2018 Is there any association between abdominal strength training before and during pregnancy and delivery outcome - The Norwegian Mother and Child Cohort Study

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ARTICLE IN PRESS+ModelBJPT 135 1---8
Brazilian Journal of Physical Therapy 2018;xxx(xx):xxx---xxx
https://www.journals.elsevier.com/brazilian-journal-of-physical-therapy
Brazilian Journal of
Physical Therapy
ORIGINAL RESEARCH
Is there any association between abdominal strength
training before and during pregnancy and delivery
outcome? The Norwegian Mother and Child Cohort
Study
Eirin Risea,∗, Kari Bøa,c, Wenche Nystadb
a Department of Sport Medicine, Norwegian School of Sport Sciences, Pb 4014 Ullevål Stadion, 0806 Oslo, Norway
b Department of Chronic Diseases, Norwegian Institute of Public Health, Pb 222 Skøyen, 0213 Oslo, Norway
c Department of Obstetrics and Gynecology, Akershus University Hospital, Pb 1000, 1478 Lørenskog, Norway
Received 26 March 2018; accepted 25 June 2018
KEYWORDS
Abdominals;
Gestation;
Physical activity;
Exercise;
Pre-natal;
Post-natal
Abstract
Background: Abdominal strength training before and during pregnancy has been recommended
to enhance normal vaginal birth by enabling increased force needed for active pushing. However,
to date there is little research addressing this hypothesis.
Objective: To investigate whether nulliparous pregnant women reporting regular abdominal
strength training prior to and at two time points during pregnancy have reduced risk of cesarean
section, instrumental assisted vaginal delivery and third- and fourth-degree perineal tears.
Methods: Analysis of 36 124 nulliparous pregnant women participating in the Norwegian Mother
and Child Cohort Study during the period 1999---2009 who responded to questions regards the
main exposure; regular abdominal strength training. Data on delivery outcomes were retrieved
from the Medical Birth Registry of Norway. Logistic regression analyses were used to evaluate
the association between exposure and outcome before pregnancy and at gestational weeks 17
and 30.
Results: Amongst participants, 66.9% reported doing abdominal strength training exercises
before pregnancy, declining to 31.2% at gestational week 30. The adjusted odds ratios were
0.97 (95% CI 0.79---1.19) for acute cesarean section, among those training with the same fre-
quency before and during pregnancy compared to those that never trained. The results were
similar for instrumental assisted vaginal delivery and third- and fourth-degree perineal tear.
Conclusion: There was no association between the report of regular abdominal strength training
before and during pregnancy and delivery outcomes in this prospective population-based cohort.
 de Pesquisa e Pós-Graduação em Fisioterapia. Published by Elsevier
rved.
© 2018 Associação Brasileira
Editora Ltda. All rights rese
Please cite this article in press as: Rise E, et al. Is there any
and during pregnancy and delivery outcome? The Norwegian 
https://doi.org/10.1016/j.bjpt.2018.06.006
∗ Corresponding author. Norwegian School of Sport Sciences, Departme
E-mail: enygaardr@gmail.com (E. Rise).
https://doi.org/10.1016/j.bjpt.2018.06.006
1413-3555/© 2018 Associação Brasileira de Pesquisa e Pós-Graduação em 
BJPT 135 1---8
 association between abdominal strength training before
Mother and Child Cohort Study. Braz J Phys Ther. 2018,
nt of sports Medicine. Pb 4014, Ullevål stadion, 0806 Oslo, Norway.
