Work activity in pregnancy, preventive measures, and the risk of delivering a small-for-gestational-age infant

Environmental and socio-economic determinants of infant mortality in Poland: an ecological study

BACKGROUND

Health status of infants is related to the general state of health of women of child-bearing age; however, women's occupational environment and socio-economic conditions also seem to play an important role. The aim of the present ecological study was to assess the relationship between occupational environment, industrial pollution, socio-economic status and infant mortality in Poland.

METHODS

Data on infant mortality and environmental and socio-economic characteristics for the 66 sub-regions of Poland for the years 2005-2011 were used in the analysis. Factor analysis was used to extract the most important factors explaining total variance among the 23 studied exposures. Generalized Estimating Equations model was used to evaluate the link between infant mortality and the studied extracted factors.

RESULTS

Marked variation for infant mortality and the characteristics of industrialization was observed among the 66 sub-regions of Poland. Four extracted factors: "poor working environment", "urbanization and employment in the service sector", "industrial pollution", "economic wealth" accounted for 77.3% of cumulative variance between the studied exposures. In the multivariate regression analysis, an increase in factor "poor working environment" of 1 SD was related to an increase in infant mortality of 40 (95% CI: 28-53) per 100,000 live births. Additionally, an increase in factor "industrial pollution" of 1 SD was associated with an increase in infant mortality of 16 (95% CI: 2-30) per 100,000 live births. The factors "urbanization and employment in the service sector" and "economic wealth" were not significantly related to infant mortality.

CONCLUSION

The study findings suggested that, at the population level, infant mortality was associated with an industrial environment. Strategies to improve working conditions and reduce industrial pollution might contribute to a reduction in infant mortality in Poland.

Environmental control of biological rhythms: effects on development, fertility and metabolism

Internal temporal organisation properly synchronised to the environment is crucial for health maintenance. This organisation is provided at the cellular level by the molecular clock, a macromolecular transcription-based oscillator formed by the clock and the clock-controlled genes that is present in both central and peripheral tissues. In mammals, melanopsin in light-sensitive retinal ganglion cells plays a considerable role in the synchronisation of the circadian timing system to the daily light/dark cycle. Melatonin, a hormone synthesised in the pineal gland exclusively at night and an output of the central clock, has a fundamental role in regulating/timing several physiological functions, including glucose homeostasis, insulin secretion and energy metabolism. As such, metabolism is severely impaired after a reduction in melatonin production. Furthermore, light pollution during the night and shift work schedules can abrogate melatonin synthesis and impair homeostasis. Chronodisruption during pregnancy has deleterious effects on the health of progeny, including metabolic, cardiovascular and cognitive dysfunction. Developmental programming by steroids or steroid-mimetic compounds also produces internal circadian disorganisation that may be a significant factor in the aetiology of fertility disorders such as polycystic ovary syndrome. Thus, both early and late in life, pernicious alterations of the endogenous temporal order by environmental factors can disrupt the homeostatic function of the circadian timing system, leading to pathophysiology and/or disease.

Reproductive outcomes associated with noise exposure - a systematic review of the literature

Introduction: High noise exposure during critical periods in gestation is a potential stressor that may result in increased risk of implantation failure, dysregulation of placentation or decrease of uterine blood flow. This paper systematically reviews published evidence on associations between reproductive outcomes and occupational and environmental noise exposure. Methods: The Web of Science, PubMed and Embase electronic databases were searched for papers published between 1970 to June 2014 and via colleagues. We included 14 epidemiological studies related to occupational noise exposure and nine epidemiological studies related to environmental noise exposure. There was some evidence for associations between occupational noise exposure and low birthweight, preterm birth and small for gestational age, either independently or together with other occupational risk factors. Five of six epidemiologic studies, including the two largest studies, found significant associations between lower birthweight and higher noise exposure. There were few studies on other outcomes and study design issues may have led to bias in assessments in some studies. Conclusions: There is evidence for associations between noise exposure and adverse reproductive outcomes from animal studies. Few studies in have been conducted in humans but there is some suggestive evidence of adverse associations with environmental noise from both occupational and epidemiological studies, especially for low birthweight.

