Benefits of Exercising During
Pregnancy on Child Development and Health
Ryley Carr, Amanda Cordua-von Specht, and Janice Leung
Sarah Spealler, Age 32-Spealler’s Leading Lady. (Photo courtesy
of Box Life
Magazine. Retrieved November 6, 2015.)
Current
Guidelines for Maternal Exercise and their Relationship to the Child
Expecting mothers recognize that maintaining good health is vital for
the health of their children and can be promoted through regular exercise.
Regardless of physical activity being universally sanctioned as safe during
pregnancy, in a sample of 1279 women, 50% stopped exercising due to the onset
of pregnancy (Nascimento, Surita,
Godo, Kasawara, & Morais, 2015). The
current guidelines for exercise from the American
College of Obstetricians and Gynecologists (2002) recommend that pregnant women
free of complications engage in ≥30 minutes of moderate physical activity
per day on most, if not all, days of the week.
The recommendations are based primarily on the health benefits for the
mother and the implications of these on the health and development on the child
remain unclear. However, benefits of maternal exercise for the child are
potentially apparent at various stages of development. Therefore it would be
pertinent to further investigate its effects at these various stages. In utero,
physiological compensatory mechanisms
occur in response to maternal exercise in order to maintain adequate resources
to the fetus, which also serve as an advantage for the growth and development
of the fetus. During birth, two outcomes
commonly related to maternal exercise and the growth of the child include the
delivery process and birth weight. Maternal exercise has a positive overall
influence on the type of delivery, and spares potential adverse effects on the
child. In addition, maternal exercise is seen either to have no effect or a
decrease in the incidence of potentially adverse birth weights for the child.
However, such birth weights have been associated with the development of adult
chronic diseases. Though there have been minimal studies to directly link
effects of maternal exercise to postnatal outcomes, there may be indication
that maternal exercise can prevent future chronic diseases.
Therefore the purpose of this review is to examine the potential
benefits of maternal exercise for the development of the child in utero, the
outcomes during delivery and at birth, and in postnatal health.
Potential
Benefits of Maternal Exercise in Utero
Many
believe that exercising during pregnancy is particularly dangerous for the
developing fetus due to competition with the mother for resources during
exercise. However, low levels of markers, such as erythropoietin (EPO), in the
fetal compartment indicate otherwise. EPO is synthesized in fetuses when
tissues become hypoxic (as reviewed in Teramo & Widness,
2009). However, sustained and strenuous maternal exercise was not associated
with an increase in fetal EPO levels (Clapp, Little, Appleby-Wineberg & Widness, 1995).
Therefore, implies that regular exercise during pregnancy induces a variety of
compensatory mechanisms that blunt the magnitude of any exercise-induced
decrease in placental perfusion (Clapp et al, 1995).
Many of
those compensatory mechanisms involve adaptations of the placenta, as it serves
as the transportation between the mother and developing fetus. As would be
expected, during development, a fetus requires a continuous and increasing
supply of oxygen (O2) and nutrients for its metabolism and growth
(as reviewed in Lotgering, Gilbert & Longo,
1985). A proposed mechanism by Bergmann, Zygmunt and Clapp (2004) to yield adequate resources for
both mother and fetus during exercise, included the increase in cell
proliferation in exercising women resulting in placental growth. These
observations of increased placental surface area would allow for maximal O2
exchange, which is vital for the development of the fetus, even during
exercise. Other evidence that demonstrated a
possible continuous supply of O2 during exercise was determined by Feiner,
Weksler, Ohel and Degan
(2000) when they found placental circulation during isometric exercise did not
induce a change in Doppler values. This indicated that there was no change in
blood flow. All these factors are important, as prolonged severe
reduction in supply of substrates (O2 and nutrients) can result in
death of the fetus (as reviewed in Lotgering et al.,
1985).
Exercise
is not only safe for the fetus but also has physiological advantages for
development. Increased levels of particular hormones, such as norepinephrine
(NE) and epinephrine play an essential role in mammalian heart development
during the embryonic and fetal period (Osuala et al.,
2012). Therefore, catecholamines, like NE, are
essential for fetal development. During exercise, there is a rise in
circulating catecholamines that cross the placenta.
Chronic exposure to such catecholamines may influence
fetal cardiac control. May, Glaros, Yeh, Clapp, and Gustafson (2010) suggested that this may be
why lower fetal heart rate and increased fetal heart rate variability were
observed. Studies have been inconclusive
on the exact reason of why this occurs. In conclusion, the effects in utero
provide evidence that maternal exercise is safe and beneficial for the
developing fetus.