Fisioterapia. Published by Elsevier Editora Ltda. All rights reserved.
https://doi.org/10.1016/j.bjpt.2018.06.006
https://doi.org/10.1016/j.bjpt.2018.06.006
https://www.journals.elsevier.com/brazilian-journal-of-physical-therapy
mailto:enygaardr@gmail.com
https://doi.org/10.1016/j.bjpt.2018.06.006
 IN PRESS+ModelB
2 E. Rise et al.
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Ver sion 5 MoBa
n=108 842 
Final sample
n=36124
Multiparity and/ or multiple pregnancies
n=62 418 
Pil ot study
Q1: n=1013
Q3: n=1778
Women not respond ing (main study)
Q1: n=1900
Q3: n=4652
Delyed data delivery
n=14 41
Undefi ned cesarean section
n=757 
Elective cesarean section
n=1304
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ARTICLEJPT 135 1---8
 
ntroduction
oday, healthy women are encouraged to engage in daily
hysical activity throughout pregnancy.1---3 Both endurance
raining and strength training are recommended, and from
 health perspective pregnant women are encouraged to
ngage in 30 min of moderate intensity aerobic training
very day.1 Davies et al.2 recommend strength training of
he major muscle groups 3---4 times per week and suggest
hat abdominal strength training is important to strengthen
‘the muscles of labor’’.
Several studies have investigated the level of phys-
cal activity4---6 and exercise training7 during pregnancy
n population-based studies. However, to date, there is
cant knowledge to which extent pregnant women per-
orm abdominal exercises. Strong abdominal muscles have
een claimed to contribute to a more effective birth in
erms of shorter duration of second stage of labor.8---10 Fur-
hermore, Bovbjerg and Siega-Riz11 have postulated that
trong abdominal muscles might make the second stage
f birth more effective, thereby reducing the risk of fail-
re to progress and cesarean section. The theory is that
hen the women are asked to actively push during the
terine contractions, strong and well-trained abdominals
ould improve the effectiveness of the pushing and thereby
horten the duration of the second stage of labor. Despite
he Canadian recommendations2 and the aforementioned
heories,8---11 there is a paucity of research addressing a pos-
ible association between strength training of the abdominal
uscles and delivery mode.12 For this reason, the Norwegian
other and Child Cohort Study (MoBa) included questions
n abdominal training. MoBa is linked to the Medical Birth
egistry of Norway (MBRN) and therefore allows analysis of
xercise exposure and birth outcome.
The aims of the present study were to investigate:
 The number of women reporting to engage in strength
training of the abdominal muscles before and during preg-
nancy.
 The association between self-reported abdominal
strength training before and during pregnancy and acute
cesarean section, instrumental assisted vaginal delivery
and third- and fourth-degree perineal tear.
aterial and methods
tudy design
his cohort study is based on the data from the MoBa study
onducted by the Norwegian Institute of Public Health.13,14
etting
articipants were recruited from 52 hospitals in the period
999---2008. The current prospective cohort study is based
n version 5 of the quality-assured data file released for
Please cite this article in press as: Rise E, et al. Is there any
and during pregnancy and delivery outcome? The Norwegian 
https://doi.org/10.1016/j.bjpt.2018.06.006
esearch in April/May 2011. Informed consent was obtained
rom each MoBa participant upon recruitment. The estab-
ishment and data collection in MoBa has obtained a license
rom the Regional Committee for Medical Research Ethics in
t
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107Figure 1 Flow chart of the study participants.
outh-Eastern (S-97045, S-95113) and the Norwegian Data
nspectorate (01/4325).
articipants
he Moba cohort includes a total of 108 000 pregnancies:
4 200 children, about 90 700 mothers and 71 500 fathers.
he women were recruited through postal invitation prior
o the routine ultrasound examination in gestational weeks
7 and 18.13 The inclusion of study participants is shown
n Fig. 1. Of the 108 842 women included in the data file,
pproximately 60% were excluded because of multiparity
nd multiple pregnancies. An additional group was excluded
ecause of participation in a pilot study where other ques-
ionnaires were used for our primary exposure variables
Questionnaires Q1 and/or Q3). Women not responding to
1 and/or Q3 in the main study were also excluded. This
eft 39 626 nulliparous pregnant women for inclusion in the
resent study. Due to delayed data delivery by MBRN, a group
f women were excluded because of missing information on
he study outcomes. We also excluded women with cesarean
BJPT 135 1---8
 association between abdominal strength training before
Mother and Child Cohort Study. Braz J Phys Ther. 2018,
elivery other than acute (elective and undefined cesarean
ection). Thus the final sample comprises 36 124 primiparous
omen with a singleton pregnancy.
