The association between occupational factors and preterm birth: a United States nurses' study. Research Committee of the Association of Women's Health, Obstetric, and Neonatal Nurses

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

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

Influence of Socioeconomic Status on the Association Between Pregnancy Complications and Premature Coronary Artery Disease: Linking Three Cohorts

Background

We hypothesized that there is an influence of socioeconomic status (SES) on association between pregnancy complications and premature coronary artery disease (PCAD) risk.

Materials and Methods

This project involved a data linkage approach merging three databases of South Australian cohorts using retrospective, age-matched case-control study design. Cases (n = 721), that is, women aged <60 years from Coronary Angiogram Database of South Australia (CADOSA) were linked to South Australian Perinatal Statistics Collection (SAPSC) to ascertain prior pregnancy outcomes and SES. Controls (n = 194) were selected from North West Adelaide Health Study (NWAHS), comprising women who were healthy or had health conditions unrelated to CAD, age matched to CADOSA (±5 years), and linked to SAPSC to determine prior pregnancy outcomes and SES. This project performed comparative analysis of SES using socioeconomic indexes for areas-index of relative socioeconomic advantage and disadvantage (SEIFA-IRSAD) scores across three databases.

Results

Findings revealed that SEIFA-IRSAD scores at the time of pregnancy (p-value = 0.005) and increase in SEIFA-IRSAD scores over time (p-value = 0.040) were significantly associated with PCAD. In addition, when models were adjusted for SEIFA-IRSAD scores at the time of pregnancy and age, risk factors including placenta-mediated pregnancy complications such as preterm birth (odds ratio [OR] = 4.77, 95% confidence interval [CI]: 1.74-13.03) and history of a miscarriage (OR = 2.14, 95% CI: 1.02-4.49), and cardiovascular disease (CVD) risk factors including smoking (OR = 8.60, 95% CI: 3.25-22.75) were significantly associated with PCAD. When the model was adjusted for change in SEIFA-IRSAD scores (from CADOSA/NWAHS to SAPSC) and age, pregnancy-mediated pregnancy complications including preterm birth (OR = 4.40, 95% CI: 1.61-12.05) and history of a miscarriage (OR = 2.09, 95% CI: 1.00-4.35), and CVD risk factor smoking (OR = 8.75, 95% CI: 3.32-23.07) were significantly associated with PCAD.

Conclusion

SES at the time of pregnancy and change in SES were not associated with PCAD risk.

[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.

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

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

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

OBJECTIVE

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

STUDY

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

STUDY APPRAISAL AND SYNTHESIS METHODS

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

RESULTS

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

CONCLUSION

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

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

BACKGROUD

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

OBJECTIVE

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

DATA SOURCES

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

METHODS OF STUDY SELECTION

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

TABULATION, INTEGRATION, AND RESULTS

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

CONCLUSION

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

Full-time exposure to occupational noise during pregnancy was associated with reduced birth weight in a nationwide cohort study of Swedish women

Noise is a common exposure in the occupational work environment. Earlier studies of occupational noise and pregnancy outcome are few and show mixed results. To investigate if objectively assessed exposure to occupational noise during pregnancy is associated with reduced intrauterine growth and/or preterm birth a nationwide cohort study of 857,010 single births was initiated. Individual information on occupation and risk factors was retrieved from prenatal care interviews at pregnancy week 10. Occupational noise was classified into three exposure categories <75, 75-85, >85 dBA by a job exposure matrix. Odds ratios were adjusted for BMI, smoking, parity, education, physically strenuous work and low job control. Exposure to high (>85 dBA) levels of occupational noise throughout the pregnancy (full time workers) was associated with an increased risk of the child being born small for gestational age, OR 1.44 (95% CI 1.01 to 2.03) compared to noise exposure <75 dBA. A similar increase was seen for low birth weight OR 1.36 (95% CI 1.03 to 1.80) for high levels of noise. No clear association was seen for preterm birth. No consistent effects on birth outcome was observed in women who had worked part-time or were on leave of absence >21 days (median). In summary, full-time exposure to high levels of noise during pregnancy was associated with a slightly reduced fetal growth but not with preterm birth. The effect of intermediate occupational noise exposure (75-85 dBA) showed a small, but statistically increased risk for all studied birth outcomes. The study strengthens the evidence that pregnant women should not be long-term exposed to high levels >85 dBA of occupational noise during pregnancy. Intermediate exposure should be studied further.

Registered nurses are at increased risk of hospitalization for infectious diseases and perinatal complications: A population-based observational study

Background

Nursing staff spend long periods in high-risk working environments.

Objective

The purpose of this study was to compare the hospitalization risk between nursing staff and the general population.

Design

This study adopted a retrospective observational design.

Setting

Data from the Taiwan National Health Insurance Research Database from 2011 to 2013 were analyzed.

Method

The standardized hospitalization ratio model was used to analyze the relative risk of hospitalization for various diseases between nursing staff and the general population.

Results

A total of 33,267 numbers of nursing staff in Taiwan were hospitalized, an overall crude hospitalization rate of 21.5%. After controlling for gender, calendar year, and age of nursing staff, the standardized hospitalization ratio of female nursing staff was significantly higher compared to the general population for infectious and parasitic diseases (SHR = 121.05, 95% CI = 112.66–129.89), diseases of the respiratory system (SHR = 105.12, 95% CI = 100.60–109.80), complications of pregnancy, childbirth, and the puerperium (SHR = 102.59, 95% CI = 100.85–104.35), and diseases of the skin and subcutaneous tissue (SHR = 109.71, 95% CI = 101.10–118.86).

