Exercise during pregnancy reduces the rate of cesarean and instrumental deliveries: Results of a randomized controlled trial

Abstract

Objective: In this study, the authors assessed the effects of a structured, moderate-intensity exercise program during the entire length of pregnancy on a woman's method of delivery. Methods: A randomized controlled trial was conducted with 290 healthy pregnant Caucasian (Spanish) women with a singleton gestation who were randomly assigned to either an exercise (n = 138) or a control (n = 152) group. Pregnancy outcomes, including the type of delivery, were measured at the end of the pregnancy. Results: The percentage of cesarean and instrumental deliveries in the exercise group were lower than in the control group (15.9%, n = 22; 11.6%, n = 16 vs. 23%, n = 35; 19.1%, n = 29, respectively; p = 0.03). The overall health status of the newborn as well as other pregnancy outcomes was unaffected. Conclusions: Based on these results, a supervised program of moderate-intensity exercise performed throughout pregnancy was associated with a reduction in the rate of cesarean, instrumental deliveries and can be recommended for healthy women in pregnancy.

Full text

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The Journal of Maternal-Fetal and Neonatal Medicine, 2012; 25(11): 2372–2376
© 2012 Informa UK, Ltd.
ISSN 1476-7058 print/ISSN 1476-4954 online
DOI: 10.3109/14767058.2012.696165
Objective: In this study, the authors assessed the effects of a
structured, moderate-intensity exercise program during the
entire length of pregnancy on a woman’s method of delivery.
Methods: A randomized controlled trial was conducted with 290
healthy pregnant Caucasian (Spanish) women with a singleton
gestation who were randomly assigned to either an exercise
(n = 138) or a control (n = 152) group. Pregnancy outcomes,
including the type of delivery, were measured at the end of the
pregnancy. Results: The percentage of cesarean and instrumental
deliveries in the exercise group were lower than in the control
group (15.9%, n = 22; 11.6%, n = 16 vs. 23%, n = 35; 19.1%,
n = 29, respectively; p = 0.03). The overall health status of the
newborn as well as other pregnancy outcomes was unaffected.
Conclusions: Based on these results, a supervised program of
moderate-intensity exercise performed throughout pregnancy
was associated with a reduction in the rate of cesarean, instru-
mental deliveries and can be recommended for healthy women
in pregnancy.
Keywords: Delivery, gestation, labor, outcome, physical activity
Introduction
Pregnancy is a unique process in which nearly all of the body’s
control systems are modied to maintain both maternal and fetal
homeostasis [1]. With physical exercise (PE) becoming an integral
part of many women’s lives, the question remains as to whether
this exercise has any adverse eects on pregnancy outcomes [2].
In theory, the addition of PE may represent a signicant challenge
to both the maternal and fetal well-being as the dual stresses of
pregnancy and exercise may create conicting physiological
demands and thus adversely aect pregnancy outcomes [3].
Research on exercise in pregnancy has increased over the
years, and many studies have demonstrated the benets of PE on
maternal and fetal outcomes [4,5], including positive maternal
psychological factors [6,7] and decreased risks of preeclampsia
and gestational diabetes (GD [8,9]).
Despite the advancement of knowledge on exercise during
pregnancy, a general lack of consensus persists regarding the
eect of PE on the type of delivery. Scientic evidence from
experimental studies on the inuence of exercise on the type
of delivery is limited and imprecise [10]. As most studies were
observational (with no intervention), and focused on leisure time
and occupational physical activity, little information is available
about the eects of a supervised exercise program throughout
pregnancy on the type of delivery.
Since 2000, the worldwide rate of cesarean delivery has
risen even more sharply and is currently over 31%. is rate is
concerning from a public health perspective, because the proce-
dure is not without risk to the mother and fetus [10]. Known
risks of cesarean sections include the following: maternal post-
natal complications stemming from major abdominal surgery,
placental problems in future pregnancies, neonatal respiratory
diculties, poor sucking reex in the newborn, infection, exces-
sive blood loss, maternal respiratory complications, anesthesia
reactions and longer hospitalizations [11,12].
e aim of the present study was to understand the inuence
of an exercise program during pregnancy (all three trimesters)
on the type of delivery that ultimately occurred. A secondary
objective was to determine if exercise could be a protective factor
against cesarean sections or instrumental delivery methods in
women who experienced excessive weight gain during pregnancy.
