REVISÃO REVIEW

 

Physical activity during pregnancy and maternal-child health outcomes: a systematic literature review

 

Atividade física na gestação e desfechos da saúde materno-infantil: uma revisão sistemática da literatura

 

 

Michael Maia SchlüsselI; Elton Bicalho de SouzaI; Michael Eduardo ReichenheimII; Gilberto KacI

IInstituto de Nutrição Josué de Castro, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil
IIInstituto de Medicina Social, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brasil

Correspondence

 

 


ABSTRACT

A systematic literature review was conducted to investigate the effects of physical activity during pregnancy on selected maternal-child health outcomes. The search included articles published from 1980 to 2005 in the MEDLINE and LILACS databases using key words such as physical activity, physical exercise, pregnancy, and gestation. The methodological quality of 37 selected articles was evaluated. It appears to be a consensus that some light-to-moderate physical activity is not a risk factor and may even be considered a protective factor for some outcomes. However, some studies found an association between specific activities (e.g., climbing stairs or standing for long periods) and inadequate birth weight, prematurity, and miscarriage. Few studies found an association between physical activity and maternal weight gain, mode of delivery, or fetal development. Further research is needed to fill these gaps and provide guidelines on the intensity, duration, and frequency of physical activity during pregnancy.

Motor Activity; Exercise; Pregnancy; Review


RESUMO

Realizou-se uma revisão sistemática da literatura com o objetivo de investigar o efeito da prática de atividade física durante a gestação em desfechos da saúde materno-infantil. A busca contemplou artigos publicados entre 1980 e 2005 nas bases de dados MEDLINE e LILACS utilizando-se as palavras-chave: physical activity; physical exercise; pregnancy e gestation. Foi feita uma avaliação da qualidade metodológica dos 37 artigos selecionados. Parece consenso que a prática de atividades físicas de intensidade leve ou moderada não consiste em fator de risco para alguns desfechos e pode representar fator de proteção. Contudo, alguns estudos encontraram associação entre atividades específicas, como subir escadas ou permanecer de pé por períodos prolongados e o peso inadequado do recém-nascido, prematuridade e aborto espontâneo. Poucos estudos encontraram associação entre a prática de atividades físicas e o ganho ponderal, tipo de parto e o desenvolvimento fetal. Novos estudos devem ser desenvolvidos com o objetivo de preencher essas lacunas, bem como propor recomendações acerca da intensidade, duração e freqüência das atividades físicas a serem realizadas durante a gestação.

Atividade Motora; Exercício Físico; Gravidez; Revisão


 

 

Introduction

Evidence from scientific studies points to the important role of physical activity in health promotion and quality of life and the prevention and control of various diseases 1. However, for individuals in specific physiological conditions, such benefits may not always occur, or are valid with certain restrictions.

Until a few decades ago, pregnant women were advised to reduce their activities and even interrupt their occupational work, especially in the final stage of pregnancy 1. However, since the 1990s experts have admitted the positive effect of regular physical activity during gestation and have even encouraged it, as long as the woman does not present specific adverse conditions 2.

In fact, there appears to be a consensus that maintaining light to moderate physical activity during an uncomplicated pregnancy provides various benefits for the woman's health 3. This is explained by the fact that physical activity causes a thermal response and circulatory redistribution, shifting the blood concentration from the uterus and placenta to the extremities. This process helps reduce and prevent lower back pain, fosters lower liquid retention, reduces cardiovascular stress, increases the oxygenation capacity, decreases blood pressure, reduces the risk of gestational diabetes, prevents thromboses and varicose veins, and helps control gestational weight gain 4,5,6.

The advantages also include emotional aspects, since physical activity helps make the pregnant woman more self-confident and satisfied with her appearance, in addition to raising her self-esteem, thus reducing the risks of postpartum depression 1,3.

However, physical activity during pregnancy still raises some controversy. According to Gallup 7, the published studies and guidelines on physical activity during pregnancy are insufficient. According to Morris & Johnson 8, although limited, the literature suggests that practicing moderate exercise during a pregnancy with no additional risks does not lead to undesirable outcomes for either the mother or the fetus. These authors go on to contend that more studies are necessary.

In addition, the benefits of physical activity during pregnancy do not appear to be widely publicized, and some consider the theme a taboo. Many women believe that the physiological limitations posed by pregnancy prevent them from participating in programs that promote regular exercise 9. Others believe that to remain rested and relaxed during pregnancy is significantly more important than exercising or maintaining an active lifestyle 10.