Potential Benefits of
Maternal Exercise on Type of Delivery and Birth Outcomes
It has
been observed that maternal exercise has an overall positive influence on the
delivery process. Barakat, Pelaez,
Lopez, Montejo, and Coteron (2012) found that women
who continue to exercise throughout pregnancy, compared with sedentary pregnant
women, had a lower incidence of caesarean sections (c-sections).
Similarly, in Hall and Kaufman’s study (as cited in Melzer et al., 2010) of 845
pregnant women, they reported that the incidence
of caesarean delivery was 6.7% in the high-frequency exercise group, compared
to 28.1% in the sedentary group. C-sections can have adverse effects on the
fetus; Hansen, Wisborg, Uldbjerg,
and Henriksen (2008) report an increased risk for
respiratory morbidities in the fetus following c-sections.
In addition, Kolas, Saugstad, Daltveit,
Nilsen, and Øian (2006) found higher admission to the
neonatal intensive care unit following c-sections.
Therefore, exercise has a protective role against the need for c-sections and their potential negative outcomes on the
child. Bungum, Peaslee,
Jackson, and Perez (2000) discussed in their study that many in the field do
not know why exercise influences the type of delivery and it is hypothesized
that the increased or maintained fitness during pregnancy allows the mother to
better manage the rigors of childbirth.
Exercise
may also have an influence on birth weight outcomes. Birth weight can affect an
individual's health from birth to adulthood. Acute effects will be discussed
here whereas the potential long-term effects will discussed in the subsequent
section. Babies are born with low birth weight (LBW), defined as less than
2500g (Ward, 2015), because of prematurity, poor intrauterine growth, or both (Jin, 2015). Maternal exercise and its relationship with
preterm birth, defined as birth before 37 completed weeks of gestation (Ward,
2015), has demonstrated a protective effect. Hatch, Levin, Shu, and Susser (1998) found that vigorous exercise during pregnancy
did not raise the risk of preterm delivery and the women that followed a heavy
exercise regimen long enough to be conditioned, had greater reduction in the
risk of preterm delivery. In addition, Hatch et al. (1998) also found that
regular exercise, or the conditioning that resulted from it, was associated
with delivery closer to term. The risk of preterm birth is very important to
consider for fetal development because reviewed evidence by Bernal (2007)
indicates that the last trimester of pregnancy is crucial for the full
maturation of the fetal lungs and other organs, and if this process is
interrupted by an early delivery the chances of survival of the newborn are
severely decreased. Bernal (2007) further noted in his review that preterm
births account for 75% of neonatal deaths.
The
relationship of maternal exercise and LBW due to poor intrauterine growth can
be observed by examining exercise and the incidence of babies who are small for
gestational age (SGA), defined as those who are smaller in size than normal for
their gestational age (Ward, 2015). Barakat,
Stirling, and Lucia (2008) found that exercise performed over the second and
third trimesters did not negatively affect gestational age at birth. In
addition, Gollenberg et al. (2011) reported in their
study of 1040 participants, physical activity in early pregnancy was not
associated with delivery of an SGA infant and women with high levels of total
activity mid-pregnancy had a 58% decreased risk of SGA compared to women with
low total activity levels. These results suggest that maternal exercise does
not negatively influence intrauterine growth and exercise may actually decrease
the risk of poor intrauterine growth.
Another
potential concern for newborns regarding birth weight is high birth weight
(HBW) or fetal macrosomia (≥ 4000 g). Macrosomia is associated with acute
complications that can affect the fetus such as a significantly higher
frequency of c-sections, risk of shoulder dystocia,
and risk of birth injuries (Wollschlaeger, Nieder, Köppe & Härtlein, 1999). The relationship between physical activity
in pregnancy and macrosomia is unknown as suggested in the review by Henriksen (2008), but it was recently found that there was
no statistically significant difference between exercise and control groups
(non-exercisers) in the incidence of macrosomia in previously sedentary women (Haakstad, & Bø, 2011).
In
summary, regular physical activity during pregnancy, has a positive effect on
delivery outcomes, and the timeliness of delivery. In addition, regarding the
specific LBW determinants presented, SGA and preterm birth, maternal exercise
showed either no relationship or a decreased risk in these conditions.