We hypothesized that regular exercise during pregnancy would
be associated with a lower percentage of cesarean sections in
normal pregnancy and lower cases of instrumental deliveries and
cesarean sections in pregnant women with excessive weight gain.
Methods
e present study was a randomized controlled clinical trial (RCT)
in accordance with the recently published CONSORT guidelines
(http://www.consort-statement.org [13]). e study also met the
ethical standards in Sport and Exercise Science Research [14].
e research protocol was reviewed and approved by the
Ethical Committee of Hospital Universitario de Fuenlabrada
(Madrid, Spain) and followed the ethical guidelines outlined in the
Declaration of Helsinki (last modied in 2008). e research was
performed in the obstetrics department of the Hospital. All partici-
pants were informed about the aim and study protocol, and written
informed consents were obtained from all participating women.
Study subjects
Participants were recruited from a hospital database. All
the women were healthy with uncomplicated and singleton
pregnancies. To allocate participants, a computer-generated list of
random numbers was used. e randomization process (sequence
generation, allocation concealment and implementation) was
conducted for three dierent study investigators.
Exercise during pregnancy reduces the rate of cesarean and
instrumental deliveries: results of a randomized controlled trial
Ruben Barakat, Mireia Pelaez, Carmina Lopez, Rocío Montejo & Javier Coteron
Faculty of Physical Activity and Sports Sciences, Technical University of Madrid (UPM), Madrid, Spain
Correspondence: Ruben Barakat, Faculty of Physical Activity and Sports Sciences, Technical University of Madrid (UPM), Martin Fierro, 7, Madrid, 28040
Spain. Tel: +34 91 336 40 20. E-mail: barakatruben@gmail.com
e Journal of Maternal-Fetal and Neonatal Medicine
2012
25
11
2372
2376
© 2012 Informa UK, Ltd.
10.3109/14767058.2012.696165
1476-7058
1476-4954
22November2011
12December2011
18May2012
Exercise during pregnancy reduces the rate of cesarean
R. Barakat et al.
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Exercise during pregnancy reduces the rate of cesarean 2373
©  Informa UK, Ltd.
Patients were excluded if they had any type of absolute obstet-
rical contraindication to exercise regarded by the American
College of Obstetricians and Gynecologists (ACOG) (e.g. multiple
pregnancies or risk for premature labor [15]). Other exclusion
criteria included those women not planning to give birth in the
obstetrics department of the study hospital, not receiving medical
follow-up throughout the pregnancy, participating in another
physical activity program or having a high level of pregestational
PE (four or more times per week).
Intervention
e physical conditioning program included a total of three
40–45-min sessions per week, beginning at the start of the preg-
nancy (weeks 6–9) until the end of the third trimester (weeks
38–39). us, there was an average of 85 training sessions
planned for each participant in the absence of preterm delivery.
All subjects used a heart rate (HR) monitor (Accurex Plus, Polar
Electro OY, Oulu, Finland) during the training sessions to ensure
that exercise intensity was light-to-moderate. eir HR was
consistently kept under 70% of their age-predicted maximum HR
value, calculated as 220 minus age.
Each session included a 25-minute core portion that was
preceded and followed by a gradual warm-up and cool-down
period, both of 7–8 min in duration and consisting of walking and
light, static stretching (to avoid any muscle pains) of most muscle
groups (upper and lower limbs, neck and trunk muscles).
We used exercises covering the major muscle group in the
arms and abdomen to promote good posture, prevent lower back
pain and strengthen the muscles of labor and the pelvic oor. We
also included an aerobic dance section in every session. Exercises
involving the Valsalva maneuver, extreme stretching, joint over-
extension, ballistic movements and jumping were specically
avoided. Furthermore, exercises in the supine position were
performed for no longer than 2 min.