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ARTICLEBJPT 135 1---8
Abdominal training and delivery outcome 
MoBa questionnaires was sent out during and after preg-
nancy and included items about maternal, paternal, and the
child’s health and lifestyle. Three of the questionnaires were
sent out during pregnancy. The questionnaires distributed at
gestational weeks 17---18 and 30 included specific questions
on abdominal, back, and pelvic floor muscle training and
questions regarding habitual physical activity. The overall
response rate for MoBa is 41%. Amongst women participat-
ing in MoBa, 94.9% completed the 17---18-week questionnaire
and 91.8% the 30-week questionnaire.13
Variables
The main exposure in the present study was maternal report
of strength training of the abdominal muscles 3 months prior
to pregnancy and at both time points during pregnancy.
The women were asked to report frequency of abdominal
strength training with the alternatives ‘‘never’’, ‘‘one to
three times per month’’, ‘‘once a week’’, ‘‘twice a week’’,
and ‘‘three or more times a week’’. In the analyses, the cat-
egories ‘‘once a week’’ and ‘‘twice a week’’ were collapsed
to one category ‘‘one to two times a week’’, whereas the
rest of the categories remained as original. The question
was asked retrospectively at gestational week 17---18 (Q1)
for the 3 months prior to pregnancy and cross-sectional for
gestational week 17---18 (Q1) and week 30 (Q3).
The main outcomes were acute cesarean section, for-
ceps, and/or vacuum-assisted delivery and third- and
fourth-degree perineal tear as registered in MBRN.15 The
outcomes were registered by qualified health personnel in
a standardized form at the respective birth clinics. For-
ceps and vacuum-assisted deliveries were collapsed to one
variable: instrumental assisted vaginal delivery. Third- and
fourth-degree perineal tear were collapsed to one variable:
third- and fourth-degree perineal tear.
Potential confounders for acute cesarean section,
instrumental assisted vaginal delivery, and third- and fourth-
degree perineal tear were selected based on literature
review and cross-tabulations. The included confounders in
the main analyses were: maternal age (continuous variable
in years), pre-pregnancy body mass index (BMI) (kg/m2, con-
tinuous variable), highest level of education (categorized
in primary school, secondary school, college/university),
general physical activity level (defined as the frequency
of participation in recreational activity, categories like the
main exposure), pelvic floor muscle training (PFMT) (cate-
gorized like the main exposure), head circumference (cm),
birth weight (defined as less than or more than 4000 g), and
dystocia (defined as yes or no registered by MBRN (analyzed
for instrumental assisted vaginal delivery only)). Smoking
and physically demanding work did not influence the esti-
mates in subanalyses using logistic regression models and
were consequently not included in the main analyses (in
the subanalyses, we included the factors smoking and/or
physically demanding work as additional factors to the main
analyses to see the potential influence). We included the
following covariates in additional subanalyses for each out-
Please cite this article in press as: Rise E, et al. Is there any
and during pregnancy and delivery outcome? The Norwegian 
https://doi.org/10.1016/j.bjpt.2018.06.006
come to see whether they influenced the main analyses:
(1) acute cesarean section: dystocia, fear of childbirth,
induction of labor, and epidural; (2) instrumental assisted
vaginal delivery: fear of childbirth, induction of labor, and
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3
pidural; and (3) third- and fourth-degree perineal tear:
nstrumental assisted vaginal delivery, fear of childbirth, and
pisiotomy.
tatistical methods
emographical characteristics are presented as means with
tandard deviations (SD) or frequencies and percentages.
hi-square analysis was used to investigate the change in
eported frequency of abdominal strength training during
regnancy. Separate logistic regression models were used
o assess the association between the exposure and each
f the three outcomes adjusting for potential confounders.