Conclusions

Nursing staff have a significantly higher hospitalization risk compared to the general population for infectious and parasitic diseases, diseases of the respiratory system, complications of pregnancy, childbirth, and puerperium, and diseases of the skin and subcutaneous tissue. This may be associated with the job characteristics and environment of nursing staff.

Socioeconomic status can affect pregnancy outcomes and complications, even with a universal healthcare system

Background

Low socioeconomic status can increase the risk of adverse pregnancy outcomes, but it remains unclear whether this negative association is attributed to inadequate prenatal care. Korea has been adopting a universal healthcare system. All Korean citizens must be enrolled National Health Insurance (NHI) or be recipient of Medical Aid (MA). In addition, Korean government launched a financial support system for antenatal care for all pregnant women in 2008. Therefore, in theory, there is no financial barrier to receive prenatal cares regardless of someone’s social class. However, it is still unclear whether adverse pregnancy outcomes observed in low-income women are attributable to low SES or to economic barriers specific to the utilization of medical services. The purpose of this study was to investigate whether socioeconomic status affects pregnancy outcomes after the introduction of this support system, which allows all pregnant women to receive adequate prenatal care regardless of socioeconomic status.

Methods

Using the National Health Insurance database in Korea, we selected women who gave birth between January 1, 2010 and December 31, 2010. As a proxy indicator reflecting socioeconomic status, we classified subjects as MA recipient (“low” SES) or a NHI beneficiary (“middle/high” SES).

Results

In the MA group, 29.4% women received inadequate prenatal care, compared to 11.4% in the NHI group. Mothers in the MA group were more likely to have an abortion (30.1%), rather than deliver a baby, than those in the NHI group (20.7%, P < 0.001). Mothers in the MA group were also more likely to undergo a Caesarean delivery (45.8%; NHI group: 39.6%, P < 0.001), and have preeclampsia (1.5%; NHI group: 0.6%, P < 0.001), obstetric hemorrhage (4.7%; NHI group: 3.9%, P = 0.017), and a preterm delivery (2.1%; NHI group: 1.4%, P < 0.001) than those in the NHI group.

Conclusions

Women in the MA group tended to show higher rates of abortion, Caesarean delivery, preeclampsia, preterm delivery, and obstetrical hemorrhage than those in the NHI group Therefore, health authorities should consider investigating what kind of barriers exist or what factors may affect these inequitable outcomes.

Pregnancy, birth, and infant outcomes by maternal fertility status: the Massachusetts Outcomes Study of Assisted Reproductive Technology

BACKGROUND

Births to subfertile women, with and without infertility treatment, have been reported to have lower birthweights and shorter gestations, even when limited to singletons. It is unknown whether these decrements are due to parental characteristics or aspects of infertility treatment.

OBJECTIVE

The objective of the study was to evaluate the effect of maternal fertility status on the risk of pregnancy, birth, and infant complications.

STUDY DESIGN

All singleton live births of ≥22 weeks' gestation and ≥350 g birthweight to Massachusetts resident women in 2004-2010 were linked to hospital discharge and vital records. Women were categorized by their fertility status as in vitro fertilization, subfertile, or fertile. Women whose births linked to in vitro fertilization cycles from the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System were classified as in vitro fertilization. Women with indicators of subfertility but not treated with in vitro fertilization were classified as subfertile. Women without indicators of subfertility or in vitro fertilization treatment were classified as fertile. Risks of 15 adverse outcomes (gestational diabetes, pregnancy hypertension, antenatal bleeding, placental complications [placenta abruptio and placenta previa], prenatal hospitalizations, primary cesarean delivery, very low birthweight [<1500 g], low birthweight [<2500 g], small-for-gestation birthweight [z-score ≤-1.28], large-for-gestation birthweight [z-score ≥1.28], very preterm [<32 weeks], preterm [<37 weeks], birth defects, neonatal death [0-27 days], and infant death [0-364 days of life]) were modeled by fertility status with the fertile group as reference and the subfertile group as reference, using multivariate log binomial regression and reported as adjusted risk ratios and 95% confidence intervals.

RESULTS

The study population included 459,623 women (441,420 fertile, 8054 subfertile, and 10,149 in vitro fertilization). Women in the subfertile and in vitro fertilization groups were older than their fertile counterparts. Risks for 6 of 6 pregnancy outcomes and 6 of 9 infant outcomes were increased for the subfertile group, and 5 of 6 pregnancy outcomes and 7 of 9 infant outcomes were increased for the in vitro fertilization group. For 4 of the 6 pregnancy outcomes (uterine bleeding, placental complications, prenatal hospitalizations, and primary cesarean) and 2 of the infant outcomes (low birthweight and preterm) the risk was greater in the in vitro fertilization group, with nonoverlapping confidence intervals to the subfertile group, indicating a substantially higher risk among in vitro fertilization-treated women. The highest risks for the in vitro fertilization women were uterine bleeding (adjusted risk ratio, 3.80; 95% confidence interval, 3.31-4.36) and placental complications (adjusted risk ratio, 2.81; 95% confidence interval, 2.57-3.08), and for in vitro fertilization infants, very preterm birth (adjusted risk ratio, 2.13; 95% confidence interval, 1.80-2.52), and very low birthweight (adjusted risk ratio, 2.15; 95% confidence interval, 1.80-2.56). With subfertile women as reference, risks for the in vitro fertilization group were significantly increased for uterine bleeding, placental complications, prenatal hospitalizations, primary cesarean delivery, low and very low birthweight, and preterm and very preterm birth.

