Occupational physical activities, working hours and outcome of pregnancy: findings from the Southampton Women's Survey

Impact of maternal posture on fetal physiology in human pregnancy: a narrative review

In numerous medical conditions, including pregnancy, gravity and posture interact to impact physiology and pathophysiology. Recent investigations, for example, pertaining to maternal sleeping posture during the third trimester and possible impact on fetal growth and stillbirth risk highlight the importance and potential clinical implications of the subject. In this review, we provide an extensive discussion of the impact of maternal posture on fetal physiology from conception to the postpartum period in human pregnancy. We conducted a systematic literature search of the MEDLINE database and identified 242 studies from 1991 through 2021, inclusive, that met our inclusion criteria. Herein, we provide a synthesis of the resulting literature. In the first section of the review, we group the results by the impact of maternal posture at rest on the cervix, uterus, placenta, umbilical cord, amniotic fluid, and fetus. In the second section of the review, we address the impact on fetal-related outcomes of maternal posture during various maternal activities (e.g., sleep, work, exercise), medical procedures (e.g., fertility, imaging, surgery), and labor and birth. We present the published literature, highlight gaps and discrepancies, and suggest future research opportunities and clinical practice changes. In sum, we anticipate that this review will shed light on the impact of maternal posture on fetal physiology in a manner that lends utility to researchers and clinicians who are working to improve maternal, fetal, and child health.

Night work during pregnancy and small for gestational age: a Danish nationwide register-based cohort study

OBJECTIVE

The aim was to investigate the association between night work during pregnancy and risk of having a small for gestational age (SGA) child.

METHODS

This cohort study had payroll data with detailed information on working hours for employees in all Danish administrative regions (primarily hospital employees) between 2007 and 2015, retrieved from the Danish Working Hour Database. Pregnancies, covariates and outcome were identified from the national birth registry. We used logistic regression to investigate the association between intensity and duration of night work during the first 32 pregnancy weeks and SGA. The adjusted model included age, body mass index, socioeconomic status and smoking. Using quantitative bias analysis and G-estimation, we explored potential healthy worker survivor bias (HWSB).

RESULTS

The final cohort comprised 24 548 singleton pregnancies in 19 107 women, primarily nurses and medical doctors. None of the dimensions of night work were associated with an increased risk of SGA. We found a tendency towards higher risk of SGA in pregnancies where the women stopped having night shifts during pregnancy. Using G-estimation we found an OR<1 for the association between night work and SGA if all workers continued having night work during pregnancy compared with daywork only.

CONCLUSION

We found no increased risk of SGA in association with night work during pregnancy among healthcare workers. G-estimation was not precise enough to estimate the observed indication of HWSB. We need better data on pregnancy discomforts and complications to be able to safely rule out HWSB.

Maternal Occupational Risk Factors and Preterm Birth: A Systematic Review and Meta-Analysis

Objective: This systematic review and meta-analysis aimed to summarize the evidence on the relationship between physical occupational risks (high physical workload, long working hours, shift work, whole-body vibrations, prolonged standing, and heavy lifting) and preterm birth. Methods: A systematic review and meta-analysis was conducted across six databases to investigate the relationship between physical occupational risks and preterm birth. Result: A comprehensive analysis of 37 studies with varying sample sizes found moderate evidence of positive associations between high physical workload, long working hours, shift work, whole-body vibration, and preterm birth. Meta-analysis showed a 44% higher risk (OR 1.44, 95% CI 1.25-1.66) for preterm birth with long working hours and a 63% higher risk (OR 1.63, 95% CI 1.03-2.58) with shift work. Conclusion: Pregnant women in physically demanding jobs, those working long hours or on shifts, and those exposed to whole-body vibration have an increased risk of preterm birth. Employers should establish supportive workplaces, policymakers implement protective measures, healthcare providers conduct screenings, and pregnant women must stay informed and mitigate these job-related risks. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/], Identifier [CRD42022357045].

Understanding safe water-carrying practices during pregnancy and postpartum: A mixed-methods study in Nepal

Daily carrying of heavy loads of domestic water, especially during pregnancy and postpartum, bears a threat to maternal health in low‐income countries. Using an extended health action process approach (HAPA), we examined women's reasons for and psychosocial determinants of safe water‐carrying during pregnancy and postpartum. In a mixed‐methods study, trained local interviewers conducted 1001 quantitative interviews with women of reproductive age (n = 921 analyzed) and 21 qualitative interviews with women of reproductive age, in‐laws, and spouses in rural Nepal. We analyzed the quantitative data with generalized estimating equations to model the HAPA‐based psychosocial determinants of avoiding water‐carrying during pregnancy and postpartum. Subjective perspectives were investigated with thematic analysis. Outcome expectancies (B = 0.24), self‐efficacy (B = 0.20), and injunctive norms (B = 0.23) were significantly associated with the intention to avoid water‐carrying. Self‐efficacy (B = 0.36) and instrumental support (B = 0.05) are related to behavior (all p < 0.05). Women explained water‐carrying during pregnancy by a lack of family support, a shift of health decision‐making power to in‐laws, and low behavioral control. Overall, the necessity of water, family decision‐making structures, and low support make it difficult for women to discontinue water‐carrying. Additionally to infrastructural improvements, behavioral interventions may increase women's self‐efficacy for safe water‐carrying (e.g. reducing weight) and social support.

Are leisure-time and work-related activities associated with low back pain during pregnancy?

BACKGROUND

Although working activities are associated with several pregnancy outcomes, there is scarce information regarding the association between working activities and low back pain (LBP) during pregnancy. This study aimed to investigate whether leisure-time and work-related physical activities during pregnancy are associated with LBP.

METHODS

Data from the 2015 Pelotas Birth Cohort study were used. Demographic, socioeconomic, gestational, leisure-time (prior to and during pregnancy) and work-related (days of work, hours of work, standing and heavy lifting) physical activity data were collected at birth. LPB was assessed in the 12-month follow-up period.

RESULTS

Leisure-time physical activity either prior to and during pregnancy was not associated with LBP. Working during pregnancy, days of work and standing position at work were not associated with self-reported LBP during pregnancy. However, working more than 8 h per day and always lifting heavy objects at work increased the odds ratio for LBP (OR 1.30 95%CI: 1.04; 1.63; and OR: 1.39 95%CI 1.08; 1.81, respectively). In addition, women who had lifted heavy objects often/always, reported an increase in pain intensity.

CONCLUSION

Working during pregnancy and days worked per week were not related to experiencing LBP. However, women who worked more than 8 h per day, as well as women who lifted heavy objects at work on a regular basis, were more likely to experience pregnancy-related LBP.

Self-selection of gestational lumbopelvic posture and bipedal evolution

BACKGROUND

Not all pregnant women seem to select the more curved lumbopelvic posture that their sexual dimorphic anatomy allows even though many previous researchers have assumed lumbopelvic curvature to be standard during pregnancy. This study is vital to understanding coevolution of lumbopelvic sexual dimorphism and bipedalism, and understanding some clinical implications of intervening in gestational posture changes.