An exploratory spatial analysis to assess the relationship between deprivation, noise and infant mortality: an ecological study

BACKGROUND

Few studies have explored how noise might contribute to social health inequalities, and even fewer have considered infant mortality or its risk factors as the health event of interest.In this paper, we investigate the impact of neighbourhood characteristics - both socio-economic status and ambient noise levels - on the spatial distribution of infant mortality in the Lyon metropolitan area, in France.

METHODS

All infant deaths (n = 715) occurring between 2000 and 2009 were geocoded at census block level. Each census block was assigned multi-component socio-economic characteristics and Lden levels, which measure exposure to noise. Using a spatial-scan statistic, we examined whether there were significant clusters of high risk of infant mortality according to neighbourhood characteristics.

RESULTS

Our results highlight the fact that infant mortality is non-randomly distributed spatially, with clusters of high risk in the south-east of the Lyon metropolitan area (RR = 1.44; p = 0.09). After adjustments for socio-economic characteristics and noise levels, this cluster disappears or shifts according to in line with different scenarios, suggesting that noise and socio-economic characteristics can partially explain the spatial distribution of infant mortality.

CONCLUSION

Our findings show that noise does have an impact on the spatial distribution of mortality after adjustments for socio-economic characteristics. A link between noise and infant mortality seems plausible in view of the three hypothetical, non-exclusive, pathways we propose in our conceptual framework: (i) a psychological pathway, (ii) a physiological disruption process and (iii) an unhealthy behaviours pathway. The lack of studies makes it is difficult to compare our findings with others. They require further research for confirmation and interpretation.

Maternal and Perinatal Outcomes of Exercise in Pregnant Women with Chronic Hypertension and/or Previous Preeclampsia: A Randomized Controlled Trial

Objectives. To evaluate the association between physical exercise supervised in pregnant women with chronic hypertension and/or previous preeclampsia and maternal and neonatal outcomes. Method. Randomized controlled trial, which included 116 pregnant women with chronic hypertension and/or previous preeclampsia, considered risk of preeclampsia development. They were divided into two groups: study group that performed physical exercise with a stationary bicycle once a week, for 30 minutes; the intensity was controlled (heart rate 20% above resting values), under professional supervision and a control group that was not engaged in any physical exercise. The data was retrieved from medical charts. Significance level assumed was 5%. Results. Women from study group performed 9.24 ± 7.03 of physical exercise sessions. There were no differences between groups comparing type of delivery and maternal outcomes, including maternal morbidity and hospitalization in intensive unit care, and neonatal outcomes, including birth weight, adequacy of weight to gestational age, prematurity, Apgar scale at first and fifth minutes, hospitalization in intensive unit care, and neonatal morbidity. Conclusions. Physical exercise using a stationary bicycle in pregnant women with chronic hypertension and/or previous preeclampsia, once a week, under professional supervision, did not interfere in the delivery method and did not produce maternal and neonatal risks of the occurrence of morbidity. This trial is registered with ClinicalTrials.gov NCT01395342.

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.

Roles of melatonin in fetal programming in compromised pregnancies

Compromised pregnancies such as those associated with gestational diabetes mellitus, intrauterine growth retardation, preeclampsia, maternal undernutrition, and maternal stress may negatively affect fetal development. Such pregnancies may induce oxidative stress to the fetus and alter fetal development through the epigenetic process that may affect development at a later stage. Melatonin is an oxidant scavenger that reverses oxidative stress during the prenatal period. Moreover, the role of melatonin in epigenetic modifications in the field of developmental programming has been studied extensively. Here, we describe the physiological function of melatonin in pregnancy and discuss the roles of melatonin in fetal programming in compromised pregnancies, focusing on its involvement in redox and epigenetic mechanisms.