CONCLUSION

These analyses indicate that, compared with fertile women, subfertile and in vitro fertilization-treated women tend to be older, have more preexisting chronic conditions, and are at higher risk for adverse pregnancy outcomes, particularly uterine bleeding and placental complications. The greater risk in in vitro fertilization-treated women may reflect more severe infertility, more extensive underlying pathology, or other unfavorable factors not measured in this study.

A nationwide population analysis of antenatal and perinatal complications among nurses and nonmedical working women

OBJECTIVE

Limited information is available on health issues during pregnancy and after childbirth among nurses, especially on a nationwide level. This study thus aimed to compare antenatal and perinatal complications between nurses and nonmedical working women in Taiwan.

MATERIALS AND METHODS

This nationwide population-based study was conducted using data from the Taiwan National Health Insurance Research Database. A total of 44,166 nurses and 442,107 nonmedical working women with full-time employment, aged 20-50 years, who gave birth to singletons were identified between 2007 and 2011. Logistic regression analyses (generalized estimating equation method) were used to compare risks between the two groups.

RESULTS

Multivariable analyses showed that nurses had a significantly higher risk of anemia [adjusted odds ratio (AOR) 1.37; 95% confidence intervals (CI), 1.31-1.44], placenta previa, and abruptio placentae (AOR, 1.13; 95% CI, 1.07-1.20), and pregnancy-associated hypertensive diseases and preeclampsia (AOR, 1.10; 95% CI, 1.03-1.18) during the antenatal period than nonmedical working women. Moreover, they also experienced an increased risk of malpresentation (AOR, 1.30; 95% CI, 1.26-1.34), dystocia (AOR, 1.09; 95%, CI 1.06-1.13), preterm delivery (AOR, 1.08; 95% CI, 1.03-1.13), premature rupture of membranes (AOR, 1.09; 95% CI, 1.05-1.14), and post-term delivery (AOR, 1.11; 95% CI, 1.07-1.16) during the perinatal period.

CONCLUSION

Our nationwide population-based study revealed increased risks of antenatal and perinatal complications among nurses compared with those among nonmedical working women. The large-scale observation of the increased antenatal and perinatal complications draws attention to the health issues faced by nursing personnel who represent one of the most important workforces in the healthcare system.

Practice Bulletin No. 159: Management of Preterm Labor

Preterm birth is the leading cause of neonatal mortality and the most common reason for antenatal hospitalization . In the United States, approximately 12% of all live births occur before term, and preterm labor preceded approximately 50% of these preterm births . Although the causes of preterm labor are not well understood, the burden of preterm births is clear-preterm births account for approximately 70% of neonatal deaths and 36% of infant deaths as well as 25-50% of cases of long-term neurologic impairment in children . A 2006 report from the Institute of Medicine estimated the annual cost of preterm birth in the United States to be $26.2 billion or more than $51,000 per premature infant . However, identifying women who will give birth preterm is an inexact process. The purpose of this document is to present the various methods proposed to manage preterm labor and to review the evidence for the roles of these methods in clinical practice. Identification and management of risk factors for preterm labor are not addressed in this document.

Pregnant Employee Protection Program in a Large Chemical Company

OBJECTIVES

To assess whether a structured employee protection program for pregnant workers at a chemical company has an impact on pregnancy outcomes.

METHODS

Reported pregnancies (n = 1402) between 2003 and 2010 and their outcomes were documented using questionnaires at the time of pregnancy report, end of pregnancy, and 1 year later. Potential maternal exposures were assessed using job histories, workplace inspections, and questionnaires.

RESULTS

Participation was 86% overall and was consistently high across subgroups.Pregnancy losses (10.9%), pregnancy complications, and preterm births (8.1%) were in agreement with rates in the general population and were independent of type of work and maternal exposure category.

CONCLUSIONS

Pregnancy complication rates in this chemical company are not statistically elevated than that in the general population, as suggested in a previous study. The protection program may play a role in preventing complications that may have occurred.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Do nurses have worse pregnancy outcomes than non-nurses?

BACKGROUND

Nurses encounter multiple occupational exposures at work which may harm their reproductive health. The purpose of the study was to compare pregnancy complications and outcomes including cesarean deliveries, tocolysis, miscarriage, and preterm labor between female nurses and comparable women who were not nurses in Taiwan.

METHODS

This nationwide population-based study was performed using the National Health Insurance Research Database from 1997 to 2008. We identified 3,656 pregnancies among 2,326 nurses and 111,889 pregnancies among 74,919 non-nurses. A generalized estimating equation was used to compare risks between the two groups.

