BEU, Alm.del - 2018-19 (2. samling) - Bilag 34: Orientering vedr. videnskabelig artikel om, hvad flere samtidige påvirkninger i arbejdsmiljøet betyder for gravides fravær fra arbejdet, fra beskæftigelsesministeren

Beskæftigelsesudvalget 2018-19 (2. samling)
BEU Alm.del Bilag 34
Offentligt

riginal article

Scand J Work Environ Health – online first.

The influence of multiple occupational exposures on absence from work in pregnancy: a

prospective cohort study

by Camilla Sandal Sejbaek, PhD,

Jacob Pedersen, PhD,

Vivi Schlünssen, PhD,

1, 2

Luise Mølenberg Begtrup, PhD,

Mette Juhl,

PhD,

Jens Peter Bonde, PhD,

Petter Kristensen, PhD,

Hans Bay, Cand.stat.,

Cecilia Høst Ramlau-Hansen, PhD,

Karin Sørig

Hougaard, PhD

1, 7

Sejbaek CS, Pedersen J, Schlünssen V, Begtrup LM, Juhl M, Bonde JP, Kristensen P, Bay H, Ramlau-Hansen CH, Hougaard KS.

The influence of multiple occupational exposures on absence from work in pregnancy: a prospective cohort study.

Scand J

Work Environ Health

– online first.

Objectives

Many women experience absence periods from work during pregnancy. Several single risk factors

for absence are identified, whereas the impact of multiple concurrent exposures has been sparsely studied. We

hypothesized that the presence of multiple occupational exposures would be associated with an increased risk

of absence from work during pregnancy.

working ≥30 hours/week at interview (mean gestational week 17 (standard deviation 4.0); N=50 142). Informa-

tion about five occupational exposures (job

demands,

job control, work posture, work shift, lifting) were retrieved

from the interview, each assigned values of 0/1, and summed into an index (0–5). The woman’s first absence from

work (both regular and related to pregnancy) after the interview was available from a nationwide administrative

sures (34.7%). Only 24.3% of the women were absent from work before gestational week 31. The number of

occupational exposures was associated with an increasing risk of absence. The adjusted hazard ratio for absence

increased from 1.3 [95% confidence interval (CI) 1.1–1.5] for one exposure to 2.9 (95% CI 2.5–3.3) for four to

five exposures compared to no occupational exposure.

Methods

We included women from the Danish National Birth Cohort (1996–2002), pregnant with one child and

Results

Few women experienced none of the occupational exposures (3.6%) and most experienced two expo-

Conclusion

The higher the number of potentially adverse occupational exposures pregnant women experienced,

the higher the risk for absence from work during pregnancy.

Key terms

epidemiology; pregnancy-related absence; job control; job demand; lifting; work posture; work shift.

A large proportion of women experience absence from

work during pregnancy. In Denmark, two thirds of all

pregnant women were absent from work at some point

during pregnancy, and almost one third of the pregnant

women were absent for >8 weeks during pregnancy.

Furthermore, absence from work in pregnancy seems

to increase (1). In 2016, the employment rate was 72%

for Danish women in the reproductive age (18–44 years)

(2), and each year around 60 000 children are born in

Denmark. The societal costs due to absence from work

are therefore high due to payment of benefits and reduc-

tion of manpower. Absence from work is also problem-

atic for pregnant women because work is perceived as an

important part of life. Reduction of absence from work

during pregnancy therefore

encompasses

economic as

well as individual advantages. It is therefore important

National Research Centre for the Working Environment, Copenhagen, Denmark.

Department of Public Health – Institute of Environment, Occupation and Health, Aarhus University, Aarhus, Denmark.

Department of Occupational and Environmental Medicine, Copenhagen, Denmark.

Faculty of Health, Department of Midwifery and Therapeutic Sciences, University College Copenhagen, Copenhagen, Denmark.

Department of Occupational Medicine and Epidemiology, National Institute of Occupational Health, Oslo, Norway.

Department of Public Health – Section for Epidemiology, Aarhus University, Aarhus, Denmark.

Department of Public Health, Section of Occupational and Environmental Health, University of Copenhagen, Copenhagen, Denmark.

Correspondence to: Camilla Sandal Sejbaek, PhD, National Research Centre for the Working Environment, Lersø Parkalle 105, DK-2100

Copenhagen, Denmark. [E-mail: [email protected]].

