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

Exploring melatonin's multifaceted role in female reproductive health: From follicular development to lactation and its therapeutic potential in obstetric syndromes

BACKGROUND

Melatonin is mainly secreted by the pineal gland during darkness and regulates biological rhythms through its receptors in the suprachiasmatic nucleus of the hypothalamus. In addition, it also plays a role in the reproductive system by affecting the function of the hypothalamic-pituitary-gonadal axis, and by acting as a free radical scavenger thus contributing to the maintenance of the optimal physiological state of the gonads. Besides, melatonin can freely cross the placenta to influence fetal development. However, there is still a lack of overall understanding of the role of melatonin in the reproductive cycle of female mammals.

AIM OF REVIEW

Here we focus the role of melatonin in female reproduction from follicular development to delivery as well as the relationship between melatonin and lactation. We further summarize the potential role of melatonin in the treatment of preeclampsia, polycystic ovary syndrome, endometriosis, and ovarian aging.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Understanding the physiological role of melatonin in female reproductive processes will contribute to the advancement of human fertility and reproductive medicine research.

From gestational chronodisruption to noncommunicable diseases: Pathophysiological mechanisms of programming of adult diseases, and the potential therapeutic role of melatonin

During gestation, the developing fetus relies on precise maternal circadian signals for optimal growth and preparation for extrauterine life. These signals regulate the daily delivery of oxygen, nutrients, hormones, and other biophysical factors while synchronizing fetal rhythms with the external photoperiod. However, modern lifestyle factors such as light pollution and shift work can induce gestational chronodisruption, leading to the desynchronization of maternal and fetal circadian rhythms. Such disruptions have been associated with adverse effects on cardiovascular, neurodevelopmental, metabolic, and endocrine functions in the fetus, increasing the susceptibility to noncommunicable diseases (NCDs) in adult life. This aligns with the Developmental Origins of Health and Disease theory, suggesting that early-life exposures can significantly influence health outcomes later in life. The consequences of gestational chronodisruption also extend into adulthood. Environmental factors like diet and stress can exacerbate the adverse effects of these disruptions, underscoring the importance of maintaining a healthy circadian rhythm across the lifespan to prevent NCDs and mitigate the impact of gestational chronodisruption on aging. Research efforts are currently aimed at identifying potential interventions to prevent or mitigate the effects of gestational chronodisruption. Melatonin supplementation during pregnancy emerges as a promising intervention, although further investigation is required to fully understand the precise mechanisms involved and to develop effective strategies for promoting health and preventing NCDs in individuals affected by gestational chronodisruption.

Impact of high-fat diet and exposure to constant light on reproductive competence of female ICR mice

Obesity and exposure to light at night are prevalent in modern society and associated with changes in physiology and behavior that can affect a female's ability to support offspring growth during pregnancy and lactation. A 2X3 factor study of ICR mice was conducted to determine the effect of diet [control (CON; 10% fat) or high fat (HF; 60% fat)] and exposure to regular 12 h light:dark cycles (LD) or continuous low (L5) or high (L100) lux of light on gestation length, birth litter size, milk composition and litter growth to lactation day 12. HF diet reduced birth litter size, but increased postnatal d 12 litter weight (P<0.05), whereas constant light tended to increase litter weight (P=0.07). Continuous light increased gestation length, altered dam feed intake, increased serum prolactin and increased final dam and mammary gland weight (P<0.05), while decreasing mammary ATP content and milk lactose (P<0.05). Correlation analysis indicated a positive relationship between final litter weight and mammary size, metabolic stores (e.g. maternal fat pad weight), kcal of feed intake, and gestation length (P<0.05). Although CON mice spent more time eating than HF dams, the calorically dense HF diet was related to greater rates of litter growth to peak lactation. Constant light circadian disrupting effects appear to be confounded by a potential long day photoperiod response exemplified by higher circulating levels of prolactin and increased body and mammary weight of females exposed to these conditions. Other model systems may be better to study the interacting effects of obesity and circadian disruption on reproductive competence.

Occupational Exposure during Pregnancy and Effects on Newborns: A Nested Case-Control Study

BACKGROUND

The protection of pregnant workers should be based on evidence regarding the risks to reproductive health from exposure to specific work environments and conditions. The objective of this study was to identify the effects on mothers and newborns resulting from environmental exposure to various occupational risks.

METHODS

The study cohort was composed of 399 women admitted to the Obstetrics/Postpartum ward at Hospital La Fe in Valencia, Spain. Face-to-face interviews were conducted to establish associations between workplace exposure during pregnancy and its effects on maternal and newborn health. Sex, anthropometric characteristics, and blood gas analysis in arterial and venous umbilical cord blood at delivery were collected.

RESULTS

A total of 138 women were exposed to biological and/or chemical risks, 122 to physical risks, and 139 at no risk of exposure. In the group with chemical and/or biological risks, the frequency of women who resorted to in vitro fertilization to achieve the studied pregnancy is less than half of the group exposed to physical risks, with statistically significant differences (p = 0.047). The mean values for the arterial analysis in both exposure groups were within average values, with similar pH values between them, but the mean values of PCO2 and PO2 were lower in the group of neonates of mothers exposed to physical risks, with a significant difference for arterial PO2 (p = 0.027).

CONCLUSION

Our analysis contributes evidence for planning and prioritizing preventive actions to protect women's reproductive health. The results suggest the continuation of a future project that would consider more factors and potentially increase the sample size.

Common sleep disorders in pregnancy: a review

In this review, we provide a comprehensive overview of common sleep disorders during pregnancy, including their characterization, prevalence, risk factors, and possible contribution to maternal and fetal outcomes. We conducted a quasi-systematic literature search of the MEDLINE database and identified 744 studies from 1991 through 2021, inclusive, that met our inclusion criteria. We synthesized the existing literature on sleep disorders during pregnancy and highlighted controversies, research gaps, and needed clinical developments. Our review covers a range of sleep disorders, including insomnia, obstructive sleep apnea, restless legs syndrome, and circadian rhythm disorders. We discuss the prevalence of these disorders in pregnancy and their potential impact on maternal and fetal health outcomes. We also explore the relationship between sleep disorders, pre-pregnancy comorbidities such as obesity, and pregnancy-related conditions such as gestational diabetes mellitus and preeclampsia. In addition to summarizing the existing literature on sleep disorders during pregnancy, we also highlight opportunities for further research in this area. We suggest that future studies should strive to employ validated and objective measurement tools for sleep disorders and prioritize utilization of longitudinal methods with participant follow-up through postpartum, mid-life, menopause, and beyond. We also put forward investigation into the impact of circadian rhythm disruption on reproductive physiology and early pregnancy outcomes as an area of important work. Overall, our review provides valuable insights on sleep and reproduction and into common sleep disorders during pregnancy and their potential impact on maternal and fetal health outcomes.

Maternal occupational risk factors and preterm birth: Protocol for a systematic review and meta-analysis

INTRODUCTION

Preterm birth, which accounts for 33.1% of neonatal death globally, is the main cause of under-five mortality. A growing number of studies indicate that occupational risk factors during pregnancy are linked to an increased likelihood of poor pregnancy outcomes. The effect of physical occupational risks on preterm birth has received very little attention, and previous reviews have produced inconclusive results. This systematic review aims to update the evidence on the relationship between maternal physical occupational risks and preterm birth.

METHOD AND ANALYSIS

We will search electronic databases including Ovid Medline, Embase, Emcare, CINAHL, Scopus, and Web of science to find peer-reviewed studies examining the relationship between six common maternal physical occupational risks (heavy lifting, prolonged standing, heavy physical exertion, long working hours, shift work, and whole-body vibrations) and preterm birth. Articles published in English after 1 January 2000 will be included without geographic restrictions. Two reviewers will screen titles and abstracts independently, and then select full-text articles that meet inclusion criteria. Methodological quality of the included studies will be evaluated using the Joanna Briggs Institute (JBI) critical appraisal method. The quality of evidence across each exposure and the outcome of interest will be examined by using the GRADE (Grade of Recommendations, Assessment, Development, Evaluation) method. Accordingly, a high level of evidence will lead to "strong recommendations". A moderate level of evidence will lead to "practice considerations". For all evidence levels below moderate, the message will be "not enough evidence from the scientific literature to guide policymakers, clinicians, and patients. If data permits, a meta-analysis will be conducted using Stata Software. In case where meta-analysis is not possible, we will perform a formal narrative synthesis.