Considering the persistent controversies on the theme, the current study aims to conduct a systematic review of the scientific articles on the association between physical activity during pregnancy and the occurrence of maternal-child health outcomes. The review focused specifically on two aspects of pregnant women's physical activity: occupational physical activities and leisure-time physical activities. The former include activities pertaining to the individual's occupation (paid or unpaid), i.e., all activities performed in their place of work, including housework. Leisure-time physical activities include activities performed with the purpose of health promotion or simply for leisure.

 

Methods

The search was conducted in July 2006, and the articles were identified through a literature search of the MEDLINE and LILACS databases, using the following key words: (physical activity OR physical exercise) AND (pregnancy OR gestation). As the inclusion criteria, the articles had to have been published from 1980 to 2005, in Portuguese, English, or Spanish, and refer to cross-sectional, case-control, or follow-up (cohort) epidemiological studies. The principal outcomes of the studies had to be preeclampsia; gestational arterial hypertension; gestational diabetes mellitus; gestational weight gain; miscarriage; mode of delivery; fetal growth or development; birth weight; length at birth; or prematurity.

The search process initially involved a survey of the references based on the key words, which located 3,313 articles. These references were then sifted using some of the inclusion criteria as search filters: articles with an available abstract (2,703); published from 1980 to 2005 (2,488); with a sample consisting of humans (1,269); females (1,178); and published in English, Portuguese, or Spanish (1,085).

The second stage of the process consisted of reading the remaining 1,085 abstracts, based on which the other inclusion criteria (study design and target outcomes) were verified. After excluding review articles, articles on studies with an experimental design, and those that did not aim to study any of the selected mother-child outcomes, 39 studies were identified as adequate for inclusion in the present study. It was not possible to obtain access to two of these articles, so the final total was 37 studies. Figure 1, based on the proposal of the International Committee of Medical Journal Editors 11, presents a flowchart with a brief demonstration of all the stages in the article selection process for the present review.

 

 

To conduct an appraisal of the studies' methodological quality, each of the selected articles received a score, according to the criteria proposed by Downs & Black 12. The original checklist was adapted, ruling out the criteria related exclusively to intervention studies. Nineteen items were thus evaluated, allowing a maximum score of 20 points. Table 1 shows the items actually evaluated.

 

 

The studies were evaluated independently by two of the authors of the present review (E. B. S. and M. M. S.). The concordance in the scores assigned by the evaluators was also assessed using the Intra-Class Correlation Coefficient (ICC). The result was classified according to the scale proposed by Shrout 13 to measure concordance between different evaluation methods. This scale consists of five categories: virtually no concordance (< 0.1); weak (0.11-0.40); reasonable (0.41-0.60); moderate (0.61-0.80); and substantial (0.81-1.0). To rule on possible discordances in assigning scores to the articles, a third author (G. K.) was consulted.

The studies were organized according to the following: year of publication; country of origin; language; study design (cohort, casecontrol, cross-sectional); physical activity measurement instrument; sample size; maternal-child health outcomes; age of individuals studied (years); results; estimators used in the analysis and scoring of the methodological quality.

Finally, the studies were grouped that found similar results as to a given outcome, with the objective of systematizing and facilitating the understanding of all the reviewed articles' findings. Next, the mean of the scores assigned to the studies included in each group was calculated. No articles were rejected because of methodological limitations, but the findings were considered more consistent in the studies that received higher scores.

 

Results

As shown in Table 2, the largest concentration of published articles (20) was in the 1990s. However, there was also an upward trend in publications on the subject, given that 11 studies were published in the first five years of the current decade. The majority of the studies were from the United States, and the only one conducted in Brazil 14 was also the only one not published in English.

Among the observational studies that evaluated possible associations between physical activity and maternal-child health outcomes, those with a prospective cohort design were the most common. Questionnaires were the most widely used instruments, reinforcing this as the most feasible option for measuring physical activity in epidemiological studies 15. The sample sizes varied from 67 to 21,342.

Table 3 shows that of the 37 articles reviewed, 15 used birth weight as the dependent variable, making this the most widely studied outcome. Among the articles that informed the participants' age (26), only five reported having included pregnant women younger than 18 years in their sample.