Scand J Work Environ Health – online first

BEU, Alm.del - 2018-19 (2. samling) - Bilag 34: Orientering vedr. videnskabelig artikel om, hvad flere samtidige påvirkninger i arbejdsmiljøet betyder for gravides fravær fra arbejdet, fra beskæftigelsesministeren

Multiple occupational exposures and absence in pregnancy

to study how occupational exposures may be associated

with absence from work during pregnancy to enable

formulation of efficient preventive measures.

A number of occupational factors have been

described as risk factors for absence from work during

pregnancy. Previous studies have investigated occu-

pational exposures such as job strain [defined by the

combination of job

demands

and job control (3)], work

posture, lifting, and work shift. These were each associ-

ated with the first episode of absence during gestational

week (GW) 10–29 of pregnancy in a previous Danish

study (4); while another study found similar exposures

to be associated to absence for >10% of the scheduled

work time during pregnancy among hospital employees

(5). The relationship between occupational exposures

and absence from work during pregnancy has mostly

been assessed for individual factors, one at a time, rather

than for combinations of exposures. However, one cross-

sectional study investigated an index of occupational

exposures and showed that, with an increasing number

of exposures, the risk of self-reported sickness absence

during pregnancy increased (6). Findings described in

a Danish report indicated that pregnant women concur-

rently exposed to several occupational exposures had

absences

from work than pregnant women with

fewer or no exposures at work (7). This study was cross-

sectional, sickness absence was self-reported, and details

of the analyses were not available. Hence, in research

of associations between occupational exposures and

absence from work during pregnancy, there is a need to

use prospective study designs and register rather than

self-reported data on the outcome.

We hypothesized that exposure to multiple concur-

rent occupational exposures would increase the risk of

absence from work and aimed to investigate the asso-

ciation

in two ways. First,

we constructed an index of

several occupational exposures (4) with the hypothesis

that exposures, which have been indicated to relate to

absence from work during pregnancy, will also increase

the risk of absence when they are present concurrently

and that the risk will increase for additional exposures,

ie, the higher the number of exposures the higher the

risk of absence.

mark, and

could carry out a comprehensive telephone

interview in Danish. For more details, see elsewhere (8).

We included women

if they (i)

completed DNBC’s

first pregnancy interview between the first day in GW

11 and the last day in GW 30 [mean 16.7 (SD 4.0) GW],

(ii) were pregnant with their first singleton pregnancy

registered in the DNBC, (iii) worked ≥30 hours per

week, and (iv) had full information on all exposures of

interest, covariables and outcome (figure 1, N=50 142).

The DNBC and the Danish Data Protection Agency

permitted use and storage of data at Statistics Den-

mark where the available data were fully anonymized.

According to the Danish legislation, approval from the

Ethical Committee was not needed.

Occupational exposures

An index variable constructed as described by Miranda

and colleagues (9) was generated from the five selected

occupational exposures: work posture, work shift, lift-

ing, job

demands,

and job control (table 1). These fac-

tors were included in the analyses as they had previously

been found to be associated with absence from work

during pregnancy, albeit job demands and job control

has been combined to create the

exposure of job strain

(4). Lifting was constructed from four questions, while

the rest of the exposures were based on one ques-

tion each (table 1). Each heavy and medium lift were

assigned values of 22.5 and 15 kg/lift, respectively, and

the cumulative burden of lifting was calculated (10).

The scoring of lifting, work posture and work shift (0

or 1 point; table 1) was based on the findings in Hansen

et al (4). Job demands and job control were included

as separate measures, dichotomized and scored (0 or

1 point; table 1) based on Larsen et al (11) and Juhl

et al (12). These two questions were dichotomized in

order to obtain as much contrast as possible. For the

index variable, the points were summarized across the

five occupational exposures for each woman. The final

index variable ranged from 0‒5, where 4 and 5 were

combined into one category due to an assumption that

few women would experience a high amount of occu-

pational exposures.

Outcome

Methods

Study population

We used

data from

the Danish National Birth Cohort

(DNBC) with 100 418 pregnancies (1996–2002) (8).