DISCUSSION AND CONCLUSION

Evidence suggests that preterm birth is linked to a number of maternal occupational risk factors. This systematic review will update, compile, and critically review the evidence on the effect of maternal physical occupational risk on preterm birth. This systematic review will provide guidance to support decision-makers including maternal and child health services, other health care providers, and government policy agencies.

TRIAL REGISTRATION

PROSPERO registration number: CRD42022357045.

Circadian hormone secretion of enteroendocrine cells: implication on pregnancy status

The timing of food intake is a key cue for circadian rhythms in humans and animals. In response to food intake, gut hormones called incretin are produced by intestinal enteroendocrine cells in a circadian rhythm that stimulates insulin secretion and regulates body weight and energy expenditure. Pregnancy is associated with the expansion of β cells, the risk of gestational diabetes mellitus, and excessive weight gain. The timing of food intake is a good way to address metabolic complications during pregnancy. The current review focuses on the circadian rhythms and biological actions of enteroendocrine hormones and their associations with pregnancy status, specifically topics like food intake and gut circadian rhythms, the circadian secretion of enteroendocrine peptides, and the effects of these factors during pregnancy.

Association between frequency of breakfast intake before and during pregnancy and infant birth weight: the Tohoku Medical Megabank Project Birth and Three-Generation Cohort Study

BACKGROUND

Low birth weight is associated with an increased risk of developing chronic diseases in adulthood, with a particularly high incidence in Japan among developed countries. Maternal undernutrition is a risk factor for low birth weight, but the association between the timing of food intake and infant birth weight has not been investigated. This study aimed to examine the association between breakfast intake frequency among Japanese pregnant women and infant birth weight.

METHODS

Of all pregnant women who participated in the Tohoku Medical Megabank Project Three Generation Cohort Study, 16,820 who answered the required questions were included in the analysis. The frequency of breakfast intake from pre- to early pregnancy and from early to mid-pregnancy was classified into four groups: every day and 5-6, 3-4, and 0-2 times/week. Multivariate linear regression models were constructed to examine the association between breakfast intake frequency among pregnant women and infant birth weight.

RESULTS

The percentage of pregnant women who consumed breakfast daily was 74% in the pre- to early pregnancy period and 79% in the early to mid-pregnancy period. The average infant birth weight was 3,071 g. Compared to women who had breakfast daily from pre- to early pregnancy, those who had breakfast 0-2 times/week had lower infant birth weight (β = -38.2, 95% confidence interval [CI]: -56.5, -20.0). Similarly, compared to women who had breakfast daily from early to mid-pregnancy, those who had breakfast 0-2 times/week had lower infant birth weight (β = -41.5, 95% CI: -63.3, -19.6).

CONCLUSIONS

Less frequent breakfast intake before and mid-pregnancy was associated with lower infant birth weight.

Advances in circadian clock regulation of reproduction

The mammalian circadian clock is an endogenously regulated oscillator that is synchronized with solar time and cycle within a 24-h period. The circadian clock exists not only in the suprachiasmatic nucleus (SCN) of the hypothalamus, a central pacemaker of the circadian clock system, but also in numerous peripheral tissues known as peripheral circadian oscillators. The SCN and peripheral circadian oscillators mutually orchestrate the diurnal rhythms of various physiological and behavioral processes in a hierarchical manner. In the past two decades, peripheral circadian oscillators have been identified and their function has been determined in the mammalian reproductive system and its related endocrine glands, including the hypothalamus, pituitary gland, ovaries, testes, uterus, mammary glands, and prostate gland. Increasing evidence indicates that both the SCN and peripheral circadian oscillators play discrete roles in coordinating reproductive processes and optimizing fertility in mammals. The present study reviews recent evidence on circadian clock regulation of reproductive function in the hypothalamic-pituitary-gonadal axis and reproductive system. Additionally, we elucidate the effects of chronodisruption (as a result of, for example, shift work, jet lag, disrupted eating patterns, and sleep disorders) on mammalian reproductive performance from multiple aspects. Finally, we propose potential behavioral changes or pharmaceutical strategies for the prevention and treatment of reproductive disorders from the perspective of chronomedicine. Conclusively, this review will outline recent evidence on circadian clock regulation of reproduction, providing novel perspectives on the role of the circadian clock in maintaining normal reproductive functions and in diseases that negatively affect fertility.

Pregnancy, obstetrical and neonatal outcomes in women exposed to physician-related occupational hazards: a scoping review

OBJECTIVE

Evidence is needed to guide organisational decision making about workplace accommodations for pregnant physicians. Our objective was to characterise the strengths and limitations of current research examining the association between physician-related occupational hazards with pregnancy, obstetrical and neonatal outcomes.

DESIGN

Scoping review.

DATA SOURCES

MEDLINE/PubMed, EMBASE, CINAHL/ EBSCO, SciVerse Scopus and Web of Science/Knowledge were searched from inception to 2 April 2020. A grey literature search was performed on 5 April 2020. The references of all included articles were hand searched for additional citations.

ELIGIBILITY CRITERIA

English language citations that studied employed pregnant people and any 'physician-related occupational hazards', meaning any relevant physical, infectious, chemical or psychological hazard, were included. Outcomes included any pregnancy, obstetrical or neonatal complication.

DATA EXTRACTION AND SYNTHESIS

Physician-related occupational hazards included physician work, healthcare work, long work hours, 'demanding' work, disordered sleep, night shifts and exposure to radiation, chemotherapy, anaesthetic gases or infectious disease. Data were extracted independently in duplicate and reconciled through discussion.

RESULTS

Of the 316 included citations, 189 were original research studies. Most were retrospective, observational and included women in any occupation rather than healthcare workers. Methods for exposure and outcome ascertainment varied across studies and most studies had a high risk of bias in data ascertainment. Most exposures and outcomes were defined categorically and results from different studies could not be combined in a meta-analysis due to heterogeneity in how these categories were defined. Overall, some data suggested that healthcare workers may have an increased risk of miscarriage compared with other employed women. Long work hours may be associated with miscarriage and preterm birth.

CONCLUSIONS

There are important limitations in the current evidence examining physician-related occupational hazards and adverse pregnancy, obstetrical and neonatal outcomes. It is not clear how the medical workplace should be accommodated to improve outcomes for pregnant physicians. High-quality studies are needed and likely feasible.

Chrononutrition is associated with melatonin and cortisol rhythm during pregnancy: Findings from MY-CARE cohort study

Chrononutrition has been suggested to have an entrainment effect on circadian rhythm which is crucial for metabolic health. Investigating how chrononutrition affects maternal circadian rhythm can shed light on its role during pregnancy. This study aims to determine chrononutrition characteristics of healthy primigravida during pregnancy and its association with melatonin and cortisol rhythm across gestation. A total of 70 healthy primigravidas were recruited from ten randomly selected government maternal and child clinics in Kuala Lumpur, Malaysia. During the second and third trimesters, chrononutrition characteristics including meal timing, frequency, eating window, breakfast skipping, and late-night eating were determined using a 3-day food record. Pregnant women provided salivary samples at five time-points over a 24 h period for melatonin and cortisol assay. Consistently across the second and third trimesters, both melatonin and cortisol showed a rhythmic change over the day. Melatonin levels displayed an increment toward the night whilst cortisol levels declined over the day. Majority observed a shorter eating window (≤12 h) during the second and third trimesters (66 and 55%, respectively). Results showed 23 and 28% skipped breakfast whereas 45 and 37% ate within 2 h pre-bedtime. During the third trimester, a longer eating window was associated with lower melatonin mean (β = -0.40, p = 0.006), peak (β = -0.42, p = 0.006), and AUC_G (β = -0.44, p = 0.003). During both trimesters, a lower awakening cortisol level was observed in pregnant women who skipped breakfast (β = -0.33, p = 0.029; β = -0.29, p = 0.044). Only during the second trimester, breakfast-skipping was significantly associated with a greater cortisol amplitude (β = 0.43, p = 0.003). Findings suggest that certain chrononutrition components, particularly eating window and breakfast skipping have a significant influence on maternal melatonin and cortisol rhythm. Dietary intervention targeting these characteristics may be useful in maintaining maternal circadian rhythm.