The mean methodological quality score was 15.8 points, with 9 and 20 points as the minimum and maximum obtained, respectively. The result of the comparison between the scores assigned to the studies by the different evaluators (ICC = 0.898; 95%CI: 0.835-0.961) indicates a high level of concordance, having been classified as the highest (substantial concordance) in the qualification scale used.

Table 4 provides a synthesis of the principal results of the current review. Physical activity does in fact appear to reduce the risk of preeclampsia and gestational diabetes. The results were conflicting for other outcomes, like miscarriage and gestational weight gain control. The same was true for the fetal and childhood outcomes. Some studies do not describe a harmful association between physical activity in pregnancy and inadequate weight gain or prematurity, however some specific activities, like climbing stairs or working for extended time on one's feet were identified as risk factors for these outcomes.

Few studies were identified on the effects of physical activity during pregnancy on fetal growth or development, length at birth, and mode of delivery.

 

Discussion

The production of scientific material on physical activity in pregnancy and its effects on maternal-child health outcomes has increased substantially, mainly in the last decade. According to some authors 3,8,16,17, light-to-moderate exercise also provides health benefits during pregnancy, so women should be encouraged to maintain an active lifestyle during gestation. The results of some of the reviewed articles corroborate the opinion of these authors.

Considering both light and moderate leisure-time and occupational physical activities, physically active pregnant women show a decreased risk of developing preeclampsia 18,19,20, hypertension 18,20, and gestational diabetes mellitus 21,22,23. However, in relation to the other maternal outcomes, the results tend to be conflicting. Four studies analyzed leisure-time physical activity in relation to miscarriage 24,25,26,27, and their results did not indicate an increased risk of this outcome among physically active pregnant women. Importantly, however, the studies that pointed to high-intensity occupational activity as a risk factor for miscarriage 28,29 were precisely those that showed greater methodological care, among other reasons because they based their conclusions on stratified analyses rather than crude data.

In a recent study 30, physical activity was identified as one of three behavioral determinants for gestational weight gain control. However, the studies reviewed here did not agree as to the hypothesis of greater control of weight gain among pregnant women who exercise regularly. Five of the articles reviewed 27,31,32,33,34 studied this relationship, and three of them 27,32,33 did not support the hypothesis. However, the three were precisely the ones with the lowest methodological quality scores or which failed to report the method used to evaluate this outcome.

Only four articles evaluated the effect of physical activity on mode of delivery, of which three 27,32,33 failed to show significant differences between caesarian rates in women with and without exercise during pregnancy. Only one study 39 showed an association between physical activity and mode of delivery, suggesting a considerably increased risk of caesarian among sedentary pregnant women.

As for fetal and childhood outcomes, the results also failed to show a consensus, but once again light or moderate physical exercise was not identified as a risk factor. As for birth weight, numerous studies 25,32,33,36,37,38,39,40,41,42 showed that there is no increased risk of low birth weight for pregnant women who practice leisure-time physical activities.

Among the studies that analyzed physical activity as a predictive factor for low birth weight, some 27,34,43 showed a subtle association, but the mean weight of the newborns was not inadequate in any of the groups studied. However, other studies 42,44 identified some specific activities (e.g., doing laundry on standing on one's feet for hours on end), but not regular physical activity in general, as risk factors for inadequate birth weight.

The same was observed in studies in which the principal outcome was gestational age at delivery. Numerous articles either found no association or reported a protective effect for physical activity during pregnancy in relation to premature birth 27,32,33,34,36,40,42,45,46,47. Again, some specific activities, like climbing stairs and occupational activities that require standing for prolonged periods or cause fatigue and require agility, were identified as risk factors for premature birth 25,48,49.

Little is known about the effects of physical activity on fetal development. Only two studies with this focus were identified, one with the objective of evaluating the effects of occupational activities on intrauterine growth retardation 50 and the other on leisure-time physical activities and the occurrence of neural tube defects 51. Apparently, light occupational activities do not cause problems with the fetal growth rate, but the same was not reported for women who maintained moderate or high-intensity activities. According to the authors of the second study, leisure-time physical activity appears to play a protective role against the occurrence of neural tube malformations.

As for length at birth, only one study was located 52, showing a decreased risk of large-for-gestational-age neonates among physically active pregnant women, but the study's methodological quality score was not one of the highest.