wo models were constructed for each outcome. One model
ncluded reported abdominal strength training retrospec-
ively for the period 3 months prior to pregnancy and the
econd model included reported abdominal strength training
erformed at all three time points (3 months prior to preg-
ancy, gestational weeks 17 and 30). In the analysis including
ll three time points, the exposure variable abdominal
trength training had the following categories: training with
he same frequency at all time points, training with a var-
ed frequency at all time points seen together or no strength
raining of the abdominal muscles at all timepoints.16 The
ariable PFMT was categorized like the main exposure and
he variable general physical activity level was taken from
he time point 3 months prior to pregnancy. All the other
ariables in the analysis were similar in the two models. The
eference group in both analyses was the group reporting no
bdominal strength training. Only women with informationn all included variables are included in the analyses. In the
nalysis of perineal tears, only women with vaginal deliv-
ries were included. Thus, the sample sizes included in the
ifferent analyses differ between outcomes. The results are
resented as crude and adjusted odds ratios with 95% confi-
ence intervals (CIs). Statistical analyses were conducted
ith PASW Statistics for Windows, version 18 (Chicago,
SA).
esults
ackground variables are shown in Tables 1 and 2. The
ajority of the women had normal pre-pregnancy BMI, had
ompleted higher education (college/university), and was
arried or cohabitants.
Amongst participants, 3999 (11.1%) underwent acute
esarean section, 6382 (17.7%) instrumental assisted vaginal
elivery (forceps and vacuum), and 2051 (5.7%) had third-
r fourth-degree perineal tear.
Numbers and percentages of women reporting to perform
bdominal strength training before and during pregnancy
re reported in Table 3. During pregnancy, there was a
ignificant decline in number of women reporting abdomi-
al strength training (p < 0.001). Forty-seven percent of the
omen reduced their frequency of abdominal strength train-
ng from 3 months pre-pregnancy to gestational week 17.
here was a further reduction in frequency of abdominal
BJPT 135 1---8
 association between abdominal strength training before
Mother and Child Cohort Study. Braz J Phys Ther. 2018,
trength training from gestational week 17 to gestational
eek 30, 27% of the women reported to reduce their activ-
ty. At gestational week 30, 31% of the women reported to
o abdominal strength training.
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https://doi.org/10.1016/j.bjpt.2018.06.006
ARTICLE IN PRESS+ModelBJPT 135 1---8
4 E. Rise et al.
Table 1 Demographic characteristics of the study partici-
pants (n = 36 124). Data presented as means with standard
deviation (SD) or frequency (n) and percentages (%).
N/mean % SD
Age (years)(mean) 28.3 4.4
Pre-pregnancy BMI (kg/m2) (mean) 23.7 3.9
Underweight: <18.5 1199 3.3
Normal weight: 18.6---24.9 24 056 66.6
Overweight: 25---29.9 7080 19.6
Obesity class I: 30---34.9 2268 6.3
Obesity class II: ≥35 692 1.9
Missing 829 2.3
Highest level of education
Primary school: 9 years 863 2.4
Secondary school: 12 years 10 640 29.5
College/university: >12 years 22 283 61.7
Missing 2338 6.5
Marital status
Married/cohabitant 34 236 94.8
Other 1888 5.2
BMI = body mass index.
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Table 2 Participation in general physical activity of the
study participants (n = 36 124). Data presented as frequency
(n) and percentages (%).
N %
Three months pre-pregnancy
Never 2583 7.2
1---3 times per month 4169 11.5
1 time per week 4204 11.6
2 times per week 4776 13.2
≥3 times per week 20 147 55.8
Missing 245 0.7
Gestational week 17
Never 5926 16.4
1---3 times per month 6238 17.3
1 times per week 5650 15.6
2 times per week 5037 13.9
≥3 times per week 12 383 34.3
Missing 890 2.5
Gestational week 30
Never 9386 26.0
1---3 times per month 6441 17.8
1 time per week 5895 16.3
2 times per week 4542 12.6
≥3 times per week 9661 26.7
D
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sures and plausible confounders. The MBRN is considered
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Table 4 shows crude and adjusted odds ratios for report of
bdominal strength training 3 months before pregnancy and
cute cesarean section, instrumental assisted vaginal deliv-
ry, and third- and fourth-degree perineal tear. There was no
ignificant association between abdominal strength training
nd any of the delivery outcomes. Adjusting for fear of child-
irth, dystocia, induction of labor, epidural, episiotomy (for
erineal tear only), or instrumental assisted vaginal delivery
for perineal tear only) had no influence on the results.