During the first antenatal visit, the general practitioner

invited the pregnant women to participate in the cohort

if they planned to complete the pregnancy, lived in Den-

Information on doctor-certified absence from work was

obtained from the Danish Register for Evaluation of

Marginalization (DREAM). This register contains data

for all types of social payments with unique codes for

each benefit, eg, sickness and maternity benefit, edu-

cational funds, and retirement pension. The data has a

hierarchical structure and is assessed on a weekly basis

with one code registered in DREAM per week. Absence

from work during pregnancy was registered as either

Scand J Work Environ Health – online first

Sejbaek et al

Figure 1.

Flowchart of the study popula-

tion, the Danish National Birth Cohort

(DNBC), 1996–2002.

regular or pregnancy-related. Regular sickness absence

was registered if the women were absent from work for

≥15 days and subsequently backdated to day 1. Preg-

nancy-related absence from work relates to absence due

to pregnancy factors, eg, pelvic pain or harmful working

condition(s) for mother or child and was registered from

the first day of absence. In order for the absence period,

no matter the type, to be entered into DREAM it had to

be doctor-certified. For the two types of absence, the

employers were reimbursed for the sickness benefit from

day 15 and 1, respectively. Pregnancy-related absence

constituted 88.0% and regular sickness absence 12.0%

of the total absences from work during pregnancy. These

two were in the statistical analyses combined into a

single outcome (yes/no) and the term “absence from

work” is used for the outcome measure in the following.

Potential confounders

We investigated the previous literature and incorporated

the identified potential confounders in a directed acyclic

graph (DAG). This served as partial basis for selec-

tion of confounders together with the availability of

information in the interview and the DREAM register.

We included sickness absence during the year prior to

pregnancy and during early pregnancy (until the first

interview), which were combined into the variable previ-

ous sickness absence. The other confounders included

were maternal age at conception, parity, fertility treat-

ment,

socio-economic status (SES),

pre-pregnancy body

mass index, during pregnancy smoking and leisure

time exercise. SES was based on self-reported job titles

converted into the Danish International Standard Clas-

sification of Occupations (DISCO-88). The confounders

are presented in table 2.

Statistical analysis

In the analyses, we investigated the association between

the index variable and absence from work. We analyzed

data in Cox proportional hazard regression models with

adjustment for covariates with gestational age (days) as

the underlying time variable. Calculation of gestational

age was based on the self-reported first day of the last

menstrual period from the interview. Entry time was

the date of the interview, and end time was the date of

Scand J Work Environ Health – online first

Multiple occupational exposures and absence in pregnancy

Table 1.

Occupational exposures included in the index variable. The

questions from the Danish National Birth Cohort, response keys and

allocation of points for each exposure.

Exposures Question

Job

demand

Job

control

Work

posture

Do you have too much to do

when at your work?

Response key

Points

Seldom or

sometimes=0

Often=1

Often or

sometimes=0

Seldom=1

Sitting=0

All other

responses=1

Work

shift

Often

Sometimes

Seldom

Do you have the opportunity Often

to influence your tasks and Sometimes

working conditions?

Seldom

In your job, do you sit,

Primarily sitting

stand or walk most of the

Primarily standing

time, or can you change as Primarily walking

you like?

Primarily standing

and walking

Changeable

Other

What are your normal

Fixed day

working hours, day, evening Fixed evening

or night, or do you have

Fixed night

shifting working hours?

Shifting, without

night shifts

Shifting, with night

shifts

Heavy:

0–1875 kg/day

In your job, do you daily lift

>20 kg at a time, similar to a

case of beer?

How many times a day do you

lift >20 kg?

Medium:

Do you have daily lifts 11–20

kg, less than a case of beer

and more than a bucket of

water?

How many times a day do you

lift 11–20 kg?

above). As a sensitivity analysis, we investigated the

index variable with six categories instead of five in rela-

tion to absence from work.

The statistical analyses were conducted in SAS 9.4

(SAS Institute Inc, Cary, NC, USA).

Results

In this study, 24.3% of the women had their first spell

of absence from work before GW 31, on average at

GW 24.0 (SD 4.7). About 80% of the women expe-

rienced between 1‒3 occupational exposures, while

<4% experienced 0 exposure at work of interest for

this study. Women in the youngest age group and with

lower educational level, more children, more smoking,

and higher BMI experienced more exposures at work.

