,03-1,15)b | 12.46 | 1,24 (1,15-1,35)c | 10.69 | 1,12 (0,96-1,31) | 8.38 | 0,99 (0,76-1,30) | 12.65 | 1,42 (1,01-1,99)a |
Employed (n) | ||||||||||
Yes (%) | 10.27 | 1 | 10.89 | 1 | 9.83 | 1 | 8.15 | 1 | 9.64 | 1 |
No - social recipient (%) | 12.48 | 1,24 (1,14-1,34)c | 16.28 | 1,59 (1,36-1,86)c | 16.90 | 1,86 (1,42-2,43)c | 8.53 | 1,05 (0,82-1,33) | 12.82 | 1,37 (1,11-1,70)b |
No - other (%) | 11.21 | 1,10 (1,04-1,16)c | 12.15 | 1,13 (1,05-1,21)c | 12.67 | 1,33 (1,09-1,62)b | 7.97 | 0,97 (0,81-1,16) | 13.01 | 1,40 (1,06-1,84) |
Other (%) | 10.13 | 0,98 (0,93-1,03) | 10.50 | 0,96 (0,84-1093) | 9.16 | 0,92 (0,82-1,04) | 8.95 | 1,10 (0,96-1,28) | 13.45 | 1,45 (1,18-1,79) |
Maternal education (n) | ||||||||||
Superior (%) | 9.99 | 1 | 10.45 | 1 | 9.41 | 1 | 9.35 | 1 | 10.98 | 1 |
secondary superior (%) | 10.77 | 1,08 (1,03-1,14)b | 11.73 | 1,13 (1,05-1,22)c | 10.02 | 1,07 (0,93-1,22) | 8.82 | 0,93 (0,78-1,12) | 11.22 | 1,02 (0,81-1,28) |
< = secondary inferior (%) | 10.84 | 1,09 (1,03-1,15)c | 12.51 | 1,22 (1,12-1,33)c | 10.70 | 1,15 (0,99-1,33) | 8.22 | 0,86 (0,72-1,03) | 13.41 | 1,25 (1,01-1,55)a |
other | 10.84 | 1,09 (1,01-1,19)a | 11.18 | 1,08 (0,93-1,24) | 11.27 | 1,22 (0,95-1,57) | 9.21 | 0,98 (0,79-1,22) | 14.29 | 1,35 (1,01-1,82)a |
Living alone (n) | ||||||||||
No - married (%) | 9.43 | 1 | 9.80 | 1 | 8.85 | 1 | 8.35 | 1 | 12.10 | 1 |
No - not married (%) | 11.66 | 1,26 (1,19-1,34)c | 12.16 | 1,27 (1,18-1,37)c | 11.70 | 1,36 (1,18-1,57)c | 8.31 | 0,99 (0,67-1,46) | 9.38 | 0,75 (0,57-0,98) |
Yes (%) | 12.54 | 1,37 (1,29-1,45)c | 14.19 | 1,52 (1,39-1,66)c | 13.20 | 1,56 (1,31-1,86)c | 9.56 | 1,15 (0,97-1,37) | 13.12 | 1,09 (0,92-1,30) |
Unknown | 12.70 | 1,39 (1,28-1,52)c | 14.46 | 1,55 (1,36-1,78)c | 11.67 | 1,36 (0,98-1,88) | 8.54 | 1,25 (0,97-1,60) | 11.63 | 0,95 (0,71-1,28) |
All births | Belgium | EU27 | North Africa | SS Africa | |
---|---|---|---|---|---|
OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | |
LBW | |||||
Household income | |||||
high | 1 | 1 | 1 | 1 | 1 |
median | 1,15 (1,05-1,27)b | 1,10 (0,97-1,25) | 0,97 (0,74-1,27) | 1,00 (0,65-1,53) | 2,28 (1,25-4,17)b |
low (at risk of poverty) | 1,11 (0,99-1,24) | 1,07 (0,91-1,26) | 1,05 (0,79-1,39) | 0,90 (0,58–140) | 2,28 (1,22-4,22)b |
Employed | |||||
Yes | 1 | 1 | 1 | 1 | 1 |
No - social recipient | 1,17 (1,02-1,34)a | 1,49 (1,17-1,91)c | 1,37 (0,87-2,16) | 0,91 (0,62-1,35) | 1,03 (0,72-1,49) |