RESULTS

The rates of tocolysis (28.6 vs 22.3%), miscarriage (6.0 vs 5.3%), and preterm labor (8.1 vs 4.4%) were significantly higher among nurses than non-nurses. After adjustment for background differences, nurses had significantly higher risks for cesarean section (adjusted OR 1.12 [95% confidence interval (CI) 1.03-1.22]), tocolysis (OR 1.18 [95% CI 1.09-1.29]), and preterm labor (OR 1.46 [95% CI 1.28-1.67]) than non-nurses.

CONCLUSIONS

Nurses are at higher risk for cesarean section, tocolysis, and preterm labor than non-nurses. Occupational exposure related to these adverse pregnancy outcomes should be examined. Strategies to decrease the risks should be developed to improve reproductive health among nurses.

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.

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

Background

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

Methods

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

Results

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

Conclusion

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

Electronic supplementary material

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

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Occupational exposures and adverse pregnancy outcomes among nurses: a systematic review and meta-analysis

BACKGROUND

The nursing profession has been associated with several adverse pregnancy outcomes. However, the associations between occupational exposures and adverse pregnancy outcomes among this group have not been systematically examined. This review collates all epidemiological evidence to examine the strength of associations and consistency among eligible studies.

METHODS

A computer search of EMBASE and PubMed from 1966 through August 2009 was performed, followed by a search of reference lists of relevant studies and narrative reviews

RESULTS

Fourteen studies explored the relation between anesthetic gases and spontaneous abortion, 8 the relation between anesthetic gases and congenital malformations, 7 the relation between chemotherapy agents and congenital malformations, and 4 the relation between shift work and spontaneous abortion. In the random-effects models the summary odds ratio (OR) was moderately elevated for all the relations: OR = 1.27, 95% confidence interval (CI) 0.99-1.63 for anesthetic gases and spontaneous abortion. The summary OR was between 1.05 and 1.09 in high-quality studies, registry-based studies, and cohort studies: OR = 1.33, 95% CI 1.09-1.68 for anesthetic gases and congenital malformation. The summary OR was between 0.97 and 1.22 for high-quality studies, registry-based studies, and cohort studies: OR = 1.35; 95% CI 0.91-2.01 for chemotherapy agent and spontaneous abortion. The summary OR was between 1.34 and 1.69 for high-quality studies, registry-based studies, and cohort studies: OR = 1.44, 95% CI 1.06-1.95 for shift work and spontaneous abortion.

CONCLUSIONS

Nurses were found to be at increased risk of adverse pregnancy outcomes, but the strength of association was weaker in the well-designed studies. The significance of the findings is limited by the number and heterogeneity of the studies.

Cyclo-oxygenase (COX) inhibitors for preventing preterm labour

BACKGROUND

Preventing preterm labour is the most important step in preventing preterm birth. Prostaglandins play an important role in labour and birth. Prostaglandin production can be obstructed by inhibition of the cyclo-oxygenase (COX) enzyme and this may arrest uterine contraction. A Cochrane review on COX inhibitors for the treatment of preterm labour found insufficient data to draw conclusions about its effectiveness.

OBJECTIVES

To assess the effectiveness and safety of COX inhibitors for preventing preterm labour in high-risk women.

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trial Register (30 June 2012).

SELECTION CRITERIA

All published and unpublished randomised trials evaluating administration of any COX inhibitor for prevention of preterm labour in pregnant women at gestational age less than 36 weeks at risk of, but not experiencing, preterm labour. Cluster-randomised trials were eligible for inclusion. Quasi-randomised trials and studies with cross-over designs were excluded.

DATA COLLECTION AND ANALYSIS

Two review authors (T Khanprakob and U Sangkomkamhang) independently assessed all potential studies for inclusion. Disagreement was resolved by discussion and, where necessary, by consultation with a third review author. Two review authors independently assessed trial quality and extracted data. Data were checked for accuracy.

MAIN RESULTS

We included one randomised trial (involving 98 women) that evaluated the effectiveness of one type of COX inhibitor (rofecoxib) for preventing preterm birth. The included study did not report any data for one of our primary outcomes: preterm labour. Rofecoxib use was associated with an increased risk for preterm birth and preterm premature rupture of membranes (PPROM). Rofecoxib was associated with a higher risk of oligohydramnios and low fetal urine production but the effects were reversible after stopping treatment. There were no differences in the number of women who discontinued treatment before 32 weeks of gestation. There was no difference in neonatal morbidities and admission to neonatal intensive care unit. There were no maternal adverse effects or perinatal mortalities in either group.

AUTHORS' CONCLUSIONS

There was very little evidence about using COX inhibitors for preventing preterm labour. There are inadequate data to make any recommendation about using COX inhibitor in practice to prevent preterm labour. Future research should include follow-up of the babies to examine the short-term and long-term effects of COX inhibitors.

Relationship between handling heavy items during pregnancy and spontaneous abortion: a cross-sectional survey of working women in South Korea

The researchers conducted a cross-sectional survey to determine the relationship between handling heavy items during pregnancy and spontaneous abortion among working women in South Korea. One thousand working women were selected from a database of those eligible for maternity benefits under the National Employment Insurance Plan. Study results showed that handling heavy items during pregnancy was associated with an increased risk of spontaneous abortion after adjusting for general characteristics of the participants and their work environment. A collective effort is needed on the parts of employers, employees, occupational health nurses, and the government to protect working women from lifting heavy items while pregnant.