In order to maximize safety, adherence to the training program
and its ecacy, all sessions were (1) supervised by a qualied
tness specialist (working with groups of 10–12 subjects) with
an obstetrician’s assistance; (2) accompanied by music; and
(3) performed in the Health Care Center in a spacious, well-lit
room under favorable environmental conditions (altitude 600 m;
temperature = 19–21°C; humidity = 50–60%). An adequate
intake of calories and nutrients was assured before the start of
the exercise session.
Measurement of variables
We obtained the type of delivery (normal, instrumental, or
cesarean) and pregnancy outcomes from hospital perinatal
records including gestational age (days), preterm deliveries (before
the completion of 37 weeks gestation), maternal weight gain (kg),
blood pressure, 1-h oral glucose tolerance test, cases of GD, birth
weight/length, pH of the umbilical cord blood and Apgar score.
e following maternal characteristics were obtained by an
initial interview at the rst prenatal visit: maternal age, parity,
smoking habits during pregnancy, occupational activity, time
standing per day, time spent on domestic activities and educa-
tional level.
We measured weight and height of the mother by standard
procedures at the start of the study. Body mass index (BMI) was
calculated as weight (in kg) divided by height (in m) squared.
Adherence (attendance) to the training program was measured
using a checklist at every session.
Data analysis
Our data (presented in Tables I and II) were analyzed using
Student’s t tests for independent samples, one-way ANOVA and
χ2 tests.
Maternal characteristics of the study sample by group (EG and
CG) were reported in terms of means and standard deviation
(SD), unless otherwise stated. Relative to frequencies, χ2 tests were
used. For group comparisons of pregnancy outcomes, continuous
and nominal data were analyzed with t tests for unpaired data and
χ2 tests, respectively. To estimate the eect size, relative risk and
95% condence intervals for the dierence were calculated.
An interim analysis was conducted to assure the safety of
the intervention during the trial (n = 60). e levels of signi-
cance maintained an overall p value of 0.05 and were calculated
according to the O’Brien-Fleming stopping boundaries [16].
Determination of sample size: To detect a 10% reduction in
cesarean sections with a two-sided 5% signicance level and
a power of 80%, a sample size of 125 pregnant per group was
necessary, given an anticipated dropout rate of 15% [17].
Table I. Maternal characteristics: comparison between control and exercise
groups.
Controls (n = 152) Exercise (n = 138)
p valueMean (SD) or n/% Mean (SD) or n/%
Maternal age
(years)
31.7 (4.5) 31.4 (3.2) 0.54
BMIa23.6 (4.0) 24.0 (4.3) 0.45
Parity
0 83/54.6 88/60.9 0.19
1 60/39.5 46/33.3
>1 9/5.9 4/2.9
Occupational activity
Active 51/33.6 55/39.9 0.50
Sedentary 68/44.7 58/42
Housewives 33/21.7 25/18.1
Educational level
College 45/29.6 29/21 0.23
High school 67/44.1 70/50.7
<High school 40/26.3 39/28.3
Smoked during pregnancy
Yes 29/19.1 18/13 0.16
No 123/80.9 120/87
Standing hours/day
>3 h/day 95/62.5 92/66.7 0.45
3 or <3 h/day 57/37.5 46/33.3
Previous preterm deliveries
0 146/96.1 130/94.2 0.46
1 or >1 6/3.9 8/5.8
Previous miscarriages
0 104/68.4 107/77.5 0.20
1 42/27.6 28/20.3
>1 6/3.9 3/2.2
Previous low birth weight deliveries
0 147/96.7 135/97.8 0.56
1 or >1 5/3.3 3/2.2
Housework hours/day
>2 h/day 81/53.3 83/60.1 0.24
2 or <2 h/day 71/45.5 55/39.9
aBMI at rst prenatal medical visit.