Two selected articles were not included in the present review due to lack of access to the full text. One of the articles 53 investigates the effects of physical activity during pregnancy on labor among mothers of premature infants. Based on the results, the authors suggest that physical activity in pregnancy can substantially reduce (by up to 32 minutes) the duration of the second stage of labor, as well as the risk of obstetric complications in this group of women. The second article 54 describes the results of two studies that investigated the effects of jogging during pregnancy. In the first, no significant differences were observed between the groups of mothers who jogged (versus those who did not jog) in relation to gestational weight gain and birth weight. Few obstetric complications were also observed in the group of women who jogged during pregnancy. The second study refers to the effects of jogging on maternal and fetal heart rates, and was outside the scope of the current review.

Although more than a decade has transpired since the first recommendation by the American College of Obstetricians and Gynecologists (ACOG) 2 in favor of physical activity during pregnancy, little knowledge has been accumulated on the effects of this continuous practice on outcomes like fetal development, length at birth, miscarriage, mode of delivery, and gestational weight gain control. However, for other outcomes like birth weight and prematurity, a consensus appears to be taking shape that light or moderate leisure-time or occupational physical activities do not constitute a risk factor, and in some cases may be considered a protective factor.

Although displaying some important limitations, several studies received high scores for their methodological quality. The internal consistency of the scores assigned to the studies gave greater robustness to this evaluation. Among the Downs & Black criteria 12 considered here, the principal limitations observed in the studies were: failing to commenting on the sample's representativeness, not presenting the list of the principal confounders and/or not including them in the analysis or not making this clear in the text, and not presenting the study's power to detect differences between the groups. The lowest scores were assigned to articles from the first two decades, suggesting that current studies are possibly being developed and reported with greater methodological care. Since this review was conducted in databases with rigorous indexing criteria, incorporating only articles published in certain languages, a publication bias cannot be ruled out.

Importantly, the description was rather precarious for the individuals comprising the samples in some of the studies reviewed here. Gottlieb 55, in a brief communication, suggests that some of the contradictions observed in the results of studies on physical activity in pregnancy may result from the different methodologies, particularly differences among the individuals comprising the samples.

In relation to the sample group, Dye & Oldenettel 56 already indicated that analyses based on special groups like elite athletes may lead to an error in their comparison with sedentary pregnant women. The present review did not include studies that specifically analyzed pregnant athletes. Even so, it is not difficult to imagine that physically fit pregnant women, with physical activity incorporated into their lives as a daily practice since before pregnancy, may constitute a particular group, quite different from sedentary pregnant women. The results of some of the studies reviewed here even demonstrated these peculiarities by presenting different effects for groups of pregnant women who practiced leisure-time physical activities before pregnancy and those who began exercising during gestation. Therefore, the knowledge should be interpreted in light of this consideration.

Another aspect that merits reflection is the fact that the Downs & Black criteria 12 do not include any assessment of the quality of the research instruments or the exposure measurement process. Since most of the studies used questionnaires to assess the target phenomena, it would be interesting for future reviews to systematically incorporate these important methodological aspects.

The authors of the current review believe that the ACOG recommendations, especially those referring to care in the monitoring and follow-up of pregnant women, should be considered the baseline for any proposal to encourage a more active lifestyle for women experiencing the unique physiological moment of pregnancy.

In addition, the information presented here on what are considered risk activities for the occurrence of certain maternal-child health outcomes should be widely publicized and especially incorporated into prenatal care guidelines. We were only able to find vague guidelines from the Brazilian Ministry of Health concerning physical activity during pregnancy. The Ministry's technical handbook for prenatal care and postpartum follow-up 57 suggests that physical activities should be encouraged to assist control of blood pressure and that pregnant women presenting gestational diabetes mellitus should exercise regularly. However, there was no recommendation for pregnant women as to exercise modality or even frequency.

Although light-to-moderate physical activity does not appear to be significantly associated with increased risk, more studies are needed to fill the gaps identified here. Most studies in the current review lacked any kind of standardization as to the type of activities evaluated, merely defining them as either leisure-time or occupational physical activities. It thus becomes practically impossible to compare the studies' results, so that discussion of the findings becomes basically descriptive.