Relationship between handling heavy items during pregnancy and spontaneous abortion: a cross-sectional survey of working women in South Korea

The researchers conducted a cross-sectional survey to determine the relationship between handling heavy items during pregnancy and spontaneous abortion among working women in South Korea. One thousand working women were selected from a database of those eligible for maternity benefits under the National Employment Insurance Plan. Study results showed that handling heavy items during pregnancy was associated with an increased risk of spontaneous abortion after adjusting for general characteristics of the participants and their work environment. A collective effort is needed on the parts of employers, employees, occupational health nurses, and the government to protect working women from lifting heavy items while pregnant.

Prenatal care: touching the future

The provision of preconception and prenatal care is a critical and time-honored role for family physicians. It could even be termed the first preventive care a human being receives. It has been suggested by some studies that, because of the continuity of care that is considered a cornerstone of family practice, family physicians provide prenatal care that may improve birth outcome. Although prenatal care is acknowledged as important for a healthy pregnancy and delivery, there is debate regarding the true efficacy of prenatal care.

The use of psychosocial stress scales in preterm birth research

Psychosocial stress has been identified as a potential risk factor for preterm birth. However, an association has not been found consistently, and a consensus on the extent to which stress and preterm birth are linked is still lacking. A literature search was performed with a combination of keywords and MeSH terms to detect studies of psychosocial stress and preterm birth. Studies were included in the review if psychosocial stress was measured with a standardized, validated instrument and if the outcomes included either preterm birth or low birthweight. Within the 138 studies that met inclusion criteria, 85 different instruments were used. Measures that had been designed specifically for pregnancy were used infrequently, although scales were sometimes modified for the pregnant population. The many different measures that have been used may be a factor that accounts for the inconsistent associations that have been observed.

AORN Ergonomic Tool 4: Solutions for Prolonged Standing in Perioperative Settings

Prolonged standing during surgical procedures poses a high risk of causing musculoskeletal disorders, including back, leg, and foot pain, which can be chronic or acute in nature. Ergonomic Tool 4: Solutions for Prolonged Standing in Perioperative Settings provides recommendations for relieving the strain of prolonged standing, including the use of antifatigue mats, supportive footwear, and sit/stand stools, that are based on well-accepted ergonomic safety concepts, current research, and access to new and emerging technology.

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.

Work as a nurse and a midwife and adverse pregnancy outcomes: a Finnish nationwide population-based study

OBJECTIVE

To assess whether work as a nurse and a midwife during pregnancy increases the risk of adverse pregnancy outcomes.

METHODS

We identified from the 1990-2006 Finnish Medical Birth Registry all singleton births to nurses (n=109,542), midwives (n=3,009), and teachers (n=23,454) (referents). The main outcomes were sexual differentiation, low and high birth weight, preterm and postterm delivery, small and large for gestational age, and perinatal death.

RESULTS

The prevalence of low birth weight (2.9% vs. 2.5%), preterm delivery (4.4% vs. 4.1%), postterm delivery (4.7% vs. 4.1%), small for gestational age (1.8% vs. 1.4%), perinatal death (0.45% vs. 0.41%) and stillbirth (0.30% vs. 0.25%) was higher among the newborns of nurses than those of teachers. The adjusted odds ratio (OR) from generalized estimating equations was 1.17 (95% confidence interval [CI] 1.07-1.26) for low birth weight, 1.09 (95% CI 1.02-1.16) for preterm delivery, 1.11 (95% CI 1.03-1.18) for postterm delivery, 1.17 (95% CI 1.05-1.30) for small for gestational age, 1.12 (95% CI 0.90-1.35) for perinatal death, and 1.27 (95% CI 0.98-1.56) for stillbirth. For midwives, the risk of small for gestational age (OR=1.25, 95% CI 0.95-1.55) was elevated, but the 95% CI included unity. There was no substantial difference in the sex distribution.

CONCLUSIONS

This study provides evidence that work as a nurse may reduce fetal growth and duration of pregnancy. The inference is based on the newborns of teachers as the reference group. However, the prevalence of most of the outcomes was higher among the newborns of all other working women combined than in the newborns of both nurses and teachers.

Physical activity and preterm birth: a literature review

Preterm birth is a major reason for infant mortality and morbidity, representing a public health concern worldwide. Regular and voluntary physical activity is healthy behaviour that should be incorporated by everyone, including pregnant women. On the other hand, some women are exposed to highly demanding occupational physical activities during pregnancy that might represent a threat to the fetus and to their own health. This paper is a literature review of studies (1987-2007) on physical activity during pregnancy and its relationship to preterm birth. Although the effects measured by the studies are not strong and the evidence is impaired by many methodological flaws, it seems that recreational or leisure-time physical activities performed regularly provide protection against prematurity. Studies on occupational physical activities, especially standing for long periods, present contrasting results - some presenting standing as a risk factor, but most showing no association. Housework and other daily activities do not seem to be associated with preterm birth. Regardless of the methodological aspects of the studies reviewed, there is a chance that the real effect of occupational physical activity is being blurred by some underlying factors not easily measured in epidemiological investigations. Our conclusions do not reject the idea that working conditions might represent danger for the pregnancy outcome, but only raise the question that maybe the mechanisms through which employment-related physical activities have been considered up till now could be better and more thoroughly studied. Future studies should pay additional attention to psychological and socioeconomic characteristics, without neglecting biological plausibility.

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.