Alternating mealtimes during pregnancy and weaning triggers behavioral changes in adult offspring

In brief

Mealtime changes in pregnant mice revealed impaired neurobehavioral development in mouse offspring. This study is the basis for investigating diseases associated with neurobehavioral development of adult offspring of pregnant shift-working women.

Abstract

Most organisms on Earth have a biological clock, and their physiological processes are regulated by a 1-day cycle. In modern society, several factors can disturb these biological clocks in humans; in particular, individuals working in shifts are exposed to stark environmental changes that interfere with their biological clock. They have a high risk of various diseases. However, there are scarce experimental approaches to address the reproductive and health consequences of shift work in the offspring of exposed individuals. In this study, considering the fact that shift workers usually have their meals during their adjusted working time, we aimed to examine the effects of a 12-h shift with usual mealtime as a plausible night work model on the neurobehavioral development of adult mouse offspring. In these offspring, early exposure to this mealtime shift differentially affected circadian rhythmic variables and total locomotor activity depending on the timing and duration of restrictive feeding. Moreover, neurobehavioral alterations such as declined short-term memory and depressive-like behavior were observed in adulthood. These results have implications for the health concerns of shift-working women and their children.

Greater Risk of Pregnancy Complications for Female Surgeons: A Cross-Sectional Electronic Survey

BACKGROUND

Female surgeons are exposed to physical and mental stressors that differ from those of other specialties. We aimed to assess whether female surgeons are more at risk of pregnancy complications than women in other medical specialties.

METHODS

We used a cross-sectional electronic survey of female physicians working in the French Region Nouvelle-Aquitaine who were pregnant between 2013 and 2018. A pregnancy complication was defined as the occurrence of miscarriage, ectopic pregnancy, fetal growth restriction, prematurity, fetal congenital malformation, stillbirth, or medical termination of the pregnancy. Multivariate logistic regression models were used to evaluate the risk of pregnancy complications for female surgeons relative to women practicing in other medical specialties.

RESULTS

Among the 270 women included, 52 (19.3%) experienced pregnancy complications and 28 (10.4%) were surgeons. In the multivariate analysis, female surgeons had a higher risk of pregnancy complications: adjusted odds ratio = 3.53, 95% confidence interval [1.27-9.84].

CONCLUSION

Further research is necessary to identify the hazards specifically involved in the practice of surgery to be able to propose preventive actions targeted to female surgeons during their pregnancy.

Artificial Dim Light at Night during Pregnancy Can Affect Hormonal and Metabolic Rhythms in Rat Offspring

Artificial light at night (ALAN) is considered an environmental risk factor that can interfere with the circadian control of the endocrine system and metabolism. We studied the impact of ALAN during pregnancy on the hormonal and biochemical parameters in rat pups at postnatal (P) days P3, P10, and P20. Control dams (CTRL) were kept in a standard light-dark regime, and ALAN dams were exposed to dim ALAN (<2 lx) during the whole pregnancy. A plasma melatonin rhythm was found in all CTRL groups, whereas in ALAN pups, melatonin was not rhythmic at P3, and its amplitude was lowered at P10; no differences were found between groups at P20. Plasma corticosterone was rhythmic at P20 in both groups, with decreased mesor in ALAN pups. Plasma thyroid hormones exhibited an inconsistent developmental pattern, and vasopressin levels were suppressed at the beginning of the dark phase at P20 in ALAN compared to CTRL. Glucose and cholesterol showed significant daily rhythms in CTRL but not in ALAN offspring at P3. Exposure to ALAN during pregnancy disturbed the development of daily rhythms in measured hormones and metabolites, suggesting that ALAN during pregnancy can act as an endocrine disruptor that can interfere with the normal development of the progeny.

Co-alterations of circadian clock gene transcripts in human placenta in preeclampsia

Pre-eclampsia (PE) is a hypertensive condition that occurs during pregnancy and complicates up to 4% of pregnancies. PE exhibits several circadian-related characteristics, and the placenta possesses a functioning molecular clock. We examined the associations of 17 core circadian gene transcripts in placenta with PE vs. non-PE (a mixture of pregnant women with term, preterm, small-for-gestational-age, or chorioamnionitis) using two independent gene expression datasets: GSE75010-157 (80 PE vs. 77 non-PE) and GSE75010-173 (77 PE and 96 non-PE). We found a robust difference in circadian gene expression between PE and non-PE across the two datasets, where CRY1 mRNA increases and NR1D2 and PER3 transcripts decrease in PE placenta. Gene set variation analysis revealed an interplay between co-alterations of circadian clock genes and PE with altered hypoxia, cell migration/invasion, autophagy, and membrane trafficking pathways. Using human placental trophoblast HTR-8 cells, we show that CRY1/2 and NR1D1/2 regulate trophoblast migration. A subgroup study including only term samples demonstrated that CLOCK, NR1D2, and PER3 transcripts were simultaneously decreased in PE placenta, a finding supported by CLOCK protein downregulation in an independent cohort of human term PE placenta samples. These findings provide novel insights into the roles of the molecular clock in the pathogenesis of PE.

Association between maternal shift work during pregnancy child overweight and metabolic outcomes in early childhood

Background

Previous studies found that maternal shift work during pregnancy was associated with many reproductive hazards, including small for gestational age, preterm birth, stillbirth, and neurodevelopmental impairment. Some studies also showed that these children are more likely to become overweight in early childhood. However, the association with metabolic factors, such as insulin resistance and dyslipidemia, was less studied. Hence, we aimed to understand better the relationship between maternal shift work during pregnancy and the risk of childhood overweight and metabolic outcomes. Confounding factors were also discussed, including diet, exercise, and demographical factors.

Methods

We enrolled pregnant women before delivery in the Taiwan Birth Panel Study (TBPS) II conducted between 2010 and 2012, and followed the children of these participants in 2018. The objective of this study is to investigate the influence of prenatal and postnatal factors on infant and early childhood health. During the follow-up in 2018, we checked children's demographic data, obtained blood specimens, and checked their blood sugar, blood insulin, and lipid profiles. Structured questionnaires were used to evaluate demographic data. Multiple linear and logistic regressions were used to examine the associations between maternal shift work during pregnancy and child overweight, metabolic disorders, such as HOMA-IR, and lipid profiles.

Results

In this study, we included 407 mother-children pairs with different work shifts (350 day workers and 57 shift workers), and a sub-population without underweight children was also created (290 day workers and 47 shift workers). Shift work during pregnancy was associated with a higher Homeostasis Model Assessment-Insulin Resistance index (HOMA-IR) and a higher odds ratio for overweight in children born from mothers doing shift work during pregnancy after adjustment. The findings were attenuated when we investigated the effect of shift work before pregnancy.

Conclusion

Our study suggested that maternal shift work during pregnancy was associated with child overweight and insulin resistance in early childhood.

Shift work and sleep duration are associated with adverse pregnancy outcomes in a predominantly Latinx population with high rates of obesity

Background

Shift work has been associated with adverse pregnancy outcomes. The objective of this study was to evaluate the association between sleep disturbances and adverse pregnancy outcomes.

Methods and findings

This was a secondary analysis of a prospective study of participants enrolled in a prospective observational study wherein gravidae were screened for sleep apnea (2010–2012). A screening questionnaire with standard sleep apnea questionnaires as well as novel items about shift work and nocturnal sleep duration was administered at a prenatal care visit. Short sleep duration was defined as less than 7 hours. Prolonged sleep duration was defined as greater than 9 hours.