Table 5 shows the crude and adjusted odds ratios for
eport of abdominal strength training before pregnancy and
t all time points during pregnancy combined and the deliv-
ry outcomes. There was no association between either
aried training frequency or training with the same fre-
uency before and during pregnancy with mode of delivery
r perineal tears. Adjusting for plausible confounders (fear
f childbirth, dystocia, induction or epidural, episiotomy
Please cite this article in press as: Rise E, et al. Is there any
and during pregnancy and delivery outcome? The Norwegian 
https://doi.org/10.1016/j.bjpt.2018.06.006
for perineal tear only), instrumental assisted vaginal deliv-
ry (for perineal tear only)) had no influence on the results.
a
N
Table 3 Frequency of abdominal strength training during three
week 17 and 30 (n = 36 124). Data presented as numbers of women
Time per
Frequency of training 3 month
pre-pregnancy
% 
Never 10 964 30.4 
1---3 times per month 6853 19.0 
1 time per week 5401 15.0 
2 times per week 6724 18.6 
≥3 times per week 5218 14.4 
Total 35 160 97.3 
Missing 964 2.7 
Missing 199 0.6
iscussion
he main findings of this prospective pregnancy cohort study
n abdominal strength training and delivery outcome were
hat two-thirds of the women reported to engage in strength
raining of the abdominal muscles before pregnancy. This
eclined to a third of the participants at gestational week
0. However, there was no association between maternal
eports of abdominal strength training before and during
regnancy and acute cesarean section, instrumental assisted
aginal delivery, or third- and fourth-degree perineal tears.
The main strengths of the study are the large sample
ize and the access to longitudinal data on several expo-
BJPT 135 1---8
 association between abdominal strength training before
Mother and Child Cohort Study. Braz J Phys Ther. 2018,
 reliable source of information related to birth,17 and in
orway this registration is mandatory for all women giving
 different time points: 3 months pre-pregnancy, gestational
 (n) and percentages (%).
iod
Gestational
week 17
% Gestational
week 30
%
19 001 52.6 23 425 64.8
6183 17.1 3887 10.8
4132 11.4 3538 9.8
2804 7.8 2320 6.4
1449 4.0 1556 4.3
33 569 92.9 34 726 96.1
2555 7.1 1398 3.9
259
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https://doi.org/10.1016/j.bjpt.2018.06.006
Please cite this article in press as: Rise E, et al. Is there any
and during pregnancy and delivery outcome? The Norwegian 
https://doi.org/10.1016/j.bjpt.2018.06.006
ARTICLE IN+ModelBJPT 135 1---8
Abdominal training and delivery outcome 
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 PRESS
5
irth. The follow-up rate of more than 90% also strengthens
he study.13 The study’s hypotheses was not known to the
omen when they answered the questionnaires, which may
imit the potential impact of information bias.
The main limitation of the study is the use of ques-
ionnaire data to assess frequency of abdominal strength
raining without any clinical assessment of actual abdominal
uscle strength. Self-report may overestimate all training
stimates and recall bias is a possible threat to the accuracy
f self-report, in general. In the present study, retrospective
aternal report of training 3 months before conception may
e a special weakness.18 In addition, we have no informa-
ion of the type of abdominal exercises (e.g. sit up or core
tability training). Even with reliable self-reporting, there is
o guarantee that the conducted abdominal strength train-
ng resulted in stronger abdominal muscles. Nevertheless, to
ate, there is scant knowledge about the effect of abdom-
nal strength training in general during pregnancy, and as
ar as we have ascertained there are no studies evaluat-
ng the validity of report of abdominal strength training and
ctual increase in muscle strength. Combining the answers
rom three exposure points into one variable may improve
he validity of the report as it indicates that the respon-
ers are ‘‘true’’ exercisers. Low response rate is one of
he main challenges of conducting population-based studies.