Goals and strategies for prevention of preterm birth: an obstetric perspective

Complications of prematurity surpass congenital malformations as the leading cause of infant mortality in the United States. Since 1990, there has been a steady rise in preterm birth, alarming health professionals from all disciplines. This review from a prenatal perspective confirms those concerns and describes the risks and opportunities that may attend efforts to improve the health of fetuses, newborns, and infants. Fetal and live-born outcomes are included.

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.

Occupational factors and risk of preterm birth in nurses

OBJECTIVE

We evaluated first-trimester exposures and the risk of preterm birth in the most recent pregnancy of participants of the Nurses' Health Study II.

STUDY DESIGN

Log binomial regression was used to estimate the relative risk (RR) for preterm birth in relation to occupational risk factors, such as work schedule, physical factors, and exposures to chemicals and x-rays, adjusted for age and parity.

RESULTS

Part-time work (<or= 20 hours a week) was associated with a lower risk of preterm birth [RR, 0.7; 95% confidence interval [CI], 0.6-0.9]. Working nights was associated only with early preterm birth (< 32 weeks of gestation) (RR, 3.0; 95% CI, 1.4-6.2). Although based on only 11 exposed preterm cases, self-reported exposure to sterilizing agents was associated with an increased risk (RR, 1.9; 95% CI, 1.1-3.4).

CONCLUSION

These data suggest that night work may be related to early but not late preterm birth, whereas physically demanding work did not strongly predict risk.

Demographic, clinical and occupational characteristics associated with early onset of delivery: findings from the Duke Health and Safety Surveillance System, 2001-2004

BACKGROUND

This cross-sectional study explores associations between preterm delivery and demographic, clinical and occupational characteristics of women employed within a university and health system.

METHODS

A comprehensive surveillance system linking individual-level data from Human Resources, medical insurance claims and a job-exposure matrix was used to identify women with a single live birth between 2001 and 2004 and describe maternal characteristics during pregnancy.

RESULTS

Preterm delivery occurred in 7.1% (n = 74) of the 1,040 women, a lower preterm delivery prevalence than observed in the general U.S. population. Nearly all (>99.5%) women utilized prenatal care services. Prevalence of preterm delivery was highest for inpatient nurses, nurses' aides and office staff. In multivariate analyses, preterm delivery was positively associated with several clinical conditions: placenta previa, diabetes and cardiovascular disorder/disease.

CONCLUSIONS

We observed associations between preterm delivery and several previously indicated clinical conditions. Further study of the effect of job characteristics on preterm delivery is warranted.

Maternal Work and Birth Outcome Disparities

OBJECTIVES

We tested relations between aspects of maternal work and birth outcomes in a national sample and in subgroups known to experience disparities.

METHODS

Three indices of work attributes (Status and Recognition, Physical Demands, and Exposure to Conflict) were derived by factor analysis of variables extracted from the Department of Labor's O*Net database. The indices were linked to the National Longitudinal Survey of Youth using occupation codes for the primary jobs held by women who gave birth between 1979 and 2000 and worked during the quarter prior to birth (n = 3,386 births to n = 2,508 mothers). Multiple regression was used to model birth outcomes as functions of the work attribute indices, controlling for several measures of socioeconomic status and risk factors for adverse birth outcomes.

RESULTS

In the full sample, work-related Physical Demands were associated with lower average birthweight and increased odds of preterm birth while Status and Recognition was associated with higher average birthweight and lower odds of fetal growth restriction. In stratified models, Status and Recognition was associated with higher birth weight among women with low (versus high) income and with lower odds of preterm birth among women with low (versus high) education. Physical Demands were associated with higher rates of preterm birth among women with low (versus high) income and education and among African-American mothers (compared to Whites).

CONCLUSIONS

The work environment is an important predictor of healthy births. Relations between maternal work attributes and birth outcomes differ by race/ethnicity and socioeconomic status and according to the outcome under investigation. Further research with measures of work attributes specific to maternal work experiences is recommended to confirm our findings.

Evidence-based clinical hypnosis for obstetrics, labor and delivery, and preterm labor

This paper reviews the benefits and effectiveness of hypnosis in obstetrics and labor and delivery, demonstrating significant reductions in the use of analgesics and anesthesia and in shorter Stages 1 and 2 labors. It presents empirical and theoretical rationales for use of hypnosis in preterm labor (PTL) and labor and delivery at term. The benefits of hypnosis in relation to labor length, pain levels, and the enjoyment of labor, as well as its effectiveness in preterm labor are noted in randomized controlled trials and in a meta-analysis. Risk factors are reported for preterm delivery; hypnosis significantly prolongs pregnancy. Six cases are presented of hypnosis stopping PTL a number of times and when indicated at term. A case report of successful use of hypnosis in quadruplets is presented with some scripts. Suggestions are made for further research.

Risk of prematurity, low birthweight and pre-eclampsia in relation to working hours and physical activities: a systematic review

BACKGROUND

Occupational activities are suspected of having an adverse impact on outcomes of pregnancy.

AIM

To assess the evidence relating three major adverse outcomes (preterm delivery, low birthweight (LBW) and pre-eclampsia/gestational hypertension) to five common occupational exposures (prolonged working hours, shift work, lifting, standing and heavy physical workload).