In a cohort of 1125 pregnant people, 9.4% reported shift work at the time of screening. Gravidae who reported shift work were more likely than gravidae who reported no shift work to develop preeclampsia (28.3% versus 13.0%, P<0.001), preeclamspsia with severe features (16.0% versus 8.5%, P = 0.010), gestational diabetes (28.3% versus 19.9%, P = 0.041), and a composite of adverse obstetric outcomes (61.3% versus 47.8%, P = 0.008). After adjusting for potentially confounding variables, shift work was associated with an increased risk for preeclampsia with (adjusted relative risk (aRR) 1.70, 95% CI 1.03–2.79, p = 0.036) and without (aRR 2.03, 95% CI 1.43–2.90, p<0.001) severe features, and gestational diabetes mellitus class A1 (aRR 1.47, 95% CI 1.05–2.05, p = 0.023) and class A2 (aRR 1.67, 95% CI 1.13–2.44, p = 0.009). Sleep duration was associated with gestational diabetes (31.3% among those with short sleep duration, 25.2% among those with normal sleep duration and 14.0% among those with prolonged sleep duration, P<0.001) and gestational diabetes class A2 (29.5%, 17.9%, and 10.1%, respectively, P<0.001). Gravidae with prolonged sleep duration experienced less composite adverse pregnancy outcomes at 42.6% compared to 57.4% for those with short sleep duration or 52.5% for those with normal sleep duration, P = 0.002.

Conclusions

Shift work and sleep duration are both associated with adverse pregnancy outcomes. Further research on the impact of sleep disturbance on pregnancy outcomes is warranted.

Preterm Singleton Birth Rate during the COVID-19 Lockdown: A Population-Based Study

OBJECTIVE

The aim of the study is to evaluate the effect of the coronavirus disease 2019 (COVID-19) pandemic national lockdown period on the rate of singleton preterm births in Israel.

STUDY DESIGN

This is a population-based cohort study of 3,41,291 singleton infants born in the months of January to July 2017 to 2020. Multivariable logistic regression analyses were used to estimate the influence of period and year on the rates of preterm births during the lockdown period (11^th March - 5^th May 2020) compared with rates before (January 1^st 2020 - March 10^th 2020), and after the lockdown (May 6^th 2020-June 30^th 2020) and to the corresponding periods in 2017to 2019.

RESULTS

During the lockdown period the preterm birth rate (primary outcome) decreased by 9.7% from 5.05 to 4.56% in the pre-lockdown period (p = 0.006), an adjusted decrease of -0.52% (95% confidence interval -0.89%; -0.15%), odds ratio 0.898 (95% confidence interval 0.832; 0.970).

CONCLUSION

The rate of singleton preterm births declined by 9.7% during the COVID-19 pandemic national lockdown period in Israel.

KEY POINTS

· A 10% decline in all preterm deliveries was observed during the COVID-19 pandemic national lock-down period.. · The lock-down might influence environmental changes which contribute to the decrease in preterm deliveries.. · Changes in lifestyle, and societal behavior might contribute to the decrease in preterm deliveries..

The association between shift work disorder and turnover intention among nurses

Background

Shift work disorder (SWD) is highly prevalent among shift-working nurses and has multiple negative health-related effects. There is a dearth of insight into career-related decisions made by nurses suffering from SWD, for instance in terms of their intention to quit work (turnover intention). In this study, we aimed to investigate the association between SWD and turnover intention among nurses, and the individual and work-related correlates of turnover intention.

Method

Data were derived from the ongoing longitudinal cohort study “SUrvey of Shift work, Sleep and Health (SUSSH)” among Norwegian nurses. An annual survey was initiated in 2008/2009 (N = 2965). The present study used data collected in year 2015 (wave 7) and 2016 (wave 8). Nurses were included if: 1) they were working as nurses in both 2015 and 2016, and 2) had completed a three-item scale adapted from the Michigan Organizational Assessment Questionnaire assessing turnover intention (in wave 8), and 3) did not only work day-shifts. SWD was measured in wave 7 with three questions based on the minimal criteria from the third edition of the International Classification of Sleep Disorders. Job demands, decision latitude, and social support at the workplace were measured with subscales of the Swedish Demand-Control-Support Questionnaire.

Results

Eight Hundred eighty-nine nurses were included. The results from the hierarchical linear regression showed that SWD predicted turnover intention one year later, i.e. from 2015 to 2016 (F_1,835 = 6.00, p < 0.05; β = 0.084, p = 0.015). The findings remained significant when controlling for age, sex, organizational tenure, number of nights worked, shift work schedule and workplace social support, job demands and decision latitude.

Conclusion

This study showed that SWD is associated with turnover intention, even when controlling for individual and work-related variables.

Sleep Disturbance in Pregnancy

Sleep is vital to life, even when women enter into pregnancy state. Good sleep is important for a healthy pregnancy. Sleep disturbances are common during pregnancy and can be due to the change of pregnancy itself or the results of sleep disorders. There is growing evidence linking sleep disturbances with adverse maternal and fetal outcomes. Differentiation of sleep disorders in order to provide appropriate treatment as well as promoting good sleep for pregnant women is important. A multidisciplinary team to provide sleep care during antenatal period may be needed.

Obstructive Sleep Apnea: Another Condition to Screen for in Women with Infertility

Women with obstructive sleep apnea (OSA) are at increased risk of poor pregnancy outcomes such as fetal growth restriction, hypertensive disorders of pregnancy, and gestational diabetes mellitus. Given this increased risk, we aimed to study the screening prevalence of OSA in women seeking fertility treatment. We performed a cross sectional study of patients presenting to a university-affiliated fertility clinic between March-April 2021. Patients were asked to complete OSA screening (STOP-BANG), anxiety screening (GAD-7), and depression screening (PHQ-2) questionnaires. 107 women completed the surveys. Mean age was 35.1 years and mean body mass index (BMI) was 25.7 kg/m2. Nine (8.4%) women screened positive for OSA using the STOP-BANG screening tool. Women who screened positive for OSA were more likely to be older (37.8 years vs. 34.7 years, p = 0.02) and have a higher BMI (42.6 kg/m2 vs. 27.4 kg/m2, p < 0.001). Women who screened positive for OSA were also more likely to screen positive for mild-severe depressive symptoms (22.2% vs. 3.1%, p = 0.006) and mild-severe anxiety (66.7% vs. 21.4%, p = 0.003) symptoms. 24.3% of the population had polycystic ovary syndrome (PCOS). Women with PCOS were more likely to screen positive for OSA (19.2% vs. 4.9%; p = 0.04). Despite this being a low-risk population of young women seeking fertility evaluation or treatment, 8% screened positive for OSA. Given the association between OSA and adverse pregnancy outcomes, our results underline the need to screen women seeking fertility treatment.

Shift and night work during pregnancy and preterm birth-a cohort study of Swedish health care employees

BACKGROUND

Previous studies of preterm birth (PTB) concerning night work have been inconclusive and partly limited by imprecise data on working schedules. This study investigated the risk of PTB in relation to detailed, registry-based data on working hours.

METHODS

In a register-based prospective cohort study, we identified 4970 singleton births with information on PTB from the Swedish Medical Birth Register of health care employees in Stockholm. Day-by-day information on working hours 2008-16 was obtained from a computerized employee register. Odds ratios (ORs) of PTB according to work hour characteristics were analysed by logistic regression adjusted for mother's age, stature, body mass index (BMI), parity, smoking habits, education, profession and country of birth.

RESULTS

There was an increased risk of PTB among those who frequently worked night shifts (>25 times) [OR, 1.62; 95% confidence interval (CI), 1.03-2.53] and who ever worked ≥3 consecutive night shifts (OR, 1.43; 95% CI, 1.03-1.99) during the first trimester. Frequently (> 8 times) working 3 or more consecutive nights, and frequently (>18 times) having quick returns from night shifts (<28 h) during the first trimester showed 3-4 fold increased risk of PTB. Moreover, working frequent (>20 times) long shifts (≥10 h) (OR 1.63; 95% CI, 1.07-2.49) during the first trimester and working any Week >40 h (OR 2.05; 95% CI, 1.31-3.22) during the third trimester were associated with PTB.

CONCLUSIONS

In this cohort of Swedish health care employees with registry-based data on working hours, night work, especially working frequent consecutive nights, and quick returns from night shifts during the first trimester were associated with increased risk of PTB among pregnant women.