RESEARCH QUESTIONS

Are there anthropometric changes that correspond with selection of lumbopelvic curvature change during pregnancy? What are the biomechanical costs and benefits of gestational lumbopelvic curvature change?

METHODS

Twenty pregnant women were tested at five different times in the 2nd and 3rd trimesters of pregnancy. Lumbopelvic posture, standing kinetics and gait kinetics were measured longitudinally. Additionally, we modeled the effects on standing and gait without lumbopelvic postural changes, but with anthropometric changes, for each individual.

RESULTS

We found greater lumbopelvic angulation to correspond with a shorter body height (6 cm difference between groups, p = 0.048) and deeper 2nd trimester abdomen (2 cm difference between groups, p = 0.013). Lumbopelvic angulation lowers support requirements (in standing and walking (6% lower support impulse, p = 0.056), but at the cost of shifting the propulsive actions to a less efficient pulling action rather than pushoff (13 % reduction in pushoff time, p = 0.001). We observed minimal effects on walking kinematics and balance control.

SIGNIFICANCE

Our findings suggest the evolutionary advantage of the female lumbopelvic unit is the adaptability it provides to adjust for the individual needs of the pregnant woman. We discuss multiple potential contributing factors that may have shaped hominin female lumbopelvic evolution and are involved in self-selecting lumbopelvic posture.

First trimester employment, working conditions and preterm birth: a prospective population-based cohort study

Objectives

To explore the association between working conditions during first trimester and total preterm birth (PTB), and subtypes: spontaneous PTB and iatrogenic PTB, additionally to explore the role of hypertension.

Methods

Pregnant women from the Amsterdam Born Children and their Development study, filled out a questionnaire between January 2003 and March 2004, two weeks after first prenatal screening (singleton liveborn, n=7561). Working conditions were working hours/week, standing/walking hours/week, physical work load and job strain.

Results

Prolonged standing/walking during first trimester was associated with an increased risk for total PTB (OR=1.5; 95% CI 1.0–2.3, after adjustments). Other working conditions were not related to total PTB. The separation into spontaneous and iatrogenic PTB revealed that standing/walking was associated with iatrogenic PTB only (OR=2.09; 95% CI 1.00–4.97). The highest risk was found for the combination of a long workweek with high physical work load (OR=3.42; 95% CI 1.04–8.21). Hypertension did not mediate these associations; however, stratified analysis revealed that high physical work load was only related to iatrogenic PTB when pregnancy-induced hypertension was present (OR=6.44; 95% CI 1.21–29.76).

Conclusion

This study provides evidence that high physically demanding work is associated with an increased risk for iatrogenic PTB and not with spontaneous PTB. Pregnancy-induced hypertension may play a role: when present, high physical work load leads to a more severe outcome.

Neonatal near misses and associated factors among mother's who give a live neonate at Hawassa City governmental hospitals, 2019: a facility based cross-sectional study design

BACKGROUND

Neonatal near miss is a neonate who nearly died but survived from a severe complication occurred during pregnancy, birth or within 0-28 days of extra-uterine life. However, there is no available data that quantifies the magnitude of neonatal near miss (NNM) in Ethiopia where there is high prevalence of neonatal mortality. Therefore, this study is designed to provide information about the magnitude and associated factors of neonatal near miss among women who give a live birth at Hawassa City Governmental hospitals, 2019.

METHODS

A facility based cross-sectional study design was conducted on 604 mothers who gave live neonates at Adare General Hospital and Hawassa University Comprehensive and Specialized Hospital from May 9, 2019 to June 7, 2019. Face to face interviewer administered structured questionnaire with a supplementation of maternal and neonatal medical records with checklists were used to collect the data. Data were coded and entered in to Epi data version 3.1 and then exported to the Statistical Package for Social Science IBM version 25 for analysis. Descriptive statistics was run and the data were presented using frequency tables and figure. The bi-variable and multivariable logistic regression was used to identify the possible factors of neonatal near miss. Finally, Adjusted Odds Ratio and 95% Confidence Intervals were used to declare statsticall significance.

RESULT

Among all 604 selected live births an overall proportion of NNM cases, 202 (33.4%) (95% CI: 29.7-37.1%) was obtained at Hawassa City Government Hospitals. Respiratory distress 158 (94%) and infection or sepsis 138 (84%) were found to be the leading causes of NNM cases in our study. Governmental and non-governmental employed mother (AOR = 3.05, 95% CI: 1.46-6.44) and Cesarean Section delivery (AOR = 1.89, (95% CI: 1.25-2.83)) were positively significantly associated with neonatal near miss. Whereas, pregnancy induced Hypertension (AOR = 0.43, 95%CI: 0.27-0.69) was negatively associated with neonatal near miss.

CONCLUSION

This study revealed relatively high prevalence of NNM in the study areas. Employed women, pregnancy induced hypertension and cesarean section mode of delivery were found to be independent factors affecting the prevalence of NNM cases. Therefore, HUCSH and Adare general Hospitals should focus on proving quality antenatal care and prevention of occupational related problems among pregnant women.

Shiftwork and Light at Night Negatively Impact Molecular and Endocrine Timekeeping in the Female Reproductive Axis in Humans and Rodents

Shiftwork, including work that takes place at night (nightshift) and/or rotates between day and nightshifts, plays an important role in our society, but is associated with decreased health, including reproductive dysfunction. One key factor in shiftwork, exposure to light at night, has been identified as a likely contributor to the underlying health risks associated with shiftwork. Light at night disrupts the behavioral and molecular circadian timekeeping system, which is important for coordinated timing of physiological processes, causing mistimed hormone release and impaired physiological functions. This review focuses on the impact of shiftwork on reproductive function and pregnancy in women and laboratory rodents and potential underlying molecular mechanisms. We summarize the negative impact of shiftwork on female fertility and compare these findings to studies in rodent models of light shifts. Light-shift rodent models recapitulate several aspects of reproductive dysfunction found in shift workers, and their comparison with human studies can enable a deeper understanding of physiological and hormonal responses to light shifts and the underlying molecular mechanisms that may lead to reproductive disruption in human shift workers. The contributions of human and rodent studies are essential to identify the origins of impaired fertility in women employed in shiftwork.

Pregnancy disorders in female workers at the industrial area of Sidoarjo, Indonesia

Background: The number of female workers in Indonesia has increased and female workers have been discovered to be very vulnerable to several hazards and health problems in the workplace environment linked to their menstrual cycle and pregnancy. Therefore, this study was conducted to analyze risk factors associated with pregnancy disorders in female workers. Design and Methods: The research was conducted through the use of a cross-sectional design with 307 female workers using simple random sampling. Furthermore, a descriptive analysis was conducted to describe the conditions of the respondents during pregnancy to childbirth process. Results: The results showed 45% of respondents had pregnancy disorders, 16% had miscarriages, and despite the fact most of the prenatal care processes was assisted by doctors or midwives, 2.6% of the respondents consulted Traditional Birth Attendants, who were also recorded and was found to account for 2.9% of the deliveries. Moreover, the risk factors associated with pregnancy disorders include vibrations (P=0.004), irritants (P=0.002) and repetitive works (P=0.009). Conclusions: It is recommended that companies should provide maternal and child health protection and control for any risk associated with female workers.