METHODS

A systematic search of Medline and Embase (1966-December 2005) using combinations of keywords and medical subject heading terms was conducted. For each relevant paper, standard details were abstracted that were then used to summarise the design features of studies, to rate their methodological quality (completeness of reporting and potential for important bias or confounding) and to provide estimates of effect. For studies with similar definitions of exposure and outcome, pooled estimates of relative risk (RR) in meta-analysis were calculated.

RESULTS

53 reports were identified-35 on preterm delivery, 34 on birth weight and 9 on pre-eclampsia or gestational hypertension. These included 21 cohort investigations. For pre-term delivery, extensive evidence relating to each of the exposures of interest was found. Findings were generally consistent and tended to rule out a more than moderate effect size (RR >1.4). The larger and most complete studies were less positive, and pooled estimates of risk pointed to only modest or null effects. For small-for-gestational age, the position was similar, but the evidence base was more limited. For pre-eclampsia and gestational hypertension, it was too small to allow firm conclusions.

CONCLUSIONS

The balance of evidence is not sufficiently compelling to justify mandatory restrictions on any of the activities considered in this review. However, given some uncertainties in the evidence base and the apparent absence of important beneficial effects, it may be prudent to advise against long working hours, prolonged standing and heavy physical work, particularly late in pregnancy. Our review identifies several priorities for future investigation.

Significant changes in physical activity among pregnant women in the UK as assessed by accelerometry and self-reported activity

OBJECTIVE

Research on the impact of maternal physical activity on pregnancy outcomes has often employed subjective measures of physical activity obtained by diary or questionnaire. This study investigates the feasibility of using accelerometry as an objective measure of physical activity of pregnant women compared with subjective data obtained via activity recall among pregnant women.

DESIGN

Activity data were collected prospectively on 57 women at 12, 16, 25, 34 and 38 weeks of gestation. Total daily physical activity was assessed by ambulatory accelerometer and activity interview (self-report). Maternal personality variables (health value, extroversion) were assessed by established scales.

SETTING

Leicestershire, UK.

SUBJECTS

Pregnant women were recruited by voluntary participation via antenatal booking clinics. In all, 64 pregnant women with low-risk pregnancy were enrolled onto the study, of whom 57 completed the study.

RESULTS

Mean 24 h physical activity levels (PAL) decreased significantly from second to third trimester as assessed by self-report interview (1.51-1.29 Metabolic Equivalent TEE-h/day, P<0.01) and accelerometry (200.05-147.42 counts/min, P<0.01). The correlation between the two measures declined as pregnancy progressed (r value ranging from 0.55 to 0.08). Compliance with the accelerometers declined from 90% at 12 weeks to 47% at 34 weeks (P<0.01). Compliance with the self-report interviews was 100%. Those who fully complied with the accelerometry demonstrated a significantly higher health value (P<0.05) and a significantly greater level of extroversion (P<0.05) than those who did not.

CONCLUSIONS

Accelerometers and self-reported activity interviews both indicated a significant decline in PAL during pregnancy. Although subjects showed a willingness to use both methods, accelerometers resulted in variable compliance with 72 h monitoring. Both techniques may be limited by the need to measure low levels of physical activity during the third trimester.

SPONSORSHIP

Cambridge Neurotechnology Ltd, UK, assisted with the provision of Actiwatch accelerometers.

Occupational working conditions as risk factors for preterm birth in Benin, West Africa

BACKGROUND

Although many studies from developed countries have established a relationship between various occupational working conditions during pregnancy and preterm birth, there is little data available in developing countries where both maternal physical labor during pregnancy and preterm birth are common. The aim of this study was to examine the association between difficult occupational working conditions of pregnant women and premature births in the Republic of Benin in West Africa.

METHOD

The case-control study included 99 women with preterm babies and 104 women with full-term babies. The participants were residents of the Republic of Benin who delivered between May 1, 2000 and April 30, 2002. Preterm delivery was defined as delivery prior to 37 completed weeks of gestation. The study sample was selected randomly from birth records. Data were collected both reviewing birth records and conducting semi-structured personal interviews with mothers. Logistic regression models were adjusted for mother's age, mother's education, health problems during pregnancy, and twin birth.

RESULTS

Although working state of mother during pregnancy did not increase the risk for preterm delivery, carrying heavy loads more than 5 days per week was significantly associated with having a preterm baby (adjusted OR: 5.0; 95% CI: 1.38-18.8; P=0.018). Carrying heavy loads and having worked a lot more than 5 days per week was also significantly associated with preterm birth (adjusted OR: 6.88; 95% CI: 1.45-32.2; P=0.015).

CONCLUSION

Reducing heavy loads carrying during pregnancy may also prevent preterm delivery in developing countries. Though replication of these data using a prospective design is needed, our results suggest that educating women about the risks associated with heavy labor during pregnancy is indicated.

Physical exertion at work and the risk of preterm delivery and small-for-gestational-age birth

OBJECTIVE

To assess whether exposure to standing, lifting, night work, or long work hours during 3 periods of pregnancy are associated with an increased risk of preterm or small-for-gestational-age birth.

METHODS

The Pregnancy, Infection and Nutrition study is a prospective cohort with a nested case-control component that was conducted through clinic and hospital settings in Central North Carolina. A total of 1,908 women pregnant with a singleton gestation were recruited during prenatal visits from January 1995 through April 2000 and provided information during telephone and face-to-face interviews about physical exertion for the 2 longest-held jobs during pregnancy.

