Employment, exertion, and pregnancy outcome: assessment by kilocalories expended each day

Physical activity and the risk of preterm birth: a systematic review and meta-analysis of epidemiological studies

BACKGROUND

Physical activity has been inconsistently associated with risk of preterm birth, and the strength of the association and the shape of the dose-response relationship needs clarification.

OBJECTIVES

To conduct a systematic review and dose-response meta-analysis to clarify the association between physical activity and risk of preterm birth.

SEARCH STRATEGY

PubMed, Embase and Ovid databases were searched for relevant studies up to 9 February 2017.

SELECTION CRITERIA

Studies with a prospective cohort, case-cohort, nested case-control or randomized study design were included.

DATA COLLECTION AND ANALYSIS

Data were extracted by one reviewer and checked for accuracy by a second reviewer. Summary relative risks (RRs) were estimated using a random effects model.

MAIN RESULTS

Forty-one studies (43 publications) including 20 randomized trials and 21 cohort studies were included. The summary RR for high versus low activity was 0.87 [95% confidence interval (CI): 0.70-1.06, I² = 17%, n = 5] for physical activity before pregnancy, and it was 0.86 (95% CI: 0.78-0.95, I² = 0%, n = 30) for early pregnancy physical activity. The summary RR for a 3 hours per week increment in leisure-time activity was 0.90 (95% CI: 0.85-0.95, I² = 0%, n = 5). There was evidence of a nonlinear association between physical activity and preterm birth, P_nonlinearity < 0.0001, with the lowest risk observed at 2-4 hours per week of activity.

CONCLUSION

This meta-analysis suggests that higher leisure-time activity is associated with reduced risk of preterm birth. Further randomized controlled trials with sufficient frequency and duration of activity to reduce the risk and with larger sample sizes are needed to conclusively demonstrate an association.

TWEETABLE ABSTRACT

Physically active compared with inactive women have an 10-14% reduction in the risk of preterm birth.

Mode of Delivery according to Leisure Time Physical Activity before and during Pregnancy: A Multicenter Cohort Study of Low-Risk Women

Objectives. To examine the association between maternal leisure time physical activity and mode of delivery. Study Design. Population-based multicentre cohort. From the Danish Dystocia Study, we included 2,435 nulliparous women, who delivered a singleton infant in cephalic presentation at term after spontaneous onset of labor in 2004-2005. We analysed mode of delivery according to self-reported physical activity at four stages, that is, the year before pregnancy and during first, second, and third trimester, in logistic regression models. Further, we combined physical activity measures at all four stages in one variable for a proportional odds model for cumulative logits. Main Outcome Measures. Mode of delivery (emergency caesarean section; vacuum extractor; spontaneous vaginal delivery). Results. The odds of emergency caesarean section decreased with increasing levels of physical activity with statistically significant trends at all four time stages except the third trimester. This tendency was confirmed in the proportional odds model showing 28% higher odds of a more complicated mode of delivery among women with a low activity level compared to moderately active women. Conclusions. We found increasing leisure time physical activity before and during pregnancy associated with a less complicated delivery among low-risk, nulliparous women.

Measuring Physical Activity During Pregnancy

Few studies exist that identify a useful self-report measure of physical activity for pregnant women. The purpose of this study was to compare the self-report exercise diary with the pedometer and determine if self-report measurement provided useful physical activity measures during pregnancy. The pregnant women’s sleep, parity, and related demographic factors were further analyzed for relationships to the physical activity measures. Physical activity was assessed in a sample of 94 pregnant midwestern U.S. women ages 18 to 38 years. The women wore a pedometer during all waking hours for 3 consecutive days at 14 and 28 weeks of pregnancy for a total of 6 days. During the same 6 days of monitoring, the women kept a diary account of the minutes they exercised per day. The pedometer and self-report exercise diary results correlated significantly (r = 49, p = .02). When examining for usefulness in measuring physical activity, a comparison of the women’s occupational categories revealed no significant differences in self-reported minutes of exercise or pedometer counts per day.