Maternal Work and Spontaneous Preterm Birth: A Multicenter Observational Study in Brazil

Spontaneous preterm birth (sPTB) is a major pregnancy complication involving biological, social, behavioural and environmental mechanisms. Workload, shift and intensity may play a role in the occurrence of sPTB. This analysis is aimed addressing the effect of occupational activities on the risk for sPTB and the related outcomes. We conducted a secondary analysis of the EMIP study, a Brazilian multicentre cross-sectional study. For this analysis, we included 1,280 singleton sPTB and 1,136 singleton term birth cases. Independent variables included sociodemographic characteristics, clinical complications, work characteristics, and physical effort devoted to household chores. A backward multiple logistic regression analysis was applied for a model using work characteristics, controlled by cluster sampling design. On bivariate analysis, discontinuing work during pregnancy and working until the 7^th month of pregnancy were risks for premature birth while working during the 8^th - 9^th month of pregnancy, prolonged standing during work and doing household chores appeared to be protective against sPTB during pregnancy. Previous preterm birth, polyhydramnios, vaginal bleeding, stopping work during pregnancy, or working until the 7^th month of pregnancy were risk factors in the multivariate analysis. The protective effect of variables compatible with exertion during paid work may represent a reverse causality. Nevertheless, a reduced risk associated with household duties, and working until the 8^th-9^th month of pregnancy support the hypothesis that some sort of physical exertion may provide actual protection against sPTB.

Occupational lifting and adverse pregnancy outcome: a systematic review and meta-analysis

This systematic review was conducted to help clarify the effect of lifting at work on pregnancy outcome, by focusing on specific exposure categories. A search in Medline and Embase identified 51 articles reporting association of spontaneous abortion (SA), preterm delivery (PTD) or small-for-gestational-age (SGA) infant with exposure to occupational lifting. A global validity score was assigned to each study and six potential sources of bias were considered in sensitivity analyses. For each exposure–outcome combination, a summary risk estimate (RE) was obtained from all studies and from a subset of studies with high validity score, this latter summary RE was selected as a final result. Statistical heterogeneity was measured with I2 and Q tests and the possibility of a publication bias was also assessed. For each meta-analysis, the strength of evidence was established from explicit criteria. Heavy (or ≥10 kg) loads often (or ≥10x/day) lifted were associated with increased risks of SA (summary RE=1.31, 95% CI 1.17 to 1.47) and PTD (summary RE=1.24, 95% CI 1.07 to 1.43), with good strength of evidence. No association was identified with SGA, nor with lower exposure levels and SA or PTD. These results are reassuring for lower levels of exposure; however, observed associations can guide health professionals’ recommendations aimed at the prevention of SA and PTD for pregnant women who frequently lift (or ≥10x/day) heavy (or ≥10 kg) loads at work.

Résumé

The impact of occupational activities during pregnancy on pregnancy outcomes: a systematic review and metaanalysis

OBJECTIVE

Data: An increasing number of studies suggest that exposure to physically demanding work during pregnancy could be associated with increased risks of adverse pregnancy outcomes, but the results remain conflicted and inconclusive. The purpose of this study was to examine the influence of occupational activities during pregnancy on maternal and fetal health outcomes.

STUDY

Studies of all designs (except case studies and reviews) that contained information on the relevant population (women who engaged in paid work during pregnancy), occupational exposures (heavy lifting, prolonged standing, prolonged walking, prolonged bending, and heavy physical workload), comparator (no exposure to the listed physical work demands), and outcomes (preterm birth, low birthweight, small for gestational age, miscarriage, gestational hypertension, preeclampsia, gestational diabetes mellitus, stillbirth, and intrauterine growth restriction) were included.

STUDY APPRAISAL AND SYNTHESIS METHODS

Five electronic databases and 3 gray literature sources were searched up to March 15, 2019.

RESULTS

Eighty observational studies (N=853,149) were included. Low-to-very low certainty evidence revealed that lifting objects ≥11 kg was associated with an increased odds ratio of miscarriage (odds ratio, 1.31; 95% confidence interval, 1.08-1.58; I²=79%), and preeclampsia (odds ratio, 1.35; 95% confidence interval, 1.07-1.71; I²=0%). Lifting objects for a combined weight of ≥100 kg per day was associated with an increased odds of preterm delivery (odds ratio, 1.31; 95% confidence interval, 1.11-1.56; I²=0%) and having a low birthweight neonate (odds ratio, 2.08; 95% confidence interval, 1.06-4.11; I²=73%). Prolonged standing was associated with increased odds of preterm delivery (odds ratio, 1.11; 95% confidence interval, 1.02-1.22; I²=30%) and having a small-for-gestational-age neonate (odds ratio, 1.17; 95% confidence interval, 1.01-1.35; I²=41%). A heavy physical workload was associated with increased odds of preterm delivery (odds ratio, 1.23; 95% confidence interval, 1.07-1.41; I²=32%) and having a low birthweight neonate (odds ratio, 1.79; 95% confidence interval, 1.11-2.87; I²=87%). All other associations were not statistically significant. Dose-response analysis showed women stand for >2.5 hours per day (vs no standing) had a 10% increase in the odds of having a preterm delivery.

CONCLUSION

Physically demanding work during pregnancy is associated with an increased risk of adverse pregnancy outcomes.

The impact of occupational shift work and working hours during pregnancy on health outcomes: a systematic review and meta-analysis

BACKGROUD

An increasing number of original studies suggest that exposure to shift work and long working hours during pregnancy could be associated with the risk of adverse pregnancy outcomes, but the results remain conflicting and inconclusive.

OBJECTIVE

To examine the influences of shift work and longer working hours during pregnancy on maternal and fetal health outcomes.

DATA SOURCES

Five electronic databases and 3 gray literature sources were searched up to March 15, 2019.

METHODS OF STUDY SELECTION

Studies of all designs (except case studies and reviews) were included, which contained information on the relevant population (women who engaged in paid work during pregnancy); exposure (rotating shift work [shifts change according to a set schedule], fixed night shift [typical working period is between 11:00 pm and 11:00 am] or longer working hours [>40 hours per week]);comparator (fixed day shift [typical working period is between 8:00 am and 6:00 pm] or standard working hours [≤40 hours per week]); and outcomes (preterm delivery, low birthweight [birthweight <2500 g], small for gestational age, miscarriage, gestational hypertension, preeclampsia, intrauterine growth restriction, stillbirth, and gestational diabetes mellitus).