The definition of physical activity encompasses a series of aspects including all voluntary activities, like leisure-time, domestic, occupational, and commuting activities 60. When counseling the pregnant woman as to physical activity during pregnancy, it is thus necessary to mention the frequency, intensity, and duration of such activities. These are the points that appear to lack the most information, since neither the ACOG nor the Brazilian Ministry of Health guidelines mention such specifications.

 

Contributors

M. M. Schlüssel participated in all stages of the study, from planning the review to the literature survey, article selection, Downs & Black scoring, analysis of the results, and drafting of the article. E. B. Souza contributed to the literature review, Downs & Black scoring, and revisions of all the versions of the manuscript. M. E. Reichenheim collaborated in the methodological review and final revision of the article. G. Kac participated in planning the review and orientation and revision of all versions of the article.

 

Acknowledgments

The authors wish to thank the Brazilian National Research Council (CNPq) and the Coordinating Division for the Support of Graduate Studies (CAPES).

 

References

1. Batista DC, Chiara VL, Gugelmin SA, Martins PD. Atividade física e gestação: saúde da gestante não atleta e crescimento fetal. Rev Bras Saúde Matern Infant 2003; 3:151-8.         

2. American College of Obstetricians and Gynecologists. Exercise during pregnancy and the postpartum period. Washington DC: American College of Obstetricians and Gynecologists; 1994.         

3. Lima FR, Oliveira N. Gravidez e exercício. Rev Bras Reumatol 2005; 45:188-90.         

4. ACOG Committee on Obstetric Practice. Committee opinion #267: exercise during pregnancy and the postpartum period. Obstet Gynecol 2002; 99:171-3.         

5. Shills ME, Olson JA, Shike M, Ross AC, organizadores. Tratado de nutrição moderna na saúde e na doença. São Paulo: Edições Manole; 2003.         

6. Hills AP, Byrne NM. Physical activity in the management of obesity. Clin Dermatol 2004; 22:315-8.         

7. Gallup E. Aspectos legais da prescrição de exercícios para a gravidez. Seção III: aplicações práticas. In: Artal R, Wiswell AR, Drinkwater LR, organizadores. O exercício na gravidez. São Paulo: Edições Manole; 1999. p. 293-8.         

8. Morris SN, Johnson NR. Exercise during pregnancy: a critical appraisal of the literature. J Reprod Med 2005; 50:181-8.         

9. Downs DS, Hausenblas HA. Women's exercise beliefs and behaviors during their pregnancy and postpartum. J Midwifery Women's Health 2004; 49:138-44.         

10. Clarke PE, Gross H. Women's behavior, beliefs and information sources about physical exercise in pregnancy. Midwifery 2004; 20:133-41.         

11. International Committee of Medical Journal Editors. Improving the quality of reports of meta-analyses of randomised controlled trials: the QUOROM statement checklist. http://www.consort-statement.org/QUOROM.pdf (accessed on 14/May/2007).         

12. Downs SH, Black N. The feasibility of creating a checklist for the assessment of the methodological quality both of randomised and non-randomised studies of health care interventions. J Epidemiol Community Health 1998; 52:377-84.         

13. Shrout PE. Measurement reliability and agreement in psychiatry. Stat Methods Med Res 1998; 7:301-17.         

14. Takito MY, Benício MHD, Latorre MRDO. Postura materna durante a gestação e sua influência sobre o peso ao nascer. Rev Saúde Pública 2005; 39: 325-32.         

15. Reis RS, Petroski EL, Lopes AS. Medidas da atividade física: revisão de métodos. Rev Bras Cineantropom Desempenho Hum 2000; 2:89-96.         

16. Dewey KG, McCrory MA. Effects of dieting and physical activity on pregnancy and lactation. Am J Clin Nutr 1994; 59(2 Suppl):446S-53S.         

17. Clapp JF 3rd. Exercise during pregnancy: a clinical update. Clin Sports Med 2000; 19:273-83.         

18. Marcoux S, Brisson J, Fabia J. The effect of leisure time physical activity on the risk of pre-eclampsia and gestational hypertension. J Epidemiol Community Health 1989; 43:147-52.         

19. Sorensen TK, Williams MA, Lee IM, Dashow EE, Thompson ML, Luthy DA. Recreational physical activity during pregnancy and risk of preeclampsia. Hypertension 2003; 41:1273-80.         

20. Saftlas AF, Logsden-Sackett N, Wang W, Woolson R, Bracken MB. Work, leisure-time physical activity, and risk of preeclampsia and gestational hypertension. Am J Epidemiol 2004; 160:758-65.         