ilsen et al.14 evaluated the differences between the parti-
ipants in MoBa and the population in general to see whether
here was a case of selection bias in MoBa. They found
hat younger and single women were underrepresented in
oBa, as also smokers. There were also a lower rate of
reterm deliveries, lower gestational age, and babies with
igher Apgar score and larger head circumference in the
oBa group. This can indicate a socioeconomic difference
etween MoBa participants and the population, in general.13
uch differences might affect the associations between the
xposures during pregnancy and different outcomes.14 Thus,
e cannot exclude that selection bias might have influenced
ur results. The gold standard design to rule out causality for
bdominal strength training to influence delivery outcome
ould be a randomized controlled trial (RCT). However,
iven the low incidence of the main outcomes, a random-
zed controlled trial with these as main outcome variables
ould require a huge sample size and may not be feasible.
A few RCTs have reported the effect of strength train-
ng in relation to pregnancy and delivery.19---23 None of these
tudies found differences between the group that performed
trength training and the group that did not train on deliv-
ry outcomes (acute cesarean section, instrumental assisted
aginal delivery). However, none of these RCTs had a primary
im to investigate the effect of abdominal strength training
lone on acute cesarean section rate, instrumental assisted
aginal delivery, and third- and fourth-degree perineal tear.
n addition, none measured abdominal strength before and
fter the intervention and none reported on which abdomi-
al exercises that had been performed. Hence, to date, the
vidence for the effect of abdominal strength training on
elivery outcome is not clear.
To date, there is also scant knowledge about normal
BJPT 135 1---8
 association between abdominal strength training before
Mother and Child Cohort Study. Braz J Phys Ther. 2018,
ctivity of the abdominal muscles during pregnancy and
abor. Early studies from the 1950s and 1960s found that
he electrical activity of the abdominal muscles decline as
he pregnancy progresses.24,25 More recently, Oliveira et al.26
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https://doi.org/10.1016/j.bjpt.2018.06.006
BJPT
 135
 1---8
Please
 cite
 this
 article
 in
 press
 as:
 Rise
 E,
 et
 al.
 Is
 there
 any
 association
 betw
een
 abdom
inal
 strength
 training
 before
and
 during
 pregnancy
 and
 delivery
 outcom
e?
 The
 N
orw
egian
 M
other
 and
 Child
 Cohort
 Study.
 Braz
 J
 Phys
 Ther.
 2018,
https://doi.org/10.1016/j.bjpt.2018.06.006
A
R
T
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 IN
 P
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+M
odel
BJPT
 135
 1---8
6
 
E.
 Rise
 et
 al.
Table 5 Logistic regressions for abdominal strength training before and during pregnancy (3 months pre-pregnancy, gestational weeks 17 and 30) and acute cesarean section
(n = 29 034), instrumental assisted vaginal delivery (n = 29 034), and third- and fourth-degree perineal tear (n = 25 992) for the women in MoBa. Data presented as cOR and aOR
with 95% CI.
Frequency of training Acute cesarean section Instrumental assisted vaginal delivery Third-and fourth-degree perineal tear
N %so cOR 95% CI aORcs 95% CI N %so cOR 95% CI aORid 95% CI N %so cOR 95% CI aORpt 95% CI
Never 6764 11.3 1.00 1.00 6764 17.4 1.00 1.00 6003 6.9 1.00 1.00
The same frequency 2041 9.6 0.84 0.71---0.99 0.97 0.79---1.19 2041 17.5 1.00 0.88---1.14 0.99 0.83---1.17 1845 5.7 0.82 0.66---1.02 0.99 0.76---1.29
Varied frequency 20 229 10.3 0.91 0.83---0.99 1.05 0.95---1.17 20 229 17.6 1.01 0.94---1.08 1.04 0.96---1.14 18 144 6.4 0.92 0.82---1.03 1.08 0.94---1.24
aOR, adjusted odds ratio; cOR, crude odds ratio; CI, confidence interval; N, frequency of participants.