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2374 R. Barakat et al.
e Journal of Maternal-Fetal and Neonatal Medicine
Statistical analysis was performed using the Statistical Package
for Social Sciences soware (version 14.0 for Windows; SPSS Inc.,
Chicago, IL, USA) with the level of statistical signicance set to <0.05.
Results
Out of the 595 women originally contacted at their rst prenatal
visit, 320 Caucasian, healthy gravid women [aged 31 (SD = 4)
years] were randomly assigned to either an exercise group (EG,
n = 160) or a control group (CG, n = 160). Of these women, 290
belonged to a low-to-medium socioeconomic class.
A ow diagram of the randomization process of the study
participants is shown in Figure 1. Fourteen percent (22/160) and
5% (8/160) of pregnant women in the EG and CG, respectively,
were lost to follow-up. We excluded 22 women in the EG for the
following reasons: discontinued intervention (n = 8), risk for
premature labor (n = 3), pregnancy-induced hypertension (n =
2) and personal reasons, such as change of residence or work-
related issues (n = 9). Eight women were excluded in the CG for
pregnancy-induced hypertension (n = 2), threat of premature
delivery (n = 3) and personal reasons (n = 3).
Adherence to training and possible adverse effects
Adherence to the training program in the EG was 87%. In the EG,
138 pregnant completed the program with a high level of satis-
faction. Because participating in another exercise program was
an exclusion criterion for the CG, this was veried via telephone
interview at week 20 and at the end of pregnancy. In the end, 138
women in the EG and 152 women in the CG were included in the
analysis.
Maternal characteristics: Background variables of the study
populations are shown in Table I. ere were no signicant
dierences (p > 0.05) in background variables between the two
study groups; these background variables included maternal age,
BMI, parity, previous preterm delivery, previous miscarriages and
previous low birth weight. Maternal characteristics that could be
potentially inuence the main study outcome (e.g. occupational
activity, educational level, smoking during pregnancy, standing
and housework) were also not signicantly dierent between the
groups.
Type of delivery and other pregnancy outcomes
We observed that the percentage of cesarean sections (15.9%,
n = 22) and instrumental deliveries (11.6%, n = 16) in the EG
was lower than those in the CG (23%, n = 35; 19.1%, n = 29,
respectively; Z = 2.73; p = 0.03; 1−β=0.65). We observed a relative
risk (RR) of cesarean section for women in the EG compared
with the CG (0.69, 95% CI = 0.42, 0.82). Nine women delivered
before term in the EG (6.5%) and 10 (6.6%) in the CG. e mean
gestational age was similar in both groups [EG = 278.0 (SD = 9.9),
CG = 278.3 (SD = 10.3) days].
When other pregnancy outcomes were examined, we found
similar results between groups for Oral Glucose Tolerance Test,
GD and mean blood pressure during pregnancy. Maternal weight
gain was lower in the EG [11.9 (SD = 3.7) kg] compared to the
CG [13.7 (SD=4.1) kg] (p = 0.0001). We observed no dier-
ences between the groups in the newborn’s overall health status,
including Apgar scores at one and ve minutes, birth weight,
birth length and the pH of umbilical cord blood.
An additional analysis was conducted to compare the types
of deliveries between groups of pregnant women with excessive
weight gain. ere was a lower rate of cesarean sections in the EG
(16.1%, n = 5) compared to the CG (39.7%, n = 27), although the
dierence was not statistically signicant.
Discussion
is study is the rst randomized controlled trial that specically
and objectively shows a positive association between the type of
delivery and supervised, regular exercise when performed by a
large sample of previously sedentary, gravid women throughout
the duration of their entire pregnancy. An additional novel inter-
vention of our study was the integration of light resistance, toning,
aerobic dance and pelvic oor exercises in the training program,
which is not commonly available to pregnant women.
We examined the inuence of PE on the delivery method,
providing an opportunity to determine the possible inuence of
a physical activity program during pregnancy (during all three
trimesters) on the type of delivery.
e main nding of our study was that supervised resistance
training is associated with a lower percentage of cesarean and
instrumental deliveries. ese ndings have clinical relevance
given that the cesarean rate is a public health concern because the
procedure is not without risks and can adversely aect perinatal
outcomes [10,12].
e overall health status of the baby was unaected with
exercise, as reected and reinforced by the results of the globally
used Apgar score. Moreover, some pregnancy outcomes (e.g.