Impact of chronodisruption during primate pregnancy on the maternal and newborn temperature rhythms

Disruption of the maternal environment during pregnancy is a key contributor to offspring diseases that develop in adult life. To explore the impact of chronodisruption during pregnancy in primates, we exposed pregnant capuchin monkeys to constant light (eliminating the maternal melatonin rhythm) from the last third of gestation to term. Maternal temperature and activity circadian rhythms were assessed as well as the newborn temperature rhythm. Additionally we studied the effect of daily maternal melatonin replacement during pregnancy on these rhythms. Ten pregnant capuchin monkeys were exposed to constant light from 60% of gestation to term. Five received a daily oral dose of melatonin (250 µg kg/body weight) at 1800 h (LL+Mel) and the other five a placebo (LL). Six additional pregnant females were maintained in a 14∶10 light:dark cycles and their newborns were used as controls (LD). Rhythms were recorded 96 h before delivery in the mother and at 4-6 days of age in the newborn. Exposure to constant light had no effect on the maternal body temperature rhythm however it delayed the acrophase of the activity rhythm. Neither rhythm was affected by melatonin replacement. In contrast, maternal exposure to constant light affected the newborn body temperature rhythm. This rhythm was entrained in control newborns whereas LL newborns showed a random distribution of the acrophases over 24-h. In addition, mean temperature was decreased (34.0±0.6 vs 36.1±0.2°C, in LL and control, respectively P<0.05). Maternal melatonin replacement during pregnancy re-synchronized the acrophases and restored mean temperature to the values in control newborns. Our findings demonstrate that prenatal melatonin is a Zeitgeber for the newborn temperature rhythm and supports normal body temperature maintenance. Altogether these prenatal melatonin effects highlight the physiological importance of the maternal melatonin rhythm during pregnancy for the newborn primate.

Timed maternal melatonin treatment reverses circadian disruption of the fetal adrenal clock imposed by exposure to constant light

Surprisingly, in our modern 24/7 society, there is scant information on the impact of developmental chronodisruption like the one experienced by shift worker pregnant women on fetal and postnatal physiology. There are important differences between the maternal and fetal circadian systems; for instance, the suprachiasmatic nucleus is the master clock in the mother but not in the fetus. Despite this, several tissues/organs display circadian oscillations in the fetus. Our hypothesis is that the maternal plasma melatonin rhythm drives the fetal circadian system, which in turn relies this information to other fetal tissues through corticosterone rhythmic signaling. The present data show that suppression of the maternal plasma melatonin circadian rhythm, secondary to exposure of pregnant rats to constant light along the second half of gestation, had several effects on fetal development. First, it induced intrauterine growth retardation. Second, in the fetal adrenal in vivo it markedly affected the mRNA expression level of clock genes and clock-controlled genes as well as it lowered the content and precluded the rhythm of corticosterone. Third, an altered in vitro fetal adrenal response to ACTH of both, corticosterone production and relative expression of clock genes and steroidogenic genes was observed. All these changes were reversed when the mother received a daily dose of melatonin during the subjective night; supporting a role of melatonin on overall fetal development and pointing to it as a 'time giver' for the fetal adrenal gland. Thus, the present results collectively support that the maternal circadian rhythm of melatonin is a key signal for the generation and/or synchronization of the circadian rhythms in the fetal adrenal gland. In turn, low levels and lack of a circadian rhythm of fetal corticosterone may be responsible of fetal growth restriction; potentially inducing long term effects in the offspring, possibility that warrants further research.

Prevalence of exposure to occupational risks during pregnancy in Spain

OBJECTIVES

We describe reported exposures to main categories of occupational agents and conditions in Spanish pregnant workers.

METHODS

Women were recruited at 12th week of pregnancy from main public gynaecological consults to be included in the INMA Spanish cohorts study (n=2,058). Through personal interviews with structured questionnaires, information on working situation and working conditions during pregnancy was obtained.

RESULTS

Fifty percent of the women reported frequent exposure to physical load (standing, heavy lifting) and 45% reported exposure to three or more indicators of job strain. Exposure to at least one physical agent (noise, vibrations, etc.) affected 25% of the women. Exposure to chemicals was reported by 20% of the women, mostly including solvents and cleaning products. Eight percent of the women worked at night shifts. Job strain was more prevalent in office workers and industrial operators. Industrial workers showed the highest prevalence of exposure to chemical and physical pollutants.

CONCLUSIONS

Our data suggest that working conditions of pregnant women may need increased control in Spain.

Childbearing and pregnancy characteristics of female orthopaedic surgeons

BACKGROUND

The number of women entering orthopaedic surgery is steadily increasing. Information regarding pregnancy and childbearing is important to understand as it increasingly affects residency programs, clinical practices, and the female surgeons and their offspring.