Therefore if these risks are decreased, fetal growth may be optimized. Lastly,
maternal exercise showed no effect on the incidence of macrosomia, therefore
not indicating an increase in likelihood of adverse conditions associated with
HBW in these children.
Potential Benefits of
Maternal Exercise on Postnatal Health
Research
has been expanding vastly to explore the impact of maternal exercise on
different postnatal health outcomes. The focus of this discussion will be on
the current establishments of the role of the in utero environment influenced
by maternal exercise and the risk of adult disease. Although birth weight is a
crude estimation of fetal growth, it is the easiest measurement indicative of
in utero environment and is used to investigate
the associations with later postnatal health outcomes from maternal exercise
(Eriksson, Forsén, Tuomilehto,
Osmond, & Barker, 2001; as reviewed in Hopkins & Cutfield,
2011). As previously discussed, mothers that did exercise during pregnancy were
not more likely to give birth to offspring that were either LBW or HBW. For
offspring born with LBW, it is proposed that increased postnatal “catch-up”
growth occurs to compensate for undesirable intrauterine conditions, which may
predispose offspring to adult obesity and comorbidities, such as type 2
diabetes mellitus and cardiovascular disease (as reviewed in Hopkins & Cutfield, 2011). Concerning HBW, positive correlations have
been drawn between birth weight and future adult obesity, according to body
mass index 
30 kg/m2, though predominantly in
males (Eriksson et al., 2001; Philips & Young, 2000). Taken together,
although the research has not provided a direct relationship between maternal
exercise and future chronic disease when birth weight is concerned, there may
be a possibility that this could suggest that exercise has the ability to
decrease the prevalence of chronic diseases associated with both ends of the
birth weight spectrum.
In an attempt to directly conclude potential postnatal benefits of
maternal exercise, Clapp (1996) compared the morphometric measurements of offspring,
at birth and at five years of age, born to mothers who exercised to those who
did not exercised as the control group, during gestation. No evidence of growth restriction was
observed after five years in the offspring of exercising mothers, as height and
weight were measured at 50th percentile for age (Clapp, 1996)
according to national statistics or developmental cohorts. Interestingly,
weight, sum of five skinfold thicknesses and subcutaneous fat area in the upper
arm were about 10% less in these offspring compared to the control group at
both times of measurement (Clapp, 1996). Similar findings and conclusions were
made by Clapp, Simonian, Lopez, Appleby-Wineberg and Harcar-Sevcik (1998) when assessing offspring at birth and
after one year. Clapp (1996) surmised that it was not that the offspring of
exercising mothers were excessively lean, but offspring of the control group
had greater adiposity. It was unknown whether the morphometric differences
would persist into later years (Clapp, 1996), but this could suggest that
maternal exercise during pregnancy can be a preventative measure against future
chronic diseases associated with adiposity in the later years of the offspring.
Overall, further longitudinal studies are required to adequately establish the
long-term benefits of maternal exercise for the development and health of the
child.
Conclusion
Positive effects of maternal exercise have been hypothesized to occur
throughout the child’s lifespan. Potential benefits discussed in this review include physiological adaptations that
occur in utero to ensure that adequate O2 and nutrients cross the
placenta during exercise, which makes maternal exercise safe for both the
mother and fetus. This allows for the potential gain of other benefits for the
fetus occurring because of maternal exercise. At the time of birth it was also
discovered that there are two possible outcomes related to maternal exercise: a
decrease risk of c-section delivery and either no
association or a decreased risk of adverse birth weights. Adult chronic
diseases have been linked to adverse birth weight outcomes. Initial
observations suggest that there may be a relationship between maternal exercise
and the prevention of these postnatal outcomes, which indicates that maternal
exercise can serve as a potential preventative measure against later postnatal
chronic diseases.
Though
health benefits of maternal exercise for the child have been reported to occur,
there is a lack of clear presentation of these benefits both in the literature
and to pregnant mothers themselves. Therefore, there is an increased need for
additional evidence to aid in determining the relationship between maternal
exercise and its positive influences on child development and health.
|
Exercise during pregnancy helps keep you in
shape and relieve basic pregnancy discomforts. (Photo courtesy of Getty
Images presented by How Stuff
Works Health. Retrieved November 6, 2015.) |
Incredible: Alysia Montano, 34 weeks
pregnant, competes in the 800m at the US Track and Field Championships.