TABULATION, INTEGRATION, AND RESULTS

From 3305 unique citations, 62 observational studies (196,989 women) were included. "Low" to "very low" certainty evidence from these studies revealed that working rotating shifts was associated with an increased odds of preterm delivery (odds ratio, 1.13; 95% confidence interval, 1.00-1.28, I² = 31%), an infant small for gestational age (odds ratio, 1.18, 95% confidence interval, 1.01-1.38, I² = 0%), preeclampsia (odds ratio, 1.75, 95% confidence interval, 1.01-3.01, I² = 75%), and gestational hypertension (odds ratio, 1.19, 95% confidence interval, 1.10-1.29, I² = 0%), compared to those who worked a fixed day shift. Working fixed night shifts was associated with an increased odds of preterm delivery (odds ratio, 1.21; 95% confidence interval, 1.03-1.42; I² = 36%) and miscarriage (odds ratio, 1.23; 95% confidence interval, 1.03-1.47; I² = 37%). Compared with standard hours, working longer hours was associated with an increased odds of miscarriage (odds ratio, 1.38; 95% confidence interval, 1.08-1.77; I² = 73%), preterm delivery (odds ratio, 1.21; 95% confidence interval, 1.11-1.33; I² = 30%), an infant of low birthweight (odds ratio, 1.43; 95% confidence interval, 1.11-1.84; I² = 0%), or an infant small for gestational age (odds ratio, 1.16, 95% confidence interval, 1.00-1.36, I² = 57%). Dose-response analysis showed that women working more than 55.5 hours (vs 40 hours) per week had a 10% increase in the odds of having a preterm delivery.

CONCLUSION

Pregnant women who work rotating shifts, fixed night shifts, or longer hours have an increased risk of adverse pregnancy outcomes.

Reproductive health problems among female shift workers: A qualitative study in Iran

BACKGROUND

Shift work (i.e. working between 18:00 and 07:00) is associated with sleeplessness and fatigue and hence, can cause female shift workers different health problems. This study aimed to explore reproductive health problems among female shift workers.

MATERIALS AND METHODS

This qualitative study was conducted in Amol and Babol cities, Iran, on 19 female shift workers with previous history of pregnancy and breastfeeding. Participants were selected purposively and with maximum variation respecting their age, work experience, educational level, and financial and employment status. Face-to-face semi-structured interviews were held for data collection and conventional qualitative content analysis was employed for data analysis.

RESULTS

Female shift workers' reproductive health problems were categorized into fourteen subcategories and the five main categories of conflict between pregnancy and shift work, breastfeeding-related challenges, impaired sexual relationships, childbearing limitations, and gynecological problems.

CONCLUSION

Impaired sexual problems are the most significant reproductive health problem among female shift workers. Their reproductive health can be promoted through periodical reproductive health assessments by midwives, reproductive health specialists, psychologists, and gynecologists.

Spontaneous and repeat spontaneous abortion risk in relation to occupational characteristics among working Korean women: a cross-sectional analysis of nationally representative data from Korea

Background

The association between spontaneous abortion (SA) and occupational characteristics among working women is not well-studied. This study aimed to assess the risk of SA and occupational factors such as occupational classification, working hours, and work schedules among working Korean women aged > 19 years.

Methods

In this cross-sectional study, 4078 working women were identified from among 25,534 workers in the Korea National Health and Nutrition Examination Surveys V (2010–2012) database, to obtain data on SA history and the number of SAs. Odds ratios (ORs) and 95% confidence intervals (CIs) for SA were calculated using multiple logistic regression models after adjusting for age, education, household income, cigarette smoking, alcohol consumption, and obesity status. The weighted prevalence for the number of SAs was calculated according to occupational characteristics to demonstrate the SA status among working Korean women.

Results

SA occurrence was reported in 5.7% of the study participants. The ORs (95% CIs) for SA were significantly higher in pink-, green-, and blue-collared workers than in white-collared workers. Regarding weekly working hours, compared with ≤50 h spent working, the ORs (95% CIs) for 51–60, 61–70, and > 70 h per week were 1.26 (0.87–1.84), 1.63 (1.04–2.56), and 1.73 (1.10–2.70), respectively. A significantly higher weighted prevalence of repeat SAs was observed in pink- and green-collared workers and in those who worked long hours.

Conclusion

We found a significant association between SA, repeat SA, and occupational characteristics among working Korean women.

Occupational Hazard Exposures and Depressive Symptoms of Pregnant Workers

OBJECTIVES

The aim of this study was to explore the prevalence of exposure to occupational hazards and depressive mood with associated underlying risk factors among pregnant workers.

METHODS

Women at 12 weeks of gestation (n = 172) were recruited during regular prenatal screening. Data were obtained via questionnaires that explored job details and Edinburgh Postnatal Depression Scale.

RESULTS

The most commonly encountered hazard was prolonged standing. The majority of women reported that the workplace provided no information on the safety or rights of pregnant women, but those exposed to at least four hazards had more access to such services (P < 0.05). Thirteen percent may have suffered from depressive symptomatology. Higher-level work-related burnout, lower job control, and reduced workplace support were significantly associated with possible antenatal depressive symptoms.

CONCLUSION

Pregnant workers are exposed to substantial levels of occupational hazards and may experience depressive symptoms; thus, their work conditions require monitoring and improvement.

Maternal Night-Fasting Interval during Pregnancy Is Directly Associated with Neonatal Head Circumference and Adiposity in Girls but Not Boys

Background: Synchrony between daily feeding-fasting signals and circadian rhythms has been shown to improve metabolic health in animals and adult humans, but the potential programming effect on fetal growth is unknown.Objective: We examined the associations of the maternal night-fasting interval during pregnancy with offspring birth size and adiposity.Methods: This was a cross-sectional study of mother-offspring dyads within the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort. For 384 mothers aged 30.8 ± 4.8 y (mean ± SD), the night-fasting interval at 26-28 wk of gestation was determined from a 3-d food diary based on the average of the fasting duration at night (1900-0659). Offspring birth weight, length, and head circumference were measured and converted to weight-for-gestational age (GA), length-for-GA, and head circumference-for-GA z scores, respectively, by using local customized percentile charts. The percentage of neonatal total body fat (TBF) was derived by using a validated prediction equation. Multivariable general linear models, stratified by child sex, were performed.Results: The mean ± SD maternal night-fasting interval was 9.9 ± 1.3 h. In infant girls, each 1-h increase in the maternal night-fasting interval was associated with a 0.22-SD (95% CI: 0.05-, 0.40-SD; P = 0.013) increase in birth head circumference-for-GA and a 0.84% (95% CI: 0.19%, 1.49%; P = 0.012) increase in TBF at birth, after adjustment for confounders. In infant boys, no associations were observed between the maternal night-fasting interval and birth size or TBF.Conclusions: An increased maternal night-fasting interval in the late second trimester of pregnancy is associated with increased birth head circumference and TBF in girls but not boys. Our findings are in accordance with previous observations that suggest that there are sex-specific responses in fetal brain growth and adiposity, and raise the possibility of the maternal night-fasting interval as an underlying influence. This trial was registered at clinicaltrials.gov as NCT01174875.

Non-occupational physical activity during pregnancy and the risk of preterm birth: a meta-analysis of observational and interventional studies

A meta-analysis was conducted to evaluate the association between non-occupational physical activity (PA) during pregnancy and the risk of preterm birth (PTB). By searching PubMed and EMBASE from inception to August 20, 2016, 25 observational studies (18 cohorts and 7 case-controls) and 12 interventional studies were identified. Comparing the highest to the lowest category of leisure-time PA during pregnancy, the pooled relative risk (RR) of PTB was 0.83 [95% confidence interval (CI) = 0.74-0.93] for cohort studies and 0.60 (95% CI = 0.43-0.84) for case-control studies. No overall significant association was found between domestic or commuting PA and the risk of PTB. In addition, PA intervention did not indicate significant beneficial effect on the risk of PTB. Evidence from the observational studies suggested that leisure-time, but not domestic or commuting, PA during pregnancy was inversely associated with the risk of PTB. The findings were not supported by small-scale and short-term interventional studies. Further research with objective measurement on leisure-time PA is warranted.