METHODS

One thousand and twenty-one female surgeons completed an anonymous, voluntary, 199-item online survey distributed via individual female surgeon interest groups and word of mouth in nine specialties: general surgery, gynecology, neurosurgery, ophthalmology, orthopaedics, otolaryngology, plastic surgery, podiatry, and urology. Two hundred and twenty-three survey responses from orthopaedic surgeons were compared with those of the other surgical specialists as well as American Pregnancy Association national data to assess differences, if any, in pregnancy characteristics, demographics, and satisfaction.

RESULTS

The overall reported complication rate for all pregnancies among orthopaedic surgeons was significantly higher than the rate in the general American population (31.2% [eighty-two of 263] compared with 14.5%). There was an increased risk of preterm delivery among orthopaedic surgeons compared with a cohort of the general U.S. population matched according to age, race, health, and socioeconomic status (risk ratio, 2.5; 95% confidence interval [CI], 1.3 to 4.6). There was an increased risk of preterm labor and preterm delivery among women who reported working more than sixty hours per week (odds ratio, 4.95; 95% CI, 1.4 to 36.6). Female orthopaedic surgeons took shorter maternity leave during training than during clinical practice (median, four compared with seven weeks). The mean duration of breastfeeding was significantly shorter during training than during clinical practice (4.7 compared with 8.3 months, p = 0.03).

CONCLUSIONS

Female orthopaedic surgeons had an increased risk of pregnancy complications, particularly preterm delivery, compared with the general U.S. population. We found an increased risk of increased risk of preterm labor and delivery in surgeons working more than sixty hours per week during pregnancy.

Leisure-time physical activity in pregnancy and the birth weight distribution: where is the effect?

BACKGROUND

Leisure-time physical activity (LTPA) is recommended during pregnancy and has been associated with lower risk of delivering a large infant. We sought to characterize the effect of LTPA across the entire birth weight distribution.

METHODS

Women enrolled in the Pregnancy Outcomes and Community Health (POUCH) Study (1998-2004) were followed-up in 2007. Follow-up efforts were extensive for a subcohort and minimal for the remainder (nonsubcohort). Thus, 596 subcohort and 418 nonsubcohort women who delivered at term participated. Offspring were categorized as small-, appropriate-, or large-for-gestational-age (SGA, AGA, and LGA, respectively) based on gender and gestational age-specific birth weight z-scores (BWz). At follow-up, women recalled pregnancy LTPA and were classified as inactive, insufficiently active or meeting LTPA recommendations. Linear, logistic, and quantile regression analyses were conducted separately by subcohort status.

RESULTS

Meeting LTPA recommendations decreased odds of LGA significantly among the nonsubcohort (aOR = 0.30, 95% CI: 0.14-0.64) and nonsignificantly among the subcohort (aOR = 0.68, 95% CI: 0.34-1.34). In quantile regression, meeting LTPA recommendations reduced BWz among the upper quantiles in the nonsubcohort.

CONCLUSIONS

LTPA during pregnancy lowered odds of LGA and reduced BWz among the upper quantiles, without shifting the entire distribution. LTPA during pregnancy may be useful for reducing risks of large fetal size.

Grossesse et travail : au-delà des facteurs de risques pour la santé

Cet article met en lumière les risques pour la santé liés au travail des femmes en abordant la problématique de la conciliation travail-grossesse. Cette analyse adopte comme cadre de référence la division sexuelle du travail (Kergoat, 2004). Cette perspective analytique est rarement intégrée dans les études portant sur la santé des femmes au travail. Le contexte de pénurie de main d'oeuvre qui touche actuellement le Québec en raison du vieillissement de sa population active, et dans certains secteurs en raison de la pénibilité des conditions de travail, marque l'importance d'ajouter cette perspective dans l'analyse de la santé des femmes au travail. Pour les femmes, l'expérience vécue du travail durant la grossesse constitue l'élément annonciateur du degré d'acceptation de la part des milieux de travail et de la société québécoise des spécificités féminines au travail. L'article fait ressortir où en sont rendues les organisations sur ce plan, à travers l'étude du traitement des demandes de retrait préventif de la travailleuse enceinte, droit inclus au Québec dans la Loi sur la santé et sécurité au travail. Malgré des avancées significatives dans certains milieux, on constate encore la prédominance d'une logique gestionnaire traditionnelle et sexiste dans l'application du droit qui mène les travailleuses au retrait du travail durant leur grossesse. La recherche a été menée auprès d'employeurs, de représentants syndicaux et de travailleuses du secteur hospitalier.