(Photo courtesy of Daily Mail. Retrieved
November 6, 2015.) |
Related Sites of Interest
1. ACOG -
Physical Activity and Exercise During Pregnancy and
the Postpartum Period*
2. Mayo
Clinic - Pregnancy and exercise: Baby, let's move!
3. Public
Health Agency of Canada - The Healthy Pregnancy Guide
4. Virtual
Medical Centre - Benefits and Risks of Exercise During
Pregnancy
6. Health
Link BC - Exercise During Pregnancy
7. WebMD - Pregnancy: Exercise During Pregnancy
8. ACSM -
Current Comment: Exercise During Pregnancy
9. WebMD -
Exercise During Pregnancy: Myth vs. Fact
10. Cleveland
Clinic - Exercise During Pregnancy
*ACOG
updated their guidelines very recently, after we had finished our review paper,
replacing their 2002 guidelines that were reaffirmed in 2009. Now they include
further commentary on exercise intensity as well as fetal response to maternal
exercise.
References
American College of Obstetricians and
Gynecologists. (2002). Exercise during pregnancy and the postpartum period. Obstetrics & Gynecology, 99(1),
171-173. Retrieved from http://journals.lww.com/greenjournal/pages/default.aspx
Barakat, R., Pelaez, M., Lopez, C., Montejo, R., & Coteron, J. (2012). Exercise during pregnancy reduces the
rate of cesarean and instrumental deliveries: results of a randomized
controlled trial. The Journal of Maternal-Fetal & Neonatal Medicine,
25(11), 2372-2376.
doi:10.3109/14767058.2012.696165
Barakat, R., Stirling,
J. R., & Lucia, A. (2008). Does exercise training during pregnancy affect
gestational age? A randomised controlled trial. British
Journal of Sports Medicine, 42(8), 674-678. doi:10.1136/bjsm.2008.047837
Bergmann, A., Zygmunt, M., & Clapp, J. F., (2004). Running throughout
pregnancy: Effect on placental villous vascular volume and cell proliferation. Placenta,
25(8-9), 694-698. doi:10.1016/j.placenta.2004.02.005
Bernal, L. A. (2007). Overview. Preterm
labour: Mechanisms and management. BMC Pregnancy
and Childbirth, 7(Suppl 1), S2. doi:10.1186/1471-2393-7-S1-S2
Bungum, T. J., Peaslee, D. L., Jackson, A. W., & Perez, M. A.
(2000). Exercise during
pregnancy and type of delivery in nulliparae. Journal of Obstetric, Gynecologic, &
Neonatal Nursing, 29(3), 258-264.
doi:10.1111/j.1552-6909.2000.tb02047.x
Clapp, J. F, III.
(1996). Morphometric and neurodevelopmental outcome at age five years of the
offspring of women who continued to exercise regularly throughout pregnancy. The Journal of Pediatrics, 129(6),
856-863. doi:10.1016/s0022-3476(96)70029-x
Clapp, J. F. III,
Little, K. D., Appleby-Wineberg, S. K., & Widness, J. A. (1995). The effect of regular maternal
exercise on erythropoietin in cord blood and amniotic fluid. American Journal of Obstetrics and
Gynecology, 172(5), 1445-1451. doi:10.1016/0002-9378(95)90476-x
Clapp, J. F. III,
Simonian, S., Lopez, B., Appleby-Wineberg, S., & Harcar-Sevcik, R. (1998). The one-year morphometric and
neurodevelopmental outcome of the offspring of women who continued to exercise
regularly throughout pregnancy. American
Journal of Obstetrics and Gynecology, 178(3), 594-599. doi:10.1016/s0002-9378(98)70444-2
Eriksson, J., Forsén, T., Tuomilehto, J.,
Osmond, C., & Barker, D. (2001). Size at birth, childhood growth and
obesity in adult life. International
Journal of Obesity, 25(5), 735-740. doi:10.1038/sj.ijo.0801602
Feiner, B., Weksler, R., Ohel, G., & Degan, S. (2000).