Biomechanical and organisational stressors and associations with employment withdrawal among pregnant workers: evidence and implications

The distribution of exposure to biomechanical and organisational job stressors (BOJS) and associations with employment withdrawal (antenatal leave, unemployment) was examined in a case-control study of 1114 pregnant workers in California. We performed descriptive and multivariate logistic and multinomial regression analyses. At pregnancy onset, 57% were exposed to one or more biomechanical stressors, including frequent bending, heavy lifting and prolonged standing. One-third were simultaneously exposed to BOJS. Exposure to biomechanical stressors declined as pregnancy progressed and cessation often (41%) coincided with employment withdrawal (antenatal leave and unemployment). In multivariate modelling, whether we adjusted for or considered organisational stressors as coincident exposures, results showed that pregnant workers exposed to biomechanical stressors had increased employment withdrawal compared to the unexposed. Work schedule accommodations moderate this association. Paid antenatal leave, available to few US women, was an important strategy for mitigating exposure to BOJS. Implications for science and policy are discussed. Practitioner Summary: This case-control study showed that exposure to biomechanical stressors decline throughout pregnancy. Antenatal leave was an important strategy used for mitigating exposure among sampled California women with access to paid benefits. Employment withdrawal among workers exposed to BJOS may be reduced by proactive administrative and engineering efforts applied early in pregnancy.

Survey of occupational hazards in Minnesota veterinary practices in 2012

OBJECTIVE

To identify the scope of occupational hazards encountered by veterinary personnel and compare hazard exposures between veterinarians and technicians working in small and large animal practices.

DESIGN

Cross-sectional survey.

POPULATION

Licensed veterinarians and veterinary staff in Minnesota.

PROCEDURES

A survey of Minnesota veterinary personnel was conducted between February 1 and December 1, 2012. Adult veterinary personnel working in clinical practice for > 12 months were eligible to participate. Information was collected on various workplace hazards as well as on workplace safety culture.

RESULTS

831 eligible people responded, representing approximately 10% of Minnesota veterinary personnel. A greater proportion of veterinarians (93%; 368/394) reported having received preexposure rabies vaccinations than did veterinary technicians (54%; 198/365). During their career, 226 (27%) respondents had acquired at least 1 zoonotic infection and 636 (77%) had been injured by a needle or other sharps. Recapping of needles was reported by 87% of respondents; the most common reason reported by veterinarians (41%; 142/345) and veterinary technicians (71%; 238/333) was being trained to do so at school or work. Recent feelings of depression were reported by 204 (25%) respondents. A greater proportion of technicians (42%; 155/365) than veterinarians (21%; 81/394) indicated working in an environment in which employees experienced some form of workplace abuse.

CONCLUSIONS AND CLINICAL RELEVANCE

Veterinary personnel in Minnesota were exposed to several work-related hazards. Practice staff should assess workplace hazards, implement controls, and incorporate instruction on occupational health into employee training.

The Relationship between Maternal Employment Status and Pregnancy Outcomes

Background and Objectives:

Women comprise a large percentage of the workforce in industrial countries. In Europe and many other places in the world, women of reproductive age comprise a significant proportion of the workforce at the workplaces, and the rules and regulations require employers to evaluate and minimize health risks to pregnant women. In U.K, 70%, and in the United States 59% of women are employed. In Iran, 13% of women are employed, which comes down to less than 5% at Sistan& Baluchestan Province. Various studies have reported contradictory results about the effects of maternal employment tasks such as standing, repetitive bending, climbing stairs, and lifting heavy objects during pregnancy on fetal growth, preterm birth and other obstetric complications. Given the growing number of working women, and potential complications for mothers, the present study has conducted to investigate the relationship between maternal employment status and pregnancy outcomes in Zahedan city, Iran.

Materials and Methods:

This cross-sectional study was based on survey conducted on 227 women (121 housewives, and 106 employed women) attending health centers in 2014. Using purposive convenient sampling method, eligible pregnant mothers (with no chronic diseases, singleton pregnancy, gravida 1-3, and no addiction) were selected as study subjects. Data were collected and recorded through a researcher-made questionnaire and also from mothers’ medical records, including personal details, prenatal and labor complications, and infant’s details. Collected data were fed into the SPSS version 21(IBM Corp, USA).

Results:

Frequency of placental abruption was greater among housewives (P=0.02), and a significant relationship was found between employment status and lifting heavy objects, which was more frequent among housewives (P=0.01). Lifting heavy objects during pregnancy was only significantly related to reduced amniotic fluid (P=0.001) and low birth weight (P=0.01). Frequency of preterm labor was higher among housewives compared to employed women, but not significantly. Type of delivery was significantly related to employment, and employed mothers had more cesarean deliveries (P=0.0001).

Conclusion:

The results suggest more frequent lifting of heavy objects by housewives than by employed mothers, leading to increased complications such as reduced amniotic fluid, placental abruption, and low birth weight. Perhaps due to higher education levels, frequency of cesarean section and preterm labor was higher among employed mothers. However, employment alone does not predict pregnancy outcomes.

Association of Maternal Working Condition with Low Birth Weight: The Social Determinants of Health Approach

Background:

The socioeconomic conditions have made more job opportunities available to women. This has created interest to conduct studies on the effect of working lifestyle on pregnancy outcomes.

Aim:

This study was conducted with the aim to assess the relationship between mothers' working status as a social determinant and the incidence of low birth weight (LBW) of the newborn.

Subjects and Methods:

This case–control study was conducted on 500 women with normal weight infants (control group) and 250 women with LBW infants (case group) in selected hospitals in Tehran. Data were collected using a researcher-made questionnaire, designed to assess the effect of mothers' prenatal lifestyle, as a social determinant, on LBW of the newborn. A section of the questionnaire involved assessment of mother's working condition in terms of the work environment, activities, and job satisfaction. Data were analyzed using Chi-square and logistic regression tests.

Results:

LBW among employed mothers was 5 times more likely than unemployed ones (odds ratio = 5.35, P < 0.001). Unfavorable work conditions such as humid environment, contact with detergents, and being in one standing or sitting position for long hours were significantly associated with LBW (P < 0.001).

Conclusion:

The present study showed that unfavorable work conditions were associated with LBW; therefore, they need special attention.

Explaining racial disparities in infant health in Brazil

OBJECTIVES

We sought to quantify how socioeconomic, health care, demographic, and geographic effects explain racial disparities in low birth weight (LBW) and preterm birth (PTB) rates in Brazil.

METHODS

We employed a sample of 8949 infants born between 1995 and 2009 in 15 cities and 7 provinces in Brazil. We focused on disparities in LBW (< 2500 g) and PTB (< 37 gestational weeks) prevalence between infants of African ancestry alone or African mixed with other ancestries, and European ancestry alone. We used a decomposition model to quantify the contributions of conceptually relevant factors to these disparities.