TABLE II. Type of delivery and other pregnancy outcomes – comparison
between control and exercise groups.
Controls (n = 152) Exercise (n = 138)
p valueMean (SD) or n/% Mean (SD) or n/%
Type of delivery
Normal 88/57.9 100/72.5 *0.03 χ2 = 6.8Z
= 2.73 RR =
0.47 (0.26, 0.82)
Instrumental 29/19.1 16/11.6
Cesarean 35/23 22/15.9
Preterm delivery 10/6.6 9/6.5 0.98
Maternal weight
gain (kg)
13.7 (4.1) 11.9 (3.7) *0.0001
**d = 0.56
Gestational age
(days)
278.0 (10.3) 278.3 (9.9) 0.81
Apgar Score 1 min. 8.6 (1.3) 8.7 (1.4) 0.34
Apgar Score 5 min. 9.8 (0.8) 9.7 (0.6) 0.22
Birth weight (g) 3232 (448) 3203 (461) 0.56
Birth length (cm) 49.5 (2.07) 49.7 (2.06) 0.98
pH Umbilical cord 7.26 (0.07) 7.28 (0.08) 0.29
Oral glucose toler-
ance test (g/dL).
119.2 (28.5) 117.2 (30.7) 0.59
Gestational diabetes
Yes 12/7.9 6/4.3 0.21
No 140/92.1 132/95.7
Blood pressurea
Diastolic 70.8 ± 8.5 69.6 ± 9.6 0.29
Systolic 115.6 ± 11.7 113.8 ± 15.1 0.25
EWGDP type of
delivery (n/%)
Control (n = 53) Exercise (n = 31)
Normal 25/47.2 22/71 0.07
Instrumental 8/15.1 4/12.9
Cesarean 20/37.7 5/16.1
EWGDP, excessive weight gain during pregnancy.
*Signicant level at p = 0.05.
**Cohen’s d.
aMean during pregnancy.
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Exercise during pregnancy reduces the rate of cesarean 2375
©  Informa UK, Ltd.
maternal weight gain) improved in the EG, which could explain
the protective eect of PE against pregnancy complications.
In additional analyses, our results show a lower percentage
of cesarean sections in women with excessive weight gain in the
EG. In concordance, many researchers have found that normal
maternal BMI and appropriate weight gain during pregnancy is
strongly related to the ability of pregnant women to delivery vagi-
nally without diculty [18–20].
In the past, studies on the inuence of leisure-time physical
activity on the type of delivery have generated mixed results. Most
of these studies refer to the relationship between occupational
activity or working conditions and pregnancy outcomes, though
few clinical trials existed.
Our results are in agreement with other study ndings. In an
experimental study, Clapp found that women who continue to
exercise during pregnancy compared with sedentary pregnant
women had a lower incidence of cesarean sections (6 %, n = 5 vs.
30%, n = 13) and instrumental deliveries (6 %, n = 5 vs. 20%, n =
9 [15]). Recently, in an observation study, Melzer et al. measured
energy expenditure, aerobic tness and sleeping HR in 44 healthy
women in late pregnancy and found that the risk for operative
delivery was lower in active women compared with those that
were inactive (odds ratio of 3.7 [21]).
Bungun et al., by a non-experimental, retrospective study,
assessed the association between participation in aerobic exercise
during the rst two trimesters of pregnancy and type of delivery
in 137 nulliparous women. ey found that sedentary women
(n = 93) were 2.05 times more likely to deliver via cesarean section
than active women (n = 44), though this dierence was not statis-
tically signicant [11].
A notable group of studies found no inuence of physical
activity on the type of delivery [5, 22–24]. In a recent study, Bø
et al. found that exercising at least three times per week was not
associated with vacuum or forceps deliveries or acute cesarean
deliveries [25].