The influence of maternal exercise on placental blood flow measured by
Simultaneous Multigate Spectral Doppler Imaging
(SM-SDI). Ultrasound in Obstetrics & Gynecology, 15(6), 498-501.
doi:10.1046/j.1469-0705.2000.00146.x
Gollenberg, A. L., Pekow, P., Bertone-Johnson, E. R., Freedson,
P. S., Markenson, G., & Chasan-Taber,
L. (2011). Physical activity and risk of small-for-gestational-age birth among
predominantly puerto rican women. Maternal Child
and Health Journal, 15(1),
49-59. doi:10.1007/s10995-009-0563-1
Haakstad, L. A. & Bø,
K. (2011). Exercise in pregnant women and birth weight: A randomized controlled
trial. BMC Pregnancy and Childbirth, 11(1), 66. doi:10.1186/1471-2393-11-66
Hansen, A. K., Wisborg, K., Uldbjerg, N., & Henriksen, T. B. (2008). Risk of respiratory morbidity in
term infants delivered by elective caesarean section: Cohort study. British
Medical Journal, 336(7635), 85-87. doi:10.1136/bmj.39405.539282.BE
Hatch,
M., Levin, B., Shu, X. O., & Susser, M. (1998).
Maternal leisure-time exercise and timely delivery. American Journal of
Public Health, 88(10), 1528-1533. doi:10.2105/ajph.88.10.1528
Henriksen, T. (2008). The macrosomic fetus: A challenge in current obstetrics. Acta Obstetricia Gynecologica Scandinavica, 87(2),
134-145. doi:10.1080/00016340801899289.
Hopkins, S. A., & Cutfield, W. S. (2011). Exercise in pregnancy: Weighing up
the long-term impact on the next generation. Exercise and Sport Sciences Reviews, 39(3), 120-127.
doi:10.1097/jes.0b013e31821a5527
Jin, J. (2015). Babies
with low birth weight. The Journal of the American Medical Association, 313(4),
432. doi:10.1001/jama.2014.3698
Kolas, T., Saugstad, O.D., Daltveit, A.K.,
Nilsen, S.T., & Øian, P. (2006). Planned
cesarean versus planned vaginal delivery at term: Comparison of newborn infant
outcomes. American Journal of Obstetrics and Gynecology, 195(6), 1538-1543.
doi:10.1016/j.ajog.2006.05.005
Lotgering F., Gilbert R., &
Longo L. (1985). Maternal and fetal responses to exercise during pregnancy. Physiological
Reviews, 65(1), 1-36. Retrieved from http://physrev.physiology.org/
May, L., Glaros, A., Yeh, H., Clapp, J.,
& Gustafson, K. (2010). Aerobic exercise during pregnancy influences
fetal cardiac autonomic control of heart rate and heart rate variability. Early
Human Development, 86(4), 213-217. doi:10.1016/j.earlhumdev.2010.03.002
Melzer, K., Schutz,
Y., Soehnchen, N., Othenin-Girard,
V., Martinez de Tejada. B., Irion, O., . . . Kayser, B. (2009). Effects of recommended levels of
physical activity on pregnancy outcomes. American Journal of Obstetrics and
Gynecology, 202(3), 266.e1–266.e6. doi: 10.1016/j.ajog.2009.10.87
Nascimento, S. L., Surita, F. G., Godoy, A. C., Kasawara,
K. T., & Morais, S. S. (2015). Physical activity
patterns and factors related to exercise during pregnancy: A cross sectional
study. PLoS One, 10(6), e0128953.
doi:10.1371/journal.pone.0128953
Osuala, K., Baker, C. N.,
Nguyen, H., Martinez, C., Weinshenker, D., & Eben, S. N. (2012). Physiological and genomic consequences
of adrenergic deficiency during embryonic/fetal development in mice: impact on
retinoic acid metabolism. Physical Genomics, 44(19), 934-947.
doi:10.1152/physiolgenomics.00180.2011
Phillips, D. I. W.
& Young, J. B. (2000). Birth weight, climate at birth and the risk of
obesity in adult life. International
Journal of Obesity, 24(3), 281-287. doi:10.1038/sj.ijo.0801125
Teramo K. A., & Widness J.A., (2009). Increased fetal plasma and amniotic
fluid erythropoietin concentrations: Markers of intrauterine hypoxia. Neonatology,
95(2), 105-116. doi:10.1159/000153094
Ward, R. (2015). The Prenatal Environment and Growth
[PowerPoint slides]. Retrieved from Lecture Notes Online Web site: http://www.sfu.ca/~ward/Placenta%20Fall%202015.ppt
Wollschlaeger, K., Nieder,
J., Köppe, I., & Härtlein,
K. (1999). A study of fetal macrosomia. Archives of Gynecology and
Obstetrics, 263(1-2), 51-55. doi:10.1007/s004040050262