Previous sickness absence was also associated with

more exposures at work. Women who had received fer-

tility treatment experienced less exposures compared to

women without fertility treatment (table 2).

The women were on average followed for 11.6

weeks; women registered with absence from work

were followed for 7.6 weeks (mean), while women

with no absence from work were followed for 12.9

weeks (mean). Both the crude and adjusted analyses

showed that with an increasing number of occupational

exposures the risk of absence from work increased (fig-

ure 2), albeit adjustment attenuated the findings both

from model 1 to 2 and from model 2 to 3. In the fully

adjusted analysis, the HR increased from 1.25 (95% CI

1.08–1.45) for one occupational exposure to 2.87 (95%

CI 2.49–3.30)

for 4–5 compared with 0 occupational

exposures

(figure 2).

In a sensitivity analysis, we investigated the index

as a 6-category variable, ie, without combining 4 and

5 occupational exposures. Being exposed to 4 occupa-

tional exposures resulted in the fully adjusted analysis

in a HR of 2.77 (95% CI 2.40–3.19) for absence from

work, exposure to 5 occupational exposures gave a HR

of 3.23 (95% CI 2.77–3.77) for absence from work.

Hence, the risk of absence from work further increased

when the number of occupational exposures increased

from 4 to 5.

We conducted subgroup analyses to test for effect

modification by previous sickness absence in two dif-

ferent analyses. First, a test of effect modification by

sickness absence prior to pregnancy (0, 1–2, 3–5 and ≥6

weeks) was investigated for the index variable. In each

of the subgroups in this variable, we found a pattern

with increasing number of occupational exposures the

risk of absence from work also increased. For women

with no sickness absence prior to pregnancy, the risk

of absence from work increased compared to the main

Fixed day=0

All other

responses=1

Lifting

Not lifting

daily (0–14

kg)=0

Yes lifting

daily (≥15

kg)=1

receiving the first episode of absence from work after

the interview. Observations were censored if the women

terminated pregnancy, gave birth (stillbirth or preterm

birth), emigrated, went on leave other than maternity

leave, received other social benefit,s or the end of the

study period was reached at 30 completed GW, which-

ever came first.

All variables were tested relative to the proportional

hazard assumption by investigating the cumulative

proportional hazards and reclassified when needed (see

footnotes to table 2).

The results are presented as hazard ratios (HR)

with 95% confidence intervals (CI) from the crude and

two adjusted models; one model including all potential

confounders except SES, and one model also including

SES. A third model was included because inclusion of

SES might result in over-adjustment.

Previous sickness absence could indicate an inher-

ent propensity for later sickness absence (13). In the

subgroup analyses, we therefore conducted the analyses

with the women stratified into four groups based on their

absence from work prior to pregnancy

(0, 1–2, 3–5, and

≥6 weeks absence)

and on their absence from work both

prior to and during early pregnancy (see categorization

Scand J Work Environ Health – online first

Sejbaek et al

Table 2.

Characteristics of the pregnant women by the index variable.

Characteristics

Total

(N = 50 142)

Maternal age at birth (years)

<25

25–29

30–34

≥35

Gestational age (weeks) at interview

<17

17–30

Socioeconomic position

High education

Medium education

Skilled work

Unskilled work

Student

Previous sickness absence

No previous sickness absence

Sickness before pregnancy

Absence in early pregnancy

Sickness absence before and

during early pregnancy

Parity

≥2

Smoking

Less than daily

Daily

Fertility treatment

Yes

Leisure-time physical exercise

Yes

Body mass index (kg/m

)