RESULTS

No significant elevations in preterm delivery were observed among women who lifted repeatedly or stood at least 30 hours per week, with no changes in risk estimates over the course of pregnancy. A 50% elevation in the risk of preterm delivery (relative risk 1.5, 95% confidence interval 1.0-2.0; first trimester) was observed among women who reported working at night (10:00 PM to 7:00 AM), whereas a 40% reduction in risk was observed among women working at least 46 hours per week (relative risk 0.6, 95% confidence interval 0.4-0.9; first trimester), regardless of period of exposure. No elevations in small-for-gestational-age birth were observed among women exposed to any of the 4 types of occupational exertion.

CONCLUSION

Physically demanding work does not seem to be associated with adverse pregnancy outcomes, whereas working at night during pregnancy may increase the risk of preterm delivery. Studies to examine the effect of shift work on uterine activity would help to clarify the possibility of a causal effect on preterm birth.

Protective medical legislation deficient knowledge of maternity (health and safety) rights for work-adjustment exists amongst flexible trainee doctors: is there a risk to maternal and foetal health?

OBJECTIVE

To assess awareness, identify knowledge source and evaluate uptake amongst doctors of "health and safety rights" (HSR) contained within the current European protective medical legislation for pregnant workers.

STUDY DESIGN

A descriptive cross-sectional pilot study, by a postal questionnaire during the period 1998-1999, targeted 97 UK doctors (West Midlands region) after their first pregnancy.

RESULTS

Of 67 respondents (response rate 73%), 41 (61%) were Registrars (SpR) and 25 (37%) SHOs: 80% work-schedules did not change during pregnancy. Only 11% (95% CI, 4-21%) of the doctors surveyed actually knew their maternity rights. 66.2% had no knowledge of maternity legislation; 80% of respondents had not taken up health and safety rights. Fifty-two percent (95% CI, 40-65%) reported maternal and neonatal complications.

CONCLUSIONS

In a self-selected group of flexible trainees following their first pregnancy, only one in five female doctors have adequate knowledge about the legislative "health and safety rights" of work-schedule adjustment. A combination of reasons may contribute to the low uptake of these rights. The question of whether or not poor knowledge and uptake of legislative rights may be detrimental towards pregnancy and neonatal complications requires a large prospective study. An improvement in the knowledge of current maternity legislation could occur by targeting all medical students, all doctors, postgraduate trainers and National Health Service (NHS) employers.

A randomized multicenter study to determine the efficacy of activity restriction for preterm labor management in patients testing negative for fetal fibronectin

OBJECTIVE

To assess the impact of activity restriction (AR) on the incidence of preterm birth in women treated for preterm labor testing negative for fetal fibronectin (fFN).

STUDY DESIGN

Women who were diagnosed with preterm labor and tocolyzed with magnesium sulfate were concurrently screened with fFN for the purpose of subsequent management. Included were consenting patients with negative fFN, gestational age 23 0/7-33 6/7 weeks, cervical dilation < or =3 cm, and minimal vaginal bleeding. Patients were randomized to AR or no AR. Primary study outcome was incidence of preterm delivery and interval from randomization to delivery.

RESULTS

A total of 73 women with negative fFN were randomized (36 with AR, 37 without AR). The overall preterm birth rate was 40%, with 44.4% of patients with AR and 35.1% of patients without AR delivering preterm, p=0.478.

CONCLUSION

Maternal AR did not impact pregnancy outcome. The incidence of preterm birth in symptomatic women testing fFN negative was higher than previously reported.

Physical exposures during pregnancy and congenital cardiovascular malformations

Congenital cardiovascular malformations (CCM) cause substantial neonatal morbidity and mortality. Known risk factors for CCM explain only 10-20% of all cases. Few studies have examined mothers' physical exposures during pregnancy and the risk of CCM in their offspring. This study examined the association between exposures to extreme temperatures, prolonged standing, and heavy lifting during early pregnancy and risk of CCM in offspring. Using a case-control study design, 502 cases and 1066 controls were drawn from the population of all liveborn infants born between January 1988 and June 1991 to mothers living in 14 counties in New York State. Cases were identified from a population-based registry of congenital malformations. Controls were randomly selected from birth certificate records. Interviews were conducted by telephone, using a structured questionnaire. Exposure estimates were based on women's self-reports of conditions in the residence and workplace. Eighty-three per cent of the mothers were white, and 66% were between 25 and 34 years old. After adjusting all results for known risk factors and confounding variables, we found no significant increased risk of CCM in subjects whose mothers reported being exposed during early pregnancy to extreme heat (OR = 1.13, 95% CI 0.59, 2.19), nor to extreme cold (OR = 1.19, 95% CI 0.66, 2.15). Mothers who reported ever using a hot tub, hot bath, or sauna during early pregnancy had no increased risk of CCM in their offspring (OR = 0.88, 95% CI 0.65, 1.18). Performing heavy lifting during early pregnancy did not increase the risk of CCM in offspring (OR = 0.80, 95% CI 0.57, 1.11). Prolonged standing during early pregnancy was not associated with an increased risk of CCM in children (OR = 1.03, 95% CI 0.82, 1.28). Thus if these maternal exposures have an adverse effect, it is unlikely to involve CCMs.