RESULTS

The model explained 45% to 94% of LBW and 64% to 94% of PTB disparities between the African ancestry groups and European ancestry. Differences in prenatal care use and geographic location were the most important contributors, followed by socioeconomic differences. The model explained the majority of the disparities for mixed African ancestry and part of the disparity for African ancestry alone.

CONCLUSIONS

Public policies to improve children's health should target prenatal care and geographic location differences to reduce health disparities between infants of African and European ancestries in Brazil.

Seasonality modifies the effect of a lipid-based nutrient supplement for pregnant rural women on birth length

BACKGROUND

Maternal nutritional status is a major determinant of low birth weight and fluctuates across seasons. Seasonality may influence the outcome of prenatal nutrition interventions that aim to enhance fetal growth.

OBJECTIVE

This study investigated seasonal modifications of the efficacy of a randomized controlled prenatal nutrition intervention trial in pregnant women to improve fetal growth in rural Burkina Faso.

METHODS

The second Micronutriments et Santé de la Mère et de l'Enfant study compared a lipid-based nutrient supplement (LNS) fortified with multiple micronutrients (MMNs) to an MMN supplement. Truncated Fourier series were used to characterize seasonality in birth outcomes. Models that included the Fourier series and newborn and maternal characteristics were used to assess seasonal effect modifications of prenatal supplementation on birth outcomes.

RESULTS

Birth weight, birth length, small for gestational age as a proxy for intrauterine growth retardation, and preterm birth were significantly related to date of birth and showed important seasonal variations. LNSs, which supply energy in addition to MMNs, resulted in a significant increase in birth length (+13.5 mm, 95% CI: 6.5, 20.5 mm) at the transition from rain to dry season (September to November) compared to MMNs alone.

CONCLUSIONS

The climatologic and agricultural seasonal patterns in Burkina Faso affect the efficacy of prenatal LNSs on birth length. In this context, prenatal MMN supplementation programs should be complemented by energy supplementation during the annual rain season to promote fetal growth. This trial was registered at clinicaltrials.gov as NCT00909974.

Shift work, long working hours and preterm birth: a systematic review and meta-analysis

PURPOSE

Specific physical activities or working conditions are suspected for increasing the risk of preterm birth (PTB). The aim of this meta-analysis is to review and summarize the pre-existing evidence on the effect of shift work or long working hours on the risk of PTB.

METHODS

We conducted a systematic search in MEDLINE and EMBASE (1990-2013) for observational and intervention studies with original data. We only included articles that met our specific criteria for language, exposure, outcome, data collection and original data that were of at least of moderate quality. The data of the included studies were pooled.

RESULTS

Eight high-quality studies and eight moderate-quality studies were included in the meta-analysis. In these studies, no clear or statistically significant relationship between shift work and PTB was found. The summary estimate OR for performing shift work during pregnancy and the risk of PTB were 1.04 (95% CI 0.90-1.20). For long working hours during pregnancy, the summary estimate OR was 1.25 (95% CI 1.01-1.54), indicating a marginally statistically significant relationship but an only slightly elevated risk.

CONCLUSION

Although in many of the included studies a positive association between long working hours and PTB was seen this did reach only marginal statistical significance. In the studies included in this review, working in shifts or in night shifts during pregnancy was not significantly associated with an increased risk for PTB. For both risk factors, due to the lack of high-quality studies focusing on the risks per trimester, in particular the third trimester, a firm conclusion about an association cannot be stated.

Long working hours and pregnancy complications: women physicians survey in Japan

Background

Previous studies have investigated the impact of occupational risk factors on health outcomes among physicians. However, few studies have investigated the effects on pregnancy outcomes among physicians. In this study, we examined the association between working hours during pregnancy and pregnancy complications among physicians.

Methods

A cross-sectional study was based on a survey conducted in 2009-2011 of 1,684 alumnae (mean age, 44 ± 8 years) who had graduated from 13 private medical schools in Japan. Data on threatened abortion (TA), preterm birth (PTB), and the number of working hours during the first trimester of pregnancy were obtained via retrospective assessments.

Results

Of the 939 physicians with a first pregnancy, 15% experienced TA and 12% experienced PTB. Women who experienced TA (mean weekly working hours: 62 h vs. 50 h, P < .0001) or PTB (62 h vs. 50 h, P < .0001) had longer weekly working hours during the first trimester than did those without pregnancy complications. Compared with women who worked 40 hours or less per week, women who worked 71 hours or more per week had a three-fold higher risk of experiencing TA (95% confidence interval (CI): 1.7-6.0) even after adjusting for medical specialty, maternal age, and current household income. The risk of experiencing PTB was 2.5 times higher (95% CI:1.2-5.2) in women who worked 51-70 hours and 4.2 times higher (95% CI: 1.9-9.2) in women who worked 71 hours or more even after adjusting for specialty, maternal age, and current household income. The trend in the P statistic reflecting the effect of the quartile of hours worked per week (40 hours, 41-50 hours, 51-70 hours, ≥71 hours) on TA or PTB was 0.0001 in the multivariate logistic regression models.

Conclusion

These results suggest that working long hours during the first trimester of pregnancy is associated with TA and PTB.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2393-14-245) contains supplementary material, which is available to authorized users.

Maternal occupation and term low birth weight in a predominantly latina population in los angeles, california

OBJECTIVES

Focusing on Latinas, we investigated whether maternal occupations during pregnancy increase term low birth weight (TLBW) (less than 2500 g; 37 weeks or more).

METHODS

In a case-control study (n = 1498) nested within a 2003 birth cohort (n = 58,316) in Los Angeles County, California (65% Latina), we assessed the influence of maternal occupation on TLBW, using Occupational Codes based on the 2000 US Census Occupational Classification System.

RESULTS

Odds ratios (ORs) for TLBW were increased among women working during pregnancy in "transportation and material moving operations" (adjusted OR = 3.28; 95% confidence interval = 1.00 to 10.73), "food preparation and serving occupations" (adjusted OR = 3.03, 95% confidence interval = 1.21 to 7.62), or "production occupations" (adjusted OR = 2.63, 95% confidence interval = 1.01 to 6.82) compared with "office occupations;" 73% to 93% of women working in these higher-risk jobs were immigrant Latinas.

CONCLUSIONS

Working conditions in various jobs held mainly by first-generation immigrant Latinas increase risks for TLBW and need to be addressed to develop strategies to reduce TLBW.

Occupational lifting, fetal death and preterm birth: findings from the Danish National Birth Cohort using a job exposure matrix

Objective

We examined the association between occupational lifting during pregnancy and risk of fetal death and preterm birth using a job exposure matrix (JEM).

Methods

For 68,086 occupationally active women in the Danish National Birth Cohort, interview information on occupational lifting was collected around gestational week 16. We established a JEM based on information from women, who were still pregnant when interviewed. The JEM provided mean total loads lifted per day within homogeneous exposure groups as informed by job and industry codes. All women were assigned an exposure estimate from the JEM. We used Cox regression models with gestational age as underlying time variable and adjustment for covariates.