Physical Activity Volumes during Pregnancy: A Systematic Review and Meta-Analysis of Observational Studies Assessing the Association with Infant's Birth Weight

Objective This study aims to examine the association between different maternal physical activity exposures during pregnancy and infant's birth weight, body composition, and risk of inadequate weight. Methods Two reviewers (M.B. and J.L.G.) identified observational studies reporting total or leisure time activity during pregnancy and birth weight outcomes. Pooled analyses were performed to summarize the risk associated with high or moderate volumes of physical activity on birth weight. Results A total of 54 studies among 4,080 reported the association between physical activity and birth weight (37 studies) or risks of small or large birth weight. The association between physical activity and birth weight was evaluated by physical activity levels (low, moderate, or high). Despite heterogeneity, pooled results (23 studies) suggested that moderate levels of activity are associated with an increased birth weight (mean difference: 61.5 g, 95% confidence interval [CI]: 16.6, 106.5, 15 studies), while high levels were associated with lower birth weight (mean difference: -69.9 g, 95% CI: -114.8, -25.0, 15 studies). Data were insufficient to provide robust estimates for other outcomes. Conclusions The results of observational studies suggest an inverted u-shaped association between physical activity and birth weight, despite methodological variability. These results could help refining physical activity guidelines for pregnancy and provide guidance for future research.

Exposure analysis methods impact associations between maternal physical activity and cesarean delivery

BACKGROUND

Previous studies report conflicting results regarding a possible association between maternal physical activity (PA) and cesarean delivery.

METHODS

Seven-day PA recalls were collected by telephone from pregnant women (n = 1205) from North Carolina, without prior cesarean, during 2 time windows: 17 to 22 weeks and 27 to 30 weeks completed gestation. PA was treated as a continuous, nonlinear variable in binomial regressions (log-link function); models controlled for primiparity, maternal contraindications to exercise, preeclampsia, pregravid BMI, and percent poverty. We examined both total PA and moderate-to-vigorous PA (MVPA) at each time. Outcomes data came from medical records.

RESULTS

The dose-response curves between PA or MVPA and cesarean risk at 17 to 22 weeks followed an inverse J-shape, but at 27 to 30 weeks the curves reversed and were J-shaped. However, only (total) PA at 27 to 30 weeks was strongly associated with cesarean risk; this association was attenuated when women reporting large volumes of PA (> 97.5 percentile) were excluded.

CONCLUSION

We did not find evidence of an association between physical activity and cesarean birth. We did, however, find evidence that associations between PA and risk of cesarean may be nonlinear and dependent on gestational age at time of exposure, limiting the accuracy of analyses that collapse maternal PA into categories.

Physical activity, sedentary behaviour and fetal macrosomia in uncomplicated pregnancies: a prospective cohort study

OBJECTIVE

to explore maternal energy balance, incorporating free living physical activity and sedentary behaviour, in uncomplicated pregnancies at risk of macrosomia.

METHODS

a parallel-group cross-sectional analysis was conducted in healthy pregnant women predicted to deliver infants weighing ≥ 4000 g (study group) or < 4000 g (control group). Women were recruited in a 1:1 ratio from antenatal clinics in Northern Ireland. Women wore a SenseWear(®) Body Media Pro3 physical activity armband and completed a food diary for four consecutive days in the third trimester. Physical activity was measured in Metabolic Equivalent of Tasks (METs) where 1 MET = 1 kcal per kilogram of body weight per hour. Analysis of covariance (ANCOVA) was employed using the General Linear Model to adjust for potential confounders.

FINDINGS

of the 112 women recruited, 100 complete datasets were available for analysis. There was no significant difference in energy balance between the two groups. Intensity of free living physical activity (average METs) of women predicted to deliver macrosomic infants (n = 50) was significantly lower than that of women in the control group (n = 50) (1.3 (0.2) METs (mean, standard deviation) versus 1.2 (0.2) METs; difference in means -0.1 METs (95% confidence interval: -0.19, -0.01); p = 0.021). Women predicted to deliver macrosomic infants also spent significantly more time in sedentary behaviour (≤ 1 MET) than the control group (16.1 (2.8) hours versus 13.8 (4.3) hours; 2.0 hours (0.3, 3.7), p = 0.020).

KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE

although there was no association between predicted fetal macrosomia and energy balance, those women predicted to deliver a macrosomic infant exhibited increased sedentary behaviour and reduced physical activity in the third trimester of pregnancy. Professionals caring for women during pregnancy have an important role in promoting and supporting more active lifestyles amongst women who are predicted to deliver a macrosomic infant given the known associated risks.

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.

A prospective study of the association between vigorous physical activity during pregnancy and length of gestation and birthweight

Current US pregnancy-related physical activity recommendations do not provide specific guidance for vigorous intensity activity. We examined the associations between vigorous physical activity during pregnancy and length of gestation and birthweight.