No - other | 1,02 (0,93-1,12) | 1,03 (0,90-1,16) | 1,09 (0,78-1,51) | 0,91 (0,68-1,21) | 1,17 (0,80-1,72) |
Other | 0,85 (0,72-0,93) | 1,02 (0,82-1,25) | 0,94 (0,74-1,19) | 0,92 (0,721,17) | 0,82 (0,58-1,15) |
Maternal education | |||||
Superior | 1 | 1 | 1 | 1 | 1 |
secondary superior | 1,17 (1,07-1,28)c | 1,27 (1,12-1,44)c | 1,20 (0,93-1,55) | 1,09 (0,80-1,48) | 0,77 (0,55-1,08) |
< = secondary inferior | 1,27 (1,15-1,40)c | 1,61 (1,39-1,86)c | 1,35(1,01-1,79)a | 0,99 (0,73-1,34) | 0,86 (0,61-1,20) |
other | 1,28 (1,12-1,47)c | 1,34 (1,08-1,65)b | 1,32 (0,86-2,04) | 1,21 (0,84-1,74) | 1,03 (0,66-1,62) |
Living alone (n) | |||||
No - married | 1 | 1 | 1 | 1 | 1 |
No - not married | 1,36 (1,24-1,48)c | 1,37 (1,19-1,58)c | 1,25 (0,98-1,59)c | 0,69 (0,35-1,37) | 1,00 (0,68-1,47) |
Yes | 1,44 (1,31-1,58)c | 1,43 (1,27-1,60)a | 1,91(1,42-2,57) | 1,43 (1,08-1,90)a | 1,19 (0,89-1,60) |
Unknown | 1,29 (1,12-1,49)c | 1,21 (0,98-1,49) | 1,03 (0,59-1,82) | 0,85 (0,53–135) | 1,40 (0,84-2,32) |
SGA | |||||
Household income | |||||
high | 1 | 1 | 1 | 1 | 1 |
median | 1,13 (1,06-1,20)c | 1,18 (1,08-1,28)c | 1,03 (0,87-1,23) | 1,09 (0,82-1,47) | 1,22 (0,84-1,76) |
low (at risk of poverty) | 1,13 (1,05-1,22)c | 1,16 (1,03-1,29)b | 1,05 (0,87-1,27) | 1,10 (0,81-1,48) | 1,20 (0,82-1,75) |
Employed | |||||
Yes | 1 | 1 | 1 | 1 | 1 |
No - social recipient | 1,03 (0,93-1,14) | 1,18 (0,98-1,42) | 1,56 (1,14-2,13)b | 0,96 (0,73-1,25) | 1,22 (0,92-1,61) |
No - other | 1,06 (0,99-1,13) | 1,04 (0,95-1,13) | 1,19 (0,96-1,48) | 1,06 (0,87-1,29) | 1,41 (1,05-1,88)a |
Other | 0,99 (0,92-1,05) | 1,01 (0,86-1,16) | 0,87 (0,74-1,02) | 1,23 (1,05-1,46)a | 1,35 (1,06-1,72)a |
Maternal education | |||||
Superior | 1 | 1 | 1 | 1 | 1 |
secondary superior | 1,07 (1,01-1,14)a | 1,10 (1,01-1,20)a | 1,14 (0,96-1,35) | 0,90 (0,75-1,10) | 0,92 (0,71-1,18) |
< = secondary inferior | 1,23 (1,15-1,32)c | 1,32(1,19-1,45)c | 1,36 (1,13-1,64)c | 0,94 (0,78-1,13) | 1,31 (1,02-1,67)a |
other | 1,05 (0,95-1,16) | 0,99 (0,85-1,15) | 1,23 (0,92-1,64) | 0,96 (0,76-1,22) | 1,12 (0,78-1,59) |
Living alone (n) | |||||
No - married | 1 | 1 | 1 | 1 | 1 |
No - not married | 1,23 (1,16-1,32)c | 1,30 (1,18-1,44)c | 1,30 (1,04-1,61)a | 1,12 (0,92-1,37) | 1,00 (0,81-1,23) |
Yes | 1,18 (1,11-1,26)c | 1,19 (1,10-1,29)c | 1,23 (1,05-1,43)b | 0,93 (0,62-1,37) | 0,74 (0,57-0,97) |
Unknown | 1,17 (1,06-1,29)c | 1,24 (1,07-1,43)c | 0,99 (0,69-1,43) | 0,96 (0,74-1,27) | 0,83 (0,55-1,26) |