Si le bruit rend sourd, rend-il nécessairement sourde ?

Au Québec, des données spécifiques concernant les conditions d’emploi, de travail et de rémunération des hommes et des femmes sont publiées régulièrement. Depuis peu, des données ventilées selon le sexe commencent à alimenter les efforts de prévention en santé au travail. Malgré ces progrès, certains défis techniques, idéologiques et politiques demeurent: allant des difficultés dans les calculs des populations à risque, à la réticence à adapter les postes de travail ou à adapter la formation à la spécificité biologique des femmes. La recherche sur la santé des femmes au travail a beaucoup progressé, mais il reste plusieurs étapes à franchir. Notons également que les spécificités associées au genre des hommes sont presqu'entièrement oubliées dans les études. Il est difficile de conserver un équilibre entre la protection de la santé et l’égalité des sexes dans la recherche et l’intervention en santé au travail. Pour assurer cet équilibre, la recherche doit se faire en collaboration avec les travailleuses et travailleurs. Ils peuvent ainsi contribuer à construire une base solide d’informations qui permettront aux gouvernements, aux organismes responsables de la prévention en santé au travail, aux employeurs et aux syndicats de tenir compte, dans leurs politiques, des besoins des deux sexes en santé au travail.

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.

Psychosocial work stress during pregnancy and birthweight

Although there is a growing interest in the health effects of psychosocial work stress, studies on the relationships between job stress and adverse reproductive outcome are limited. We, therefore, investigated the associations between prenatal maternal occupational stress and birthweight using 310 mother-infant pairs included in the Mothers and Children's Environmental Health (MOCEH) study. Information on job stress was collected by interviewing women at enrollment during the first trimester of pregnancy using standardised questionnaires, namely, the Job Content Questionnaire (JCQ) of job strain and effort-reward imbalance (ERI) questionnaires. Regression analyses were carried out. Decision latitude scores of the JCQ were found to be positively related to birthweight, while ERI ratios determined using the ERI model were found to be inversely related to gestational age. In addition, a passive job as defined by the job strain model was found to be associated with a lower birthweight, compared with a relaxed job. These results suggest that work-related psychosocial stress in pregnant women appears to affect birth outcomes, such as birthweight and gestational age.

Physical activity, health-related quality of life and depression during pregnancy

This study examines physical activity patterns among women, from pre-pregnancy to the second trimester of pregnancy, and the relationship between physical activity status based on physical activity guidelines and health-related quality of life (HRQoL) and depression over pregnancy. 56 healthy pregnant women self-reported physical activity, HRQoL and depression at 10-15 and 19-24 weeks of pregnancy and physical activity before pregnancy. Whereas vigorous leisure physical activity decreased after conception, moderate leisure physical activity and work related physical activity remained stable over time. The prevalence of recommended physical activity was 39.3% and 12.5% in the 1st and 2nd trimesters of pregnancy respectively, and 14.3% pre-pregnancy. From the 1st to the 2nd pregnancy trimester, most physical HRQoL dimensions scores decreased and only mental component increased, independently of physical activity status. No changes in mean depression scores were observed. These data suggest that physical activity patterns change with pregnancy and that physical and mental components are differentially affected by pregnancy course, independently of physical activity status.

Occupational hazards for pregnant nurses

OVERVIEW

Depending on her working environment, specific immunities, and stage of pregnancy, a pregnant nurse may find it difficult to avoid teratogenic and fetotoxic exposures, as well as working conditions that could jeopardize her pregnancy. A clinical review of the occupational hazards faced by pregnant nurses can be useful to the concerned nurse or health care system, as can suggestions on ways to reduce risk and a list of pertinent occupational safety resources.

Maternal, obstetric variables, perceived stress and health-related quality of life among pregnant women in Macao, China

OBJECTIVE

to identify associations between demographic, socio-economic and obstetric variables and health-related quality of life with perceived stress among Macao Chinese pregnant women.

DESIGN

a cross-sectional, exploratory quantitative study.

SETTING

an antenatal clinic of a university-affiliated regional public hospital in Macao.