METHODS

Women were recruited before 10 weeks gestation. At 13-16 weeks gestation, participants reported the type, frequency, and duration of their typical weekly vigorous physical activities. Activity domains included recreational, occupational, household, and child/adult care. Infant birth date was obtained from medical or vital records; if unavailable, self-report was used. Birthweight (from vital records) was studied among term births. We analyzed gestational age among 1,647 births using discrete-time survival analysis. We used logistic and linear regression to analyze preterm birth (birth at <37 weeks) and birthweight, respectively. Vigorous recreational activity was associated with longer gestation (any vs. none, hazard ratio (HR) [95% CI]: 0.85 [0.70, 1.05]) and we did not detect any dose-response association. Higher frequency of vigorous recreational activity sessions (adjusted for total volume of activity) was associated with a decreased odds of preterm birth (≥ 4 sessions/week vs. 0 or 1, OR [95% CI]: 0.08 (0.006, 1.0). Birthweight was not associated with physical activity measures. In summary, vigorous physical activity does not appear to be detrimental to the timing of birth or birthweight. Our data support a reduced risk of preterm birth with vigorous recreational activity, particularly with increased frequency of recreational activity sessions. Future studies should investigate the components of physical activity (i.e., intensity, duration, and frequency) in relation to birth outcomes.

Relationship between Daily Physical Activity During Last Month of Pregnancy and Pregnancy Outcome

BACKGROUND

Previous researchers have evaluated the influence of physical exercise or physical activity on pregnancy outcome, but the influence of daily physical activities in details including energy expenditure, biomechanical load and exercise before and during pregnancy have remained unclear. This study evaluates the relationship between daily physical activities as a biomechanical load and energy expenditure and physical exercise during household activities with birth weight, type of delivery and Apgar score.

METHODS

The participants of this study were household, first parity women who referred to a prenatal care center in southern Iran. 132 volunteer women were eligible to be enrolled according to their general health and not having any absolute or relative limitation for participating in any kind of activity. Information about daily physical activity was collected through a personal interview using a structured questionnaire during two separate days of ninth month of pregnancy. Data on delivery were recorded from recorded documents of mothers in the hospital.

RESULTS

There was no relationship between biomechanical and energy load and birth weight. There was a significant correlation between Apgar score and biomechanical and energy load. Infants of mothers who exercised before or during pregnancy had a significant higher weight than the non-exercise group. Apgar score indicated no significant difference among those having exercise and those without before and during pregnancy. There was no significant difference in the biomechanical load and energy expenditure in the two types of delivery.

CONCLUSION

Daily activities in normal range do not induce any harmful effect on birth weight; increasing biomechanical load as a result of some maternal body postures that may be harmful for infant health at birth time. Physical exercise before and during pregnancy may have a positive effect on birth weight.

Effect of psychosocial stress and physical activity on low birthweight: a cohort study

AIM

To determine the effect of physical activity and psychosocial stress on low birthweight (LBW).

METHODS

A prospective study was carried out in a district of Sri Lanka between May 2001 and April 2002. A total of 885 pregnant mothers were recruited at < or = 16 weeks of gestation and followed up until partus. Trimester-specific exposure statuses along with potential confounding factors were gathered on average at the 12th, 28th, and 36th weeks of gestation. Physical activities were assessed by inquiring about the duration of specific postures adopted per day by housewives during each trimester at home and both at home and during working hours for those who were engaged in paid employment. Psychosocial stress was assessed using the Modified Life Events Inventory and the General Health Questionnaire 30. LBW was defined as a birthweight of less than 2500 g. Multiple logistic regression analysis was applied for controlling confounders and the results were expressed as adjusted odds ratios (OR) and 95% confidence intervals (95%CI).

RESULTS

Standing > 2.5 h/day (OR 2.26; 95%CI 1.10, 4.69) during the second trimester and sleeping 8 h or less/day (OR 2.84; 95%CI 1.49, 5.40) either during the second, third or both trimesters together, an increase in maternal age in years (OR 0.92; 95%CI 0.87, 0.98), and body mass index < 19.8 kg/m(2) (OR 2.2; 95%CI 1.17, 4.22) had a statistically significant association with LBW. Psychosocial stress was not associated with LBW.

CONCLUSIONS

Standing > 2.5 h/day and sleeping < or = 8 h/day were risk factors for LBW, whereas psychosocial stress was not.

Physical activity during pregnancy and fetal outcomes: a case-control study

OBJECTIVE

To investigate the relationship between physical activity during the second trimester pregnancy and low birth weight, preterm birth, and intrauterine growth restriction.

METHODS

Case-control study including 273 low birth weight newborns and 546 controls carried out in the city of São Paulo, Southeastern Brazil, in 2005. Low birth weight cases were grouped into two subsamples: preterm birth (n=117) and intrauterine growth restriction (n=134), with their related controls. Information was collected by means of interviews with mothers shortly after birth and transcription of medical records. Data were analyzed using conditional multiple and hierarchical logistic regression.