15–24.9

25–29.9

30–50

Index variable

3.6

2.3

3.1

4.3

3.8

3.5

3.6

5.6

2.4

6.0

1.7

4.0

3.9

2.3

2.0

1.6

3.6

3.7

3.0

3.9

2.9

2.3

3.5

4.5

3.5

3.6

3.8

3.1

2.9

9763

754

3985

3809

1215

4871

4892

1808

2774

3034

1582

565

8230

833

390

310

5318

3316

1129

7879

917

967

9112

651

5867

3896

7379

1755

629

19.5

15.0

18.7

21.1

18.6

20.4

29.5

16.3

25.9

12.7

20.8

14.6

13.5

15.9

20.1

19.5

16.8

20.7

16.8

14.8

19.4

21.1

19.1

20.0

18.3

17.1

17 410

1532

7300

6458

2120

8829

8581

2402

5682

4838

3602

886

14 132

1778

877

623

9216

5981

2213

13 556

1829

2025

16 292

1118

10 571

6839

12 937

3304

1169

34.7

30.4

34.3

35.8

36.9

33.8

35.7

39.2

33.3

41.2

28.8

32.6

35.7

31.3

30.2

32.0

34.9

35.2

33.0

35.6

33.6

30.9

34.6

36.2

34.5

34.1

35.1

34.5

31.8

12 967

1489

5588

4500

1390

6763

6204

1079

4630

2592

3937

729

9764

1691

901

611

6681

4419

1867

9529

1511

1927

12 210

757

8004

4963

9335

2586

1046

25.9

29.6

26.2

24.9

24.2

25.9

25.8

17.6

27.1

22.1

31.5

26.8

24.7

29.7

31.1

31.4

25.3

26.0

27.8

25.0

27.7

29.4

26.0

24.5

26.1

25.5

25.3

27.0

28.4

8222

1146

3756

2509

811

4743

3479

500

3532

573

3158

429

5920

1256

674

372

4261

2651

1310

5696

1039

1487

7801

421

5159

3063

5845

1644

733

4–5

16.4

22.7

17.6

13.9

14.1

18.2

14.5

8.2

20.9

4.9

25.3

15.8

15.0

22.1

23.2

19.1

16.1

15.6

19.5

14.9

19.1

22.7

16.6

13.6

16.8

15.7

15.9

17.2

19.9

1780

118

669

777

216

924

856

342

415

701

213

109

1559

131

950

632

198

1473

156

151

1640

140

1074

706

1382

293

105

Leisure-time physical exercise was recategorized into two categories in order to obtain the proportional hazard assumption.

Body mass index was recategorized into three categories in order to obtain the proportional hazard assumption.

analysis, ie, for 4–5 occupational exposures, the fully

adjusted HR was 3.26 (95% CI 2.79–3.81) compared to

HR 2.87 (95% CI 2.49–3.30) in the main analysis. In the

test including sickness absence prior to and during early

pregnancy (no, before, early, and both before and during

early pregnancy), we saw a similar pattern, except for

the group of women absent from work both before and

during pregnancy, where we found no association.

Discussion

Approximately 25% of the pregnant women in the study

had ≥1 spell of absence from work during the follow-

up until the end of GW 30. We found an increasing risk

of absence with an increasing number of occupational

exposures when analyzed by use of an index variable

including exposures that were earlier shown to be asso-

ciated with the risk of absence (4). The results supported

our hypothesis that more exposures at work led to a

higher risk of absence from work.

Our findings were in line with two previous studies;

a cross-sectional study showed a dose‒response relation-

ship between an cumulated index of occupational expo-

sures and absence from work (6). However, information

about both exposures and absence was collected after

the women gave birth. A previous Danish report (7) also

found that pregnant women exposed to several occupa-

tional exposures had an increased risk of absence from

work. Our study on the other hand is, as far as we know,

the first prospective study to use register information

for the outcome investigating the association between

combinations of occupational exposures.

Each variable included in the index was dichoto-

mized into yes/no and job demands and control was

Scand J Work Environ Health – online first

Multiple occupational exposures and absence in pregnancy

Index variables:

occupational exposures

4–5

Index variables:

occupational exposures

Model 1

4‒5

Model 2

4‒5

Model 2

4‒5

1780

9763

17 410

12 967

8222

Event

212

1493

3595

3687

3218

95% CI

Event/N

(%)

11.9

15.3

20.6

28.4

39.1

1.00

1.34

1.87

2.71

4.00

1.00

1.28

1.70

2.28

3.23

1.00

1.25

1.62

2.08

2.87

1.16‒1.55

1.63‒2.14

2.36‒3.12

3.48‒4.60

1.11‒1.48

1.48‒1.96

1.98‒2.62

2.81‒3.71

1.08‒1.45

1.41‒1.86

1.81‒2.39

2.49‒3.30

Figure 2.

Hazard ratio (HR) and 95% confidence interval (CI) according to

the index variable comprised of five occupational exposures for absence

from work.