Labour classified by cervical dilatation & fetal membrane rupture demonstrates differential impact on RNA-seq data for human myometrium tissues

High throughput sequencing has previously identified differentially expressed genes (DEGs) and enriched signalling networks in human myometrium for term (≥37 weeks) gestation labour, when defined as a singular state of activity at comparison to the non-labouring state. However, transcriptome changes that occur during transition from early to established labour (defined as ≤3 and >3 cm cervical dilatation, respectively) and potentially altered by fetal membrane rupture (ROM), when adapting from onset to completion of childbirth, remained to be defined. In the present study, we assessed whether differences for these two clinically observable factors of labour are associated with different myometrial transcriptome profiles. Analysis of our tissue (‘bulk’) RNA-seq data (NCBI Gene Expression Omnibus: GSE80172) with classification of labour into four groups, each compared to the same non-labour group, identified more DEGs for early than established labour; ROM was the strongest up-regulator of DEGs. We propose that lower DEGs frequency for early labour and/or ROM negative myometrium was attributed to bulk RNA-seq limitations associated with tissue heterogeneity, as well as the possibility that processes other than gene transcription are of more importance at labour onset. Integrative analysis with future data from additional samples, which have at least equivalent refined clinical classification for labour status, and alternative omics approaches will help to explain what truly contributes to transcriptomic changes that are critical for labour onset. Lastly, we identified five DEGs common to all labour groupings; two of which (AREG and PER3) were validated by qPCR and not differentially expressed in placenta and choriodecidua.

The First Thousand Days: Kidney Health and Beyond

The global burden of chronic kidney disease (CKD) is rising. A superior strategy to advance global kidney health is required to prevent and treat CKD early. Kidney development can be impacted during the first 1000 days of life by numerous factors, including malnutrition, maternal illness, exposure to chemicals, substance abuse, medication use, infection, and exogenous stress. In the current review, we summarize environmental risk factors reported thus far in clinical and experimental studies relating to the programming of kidney disease, and systematize the knowledge on common mechanisms underlying renal programming. The aim of this review is to discuss the primary and secondary prevention actions for enhancing kidney health from pregnancy to age 2. The final task is to address the potential interventions to target renal programming through updating animal studies. Together, we can enhance the future of global kidney health in the first 1000 days of life.

Circadian Clock-Controlled Checkpoints in the Pathogenesis of Complex Disease

The circadian clock coordinates physiology, metabolism, and behavior with the 24-h cycles of environmental light. Fundamental mechanisms of how the circadian clock regulates organ physiology and metabolism have been elucidated at a rapid speed in the past two decades. Here we review circadian networks in more than six organ systems associated with complex disease, which cluster around metabolic disorders, and seek to propose critical regulatory molecules controlled by the circadian clock (named clock-controlled checkpoints) in the pathogenesis of complex disease. These include clock-controlled checkpoints such as circadian nuclear receptors in liver and muscle tissues, chemokines and adhesion molecules in the vasculature. Although the progress is encouraging, many gaps in the mechanisms remain unaddressed. Future studies should focus on devising time-dependent strategies for drug delivery and engagement in well-characterized organs such as the liver, and elucidating fundamental circadian biology in so far less characterized organ systems, including the heart, blood, peripheral neurons, and reproductive systems.

Circadian misalignment measured by social jetlag from early to late pregnancy and its association with nutritional status: a longitudinal study

A mismatch between circadian and social clocks leads to a circadian misalignment, which has been widely measured by social jetlag (SJL). There are several studies measuring SJL, but it has not been studied in pregnant women. Therefore, this study aimed to identify the occurrence of SJL throughout pregnancy and to verify whether there is an effect of pre-pregnancy body mass index (BMI) on SJL throughout pregnancy. The baseline of the present study was conducted with 205 1st trimester pregnant women of whom 100 were followed in their 2nd and 3rd trimester. SJL was calculated based on the absolute difference between mid-sleep time on workdays versus work-free days. The pre-pregnancy BMI and current BMI (kg/m²) were calculated. Linear regression and Generalised Estimating Equation (GEE) adjusted for confounders were used to determine the association between SJL and the gestational trimesters (time), and anthropometric variables. Most of the pregnant women (54.5%) presented SJL > 1 h in the first gestational trimester. We also found an isolated effect of the gestation trimester on the SJL mean. In this sense, pregnant women had a decrease in SJL from the second to the third trimester (1.33 ± 0.08 versus 1.12 ± 0.07, respectively; p = 0.012). GEE analyzes showed that pregnant women of a normal weight showed a decrease in SJL from the second to the third trimester (1.29 ± 0.11 and 0.93 ± 0.08, respectively, p = 0.032), but this was not found in the other groups of nutritional status (underweight, overweight and obesity). In addition, a positive association between SJL and pre-gestational BMI in the third trimester (β = 0.200, p = 0.046) was found. SJL is quite prevalent during the gestational period and excessive BMI both before and during pregnancy is associated with an increased risk of having SJL > 1 h in the third and second trimesters, respectively. In addition, pregnant women of normal weight—but not underweight or overweight—had decreased SJL from the second to the third trimester.

Occupational Risk Factors and Hypertensive Disorders in Pregnancy: A Systematic Review

Hypertensive disorders in pregnancy (HDP), including gestational hypertension (GH) and preeclampsia (PE), characterize a major cause of maternal and prenatal morbidity and mortality. In this systematic review, we tested the hypothesis that occupational factors would impact the risk for HDP in pregnant workers. MEDLINE, Scopus, and Web of Knowledge databases were searched for studies published between database inception and 1 April 2021. All observational studies enrolling > 10 pregnant workers and published in English were included. Un-experimental, non-occupational human studies were excluded. Evidence was synthesized according to the risk for HDP development in employed women, eventually exposed to chemical, physical, biological and organizational risk factors. The evidence quality was assessed through the Newcastle–Ottawa scale. Out of 745 records identified, 27 were eligible. No definite conclusions could be extrapolated for the majority of the examined risk factors, while more homogenous data supported positive associations between job-strain and HDP risk. Limitations due to the lack of suitable characterizations of workplace exposure (i.e., doses, length, co-exposures) and possible interplay with personal issues should be deeply addressed. This may be helpful to better assess occupational risks for pregnant women and plan adequate measures of control to protect their health and that of their children.

Maternal effects in mammals: Broadening our understanding of offspring programming

The perinatal period is a sensitive time in mammalian development that can have long-lasting consequences on offspring phenotype via maternal effects. Maternal effects have been most intensively studied with respect to two major conditions: maternal diet and maternal stress. In this review, we shift the focus by discussing five major additional maternal cues and their influence on offspring phenotype: maternal androgen levels, photoperiod (melatonin), microbiome, immune regulation, and milk composition. We present the key findings for each of these topics in mammals, their mechanisms of action, and how they interact with each other and with the maternal influences of diet and stress. We explore their impacts in the contexts of both predictive adaptive responses and the developmental origins of disease, identify knowledge gaps and research opportunities in the field, and place a particular emphasis on the application and consideration of these effects in non-model species and natural ecological systems.

Maternal pineal melatonin in gestation and lactation physiology, and in fetal development and programming

Pregnancy and lactation are reproductive processes that rely on physiological adaptations that should be timely and adequately triggered to guarantee both maternal and fetal health. Pineal melatonin is a hormone that presents daily and seasonal variations that synchronizes the organism's physiology to the different demands across time through its specific mechanisms and ways of action. The reproductive system is a notable target for melatonin as it actively participates on reproductive physiology and regulates the hypothalamus-pituitary-gonads axis, influencing gonadotropins and sexual hormones synthesis and release. For its antioxidant properties, melatonin is also vital for the oocytes and spermatozoa quality and viability, and for blastocyst development. Maternal pineal melatonin blood levels increase during pregnancy and triggers the maternal physiological alterations in energy metabolism both during pregnancy and lactation to cope with the energy demands of both periods and to promote adequate mammary gland development. Moreover, maternal melatonin freely crosses the placenta and is the only source of this hormone to the fetus. It importantly times the conceptus physiology and influences its development and programing of several functions that depend on neural and brain development, ultimately priming adult behavior and energy and glucose metabolism. The present review aims to explain the above listed melatonin functions, including the potential alterations observed in the progeny gestated under maternal chronodisruption and/or hypomelatoninemia.