RESULTS

Light physical activity for over 7 hours per day was shown to be protective against low birth weight (adjusted OR=0.61; 95% CI 0.39-0.94) with a dose-response relationship (p-value for trend=0.026). A similar trend was found for intrauterine growth restriction (adjusted OR=0.51; 95% CI 0.26-0.97). Homemaking activities were associated as a protective factor for both low birth weight and preterm birth (p-value for trend=0.013 and 0.035, respectively). Leisure-time walking was found to be protective against preterm birth.

CONCLUSIONS

Mild physical activity during the second trimester of pregnancy such as walking has an independent protective effect on low birth weight, preterm birth, and intrauterine growth restriction.

Beliefs about exercise and physical activity among pregnant women

OBJECTIVE

The objective of this study was to document self-reported beliefs about physical activity and exercise among pregnant women.

METHODS

The Pregnancy, Infection, and Nutrition (PIN3) Study asked 1306 pregnant women about beliefs regarding physical activity and exercise at 27-30 weeks' gestation.

RESULTS

While 78% of women agreed that most women can continue their regular exercise during pregnancy, fewer (68%) agreed that most women who never exercised could begin an exercise program during pregnancy. Most (89%) agreed that regular exercise was better than irregular exercise during pregnancy. While almost all women agreed with the benefits of light activity (98%), fewer agreed that there were benefits with moderate (73%) or vigorous exercise (13%). Differences in beliefs were most notable by educational level, race/ethnicity, and whether they participated in regular exercise during pregnancy.

CONCLUSION

Future studies can better elucidate the reasons behind the differences in beliefs, to explore whether cultural reasons are contributing to these differences and whether tailored messages would be more effective than general educational approaches.

PRACTICE IMPLICATIONS

This study provides information to create more successful interventions to help women understand concepts regarding the safety and benefits of physical activity during pregnancy.

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.

Physical activity by pregnant women and outcomes for newborns: a systematic review

A systematic review was carried out aiming at analyzing daily physical activity during pregnancy and the outcomes of birth weight, prematurity, and intrauterine growth restriction. Of 52 articles indexed in Medline, 22 that showed better methodological quality were included. Among the 22 articles analyzed, only two did not detect a significant association between physical activity and the outcomes studied. There was large variation between the indicators of maternal physical activity, which included occupational, household, recreational and, all or some, locomotive activities. Among ten articles that measured total daily physical activity, only one article did not find any association. The results support the hypothesis that both excessive and insufficient physical activity impact negatively on pregnancy outcomes.

Exercise and pregnancy

Exercise is an important component of a healthy lifestyle and, as such, is recommended during pregnancy. However, the response to exercise of both the expectant mother and fetus varies depending on the fitness level of the woman. The response to exercise is also affected by the known musculoskeletal and physiologic changes associated with pregnancy, such as increased ligament laxity, weight gain, change in the center of gravity, and carpal tunnel syndrome. Although the physiologic responses of the pregnant woman and fetus have been well studied, the literature contains comparatively few studies investigating response to exercise. When performed properly, activities such as aerobics, impact and nonimpact activities, resistance training, and swimming may be beneficial during pregnancy.

Gestational Diabetes Mellitus: Physical Exercise and Health Outcomes

Purpose: Gestational diabetes mellitus (GDM) is a serious complication of pregnancy associated with increased risk of adverse outcomes for both mother and infant. This study assesses the association of maternal exercise during GDM pregnancy and selected maternal and infant adverse GDM-related outcomes. The analysis uses information derived from the 1988 National Maternal Infant Health Survey (NMIHS) data. Methods: Women in the 1988 NMIHS database were identified and grouped as to having experienced a non-GDM (n = 2,952,482) or GDM (n = 105,600) pregnancy. Non-GDM and GDM groups were compared as to demographic and personal-attribute variables. The second part of this study focused on the women with GDM pregnancy, specifically a subset (n = 75,160) who met inclusion/exclusion criteria for the study of exercise during pregnancy. Each was categorized to either the exercise group or the nonexercise group. Results: The non-GDM and GDM groups of pregnant women were not different as to the variables studied, except that older age and increased body mass index (BMI) were associated with GDM pregnancy. For the study of exercise during GDM pregnancy, the only variable that was associated with the exercise group was size of the infant. Participants in the exercise group were less likely than those in the nonexercise group to have delivered a large for gestational age (LGA) infant (F [1, 4314] = 9.82, p = .0017). Implications: The results of this study suggest that moderate maternal leisure time physical exercise during GDM pregnancy may reduce the risk of delivery of an LGA infant.