21. Dye TD, Knox KL, Artal R, Aubry RH, Wojtowycz MA. Physical activity, obesity, and diabetes in pregnancy. Am J Epidemiol 1997; 146:961-5.         

22. Dempsey JC, Sorensen TK, Williams MA, Lee IM, Miller RS, Dashow EE, et al. Prospective study of gestational diabetes mellitus risk in relation to maternal recreational physical activity before and during pregnancy. Am J Epidemiol 2004; 159: 663-70.         

23. Dempsey JC, Butler CL, Sorensen TK, Lee IM, Thompson ML, Miller RS, et al. A case-control study of maternal recreational physical activity and risk of gestational diabetes mellitus. Diabetes Res Clin Pract 2004; 66:203-15.         

24. Clapp JF 3rd. The effects of maternal exercise on early pregnancy outcome. Am J Obstet Gynecol 1989; 161(6 Pt 1):1453-7.         

25. Klebanoff MA, Shiono PH, Carey JC. The effect of physical activity during pregnancy on preterm delivery and birth weight. Am J Obstet Gynecol 1990; 163:1450-6.         

26. Latka M, Kline J, Hatch M. Exercise and spontaneous abortion of known karyotype. Epidemiology 1999; 10:73-5.         

27. Magann EF, Evans SF, Weitz B, Newnham J. Antepartum, intrapartum, and neonatal significance of exercise on healthy low-risk pregnant working women. Obstet Gynecol 2002; 99:466-72.         

28. Florack EIM, Zielhuis GA, Pellegrino JEMC, Rolland R. Occupational physical activity and the occurrence of spontaneous abortion. Int J Epidemiol 1993; 22:878-84.         

29. El Metwalli AGA, Badawy AM, El Baghdadi LA, El Wehady A. Occupational physical activity and pregnancy outcome. Eur J Obstet Gynecol Reprod Biol 2001; 100:41-5.         

30. Olson CM, Strawderman MS. Modifiable behavioral factors in a biopsychosocial model predict inadequate and excessive gestational weight gain. J Am Dietetic Assoc 2003; 103:48-54.         

31. Clapp JF 3rd, Little KD. Effect of recreational exercise on pregnancy weight gain and subcutaneous fat deposition. Med Sci Sports Exerc 1995; 27: 170-7.         

32. Sternfeld B, Quesenberry Jr CP, Eskenazi B, Newman LA. Exercise during pregnancy and pregnancy outcome. Med Sci Sports Exerc 1995; 27:634-40.         

33. Horns PN, Ratcliffe LP, Leggett JC, Swanson MS. Pregnancy outcomes among active and sedentary primiparous women. J Obstet Gynecol Neonatal Nurs 1996; 25:49-54.         

34. Rao S, Kanade A, Margetts BM, Yajnik CS, Lubree H, Rege S, et al. Maternal activity in relation to birth size in rural India. The Pune Maternal Nutrition Study. Eur J Clin Nutr 2003; 57:531-42.         

35. Bungum TJ, Peaslee DL, Jackson AW, Perez MA. Exercise during pregnancy and type of delivery in nulliparae. J Obstet Gynecol Neonatal Nurs 2000; 29:258-64.         

36. Jarrett JC 2nd, Spellacy WN. Jogging during pregnancy: an improved outcome? Obstet Gynecol 1983; 61:705-9.         

37. Rabkin CS, Anderson HR, Bland JM, Brooke OG, Chamberlain G, Peacock JL. Maternal activity and birth weight: a prospective, population-based study. Am J Epidemiol 1990; 131:522-31.         

38. Rose NC, Haddow JE, Palomaki GE, Knight GJ. Self-rated physical activity level during the second trimester and pregnancy outcome. Obstet Gynecol 1991; 78:1078-80.         

39. Hatch MC, Shu XO, McLean DE, Levin B, Begg M, Reuss L, et al. Maternal exercise during pregnancy, physical fitness, and fetal growth. Am J Epidemiol 1993; 137:1105-14.         

40. Florack EI, Pellegrino AE, Zielhuis GA, Rolland R. Influence of occupational physical activity on pregnancy duration and birthweight. Scand J Work Environ Health 1995; 21:199-207.         