Maternal Chronodisruption Throughout Pregnancy Impairs Glucose Homeostasis and Adipose Tissue Physiology in the Male Rat Offspring

Compelling evidence in rats support the idea that gestational chronodisruption induces major changes in maternal circadian rhythms and fetal development and that these changes impact adult life at many physiological levels. Using a model of chronic photoperiod shifting throughout gestation (CPS), in which pregnant female rats (Sprague-Dawley strain; n = 16 per group) were exposed to lighting schedule manipulation every 3-4 days reversing the photoperiod completely or light/dark photoperiod (12/12; LD), we explored in the adult rat male offspring body weight gain, glucose homeostasis, adipose tissue content, adipose tissue response to norepinephrine (NE), and adipose tissue proteomic in the basal condition with standard diet (SD) and in response to high-fat diet (HFD). In adult CPS male (100-200 days old; n = 8 per group), we found increasing body weight, under SD and adiposity. Also, we found an increased response to intraperitoneal glucose (IGTT). After 12 weeks of HFD, white adipose tissue depots in CPS offspring were increased further, and higher IGTT and lower intraperitoneal insulin tolerance response were found, despite the lack of changes in food intake. In in vitro experiments, we observed that adipose tissue (WAT and BAT) glycerol response to NE from CPS offspring was decreased, and it was completely abolished by HFD. At the proteomic level, in CPS adipose tissue, 275 proteins displayed differential expression, compared with LD animals fed with a standard diet. Interestingly, CPS offspring and LD fed with HFD showed 20 proteins in common (2 upregulated and 18 downregulated). Based on these common proteins, the IPA analysis found that two functional pathways were significantly altered by CPS: network 1 (AKT/ERK) and network 2 (TNF/IL4; data are available via ProteomeXchange with identifier PXD026315). The present data show that gestational chronodisruption induced deleterious effects in adipose tissue recruitment and function, supporting the idea that adipose tissue function was programmed in utero by gestational chronodisruption, inducing deficient metabolic responses that persist into adulthood.

[Pregnancy outcomes in medical residents: An observational study]

OBJECTIVE

To describe the working conditions during pregnancy of medical residents. To describe adverse outcomes and to identify professional factors associated with these outcomes.

METHODS

This observational study described the working conditions during pregnancy of medical residents and the outcomes. An online questionnaire was sent to the 773 residents, of all specialties, enrolled in medical school in Nancy, France.

RESULTS

Three hundred and one residents participated in the study (38,9 %). The average daily working time of students was closed to 9hours, regardless the trimester, with a break time that rarely exceed one hour. Residents said continued to be on call beyond 10 weeks of gestation in 87.5 % of cases, the legal term for stopping these. The rate of adverse outcomes was 42.6 % (23/54). The rates of preterm labors and preterm births were 22.5 % and 15 % respectively. A significant association was found between working more than 10hours per day during 2nd trimester and adverse outcomes.

CONCLUSION

A strengthening of health monitoring at work with adaptation of workstation, information campaigns, as well as the designation of resource persons within the faculties seem essential.

Association between night-shift work, sleep quality and health-related quality of life: a cross-sectional study among manufacturing workers in a middle-income setting

OBJECTIVES

Night-shift work may adversely affect health. This study aimed to determine the impact of night-shift work on health-related quality of life (HRQoL), and to assess whether sleep quality was a mediating factor.

DESIGN

A cross-sectional study.

SETTING

11 manufacturing factories in Malaysia.

PARTICIPANTS

177 night-shift workers aged 40-65 years old were compared with 317 non-night-shift workers.

PRIMARY AND SECONDARY OUTCOMES

Participants completed a self-administered questionnaire on socio-demographics and lifestyle factors, 12-item Short Form Health Survey V.2 (SF-12v2) and the Pittsburgh Sleep Quality Index (PSQI). The Baron and Kenny's method, Sobel test and multiple mediation model with bootstrapping were applied to determine whether PSQI score or its components mediated the association between night-shift work and HRQoL.

RESULTS

Night-shift work was associated with sleep impairment and HRQoL. Night-shift workers had significantly lower mean scores in all the eight SF-12 domains (p<0.001). Compared with non-night-shift workers, night-shift workers were significantly more likely to report poorer sleep quality, longer sleep latency, shorter sleep duration, sleep disturbances and daytime dysfunction (p<0.001). Mediation analyses showed that PSQI global score mediated the association between night-shift work and HRQoL. 'Subjective sleep quality' (indirect effect=-0.24, SE=0.14 and bias corrected (BC) 95% CI -0.58 to -0.01) and 'sleep disturbances' (indirect effect=-0.79, SE=0.22 and BC 95% CI -1.30 to -0.42) were mediators for the association between night-shift work and physical well-being, whereas 'sleep latency' (indirect effect=-0.51, SE=0.21 and BC 95% CI -1.02 to -0.16) and 'daytime dysfunction' (indirect effect=-1.11, SE=0.32 and BC 95% CI -1.86 to -0.58) were mediators with respect to mental well-being.

CONCLUSION

Sleep quality partially explains the association between night-shift work and poorer HRQoL. Organisations should treat the sleep quality of night-shift workers as a top priority area for action to improve their employees' overall wellbeing.

Association between maternal shift work and infant neurodevelopmental outcomes: results from the Taiwan Birth Cohort Study with propensity-score-matching analysis

BACKGROUND

Maternal shift work is associated with preterm delivery, small-for-gestational-age new-borns, childhood obesity and future behavioural problems. However, the adverse effects on and interactions of maternal shift work with infant neurodevelopment remain uncertain. Therefore, we examined the associations between maternal-shift-work status and infant neurodevelopmental parameters.

METHODS

The Taiwan Birth Cohort Study is a nationwide birth cohort study following representatively sampled mother-infant pairs in 2005. The participants' development and exposure conditions were assessed by home interviews with structured questionnaires at 6 and 18 months of age. Propensity scores were calculated with predefined covariates for 1:1 matching. Multivariate conditional logistic regression and the Cox proportional-hazards model were used to examine the association between maternal-shift-work status and infant neurodevelopmental-milestone-achievement status.

RESULTS

In this study, 5637 term singletons were included, with 2098 cases selected in the propensity-score-matched subpopulation. Persistent maternal shift work was associated with increased risks of delays in gross-motor neurodevelopmental milestones [aOR = 1.36, 95% confidence interval (CI) = 1.06-1.76 for walking steadily], fine-motor neurodevelopmental milestones (aOR = 1.39, 95% CI = 1.07-1.80 for scribbling) and social neurodevelopmental milestones (aOR = 1.35, 95% CI = 1.03-1.76 for coming when called upon). Moreover, delayed gross-motor and social development were identified in the propensity-score-matched sub-cohort.

CONCLUSIONS

This study shows negative associations between maternal shift work and delayed neurodevelopmental-milestone achievement in the gross-motor, fine-motor and social domains at 18 months. Future research is necessary to elucidate the possible underlying mechanisms and long-term health effects.

Night shift work surrounding pregnancy and offspring risk of atopic disease

BACKGROUND

Night shift work surrounding pregnancy may contribute to the risk of developing atopic diseases in offspring due to alterations in the prenatal environment, from stress.

OBJECTIVE

To examine the association of maternal night shift work surrounding pregnancy and offspring risk of developing atopic diseases from childhood to adolescence.

METHODS

We examined the association between night shift work before and during pregnancy among 4,044 mothers in the Nurses' Health Study II (NHSII) and atopic dermatitis, asthma and hay fever risk in 4,813 of their offspring enrolled in the Growing Up Today Study (GUTS). Mothers reported whether GUTS participants had ever been diagnosed with atopic dermatitis, asthma or hay fever in the GUTS Mothers' questionnaire. Generalized estimating equation regression models were used to estimate multivariable adjusted odds ratios (OR) and 95% confidence intervals (CIs).

RESULTS

There were no significant associations between pre-conception maternal night shift work and risk of atopic dermatitis, asthma or hay fever in their offspring. Among 545 mothers with information on night shift work during pregnancy, shift work also was not associated with atopic dermatitis, asthma or hay fever in the offspring. Stratified analyses by history of parental atopy and maternal chronotype showed some statistically significant findings, but they were inconsistent and no significant interaction was seen with increasing duration of night shift work.