The Effect of Exercise During Pregnancy on Maternal Outcomes: Practical Implications for Practice

The American College of Obstetricians and Gynecologists recommends that women with low-risk pregnancies participate in moderate-intensity exercise during their pregnancy. Currently, only 15.1% of pregnant women exercise at the recommended levels, which is significantly lower than the general population's 45%. One potential reason is that exercise during pregnancy is perceived as risky. In this article, the authors provide a critical review of the literature examining the effect of exercise on preeclampsia, gestational diabetes, weight gain, labor and birth, and other issues associated with pregnancy. Overall, the evidence indicates that exercise during pregnancy is safe and perhaps even reduces the risk of preeclampsia and gestational diabetes. The evidence for weight gain and labor and birth (rates of cesarean sections, duration of labor) is mixed. Unfortunately, much of the research examining exercise during pregnancy is observational, and the few randomized controlled trials that do exist are small and inadequately powered. Taken together, given the potential benefits of exercise during pregnancy and the lack of evidence for harmful effects on the mother and newborn, practitioners should encourage their healthy pregnant patients to exercise. Practical guidelines for recommending exercise to pregnant women are presented.

Association of maternal work with adverse perinatal outcome

OBJECTIVE

To investigate the relationship between maternal work and pregnancy outcome.

METHODS

Over a 4-month period from October 2004 through February 2005, 2,419 women were interviewed shortly after delivery in the three main public and Health Insurance hospitals in Alexandria, Egypt. Of these, 730 (30.2%) were working and 1,689 (69.8%) were not working prior to delivery. A detailed description of working status was analyzed, along with a risk profile which was compared between the two groups.

RESULTS

There was no significant association between different work characteristics and perinatal outcomes except for that between working posture, stress and delivery of small-for-gestational-age (SGA) babies. There was an excess rate of SGA and perinatal death among the non-working group, while preterm delivery was significantly increased among those who worked throughout the whole pregnancy. After adjusting for confounders, the risk of preterm delivery was no longer significant (OR = 1.2, 95% CI = 0.96-1.7). On the other hand, working status had a beneficial effect on SGA and perinatal death (OR = 0.41, 95% CI = 0.26-0.64 and OR = 0.26, 95% CI = 0.14-0.48, respectively).

CONCLUSION

These results cast doubt on the risk of adverse pregnancy outcome for women who work during pregnancy. Work per se does not constitute a health risk factor and may even have a positive social impact on pregnancy. Further research on this topic in our region is recommended.

Activity levels in pregnant New Zealand women: relationship with socioeconomic factors, well-being, anthropometric measures, and birth outcome

Activity during pregnancy has health implications for mother and child. The aim of this prospective cohort study was to examine changes in activity levels during pregnancy; the influence of socioeconomic factors and well-being on activity, and the influence of activity on maternal anthropometric measures and birth outcome. Twenty-four hour activity diaries were collected for 3 d in months 4 and 7 of pregnancy in 197 volunteers. Anthropometric measures and questionnaires to determine personal details were collected at these times and 2 months post-partum. Health records were used to supply infant measures. The time spent on each activity category was calculated, and used to calculate overall daily metabolic equivalents (METs). Low socioeconomic (SES) group 24 h activity levels were significantly higher than for high SES or welfare groups (p = 0.013). Activity declined throughout pregnancy in all groups (p = 0.002). Women with children had higher 24 h activity, spending 41% more time walking and (or) on housework than nulliparous women (p = 0.013). Reduced well-being was associated with lower levels of activity. Sleep and lying down time influenced 2 month post-partum body mass (upper quartile gained 2.54 kg, lower quartile lost 0.24 kg, p < 0.001). Mean infant gestational age increased with increasing 24 h activity (p = 0.047). No infants were born prematurely to mothers who spent more than 190 min/d walking or doing housework activities in month 4. Probability of infant admission to the neonatal intensive care unit (NICU) declined with time spent walking or doing housework in month 4 (p = 0.007). Mean (SE) birth weight was 3883 (+/-165) g in the 10% of women spending less than 530 min sleeping or lying down per day, compared with 3413 (+/-104) g in the 10% of women spending 725 min or more sleeping or lying down. Socioeconomic factors were therefore important influences on activity levels during pregnancy. Inactivity, especially in early pregnancy, was associated with more maternal weight retention at 2 months post-partum and a greater probability of admission to NICU and premature delivery.

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.

Physical activity and fetal growth during pregnancy

OBJECTIVE

To assess the separate and combined relationships of aerobic physical activity during pregnancy, maternal weight gain during pregnancy, and height to the fetal growth ratio.