Results

We observed 2,717 fetal deaths and 3,128 preterm births within the study cohort. No exposure-response relation was observed for fetal death, but for women with a prior fetal death, we found a hazard ratio (HR) of 2.87 (95% CI 1.37, 6.01) for stillbirth (fetal death ≥22 completed gestational weeks) among those who lifted >200 kg/day. For preterm birth, we found an exposure-response relation for primigravid women, reaching a HR of 1.43 (95% CI 1.13, 1.80) for total loads >200 kg per day. These findings correspond to an excess fraction of 11% for stillbirth and 10% for preterm birth.

Conclusion

We found an increased risk of stillbirth among women with a prior fetal death, who lifted >200 kg/day, and an exposure-response relationship between occupational lifting and preterm birth among primigravid women. The study adds to a large body of prospective studies on occupational lifting and adverse pregnancy outcomes by refined exposure assessment.

Provisional recommended weight limits for manual lifting during pregnancy

OBJECTIVE

The National Institute for Occupational Safety and Health (NIOSH) Revised Lifting Equation (RNLE) was adapted to derive recommended weight limits (RWLs) for pregnant workers and to develop corresponding guidelines for clinicians.

BACKGROUND

In the past three decades there has been a large increase in the number of women employed outside the home and remaining in the workforce during pregnancy. Practical authoritative guidelines based on accumulated evidence are needed to inform allowable work activity levels for healthy pregnant workers.

METHOD

Empirically based lifting criteria established by NIOSH to reduce the risk of overexertion injuries in the general U.S. working population were evaluated for application to pregnant workers. Our evaluation included an extensive review of the literature linking occupational lifting to maternal and fetal health. Decision logic and supporting literature are presented, along with computational details.

RESULTS

Provisional RWLs for pregnant workers were derived from the RNLE, along with guidelines for clinicians. The guidelines advise against pregnant workers lifting below midshin and overhead.

CONCLUSION

Based on our review of the available evidence, we present lifting thresholds that most pregnant workers with uncomplicated pregnancies should be able to perform without increased risk of adverse maternal and fetal health consequences. Except for restrictions involving lifting from the floor and overhead, the provisional guidelines presented are compatible with NIOSH lifting recommendations adopted in the early 1990s for the general working population.

APPLICATION

Implementation of these provisional guidelines could protect millions of female workers in the workplace from fetal and maternal lifting-related health problems.

Physically demanding work and preterm delivery: a systematic review and meta-analysis

OBJECTIVE

Physically demanding work may increase the risk of preterm delivery (PTD), defined as delivery before 37 weeks. We assessed the available evidence.

METHODS

A systematic search in Medline, Embase and Nioshtic for the period 1990 to June 2012 for observational and intervention studies on physically demanding work (prolonged standing, heavy lifting, physical exertion, occupational fatigue and demanding posture) and PTD. Selected studies were assessed for their risk of bias and pooled using a random effects model. Results of case-control and cohort studies were reported separately in subgroups.

RESULTS

We found 10 studies with low risk of bias and seven studies with moderate risk of bias. Standing and walking at work during pregnancy for more than 3 h per day was associated with an increased risk for PTD [OR 1.3 (95% CI 1.1-1.6)], just as lifting and carrying >5 kg [OR 1.3 (95% CI 1.05-1.6)] or lifting and carrying in the third trimester of the pregnancy [OR 1.3 (95% CI 1.01-1.8)]. Jobs that required physical effort or physical exertion were associated with an increased risk of PTD [OR 1.4 (95% CI 1.19-1.66)]. Working during pregnancy in jobs with a combination of two or more physical tasks, physical effort or occupational fatigue was also associated with an increased risk of PTD [OR 1.5 (95% CI 1.1-2.0)].

CONCLUSIONS

Physically demanding work during pregnancy is associated with an increased risk of PTD, especially in jobs with a combination of tasks with physical effort. In general, only small to moderate elevations of risks were found.

Preterm birth and prenatal maternal occupation: the role of Hispanic ethnicity and nativity in a population-based sample in Los Angeles, California

OBJECTIVES

We investigated preterm birth (PTB) in relation to maternal occupational exposure and whether effect measures were modified by Hispanic ethnicity and nativity in a population-based sample with high proportion of Hispanics.

METHODS

We used a case-control study (n = 2543) nested within a cohort of 58,316 births in Los Angeles County, California, in 2003. We categorized prenatal occupations using the US Census Occupation Codes and Classification System and developed a job exposure matrix. Odds ratios for PTB were estimated using logistic regression.

RESULTS

Odds ratios for PTB were increased for all women in health care practitioner and technical occupations, but the 95% confidence intervals included the null value; effects were more pronounced among Hispanics. We estimated elevated odds ratios for foreign-born Hispanic women in building and grounds cleaning and maintenance occupations. Shift work and physically demanding work affected births among US-born but not foreign-born Hispanics.

CONCLUSIONS

Hispanic women are at particular risk for PTB related to adverse prenatal occupational exposure. Nativity may moderate these effects on PTB. Maternal occupational exposures likely contribute to ethnic disparities in PTB.

Working conditions, socioeconomic factors and low birth weight: path analysis

Background

In recent years, with socioeconomic changes in the society, the presence of women in the workplace is inevitable. The differences in working condition, especially for pregnant women, has adverse consequences like low birth weight.

Objectives

This study was conducted with the aim to model the relationship between working conditions, socioeconomic factors, and birth weight.

Patients and Methods

This study was conducted in case-control design. The control group consisted of 500 women with normal weight babies, and the case group, 250 women with low weight babies from selected hospitals in Tehran. Data were collected using a researcher-made questionnaire to determine mothers’ lifestyle during pregnancy with low birth weight with health-affecting social determinants approach. This questionnaire investigated women’s occupational lifestyle in terms of working conditions, activities, and job satisfaction. Data were analyzed with SPSS-16 and Lisrel-8.8 software using statistical path analysis.

Results

The final path model fitted well (CFI =1, RMSEA=0.00) and showed that among direct paths, working condition (β=-0.032), among indirect paths, household income (β=-0.42), and in the overall effect, unemployed spouse (β=-0.1828) had the most effects on the low birth weight. Negative coefficients indicate decreasing effect on birth weight.

Conclusions

Based on the path analysis model, working condition and socioeconomic status directly and indirectly influence birth weight. Thus, as well as attention to treatment and health care (biological aspect), special attention must also be paid to mothers’ socioeconomic factors.

Clinical guidelines for occupational lifting in pregnancy: evidence summary and provisional recommendations

Empirically based lifting criteria established by the National Institute for Occupational Safety and Health (NIOSH) to reduce the risk of overexertion injuries in the general US working population were evaluated for application to pregnant workers. This report proposes criteria to guide decisions by medical providers about permissible weights for lifting tasks performed at work over the course of an uncomplicated pregnancy. Our evaluation included an extensive review of the literature linking occupational lifting to maternal and fetal health. Although it has been 29 years since the American Medical Association's Council on Scientific Affairs published its report on the Effects of Pregnancy on Work Performance, these guidelines continue to influence clinical decisions and workplace policies. Provisional clinical guidelines derived from the NIOSH lifting criteria that account for recent evidence for maternal and fetal health are presented and aim to improve the standard of care for pregnant workers.