so Percentage of study outcome (acute cesarean section, instrumental assisted vaginal delivery, and third- and fourth-degree perineal tear).
cs Adjusted for maternal age, pre-pregnancy body mass index (BMI), highest level of education, general physical activity level (pre-pregnancy), PFMT (categories like the exposure), head
circumference, and birth weight.
id Adjusted for maternal age, pre-pregnancy BMI, highest level of education, general physical activity level (pre-pregnancy), PFMT (categories like the exposure), head circumference,
birth weight, and dystocia.
pt Adjusted for maternal age, pre-pregnancy BMI, highest level of education, general physical activity level (pre-pregnancy), PFMT (categories like the exposure), head circumference,
and birth weight.
https://doi.org/10.1016/j.bjpt.2018.06.006
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ARTICLEBJPT 135 1---8
Abdominal training and delivery outcome 
confirmed that there is activity in the abdominals during
labor. They also found a negative correlation between the
diastasis recti abdominis and electrical activity in m. rec-
tus abdominis, but no correlation between the activity in
m. rectus abdominis and m. obliquus externus and duration
of second stage of labor. Buhimschi et al.27 investigated the
change in intra-uterine pressure during contractions in the
second stage of labor and found an increase of 62% when
the mother performed the Valsava maneuver. To the best
of our knowledge, there are no published studies on the
effect of strength training on the abdominal muscles and
the ability to increase intra-abdominal pressure in pregnant
women. There is also uncertainty to the effect of different
pushing techniques during delivery (open or closed glottal
slit) and delivery mode.28,29 Women’s health physical ther-
apists are in close contact with pregnant women and are
often asked questions about exercise during pregnancy. It is
important that the advices and recommendations given by
health personnel are evidence-based. Current recommen-
dations for abdominal strength training during pregnancy
are limited to advice against doing exercises in the supine
position after the fourth month of pregnancy.30 To date,
there is sparse knowledge on which abdominal exercises
are safe for pregnant women both before and during preg-
nancy and especially the effect of abdominal training on
birth outcome. The results of the present study indicate
that abdominal training may not influence birth outcomes.
However, there is an urgent need for further clinical studies
to elaborate on this issue, both the role of the abdominal
muscles during delivery and the effect of abdominal train-
ing during pregnancy on abdominal strength and how it may
affect other outcomes. Hopefully our results will stimulate
to more research.
Conclusions
A third of the participating women engaged in strength train-
ing of the abdominal muscles before and during all time
points of their pregnancy. However, there was no associa-
tion between self-reported abdominal strength training and
delivery outcomes in this large population-based pregnancy
cohort study. To be able to give pregnant women advice
regarding abdominal strength training there is an urgent
need for further research.
Funding
This research did not receive any specific grant from fund-
ing agencies in the public, commercial, or not-for-profit
sector. The Norwegian Mother and Child Cohort Study is
however supported by the Norwegian Ministry of Health and
Care Services and the Ministry of Education and Research,
NIH/NINDS (grant no.1 UO1 NS 047537-01 and grant no. 2
UO1 NS 047537-06A1).
Acknowledgements
Please cite this article in press as: Rise E, et al. Is there any
and during pregnancy and delivery outcome? The Norwegian 
https://doi.org/10.1016/j.bjpt.2018.06.006
We are grateful to all the participating families in Norway
who take part in this on-going cohort study. We also thank
Professor Ingar Morten K. Holme for statistical advice, Maria
 PRESS
7
ristine Magnus for assistance with the MoBa data and Ingrid
ygaard for assistance with English revision.
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	Is there any association between abdominal strength training before and during pregnancy and delivery outcome? The Norwegi...
	Introduction
	Material and methods
	Study design
	Setting
	Participants
	Variables
	Statistical methods
	Results
	Discussion
	Conclusions
	Funding
	Acknowledgements
	References