METHODS

The aerobic physical activity of 51 healthy, nonsmoking pregnant women was assessed for 48 hours at both 20 and 32 weeks of pregnancy by accelerometry, heart rate monitoring, and physical activity recall. We analyzed the relationship between maternal physical activity and the fetal growth ratio.

RESULTS

All women included in the analysis completed healthy, uncomplicated pregnancies and delivered infants with a weight range of 2,743-4,943 g. Aerobic physical activity assessed by accelerometry was strongly and inversely associated with fetal growth ratio (r=-0.42; P<.002). Infants born to women in the highest quartile of physical activity weighed 608 g less than infants born to women in the lowest quartile. The inverse relationship between physical activity and fetal growth ratio was moderated by maternal height; virtually all the effect was seen in mothers taller than the sample median (1.65 m). Similar relationships were found across methods of physical activity measurement.

CONCLUSION

Aerobic physical activity in pregnancy may be an important determinant of birth weight within the normal range, especially in taller mothers.

LEVEL OF EVIDENCE

II.

Fatigue during pregnancy predicts caesarean deliveries

BACKGROUND

Previous studies on fatigue and pregnancy outcomes were confined to women with occupational fatigue and did not include women who did not work outside the home. Fatigue during mid- and late pregnancy has rarely been studied.

AIMS

This paper reports a study examining the associations between work factors, household factors, and fatigue among low-risk pregnant women in Taiwan and links the effects of fatigue to preterm births and caesarean deliveries.

METHODS

The participants were 633 women who were 20-36 weeks pregnant without evidence of obstetrical complications at the time of interview. Pregnancy outcomes were abstracted from the hospital records after delivery. Fatigue was measured using the Fatigue Symptom Checklist. Women were categorized into three groups according to their work status: non-working, sedentary work, and active work. Other work factors included hours worked and exposure to adverse work environments. Household factors included household work and childcare responsibilities. Multiple linear regression and logistic regression were used for the analysis.

RESULTS

The factors significantly associated with fatigue in the regression model were age, infection during pregnancy, bleeding after 12 weeks of pregnancy, and work status. Women who did not work outside of the home had significantly higher fatigue scores than those who did sedentary work outside the home. Younger women had higher fatigue scores than older women. Fatigue scores during pregnancy predicted caesarean deliveries, given that age and obstetrical risks were controlled in the model.

CONCLUSIONS

Fatigue is a significant problem for pregnant women. Fatigue assessments should include morbidities during pregnancy as well as household and work-related factors. Special attention should be paid to women who do not work outside the home. Staff should elicit information about fatigue and intervene early, as this may help decrease the number of caesarean deliveries.

Strenuous work, nutrition and adverse pregnancy outcomes: a brief review

This brief review explores the available epidemiologic data to investigate the question of whether strenuous work by women during pregnancy in developing countries influences micronutrient status and thereby increase risks of adverse pregnancy outcomes. Some data exist on the potential relationship between strenuous work or physical activity and nutrient compromise, strenuous work or physical activity and adverse reproductive outcomes and micronutrient intakes or status and adverse reproductive outcomes. No substantial body of data exists that has directly investigated the potential causal path of whether strenuous work during pregnancy alters micronutrient status leading to adverse reproductive outcome. Search of the literature identified only a few papers from developing countries that provided even remotely related data on the topic. Thus, the available data are insufficient for drawing firm inferences that strenuous work, in a developing country, alters a pregnant woman's nutritional status and therefore affects her risk of an adverse pregnancy outcome. Effects on nutritional status, micronutrients in particular, of pregnant women from strenuous physical activities at work or in other lifestyle events require further study in developing countries.

Postnatal home visits in teenage mothers: a randomised controlled trial

BACKGROUND

Teenage pregnancies are associated with negative socioeconomic effects. Our aim was to ascertain whether a postnatal home-visiting service for teenage mothers younger than age 18 years could reduce the frequency of adverse neonatal outcomes and improve knowledge of contraception, breastfeeding, and infant vaccination schedules in this parent group.

METHODS

We enrolled 139 adolescents, attending a teenage pregnancy clinic, in a randomised controlled trial. After completing an antenatal questionnaire designed to assess their knowledge of contraception, infant vaccination, and breastfeeding, we assigned participants to either receive five structured postnatal home visits by nurse-midwives (n=65) or not (n=71). Assessment interviews were done 6 months postpartum. Our primary endpoint was unadjusted difference in knowledge between groups, and incidence of predefined adverse neonatal outcomes. Analysis was by intention to treat.