In a randomized controlled trial, Cavalcante et al. studied 71
low-risk sedentary pregnant women to evaluate the eectiveness
and safety of water aerobics during pregnancy (activity was initi-
ated at 18–20 weeks). ey found no dierence in the type of
delivery between study groups; however, most of the deliveries in
the intervention group were normal vaginal deliveries [26].
Bovbjerg and Siega-Riz, by a Pregnancy Risk Assessment
Monitoring System, collected data (via questionnaire) on the
frequency of exercise during the last three months of pregnancy
in 1955 women. ey found that exercise was not associated with
delivery method [10].
Figure 1. Flow chart of the study participants.
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2376 R. Barakat et al.
e Journal of Maternal-Fetal and Neonatal Medicine
In contrast with these investigations, a few studies suggest that
exercise during pregnancy may have a negative impact on the
type of delivery. Dale, in a study with 33 runners and 11 controls,
reported a trend noticed in runners; this group tended to fail
to progress in labor and delivery, and thus resulted in cesarean
sections [27].
In a prospective study to evaluate the inuence of employment
and physical exertion on pregnancy outcomes (quantied by kilo-
calories expended each day), Magann et al. found an increased
proportion of nonelective cesarean sections for women in the
higher energy expenditure group (>3000 kcal/day [28]).
e dierences in our results compared to those of other studies
can be attributed to the variety of study design, type and intensity
of the exercise and duration of the programs used by other studies.
In our previous study [5], we observed no inuence of exercise on
the type of delivery in an RCT performed only during the second
and third trimesters of pregnancy. Also, other experimental studies
[25,26] start physical activity programs around 18–20 weeks of
gestation, which could be an important factor in the dierence
with the results of the present study. In addition, many obser-
vational studies derive their results from the information from
pregnant women [10,21,23] or only by the comparison between
groups of dierent exercise intensities [22]. Moreover, studies that
found physical exertion (runners, high workload) was associated
with abdominal deliveries [27,28] could demonstrate that exercise
during pregnancy should be limited to moderate intensity.
We observe that dierent studies, usually testing a small sample
or based on observational designs, have given inconsistent results
and conclusions. e main contribution of this study is evidence
that regular exercise can coexist with pregnancy and have positive
eects on the type of delivery.
In summary, our ndings encourage the growing trend in
healthy, pregnant women to join a physical activity program.
is study suggests that light-to-moderate exercise can result in
improved clinical outcomes for the mother and newborn and
serve to be an important contribution to public health.
Acknowledgements
e authors would like to acknowledge the technical assistance of
the Gynaecology and Obstetric Service of Fuenlabrada Hospital
of Madrid. is work was partially supported by the Ministerio
de Ciencia e Innovación, Spain (DEP2009-08990).
Declaration of Interest: e authors report no competing of
Interest.
References
1. Wolfe LA, Brenner IK, Mottola MF. Maternal exercise, fetal well-being
and pregnancy outcome. Exerc Sport Sci Rev 1994;22:145–194.
2. Riemann MK, Kanstrup Hansen IL. Eects on the foetus of exercise in
pregnancy. Scand J Med Sci Sports 2000;10:12–19.
3. Sternfeld B. Physical activity and pregnancy outcome. Review and
recommendations. Sports Med 1997;23:33–47.
4. Barakat R, Lucia A, Ruiz JR. Resistance exercise training during
pregnancy and newborn’s birth size: a randomised controlled trial. Int
J Obes (Lond) 2009;33:1048–1057.
5. Barakat R, Ruiz JR, Stirling JR, Zakynthinaki M, Lucia A. Type of
delivery is not aected by light resistance and toning exercise training
during pregnancy: a randomized controlled trial. Am J Obstet Gynecol
2009;201:590.e1–590.e6.
6. Barakat R, Pelaez M, Montejo R, Luaces M, Zakynthinaki M. Exercise
during pregnancy improves maternal health perception: a randomized
controlled trial. Am J Obstet Gynecol 2011;204:402.e1–402.e7.
