Maternal occupation during pregnancy, birth weight, and length of gestation: combined analysis of 13 European birth cohorts.
OBJECTIVE
We assessed whether maternal employment during pregnancy - overall and in selected occupational sectors - is associated with birth weight, small for gestational age (SGA), term low birth weight (LBW), length of gestation, and preterm delivery in a population-based birth cohort design.


METHODS
We used data from >200 000 mother-child pairs enrolled in 13 European birth cohorts and compared employed versus non-employed women. Among employees, we defined groups of occupations representing the main sectors of employment for women where potential reproductive hazards are considered to be present. The comparison group comprised all other employed women not included in the occupational sector being assessed. We performed meta-analyses of cohort-specific estimates and explored heterogeneity.


RESULTS
Employees had a lower risk of preterm delivery than non-employees [adjusted odds ratio (OR adj) 0.86, 95% confidence interval (95% CI) 0.81-0.91]. Working in most of the occupational sectors studied was not associated with adverse birth outcomes. Being employed as a nurse was associated with lower risk SGA infants (OR adj0.91, 95% CI 0.84-0.99) whereas food industry workers had an increased risk of preterm delivery (OR adj1.50, 95% CI 1.12-2.02). There was little evidence for heterogeneity between cohorts.


CONCLUSIONS
This study suggests that, overall, employment during pregnancy is associated with a reduction in the risk of preterm birth and that work in certain occupations may affect pregnancy outcomes. This exploratory study provides an important platform on which to base further prospective studies focused on the potential consequences of maternal occupational exposures during pregnancy on child development.
Centre for Research in Environmental Epidemiology, Doctor Aiguader, 88, 08003 Barcelona. Spain. mcasas@creal.cat.
Maribel
M
Casas
Sylvaine
S
Cordier
David
D
Martínez
Henrique
H
Barros
Jens Peter
JP
Bonde
Alex
A
Burdorf
Nathalie
N
Costet
Ana Cristina
AC
Dos Santos
Asta
A
Danileviciute
Merete
M
Eggesbø
Mariana F
MF
Fernandez
Joelle
J
Fevotte
Ana M
AM
García
Regina
R
Gražuleviciene
Eva
E
Hallner
Wojciech
W
Hanke
Manolis
M
Kogevinas
Inger
I
Kull
Pernille
P
Stemann Larsen
Vasiliki
V
Melaki
Christine
C
Monfort
Karl-Christian
KC
Nordby
Anne-Marie
AM
Nybo Andersen
Evridiki
E
Patelarou
Kinga
K
Polanska
Lorenzo
L
Richiardi
Loreto
L
Santa Marina
Claudia
C
Snijder
Adonina
A
Tardón
Manon
M
van Eijsden
Tanja Gm
TG
Vrijkotte
Daniela
D
Zugna
Mark
M
Nieuwenhuijsen
Martine
M
Vrijheid
D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D001724:Birth Weight; D015331:Cohort Studies; D004651:Employment / Q000145:classification / Q000706:statistics & numerical data; D005060:Europe / Q000453:epidemiology; D005865:Gestational Age; D015438:Health Behavior; D007230:Infant, Low Birth Weight; D007236:Infant, Small for Gestational Age; D018811:Maternal Exposure / Q000009:adverse effects / Q000706:statistics & numerical data; D009790:Occupations / Q000145:classification / Q000706:statistics & numerical data; D011256:Pregnancy Outcome / Q000453:epidemiology; D047928:Premature Birth; D012044:Regression Analysis; D012307:Risk Factors; D011795:Surveys and Questionnaires