FINDINGS

Three women withdrew before randomisation because of late fetal loss, 11 mothers withdrew because of adverse neonatal outcomes (adverse neonatal outcome was a primary endpoint, but resulted in withdrawal from the study for knowledge outcomes), and one left voluntarily. Follow-up data were, therefore, available for 124 teenagers. Postnatal home visits were associated with a reduction in adverse neonatal outcomes (intervention: 2; control: 9; relative risk 0.24, 95% CI 0.05-1.08), and a significant increase in contraception knowledge (mean difference 0.92, 95% CI 0.32-1.52). However, there was no significant increase in knowledge with respect to breastfeeding or infant vaccination schedules associated with the home visits.

INTERPRETATION

Postnatal home-visiting services by nurse-midwives reduce adverse neonatal events and improve contraception outcomes, but do not affect breastfeeding or infant vaccination knowledge or compliance.

Vigorous leisure activity and pregnancy outcome

BACKGROUND

Preterm birth is the leading cause of perinatal mortality in North America and Europe and a major predictor of neonatal and infant morbidity. Postterm birth is associated with increased infant mortality and morbidity, as well as increased frequency of surgical or induced labor. Because vigorous leisure activity may affect timing of delivery, this study examined association between vigorous leisure activity and birth outcomes.

METHODS

Women (N = 1,699) with a singleton pregnancy were recruited at 24-29 weeks' gestation from prenatal clinics in central North Carolina between 1995 and 1998. The type and duration of any regular vigorous leisure activity was assessed in a telephone interview covering the 3-month period before pregnancy and during the first and second trimesters of pregnancy.

RESULTS

The prevalence of vigorous leisure activity was 22% before pregnancy, 14% during the first trimester, and 8% during the second trimester. Vigorous leisure activity before pregnancy was unrelated to preterm (<37 weeks) as compared with term delivery (37 to <42 weeks). The risk of preterm birth was somewhat reduced with vigorous leisure activity during the first trimester (odds ratio = 0.80; 95% confidence interval = 0.48-1.35) and more so during the second trimester (odds ratio = 0.52; 95% confidence interval = 0.24-1.11). Vigorous leisure activity before pregnancy or during the first or second trimester was not associated with postterm delivery (>/=42 weeks).

CONCLUSIONS

Vigorous leisure activity during the first trimester, and even more so in the second trimester, was associated with a reduced risk of preterm birth. There was no association with postterm birth. To address the etiologic role of activity on pregnancy outcome and to overcome self-selection, a randomized clinical trial would be needed.

SMA statement the benefits and risks of exercise during pregnancy. Sport Medicine Australia

There are numerous benefits to pregnant women of remaining active during pregnancy. These include improved weight control and maintenance of fitness. There may also be benefits in terms of reduced risk of development of gestational diabetes meilitus and improved psychological functioning. Moderate intensity aerobic exercise has been shown to be safe in pregnancy, with a number of studies now indicating that for trained athletes it may be possible to exercise at a higher level than is currently recommended by the American College of Obstetricians and Gynecologists. Studies of resistance training, incorporating moderate weights and avoiding maximal isometnc contractions, have shown no adverse outcomes. There may be benefits of increased strength and flexibility. The risk of neural tube defects due to exercise-induced hyperthermia that is suggested by animal studies is less likely in women, because of more effective mechanisms of heat dissipation in humans. There is accumulating evidence to suggest that participation in moderate intensity exercise throughout pregnancy may enhance birth weight, while more severe or frequent exercise, maintained for longer into the pregnancy: may result in lighter babies. There have been no reports of foetal injury or death in relation to trauma or contact during sporting activities. Despite this, a risk of severe blunt trauma is present in some sporting situations as pregnancy progresses. Exercise and lactation are compatible in the post-partum period, providing adequate calories are consumed. Considerations of pelvic floor function and type of delivery are relevant in planning a return to certain types of exercise at this time.

The epidemiology of preterm labor

There are many factors that are associated with preterm labor and delivery. These include maternal conditions such as medical illness, anemia and uterine malformation. They may be related to past events such as prior obstetric complication, previous preterm labor, cervical surgery or induced abortion. They may be intrinsic to the current pregnancy, such as reproductive tract infection, multifetal gestation, maternal age, short interpregnancy interval or prolonged menstrual conception interval. Maternal behaviors such as smoking and substance abuse can be risk factors for a short gestation. Demographic variables such as race, employment and socioeconomic status can also be associated with preterm labor. This article briefly reviews these subjects.