41. Schramm WF, Stockbauer JW, Hoffman HJ. Exercise, employment, other daily activities, and adverse pregnancy outcomes. Am J Epidemiol 1996; 143:211-8.         

42. Leiferman JA, Evenson KR. The effect of regular leisure physical activity on birth outcomes. Matern Child Health J 2003; 7:59-64.         

43. Bell RJ, Palma SM, Lumley JM. The effect of vigorous exercise during pregnancy on birth-weight. Aust N Z J Obstet Gynaecol 1995; 35:46-51.         

44. Henriksen TB, Hedegaard M, Secher NJ. Standing and walking at work and birthweight. Acta Obstet Gynecol Scand 1995; 74:509-16.         

45. Berkowitz GS, Kelsey JL, Holford TR, Berkowitz RL. Physical activity and the risk of spontaneous preterm delivery. J Reprod Med 1983; 28:581-8.         

46. Misra DP, Strobino DM, Stashinko EE, Nagey DA, Nanda J. Effects of physical activity on preterm birth. Am J Epidemiol 1998; 147:628-535.         

47. Hatch M, Levin B, Shu XO, Susser M. Maternal leisure-time exercise and timely delivery. Am J Public Health 1998; 88:1528-33.         

48. Henriksen TB, Hedegaard M, Secher NJ, Wilcox AJ. Standing at work and preterm delivery. Br J Obstet Gynaecol 1995; 102:198-206.         

49. Koemeester AP, Broersen JPJ, Treffers PE. Physical work load and gestational age at delivery. Occup Environ Medicine 1995; 52:313-5.         

50. Spinillo A, Capuzzo E, Baltaro F, Piazzi G, Nicola S, Iasci A. The effect of work activity in pregnancy on the risk of fetal growth retardation. Acta Obstet Gynecol Scand 1996; 75:531-6.         

51. Carmichael SL, Shaw GM, Neri E, Schaffer DM, Selvin S. Physical activity and risk of neural tube defects. Matern Child Health J 2002; 6:151-7.         

52. Alderman BW, Zhao H, Holt VL, Watts DH, Beresford SAA. Maternal physical activity in pregnancy and infant size for gestational age. Ann Epidemiol 1998; 8:513-9.         

53. Botkin C, Driscoll CE. Maternal aerobic exercise: newborn effects. Fam Pract Res J 1991; 11:387-93.         

54. Dale E, Mullinax KM, Bryan DH. Exercise during pregnancy: effects on the fetus. Can J Appl Sport Sci 1982; 7:98-103.         

55. Gottlieb S. Exercise during pregnancy may increase birth weight. BMJ 2001; 322:193.         

56. Dye TD, Oldenettel D. Physical activity and risk of preterm labor: an epidemiological review and synthesis of recent literature. Semin Perinatol 1996; 20:334-9.         

57. Área Técnica de Saúde da Mulher, Departamento de Ações Programáticas Estratégicas, Secretaria de Atenção à Saúde, Ministério da Saúde. Pré-natal e puerpério: atenção qualificada e humanizada - manual técnico. Brasília: Ministério da Saúde; 2005.         

58. Spinillo A, Capuzzo E, Colonna L, Piazzi G, Nicola S, Baltaro F. The effect of work activity in pregnancy on the risk of severe preeclampsia. Aust N Z J Obstet Gynaecol 1995; 35:380-5.         

59. Campbell MK, Mottola MF. Recreational exercise and occupational activity during pregnancy and birth weight: A case-control study. Am J Obstet Gynecol 2001; 184:403-8.         

60. Mendonça CP, Anjos LA. Aspectos das práticas alimentares e da atividade física como determinantes do crescimento do sobrepeso/obesidade no Brasil. Cad Saúde Pública 2004; 20:698-709.         

 

 

Correspondence:
G. Kac
Instituto de Nutrição Josué de Castro
Universidade Federal do Rio de Janeiro
Avenida Brigadeiro Trompowski s/n, Bloco J
2º andar, sala 29
Rio de Janeiro, RJ
21941-590, Brasil
kacetal@gmail.com

Submitted on 14/Feb/2007
Final version resubmitted on 30/May/2007
Approved on 25/Jun/2007

Escola Nacional de Saúde Pública Sergio Arouca, Fundação Oswaldo Cruz Rio de Janeiro - RJ - Brazil
E-mail: cadernos@ensp.fiocruz.br