7. Poudevigne MS, O’Connor PJ. Physical activity and mood during
pregnancy. Med Sci Sports Exerc 2005;37:1374–1380.
8. Mottola MF. e role of exercise in the prevention and treatment of
gestational diabetes mellitus. Curr Sports Med Rep 2007;6:381–386.
9. Sorensen TK, Williams MA, Lee IM, Dashow EE, ompson ML,
Luthy DA. Recreational physical activity during pregnancy and risk of
preeclampsia. Hypertension 2003;41:1273–1280.
10. Bovbjeg ML, Siega-Ruiz AM. Exercise during pregnancy and cesarean
delivery: North Carolina PRAMS, 2004–2005. Birth. 2009; 36:200–207.
11. Bungum TJ, Peaslee DL, Jackson AW, Perez MA. Exercise during
pregnancy and type of delivery in nulliparae. J Obstet Gynecol Neonatal
Nurs 2000;29:258–264.
12. Blanchette H. e rising cesarean delivery rate in America: what are the
consequences? Obstet Gynecol 2011;118:687–690.
13. Schulz KF, Altman DG, Moher D; CONSORT Group. CONSORT 2010
Statement: updated guidelines for reporting parallel group randomised
trials. BMC Med 2010;8:18.
14. Harriss DJ, Atkinson G. International Journal of Sports Medicine -
ethical standards in sport and exercise science research. Int J Sports Med
2009;30:701–702.
15. Artal R , O’Toole M. Guidelines of the American College of Obstetricians
and Gynecologists for exercise during pregnancy and the postpartum
period. Br J Sports Med 2003;37:6–12; discussion 12.
16. Pocock SJ. When to stop a clinical trial. BMJ 1992;305:235–240.
17. Moher D, Dulberg CS, Wells GA. Statistical power, sample size, and their
reporting in randomized controlled trials. JAMA 1994;272:122–124.
18. Gawade P, Markenson G, Bsat F, Healy A, Pekow P, Plevyak M.
Association of gestational weight gain with cesarean delivery rate aer
labor induction. J Reprod Med 2011;56:95–102.
19. Linné Y. Eects of obesity on women’s reproduction and complications
during pregnancy. Obes Rev 2004;5:137–143.
20. Young TK, Woodmansee B. Factors that are associated with cesarean
delivery in a large private practice: the importance of prepregnancy
body mass index and weight gain. Am J Obstet Gynecol 2002;187:312–8;
discussion 318.
21. Melzer K, Schutz Y, Soehnchen N, Othenin-Girard V, Martinez de
Tejada B, Irion O, Boulvain M, Kayser B. Eects of recommended
levels of physical activity on pregnancy outcomes. Am J Obstet Gynecol
2010;202:266.e1–266.e6.
22. Kardel KR, Kase T. Training in pregnant women: eects on fetal
development and birth. Am J Obstet Gynecol 1998;178:280–286.
23. Sternfeld B, Quesenberry CP Jr, Eskenazi B, Newman LA. Exercise
during pregnancy and pregnancy outcome. Med Sci Sports Exerc
1995;27:634–640.
24. Wong SC, McKenzie DC. Cardiorespiratory tness during pregnancy
and its eect on outcome. Int J Sports Med 1987;8:79–83.
25. Bø K, Fleten C, Nystad W. Eect of antenatal pelvic oor muscle training
on labor and birth. Obstet Gynecol 2009;113:1279–1284.
26. Cavalcante SR, Cecatti JG, Pereira RI, Baciuk EP, Bernardo AL, Silveira
C. Water aerobics II: maternal body composition and perinatal outcomes
aer a program for low risk pregnant women. Reprod Health 2009;6:1.
27. Dale E, Mullinax KM, Bryan DH. Exercise during pregnancy: eects on
the fetus. Can J Appl Sport Sci 1982;7:98–103.
28. Magann EF, Evans SF, Weitz B, Newnham J. Antepartum, intrapartum,
and neonatal signicance of exercise on healthy low-risk pregnant
working women. Obstet Gynecol 2002;99:466–472.
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