PARTICIPANTS

a community-based sample (n = 1151) of pregnant women in the second trimester of pregnancy.

MEASUREMENTS

perceived stress was measured using the Perceived Stress Scale, and health-related quality of life was measured using the standard Short Form-12 Health Survey.

FINDINGS

a multiple linear regression analysis revealed that pregnant women who were younger (β = 0.085, p = 0.002), single, divorced, separated or cohabiting (β = 0.067, p < 0.009), had a lower level of education (β = 0.079, p = 0.003), worked long hours (β = 0.102, p < 0.001) or who had an unplanned pregnancy (β = 0.063, p = 0.014) with late initiation of antenatal care (β = 0.066, p = 0.008) or poor physical (β = -0.501, p < 0.001) or mental (β = -0.115, p < 0.001) health-related quality of life had higher levels of perceived stress.

CONCLUSION

preliminary information was provided about Macao pregnant women who had higher perceived stress during pregnancy that was associated with the demographic, socio-economic, obstetric and health-related quality-of-life variables.

IMPLICATIONS FOR PRACTICE

the development of a checklist or structured questions for clinical situations is necessary, and programmes of stress management should be tailor made during pregnancy.

The association of daily physical activity and birth outcome: a population-based cohort study

The potential relationship between daily physical activity and pregnancy outcome remains unclear because of the wide variation in study designs and physical activity assessment measures. We sought to prospectively quantify the potential effects of the various domains of physical activity on selected birth outcomes in a large unselected population. The sample consisted of 11,759 singleton pregnancies from the Avon longitudinal study of parents and children, United Kingdom. Information on daily physical activity was collected by postal questionnaire for self-report measures. Main outcome measures were birth weight, gestational age at delivery, preterm birth and survival. After controlling for confounders, a sedentary lifestyle and paid work during the second trimester of pregnancy were found to be associated with a lower birth weight, while ‘bending and stooping’ and ‘working night shifts’ were associated with a higher birth weight. There was no association between physical exertion and duration of gestation or survival. Repetitive boring tasks during the first trimester was weakly associated with an increased risk of preterm birth (<37 weeks) (adjusted odds ratio [OR] = 1.25, 95% CI 1.04–1.50). ‘Bending and stooping’ during the third trimester was associated with a reduced risk of preterm birth (adjusted OR = 0.73, 95% CI 0.63–0.84). Demanding physical activities do not have a harmful effect on the selected birth outcomes while a sedentary lifestyle is associated with a lower birth weight. In the absence of either medical or obstetric complications, pregnant women may safely continue their normal daily physical activities should they wish to do so.

A literature review of air medical work hazards and pregnancy

An increased percentage of miscarriages among coworkers at one air medical transport company in 2008 prompted a literature review of selected hazards relevant to the profession of rotor wing air medical flight crew. Because of a lack of known research specific to this population, relevant studies from 1990 to 2008 were chosen to investigate pregnancy risks associated with exposure to vibration, jet fuel, noise, altitude, and fatigue in other occupations. Findings were summarized and recommendations made for future research.

First-trimester working conditions and birthweight: a prospective cohort study

OBJECTIVES

We investigated the relationship between women's first-trimester working conditions and infant birthweight.

METHODS

Pregnant women (N = 8266) participating in the Amsterdam Born Children and Their Development study completed a questionnaire gathering information on employment and working conditions. After exclusions, 7135 women remained in our analyses. Low birthweight and delivery of a small-for-gestational-age (SGA) infant were the main outcome measures.

RESULTS

After adjustment, a workweek of 32 hours or more (mean birthweight decrease of 43 g) and high job strain (mean birthweight decrease of 72 g) were significantly associated with birthweight. Only high job strain increased the risk of delivering an SGA infant (odds ratio [OR] = 1.5; 95% confidence interval [CI] = 1.1, 2.2). After adjustment, the combination of high job strain and a long workweek resulted in the largest birthweight reduction (150 g) and the highest risk of delivering an SGA infant (OR = 2.0; 95% CI = 1.2, 3.2).

CONCLUSIONS

High levels of job strain during early pregnancy are associated with reduced birthweight and an increased risk of delivering an SGA infant, particularly if mothers work 32 or more hours per week.