Adjusted for previous sickness absence, age at conception, parity, fertility

treatment, smiking, leisure-time exercice, body mass index.

Same as

+ socieconomic status.

included as separate exposures and not as job strain (3).

Albeit the index variable does not distinguish between

the included occupational exposures, the results yield

information on the consequences of concomitant mul-

tiple occupational exposures for absence.

We had decided, a priori, to collapse exposure to

four and five occupational exposures into one category

as we did not think that many would experience all five

at the same time, but subsequently performed the analy-

ses with four and five occupational exposures as sepa-

rate groups. Both the main and the sensitivity analysis

showed a clear dose‒response relationship between the

index variable and absence from work with the highest

risk of absence in the group experiencing five occupa-

tional exposures.

One point for discussion is whether the absence we

investigate is related to work or pregnancy. The employ-

ers were reimbursed for the pregnancy-related absence

from day 1 but first from day 15 for general sickness

absence. The employer would therefore have had an eco-

nomical incentive to report absence as pregnancy-related

which might explain that regular sickness absence con-

stituted only 12.0% of the total number of absences

from work. The lack of information on the reason(s) for

the absence from work in DREAM precluded distinc-

tion between regular and pregnancy-related absence.

Unfortunately, the data did not provide the possibility

to investigate this issue further.

In this study, SES was based on the women’s self-

reported job titles. SES would be expected to be highly

correlated to the investigated occupational exposures;

perhaps mainly the physical exposures as the types of

jobs held by skilled and un-skilled workers would be

depicted by more physically straining work (14, 15).

In the analyses, we adjusted for SES only in the final

statistical models to avoid potential over-adjustment.

Sickness absence generally increases with lower SES,

in pregnant as well as non-pregnant populations (1,

16–18). An explanation of the influence of SEP could be

the presence of differential exposure and vulnerability.

Differential exposure refers to the number of differential

exposures either as type, duration, or amount that var-

ies between the social positions and thereby the health

risks (19). The lower the SES, the higher the risk of

being exposed to risk factors and not only in the profes-

sional life. This might entail that the impact of a single

(occupational) exposure could be stronger in groups of

lower compared to groups of higher SES, ie, differential

vulnerability (19). However, adjustment for SES only

discretely attenuated estimates. Another explanation

could also be different attitudes towards working during

pregnancy and personality, which we could not control

for due to lack of data.

The women from the DNBC were probably healthier

than the general population. Previously, Jacobsen and

Scand J Work Environ Health – online first

Sejbaek et al

colleagues (20) showed that women with low socioeco-

nomic resources were underrepresented in this cohort,

and furthermore, we only included women with ≥30

weekly work hours and excluded women receiving sick-

ness benefit due to special circumstances. Less than 25%

of the pregnant women were absent from work. Other

studies or reports found levels of absence from work in

pregnancy of 43–68%, irrespective of weekly working

hours and time of absence from work in pregnancy (1,

4, 21, 22). We, on the other hand, investigated the risk

of absence from work in a rather healthy cohort and

showed that even here the risk of absence increases with

an increasing number of occupational exposures.

The study was conducted within the DNBC, which

was established between 1996 and 2002, ie, around 20

years ago. The recommendations issued by the Danish

Work Environment Authorities on working conditions

for pregnant women have not changed

much since 2002

(23–25). Only one major change regarding lifting has

been introduced over the years, as the recommendation

has been eased since 2009:

the maximum lifting restric-

tion of 1000 kg per day has been removed

(23–26).

Psychosocial working conditions were first mentioned in

2002, solely to be considered together in combinations

with other factors such as lifting (24).

The findings from the subgroup analyses partly

confirmed our main findings for women with no prior

absence due to sickness. However, for women with pre-

vious sickness absence, the subgroup analyses did not

show the same results as the main findings. This might

be due to the small numbers or perhaps women with

previous sickness absence

go on leave

during pregnancy

earlier than pregnant women without previous sickness

absence, and therefore no association was shown in

these subgroups.

Our study suggests that absence from work among

pregnant women may potentially be reduced by lower-

ing the number of occupational exposures. Studies on

absence from work show that women are most often

absent due to general pregnancy-related discomfort,

which can be exacerbated when

doing

strenuous work.

Hence, job adjustment can help pregnant women to

continue working.