A randomised controlled trial of dietary energy restriction in the management of obese women with gestational diabetes

A randomised controlled trial was designed to determine the effect of moderate 30% maternal dietary energy restriction on the requirement for maternal insulin therapy and the incidence of macrosomia in gestational diabetes. Although the control group restricted their intake to a level similar to that of the intervention group (6,845 kiloJoules (kJ) versus 6,579 kJ), the resulting cohort could not identify any adverse effect of energy restriction in pregnancy. Energy restriction did not alter the frequency of insulin therapy (17.5% in the intervention group and 16.9% in the control group). Mean birthweight (3,461 g in the intervention group and 3,267 g in the control group) was not affected. There was a trend in the intervention group towards later gestational age at commencement of insulin therapy (33 weeks versus 31 weeks) and lower maximum daily insulin dose (23 units versus 60 units) which did not reach statistical significance. Energy restriction did not cause an increase in ketonemia.

Socio-economic disparities in pregnancy outcome: why do the poor fare so poorly?

In this paper, we review the evidence bearing on socio-economic disparities in pregnancy outcome, focusing on aetiological factors mediating the disparities in intrauterine growth restriction (IUGR) and preterm birth. We first summarise what is known about the attributable determinants of IUGR and preterm birth, emphasising their quantitative contributions (aetiological fractions) from a public health perspective. We then review studies relating these determinants to socio-economic status and, combined with the evidence about their aetiological fractions, reach some tentative conclusions about their roles as mediators of the socio-economic disparities. Cigarette smoking during pregnancy appears to be the most important mediating factor for IUGR, with low gestational weight gain and short stature also playing substantial roles. For preterm birth, socio-economic gradients in bacterial vaginosis and cigarette smoking appear to explain some of the socio-economic disparities; psychosocial factors may prove even more important, but their aetiological links with preterm birth require further clarification. Research that identifies and quantifies the causal pathways and mechanisms whereby social disadvantage leads to higher risks of IUGR and preterm birth may eventually help to reduce current disparities and improve pregnancy outcome across the entire socio-economic spectrum.

Exercise during pregnancy. A clinical update

Research dealing with exercise during pregnancy continues to demonstrate marked benefits for mother and fetus. The type, intensity, frequency, and duration of the exercise seem to be important determinants of its beneficial effects. Maternal benefits include improved cardiovascular function, limited weight gain and fat retention, improved attitude and mental state, easier and less complicated labor, quick recovery, and improved fitness. Fetal benefits may include decreased growth of the fat organ, improved stress tolerance, and advanced neurobehavioral maturation. Currently, the offspring are leaner at 5 years of age and have a slightly better neurodevelopmental outcome. Postpubertal effects are still unknown. In the absence of medical contraindications, women should be encouraged to maintain their prepregnancy activity level.

Determinants of participation in an epidemiological study of preterm delivery

We describe the study design and patterns of participation for a cohort study of preterm delivery, focused on genital tract infections, nutrition, tobacco use, illicit drugs and psychosocial stress. Women are recruited at 24-29 weeks' gestation from prenatal clinics at a teaching hospital and a county health department. We recruited 57% of the first 1843 eligible women; 29% refused and 8% could not be contacted. White women were somewhat more likely to participate than African-American women (61% vs. 54% respectively). More notable differences were found comparing teaching hospital and health department clinics (71% vs. 47% participation respectively), with the health department clinic having a greater proportion refuse (24% vs. 33%) and more women who could not be contacted (4% vs. 11%). Participation was affected only minimally by day or timing of recruitment, but inability to contact diminished substantially as the study continued (13-0%). Refusals were largely unrelated to patient attributes. Lower education predicted inability to contact. Risk of preterm delivery was 14% among recruited women, 10% among women who refused, and 15% among women whom we were not able to contact, demonstrating that, overall, risk status was not lower among recruited women.

Pregnancy outcome: physical activities inside versus outside the workplace

There is concern that the thermal, cardiovascular, metabolic, and biophysical changes which accompany physical activity may have detrimental effects on both mother and fetus. Research focused on physical activity in the workplace has identified four specific physical stresses (quiet standing, long hours, protracted ambulation, and heavy lifting) that are associated with an increased incidence of both prematurity and low birth weight. The physiological basis for these is believed to be that these activities cause intermittent but protracted reductions in uterine blood flow. Research focused on recreational physical activity during pregnancy has not identified similar associations. Indeed, these data indicate that the overall impact of regular recreational exercise on pregnancy outcome is positive for both mother and fetus. The physiological basis for these beneficial effects is believed to be that the interaction between the physiological adaptations to both exercise and pregnancy improve maternal cardiovascular reserve, maternal mechanisms for heat dissipation, and placental growth and functional capacity. Finally, there is preliminary evidence suggesting that the vibratory and auditory stimuli associated with regular recreational exercise may enhance functional maturation of the fetal brain.