Occupational predictors of pregnancy outcomes in Irish working women in the Lifeways cohort

OBJECTIVE

The objective of this study was to explore the association between occupational factors and pregnancy outcomes in a prospective cohort of Irish pregnant women.

DESIGN

This study has a prospective design.

POPULATION

The Lifeways cohort included 1124 pregnant women, 676 of whom delivered a single baby and were working at their first prenatal care visit when they filled in a self-administered questionnaire.

METHODS

Occupational factors were measured using this questionnaire and included eight factors describing job and working conditions. Data including pregnancy outcomes were also obtained from clinical hospital records. Logistic regression analysis was used to adjust for well-known risk factors.

MAIN OUTCOME MEASURES

Birthweight (< or =3000 g and < or =2500 g), preterm delivery (<37 gestation weeks) and small-for-gestational-age.

RESULTS

Significant associations were found between physical work demands and low birthweight (< or =2500 g) and working with between a temporary contract and preterm delivery. Trends were also observed between working 40 hours or more a week and shift work, and birthweight of 3000 g or less. The study of a cumulative index showed that being exposed to at least two of these occupational factors significantly predicted birthweight of < or =3000 g (OR = 2.44, 95% CI: 1.17-5.08) and of < or =2500 g (OR = 4.65, 95% CI: 1.08-20.07) and preterm delivery (OR = 5.18, 95% CI: 1.00-27.01).

CONCLUSIONS

Our findings suggest that occupational factors may predict birthweight through their predictive effects on preterm delivery. This is one of the few prospective studies on pregnancy outcomes that include working conditions. As they may be modifiable, occupational factors deserve more attention in relation to birth outcomes.

Circadian clocks during embryonic and fetal development

Circadian rhythmicity is a fundamental characteristic of organisms, which helps ensure that vital functions occur in an appropriate and precise temporal sequence and in accordance with cyclic environmental changes. Living beings are endowed with a system of biological clocks that measure time on a 24-hr basis, termed the circadian timing system. In mammals, the system is organized as a master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus, commanding peripheral clocks located in almost every tissue of the body. At the cell level, interlocking transcription/translation feedback loops of the genes Bmal-1, Clock, Per1-2, and Cry1-2, named clock genes, and their protein products results in circadian oscillation of clock genes and of genes involved in almost every cellular function. During gestation, the conceptus follows a complex and dynamic program by which it is simultaneously fit to develop and live in a circadian environment provided by its mother and to prepare for the very different environment that it will experience after birth. It has been known for a number of years that the mother tells the fetus the time of day and season of the year, and that the fetus uses this information to set the phase of fetal and neonatal circadian rhythms. There is evidence that the maternal rhythm of melatonin is one of the time signals to the fetus. In the last few years, the study of the development of the circadian system has turned to the investigation of the oscillatory expression of clock genes and their possible role in development, and to answering questions on the organization of the fetal circadian system. Emerging evidence shows that clock genes are expressed in the oocyte and during early and late development in embryo/fetal organs in the rat and in a fetal primate. The data available raise the intriguing possibility that the fetal SCN and fetal tissues may be peripheral clocks commanded by separate maternal signals. The rapid methodological and conceptual advances on chronobiology may help to unravel how the developing embryo and fetus faces time in this plastic period of life.

Environmental factors implicated in the causation of adverse pregnancy outcome

Adverse pregnancy outcome from environmental factors may include congenital anomalies, increased risk for miscarriage, preterm delivery, intrauterine growth restriction, and still birth. Apart from adverse pregnancy outcome, there may be effects on the other reproductive functions, like menstrual disorders and infertility. Environmental factors which have been implicated in adverse pregnancy outcome include smoking, video display terminals, anesthetic gases, antineoplastic drugs, and exposure to lead, selenium, and inorganic mercury. Among these, cigarette smoking during pregnancy has been the leading environmental factor for adverse pregnancy outcome. Cigarette smoking during pregnancy continues to be a significant public health concern. Maternal smoking during pregnancy has been associated with low birth weight (<2500 g). Mothers who smoke during pregnancy are twice as likely to give birth to low-birth weight infants. Similarly, air pollution, pesticide exposure, and stress have also been associated with low birth weight and preterm delivery. This review gives an overview of the importance of environmental factors in adverse pregnancy outcome.