This is indicated by previous studies,

showing that absence can be reduced if job adjustment

is considered relevant and implemented (27, 28). At

Akershus University Hospital in Oslo,

a new approach

was implemented

where all newly pregnant employ-

ees were offered an interview with their leader and a

midwife early in pregnancy

to explore the need for and

implement job adjustment.

The hospital subsequently

experienced a large reduction in absence among their

pregnant employees (29).

A priori, we wished to investigate the combined

effect of two specific occupational exposures ‒ lifting

and job strain ‒ in relation to absence from work. How-

ever, due to power issues when including a 16-category

variable of combined lifting (10) and job strain (3) and

the two main effects (lifting and job strain) in the same

analyses, we did not include these (data not shown).

The major strengths of this study include the large

cohort with prospective data collection combined with

national register data on the outcome. In addition, we

only included women working ≥30 hours/week because

fewer weekly work hours could increase recuperation

from work-related strain and thereby reduce the need

for reduction of work by absence. This is supported by

findings of

reduced

absence from work among pregnant

women working ≤30 hours/week (22).

In contrast,

previous study on absence during pregnancy based on

the DNBC showed that pregnant women working <37

hours/week had an increased risk of absence, while

women working >37 hours/week had a decreased the

risk of absence, both compared to women working 37

hours/week (4).

However,

women working >37 hours/

week might be a selected group and more robust, hence,

their risk of absence during pregnancy is lower.

One limitation relates to the choice of the five occu-

pational exposures included in the index. Other expo-

sures such as social relationships, including quality of

leadership and social support, or workplace violence,

including physical violence and bullying, could have

been included. However, work posture, work shift,

and lifting, were previously investigated in relation to

absence in pregnancy in DNBC (4). Job strain was also

previously studied for this outcome, albeit not with job

demands and job control as separate measures (4). Of

note, we have not taken the potential correlation of the

variables into account. However, the correlations of the

variables were tested after the index variable was cre-

ated. The results showed that only lifting and work pos-

ture were moderately to strongly correlated, while the

other variables were less correlated. The results for each

increment in the index may therefore not be completely

independent of each other, but the normal distribution

of the index variable as a variable ranging from 0 to 5

is reassuring. The questions used to generate the index

were not validated, which could have led to bias. The

most likely scenario would be non-differential misclas-

sification and potential bias toward the null.

Notwithstanding these limitations, a cautious recom-

mendation based on the presented findings would be to

raise awareness of the

number

of occupational exposures

that pregnant women experience. The novelty with the

present study is that the number of exposures could pos-

sibly be a way to assess the risk of absence in pregnancy.

This knowledge may be used to guide the employers

on how to reduce absence from work among pregnant

employees through an exposure reduction when several

concomitant exposures are present at a time. This recom-

mendation aligns well with the guidelines from the Dan-

Scand J Work Environ Health – online first

Multiple occupational exposures and absence in pregnancy

ish Working Environment Authority (23) that the work

conditions of pregnant women ought to be assessed as

a whole in cases with exposure to high physical strain.

Furthermore, initiatives of job adjustment addressing

the straining occupational exposure might be one way

to decrease absence from work in this group of workers.

Concluding remarks

We found the number of occupational exposures includ-

ing job demands, job control, work posture, work shift

and lifting, associated with an increased risk of absence

from work during pregnancy. It may be useful to develop

an index of work exposures with suggested adverse

effects on absence from work during pregnancy. Thereby

it would be possible to identify pregnant women needing

exposure reduction at work or to identify workplaces

with a general need for preventive interventions to

reduce absence among pregnant employees. Future

studies should investigate job adjustment by addressing

the number, type, and quality of occupational exposures

among pregnant women that might reduce absence from

work during pregnancy to reduce discomfort, absence,

and societal and personal costs.

Acknowledgments

The Danish National Research Foundation established

the Danish Epidemiology Science Centre that initi-

ated and created the DNBC. The cohort is furthermore

funded by major grant from this foundation. Additional

support for the DNBC is obtained from the Pharmacy

Foundation, the Egmont Foundation, the March of

Dimes Birth Defects Foundation, the Augustinus Foun-

dation and the Health Foundation. The present study was

supported by grants from the Danish Work Environment

Research Foundation (grant 20150018124/3).

The authors declare no conflicts of interest.

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