Occupational lifting of heavy loads and preterm birth: a study within the Danish National Birth Cohort

OBJECTIVES

To examine the association between occupational lifting during pregnancy and preterm birth. The risk of preterm birth was estimated for total burden lifted per day and number of medium and heavy loads lifted per day.

METHODS

In a study population of 62 803 pregnant women enrolled to the Danish National Birth Cohort from 1996 to 2002, the association between self-reported occupational lifting in the first part of pregnancy and preterm birth was analysed using logistic regression models with adjustment for age, parity, cervical cone biopsy, assisted reproduction and smoking. Associations between lifting and extremely (before 28 weeks), very (28-32 weeks) and moderately (33-37 weeks) preterm birth were analysed using Cox regression models.

RESULTS

We found a dose-response relation between total daily burden lifted and preterm birth with an OR of 1.50 (95% CI 1.03 to 2.19) with loads over 1000 kg/day. No threshold value was found. The associations were strongest for extremely and very preterm birth with HRs (95% CIs) of 4.3 (1.4 to 13.8) and 1.7 (0.7 to 4.0), respectively. Lifting heavy loads (>20 kg) more than10 times/day was associated with preterm birth up to an OR of 2.03 (95% CI 1.14 to 3.62).

CONCLUSION

In a society with social welfare and a highly regulated working environment, occupational lifting was associated with an increased risk of preterm birth.

Work activities and risk of prematurity, low birth weight and pre-eclampsia: an updated review with meta-analysis

OBJECTIVES

We assessed the evidence relating preterm delivery (PTD), low birth weight, small for gestational age (SGA), pre-eclampsia and gestational hypertension to five occupational exposures (working hours, shift work, lifting, standing and physical workload). We conducted a systematic search in Medline and Embase (1966 to 2011), updating a previous search with a further 6 years of observations.

METHODS

As before, combinations of keywords and medical subject headings were used. Each relevant paper was assessed for completeness of reporting and potential for important bias or confounding, and its effect estimates abstracted. Where similar definitions of exposure and outcome existed we calculated pooled estimates of relative risk (RR) in meta-analysis.

RESULTS

Analysis was based on 86 reports (32 cohort investigations, 57 with usable data on PTD, 54 on birth weight and 11 on pre-eclampsia/gestational hypertension); 33 reports were new to this review. For PTD, findings across a substantial evidence base were generally consistent, effectively ruling out large effects (eg, RR>1.2). Larger and higher quality studies were less positive, while meta-estimates of risk were smaller than in previous analyses and best estimates pointed to modest or null effects (RR 1.04 to 1.18). For SGA, the position was similar but meta-estimates were even closer to the null (eight of nine RRs ≤ 1.07). For pre-eclampsia/gestational hypertension the evidence base remains insufficient.

CONCLUSIONS

The balance of evidence is against large effects for the associations investigated. As the evidence base has grown, estimates of risk in relation to these outcomes have become smaller.

Explaining racial disparities in infant health in Brazil

OBJECTIVES

We sought to quantify how socioeconomic, health care, demographic, and geographic effects explain racial disparities in low birth weight (LBW) and preterm birth (PTB) rates in Brazil.

METHODS

We employed a sample of 8949 infants born between 1995 and 2009 in 15 cities and 7 provinces in Brazil. We focused on disparities in LBW (< 2500 g) and PTB (< 37 gestational weeks) prevalence between infants of African ancestry alone or African mixed with other ancestries, and European ancestry alone. We used a decomposition model to quantify the contributions of conceptually relevant factors to these disparities.

RESULTS

The model explained 45% to 94% of LBW and 64% to 94% of PTB disparities between the African ancestry groups and European ancestry. Differences in prenatal care use and geographic location were the most important contributors, followed by socioeconomic differences. The model explained the majority of the disparities for mixed African ancestry and part of the disparity for African ancestry alone.

CONCLUSIONS

Public policies to improve children's health should target prenatal care and geographic location differences to reduce health disparities between infants of African and European ancestries in Brazil.

Return to military weight standards after pregnancy in active duty working women: comparison of marine corps vs. navy

OBJECTIVE

To compare the likelihood of being within weight standards before and after pregnancy between United States Marine Corps (USMC) and Navy (USN) active duty women (ADW).

METHODS

ADW with singleton gestations who delivered at a USMC base were followed for 6 months to determine likelihood of returning to military weight standards. Odds ratio (OR), adjusted odds ratio (AOR) and 95% confidence intervals were calculated; p < 0.05 was considered significant.

RESULTS

Similar proportions of USN and USMC ADW were within body weight standards one year prior to pregnancy (79%, 97%) and at first prenatal visit (69%, 96%), respectively. However, USMC ADW were significantly more likely to be within body weight standards at 3 months (AOR 4.30,1.28-14.43) and 6 months after delivery (AOR 9.94, 1.53-64.52) than USN ADW. Weight gained during pregnancy did not differ significantly for the two groups (40.4 lbs vs 44.2 lbs, p = 0.163). The likelihood of spontaneous vaginal delivery was significantly higher (OR 2.52, 1.20-5.27) and the mean birth weight was significantly lower (p = 0.0036) among USMC ADW as compared to USN ADW.

CONCLUSIONS

Being within weight standards differs significantly for USMC and USN ADW after pregnancy.

Shift work and pregnancy outcomes: a systematic review with meta-analysis of currently available epidemiological studies

BACKGROUND

Varying work schedules are suspected of increasing risks to pregnant women and to fetal wellbeing. In particular, maternal hormonal disturbance arising from sleep deprivation or circadian rhythm disruption might impair fetal growth or lead to complications of pregnancy. Two independent meta-analyses (from 2000 to 2007) reported a small adverse effect of shift work on the risk of preterm delivery (PTD). However, these reviews were based on few high-quality studies.

OBJECTIVES

To provide an updated review of the associations of shift work with PTD, low birthweight (LBW), small-for-gestational-age (SGA) infants and pre-eclampsia.

SEARCH STRATEGY AND SELECTION CRITERIA

We conducted a systematic search of MEDLINE using combinations of keywords and MeSH terms.

DATA COLLECTION AND ANALYSIS

For each relevant paper we abstracted standard details, used to summarise design features and rate methodological quality. We calculated pooled estimates of relative risk (RR) in random-effect meta-analyses.

MAIN RESULTS

We retrieved 23 relevant studies. The pooled estimate of RR for PTD was 1.16 (95% CI 1.00-1.33, 16 studies), but when five reports of poorer methodological quality were excluded, the estimated RR decreased to 1.03 (95% CI 0.93-1.14). We also observed increased RRs for LBW (RR 1.27, 95% CI 0.93-1.74) and for SGA (RR 1.12, 95% CI 1.03-1.22), which varied little by study quality. Little evidence was found on pre-eclampsia.

CONCLUSIONS

These findings suggest that overall, any risk of PTD, LBW, or SGA arising from shift work in pregnancy is small.