CONCLUSION

In this study, night shift work before and during pregnancy did not increase offspring risk of developing atopic dermatitis, asthma or hay fever.

Shift work and long work hours and their association with chronic health conditions: A systematic review of systematic reviews with meta-analyses

Background

Previous reviews have demonstrated that shift work and long work hours are associated with increased risk for chronic conditions. However, these reviews did not comprehensively assessed the body of evidence, and some were not conducted in a systematic manner. A better understanding of the health consequences of shift work and long work hours will aid in creating policy and practice recommendations. This review revisits the epidemiologic evidence on the association of shift work and long work hours with chronic conditions with particular emphasis on assessing the quality of the evidence.

Methods and findings

We conducted a systematic review of systematic reviews with meta-analyses (SR-MA) that assessed the link between shift work or long work hours and chronic conditions (PROSPERO CRD42019122084). We evaluated the risk of bias of each SR-MA using AMSTAR v2 and assessed the overall evidence for each condition using the GRADE approach. We included 48 reviews covering cancers, cardiovascular diseases, metabolic syndrome and related conditions, pregnancy complications, depression, hypertension, and injuries. On average, only 7 of 16 AMSTAR items were fulfilled. Few SR-MAs had a registered protocol and nearly all failed to conduct a comprehensive search. We found moderate grade evidence linking shift work to breast cancer and long work hours to stroke. We found low grade evidence linking both shift work and long work hours with low to moderate increase in risk for some pregnancy complications and cardiovascular diseases. Low grade evidence also link long work hours and depression.

Conclusions

Moderate grade evidence suggest that shift work and long work hours increase the risk of breast cancer and stroke, but the evidence is unclear on other chronic conditions. There is a need for high-quality studies to address this gap. Stakeholders should be made aware of these increased risks, and additional screening and prevention should be considered, particularly for workers susceptible to breast cancer and stroke.

Light and Circadian Signaling Pathway in Pregnancy: Programming of Adult Health and Disease

Light is a crucial environmental signal that affects elements of human health, including the entrainment of circadian rhythms. A suboptimal environment during pregnancy can increase the risk of offspring developing a wide range of chronic diseases in later life. Circadian rhythm disruption in pregnant women may have deleterious consequences for their progeny. In the modern world, maternal chronodisruption can be caused by shift work, jet travel across time zones, mistimed eating, and excessive artificial light exposure at night. However, the impact of maternal chronodisruption on the developmental programming of various chronic diseases remains largely unknown. In this review, we outline the impact of light, the circadian clock, and circadian signaling pathways in pregnancy and fetal development. Additionally, we show how to induce maternal chronodisruption in animal models, examine emerging research demonstrating long-term negative implications for offspring health following maternal chronodisruption, and summarize current evidence related to light and circadian signaling pathway targeted therapies in pregnancy to prevent the development of chronic diseases in offspring.

Association between shift work and poor sleep quality in an Asian multi-ethnic working population: A cross-sectional study

BACKGROUND

We aimed to examine the association between shift work and sleep quality in a diverse occupational type.

METHODS

This was a cross-sectional study of self-reported sleep quality in 424 workers aged ≥21 using the Pittsburgh Sleep Quality Index (PSQI). We divided workers into two categories based on their PSQI score: (a) ≤5 (good sleep quality) and (b) >5 (poor sleep quality). We used multiple logistic regressions to assess the association between shift work and sleep quality adjusted for potential confounders.

RESULTS

The mean age was 39.2 (SD = 11.3) years, with shift workers being older than their counterparts. Most workers were of Chinese ethnicity (63.9%). Males were significantly more likely to undertake shift work than females (89% v 11%, p-value<0.001), but it should be noted that the majority of workers was male (78.8%) in this sample of workers. Shift workers had a 198% increased odds of poor sleep quality compared to non-shift workers (OR = 2.98; 95% CI:1.53-5.81).

CONCLUSION

Shift work was significantly and independently associated with increased odds of poor sleep quality in this sample of workers. The present findings may inform employment guidelines and help develop workplace health promotion interventions aimed at improving sleep quality among workers and ultimately lead to a healthier workforce.

Pregnancy rest-activity patterns are related to salivary cortisol rhythms and maternal-fetal health indicators in women from a disadvantaged population

Irregular rest-activity patterns can disrupt metabolic and hormonal physiology and potentially lead to disease. Little is known regarding rest-activity patterns during gestation and their association with hormonal rhythms and health in pregnant women. We conducted a pilot study to determine if 24 h rest-activity was related to saliva cortisol rhythms and maternal-fetal health in an economically disadvantaged population. Primiparous women wore a wrist actigraphy device for a week to record activity during gestational weeks 22 (G22; n = 50) and 32 (G32; n = 46) and postpartum week one (PPW1; n = 39). Participants collected saliva samples every 4 hr over a 24 hr period during G22 (n = 22), G32 (n = 20) and 24–48 hr postnatal (n = 20), and cortisol concentrations were measured with ELISA. Circadian rhythmicity was assessed using autocorrelation coefficient (r24) and cosinor analysis. Blood glucose levels, body mass index (BMI), gestational disease data, and gestational age of infant at birth were abstracted from medical charts. Time of cortisol peak (acrophase) during G22 was related with acrophase of activity (r = 0.66; p = 0.001) and blood glucose levels (r = 0.58; p = 0.006). During G22, minutes of wake after sleep onset was positively related to cortisol mesor and AUC (p <0.05). Rest-activity r24, R², and mesor during G32 were positively (p<0.05) associated with gestational age of infant at birth. Across all three time points r24 of activity was related with cortisol amplitude (r = 0.33; p = 0.01). Findings support a relationship between rest-activity patterns and saliva cortisol rhythms during pregnancy. The association of less robust activity rhythms with earlier gestational age of infant at birth indicates a potential link between circadian system disruption and maternal-fetal health outcomes.

The effect of prenatal maternity leave on short and long-term child outcomes

Maternity leave policies are designed to safeguard the health of pregnant workers and their unborn children. We evaluate a maternity leave extension in Austria which increased mandatory prenatal leave from 6 to 8 weeks. We exploit that the assignment to the extended leave was determined by a cutoff date. We find no evidence for significant effects of this extension on children's health at birth or long-term health and labor market outcomes. Subsequent maternal health and fertility are also unaffected. We conclude that employment during the 33rd and 34th week of gestation is not harmful for expecting mothers (without major problems in pregnancy) and their unborn children.

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.

"It's not easy" - A qualitative study of lifestyle change during pregnancy

BACKGROUND

Maternal lifestyle in the months leading up to conception and throughout pregnancy has both immediate and transgenerational impacts on offspring health.

AIM

To explore how women's lifestyles change when they become pregnant, and their perspectives of the lifestyle advice they receive throughout pregnancy.

METHODS

A descriptive qualitative approach was used. Semi-structured interviews with 17 childbearing women (mean gestational age, 30.2 ± 2.0 weeks) recruited from a large hospital network in Victoria, Australia between July and October 2018 were transcribed and analysed using an inductive process of thematic analysis.

FINDINGS

Three themes and six sub-themes were identified. Lifestyle change during pregnancy was highly influenced by participants' preconception lifestyle, the physiological demands of pregnancy and the pressures of daily life. While participants proactively sought lifestyle advice from a range of sources, including the Internet, they were generally less proactive in seeking advice during routine maternity care visits. Participants appreciated the lifestyle advice they received from health professionals, including midwives, as part of their maternity care despite acknowledging that they often received it only if they asked. Overall, it seemed that the lifestyle advice received from health professionals was much less influential on maternal lifestyle behaviour change than the broader socio-ecological environment.

CONCLUSION

Childbearing women want lifestyle advice that supports positive lifestyle change during pregnancy and health professionals, including midwives, must be proactive as they provide it. Other factors that impact on childbearing women's capability and opportunity to make lifestyle change should be considered when providing advice that supports positive lifestyle behaviour change.

Later sleep timing is associated with an increased risk of preterm birth in nulliparous women

BACKGROUND

Although uterine contractions have a diurnal periodicity and increase in frequency during hours of darkness, data on the relationship between sleep duration and sleep timing patterns and preterm birth are limited.

