In our study, the rate of SL in pregnant workers was very high. After adjustment, the cumulative index of occupational hazards for pregnancy was clearly associated with SL (for “at least one leave”, according to duration and for “early leave”) in a dose–response relationship. We also found deprivation, pregnancy at risk, ART, work-family conflicts, home-work commuting felt as difficult, and young age to be associated with a higher risk of SL. For some factors, the results varied according to the trimesters of pregnancy. Moreover, we observed that there were less SL in small companies or for non-fixed term contract to 2nd or 3rd trimester.

The study has a number of strengths and limitations. Among its strengths, it is noteworthy that exposure data and outcomes were collected independently of each other. The assessment of occupational exposures was carried out by OHPs with good knowledge of the workstations and the workers answered the questionnaire before visiting the OHPs. Also our results were improved by adjustment for socioeconomic deprivation based on the EPICES scale [12, 31]. The other advantages of our study were its large size and the wide range of possible confounders collected, for which we adjusted our data. The large participation of OHPs in two French regions throughout the duration of the study and the high participation rate also improved the generalisability of our work. However, several potential limitations exist. High absence rates among pregnant workers may be caused by other characteristics not captured by the variables chosen in our study (e.g. job strain, other psychosocial factors) [19]. Information on outcomes was based on retrospectively collected self-reported information which may lead to errors with respect to both time of occurrence and duration. However, according to some studies, the duration from self-reported data tend to be shorter than those based on recorded data and agreement between self-reported and recorded days of absence decreased as the total number of days increased [32, 33]. Consequently, our results tend to rather underestimate reality. Also we did not have access to medical records relating to maternity and information on “pregnancy at risk” was based on self-reporting by workers. There was no consensual definition and literature data on this variable are scarce [34, 35]. In a report from the French National Authority for Health, the rate of “pregnancy at risk” was 20% versus 24.8% for our study [34]. Our rate was probably overestimated since there was no medical control of the declarations from the workers.

The high rate of “at least one SL” (74.9%) in our study is similar to that of a Norwegian study (75.3%, similar definition) [20] but higher than other studies from Norway (51%) [24] and from Denmark (31%) [7]. Our rate of “early leave” (14.4% before 15 WG) was consistent with the results from other studies: 27.5% before 24 WG [15]; 43% before 28 WG [36]. With respect to the average number of days’ absence without inclusion of the 15 days accepted for pathological leave, one study in French hospitals from 2005 to 2008 using data obtained from employers’ records reported 33.6 days on average versus 31.9 to 53.8 days for our study (see Table 3) [9]. But it is difficult to compare the different studies globally because the populations studied and the definitions chosen are not similar [4, 19].

SL is expected when a pregnant woman is sick or medically at risk as this was confirmed by our results with the variables “pregnancy at risk” and ART, and reported by other studies [12, 15, 20]. However, our results adjusted for “pregnancy at risk” and ART argue strongly for the independent implication of occupational factors in the decision to take SL. Several studies have also reported that some working conditions were statistically related to SL: heavy lifting [7, 19, 37]; work with a lot of walking or standing [7]; uncomfortable working positions [7, 19]; night or shift work [7, 19, 24]; long working days [7]. Several studies have reported an association between the combination of occupational hazards and SL [9, 18, 37]. A French study in 1985 on hospital workers reported a longer duration of SL (including the supplementary week for pathological leave) was associated with the accumulation of occupational factors: 37 days on average for 0 to 1 risk; 50 days on average for 2 or 3 risks [18]. In another French study on hospital workers in 2008, the average number of days’ absence after exclusion of women having had a pregnancy-related illness, increased with the physical load of the workstations [9].

Like other authors, we reported an association between early SL and socioeconomic deprivation in pregnant workers [12, 20]. From literature data, early SL was more frequent among pregnant workers with unstable jobs and with less-qualified occupational categories [12]. Deprived pregnant workers were exposed to more occupational hazards for pregnancy and higher risk of pregnancy-related illnesses [12, 31]. In France, pregnant workers can adapt their jobs using occupational health services, but not all women seem to benefit from those adjustments. Consequently, some deprived pregnant workers could leave early the workplace for those different reasons. In France in 2014 before legal or pathological leaves, except for some great companies, ordinary sick leaves were paid to 50% of the salary. From our study, pregnant workers with social vulnerabilities may decide to leave their job earlier than they legally can, even if they lose part of their income [12]. But this could have financial and social important consequences (isolation, less medical care). It is important to note that, in contrast with our result about early SL, sick leaves paid to 50% of the salary could also affect the use of sick leave among the poorest workers frequently exposed to occupational hazards during pregnancy (particularly of a physical nature) and could have some consequences on adverse perinatal outcomes [31]. One French study has reported that deprived pregnant workers exposed to three or more occupational hazards were significantly associated with pre-term birth [31].

We observed an association between “at least one SL” and “number of home-work conflicts” or “home-work commuting felt as difficult”. Fatigue, pain or discomfort during pregnancy are expected to be more frequent in the last trimesters than in the 1st trimester and could explain these specific associations. However, some women also still have the double burden of combining their household and child-rearing responsibilities with their jobs [11]. Pregnant workers may need to leave their job when this double burden can no longer be ensured [11]. Furthermore, we found an association between “at least one SL” and younger women (<25 years), as in certain other studies [8, 11, 16], but not others with different cut-offs [7, 19]. First pregnancy and inexperience related to age or specific representation such as “absence from work is considered beneficial for the child” may explain this result [11]. In our study, the relationship between occupational classes and SL after adjustment is not clear. This may be explained by a lower SL rate in the reference group rather than higher rates in other groups; underreporting of SL cannot be ruled out, because in general managers/supervisors are averse to declaring SL. In contrast, the observations of less SL in small companies or for non-fixed term contract are expected results because the risk losing his job (during or after pregnancy) is more important in these situations.

Our study has some practical perspectives. French labor law provides for a visit with an OHP after delivery but not before [3]. Consequently, few pregnant workers see an OHP during pregnancy. However, the situation for an OHP who receives pregnant workers may be difficult if they cannot propose job adjustments or other preventive measures in the workplace. Indeed, sometimes job adjustment is not possible because some employers may prefer pregnant workers to take sick leave so they can employ a healthy person to replace them during their absence [37]. Moreover, social conditions and, specific attitudes (for example, related to health beliefs) among pregnant workers may explain some SLs [16]. Also, some prenatal caregivers who care for pregnant workers without real knowledge of the workstation and without contact with OHPs may opt to prescribe SL to prevent disorders associated with pregnancy [21, 22]. At present, the management of employment during pregnancy results from complex interplay between the worker, employer, prenatal caregiver and, other influences [21, 22]. In addition, some pregnant workers are likely excluded from work without having had an assessment of possible preventive measures in the workplace [2, 31]. When occupational hazards for pregnancy exist, our results argue for a risk assessment in the workplace during early pregnancy, preferably with an OHP [3]. The aim would be to avoid reproductive risks by removing hazards or adjusting work [2, 3, 23].