OBJECTIVE

We sought to examine the relationship of self-reported sleep duration and timing in pregnancy with preterm birth.

STUDY DESIGN

In the prospective Nulliparous Pregnancy Outcome Study: Monitoring Mothers-to-be cohort, women completed a survey of sleep patterns at 6-13 weeks gestation (visit 1) and again at 22-29 weeks gestation (visit 3). Additionally, at 16-21 weeks gestation (visit 2), a subgroup completed a weeklong actigraphy recording of their sleep. Weekly averages of self-reported sleep duration and sleep midpoint were calculated. A priori, sleep duration of <7 hours was defined as "short," and sleep midpoint after 5 am was defined as "late." The relationships among these sleep characteristics and all preterm birth and spontaneous preterm birth at <37 weeks gestation were examined in univariate analyses. Multivariable logistic regressions that controlled for age and body mass index alone (model 1) and with additional covariates (race, smoking, insurance, and employment schedule) following a backward elimination process (model 2) were performed.

RESULTS

Of the 10,038 women who were enrolled, sleep survey data were available on 7524 women at visit 1 and 7668 women at visit 3. The rate of short sleep duration was 17.1% at visit 1 and 20.7% at visit 3. The proportion with a late sleep midpoint was 11.6% at visit 1 and 12.2% at visit 3. There was no significant relationship between self-reported short sleep and preterm birth across all visits. However, self-reported late sleep midpoint (>5 am) was associated with preterm birth . Women with a late sleep midpoint (>5 am) in early pregnancy had a preterm birth rate of 9.5%, compared with 6.9% for women with sleep midpoint ≤5 am (P=.005). Similarly, women with a late sleep midpoint had a higher rate of spontaneous preterm birth (6.2% vs 4.4%; P=.019). Comparable results were observed for women with a late sleep midpoint at visit 3 (all preterm birth 8.9% vs 6.6%; P=.009; spontaneous preterm birth 5.9% vs 4.3%; P=.023). All adjusted analyses on self-reported sleep midpoint (models 1 and 2) maintained statistical significance (P<.05), except for visit 1, model 2 for spontaneous preterm birth (P=.07). The visit 2 objective data from the smaller subgroup (n=782) demonstrated similar trends in preterm birth rates by sleep midpoint status.

CONCLUSION

Self-reported late sleep midpoint in both early and late pregnancy, but not short sleep duration, is associated with an increased rate of preterm birth.

The psychological and physiological health effects of fatigue

Background

The issue of employee fatigue is becoming increasingly prominent, particularly in safety-critical industries.

Aims

To produce an in-depth review collating the known psychological and physiological health and work effects of fatigue to guide mitigation strategies in safety-critical industries.

Methods

Literature searches were conducted via scientific databases using appropriate filters and keywords. The available results were collated into a review and commentary.

Results

Decreased sleep duration and chronodisruption have been shown to cause both significant morbidity and mortality. There is a large body of evidence showing strong associations between fatigue, reduced cognition and occupational accidents, as well as increased metabolic and reproductive health sequelae, some forms of cancer and mortality. Additional evidence links fatigue with mental, gastrointestinal, neurological and chronic pain sequelae.

Conclusions

Fatigue risk mitigation strategies should be implemented, not only to reduce these short- and long-term health risks in employees of safety-critical industries, but also to create more efficient, productive and effective workplace personnel with longer and more fulfilling careers. This requires improved acute fatigue mitigation, as well as the prevention of cumulative fatigue build-up and the formation of acute-on-chronic fatigue. The health recommendations for fatigue mitigation outlined in this paper are pertinent to all professions where employees have high rates of both acute and chronic fatigue.

The usefulness of melatonin in the field of obstetrics and gynecology

Disorders of the female reproductive system, including those associated with hormone regulation, fertility rate and fetal health, are issues of great concern worldwide. More recently, melatonin supplementation has been suggested as a therapeutic approach in gynecological practice. In both animal models and in women, melatonin supplementation suggests a therapeutic and preventative potential, effects attributed mainly to its antioxidant properties and action as hormone modulator. The aim of this literature review is to further investigate the evidence available on the effects of melatonin supplementation in animal and human studies, focusing on its potential application to gynecology. Melatonin-containing supplements are easily found in online and high street retailers, and despite its supplementation deemed to be relatively safe, no consensus has been reached on effective dosage and supplementation period. Short term supplementation studies, of up to six months, suggest that a daily posology of 2-18 mg of melatonin may have the potential to improve fertility rate, oocyte quality, maturation and number of embryos. However, the evidence available so far on the effects of melatonin supplementation covering gestational age and gestational outcomes is very scarce. Clinical trials and longer-term supplementation studies are required to assess any clinical outcome associated with melatonin supplementation in the field of gynecology.

Pregnancy Induces an Earlier Chronotype in Both Mice and Women

Daily rhythms generated by endogenous circadian mechanisms and synchronized to the light-dark cycle have been implicated in the timing of birth in a wide variety of species. Although chronodisruption (e.g., shift work or clock gene mutations) is associated with poor reproductive outcomes, little is known about circadian timing during pregnancy. This study tested whether daily rhythms change during full-term pregnancies in mice and women. We compared running wheel activity continuously in both nonpregnant ( n = 14) and pregnant ( n = 13) 12- to 24-week-old C57BL/6NJ mice. We also monitored wrist actigraphy in women ( N = 39) for 2 weeks before conception and then throughout pregnancy and measured daily times of sleep onset. We found that on the third day of pregnancy, mice shift their activity to an earlier time compared with nonpregnant dams. Their time of daily activity onset was maximally advanced by almost 4 h around day 7 of pregnancy and then shifted back to the nonpregnant state approximately 1 week before delivery. Mice also showed reduced levels of locomotor activity during their last week of pregnancy. Similarly, in women, the timing of sleep onset was earlier during the first and second trimesters (gestational weeks 4-13 and 14-27) than before pregnancy and returned to the prepregnant state during the third trimester (weeks 28 until delivery). Women also showed reduced levels of locomotor activity throughout pregnancy. These results indicate that pregnancy induces changes in daily rhythms, altering both time of onset and amount of activity. These changes are conserved between mice and women.

Night work during pregnancy and preterm birth-A large register-based cohort study

BACKGROUND

Melatonin stimulates the production of progesterone, which is essential for the maintenance of pregnancy. Since melatonin in blood is reduced due to work under illuminated conditions during night work, it has been hypothesized that night work may increase the risk of preterm birth. Previous meta-analyses have not revealed increased risk of preterm birth in women working night shifts during pregnancy. Still, these studies might have been limited by inaccurate self-reports of timing, intensity and duration of night work most likely causing bias towards the null. The aim of this is study was to investigate if the frequency and duration of night work during the first (week 1-12) and second (week 13-22) trimester of pregnancy were associated with risk of preterm birth when objective and prospective data on night work are used.

METHOD

In a register-based prospective cohort study, we obtained individual day-to-day information on working hours from The Danish Working Hour Database (DWHD, a payroll database including all public service employees in administrative Danish Regions from 2007-2013) and information on preterm birth from the Danish Medical Birth Registry. Night-shift was defined as at least three working hours between 23:00 and 06:00. Preterm birth was defined as giving birth during gestational weeks 23-37. Odds of preterm birth according to working night shifts were analysed by logistic regression.

RESULTS

We identified 16,501 pregnant women eligible for the study, of which 10,202 women (61.8%) had at least one night-shift during the first 22 gestational weeks. The risk of preterm birth was not elevated among women working night shifts compared to women working only day shifts during either the first or second trimester. Within night-shift workers, the risk was not related to the number of night shifts, the duration of night shifts, consecutive night shifts or quick returns defined as short intervals between shifts. Odds of preterm birth was not related to change of working schedule from the first to second trimester, although women changing from night shifts in the first trimester to day work only in the second trimester displayed a weak increased odds of preterm birth (OR 1.21, 95%CI 0.98-1.49) compared to women working night shifts in both trimesters.

CONCLUSION

Our results, which are without bias from self-report of either exposure or outcome, are in line with the results of previous meta-analyses. Due to the detailed information on hours worked during pregnancy, we were able to investigate several dimensions of night work not previously investigated, of which none were associated with elevated risk of preterm birth.