Revista de Medicina Desportiva (English) November 2018 | Page 10

consumption, overweight and obe-
sity by the mother. Physical activity
has an important role in the fight
against excessive weight gain and
on the pregnancy complications,
like gestational diabetes and pre-
eclampsia, being the relation less
clear about the risk of PTD itself,
which motivates this study.
This systematic review included 41
studies (43 publications), where 20
studies were randomized and 21 of
cohort, and most of the studies were
published in Europe and in North
America. The authors included any
type of physical activity, that could
be the practice of varied physical
exercise, leisure activities or occu-
pational activity. From the main
results, it is highlighted that the
superior levels of physical activ-
ity during the free time during the
pregnancy were associated with the
statistically significant 14% decrease
of the risk for PTD and for each
increase of three weekly hours on
leisure activities there was a 10%
reduction of the relative risk for PTD.
The authors concluded the existence
of a not linear association between
physical activity during pregnancy
and the risk of PTD, where the lowest
risk was for the period of 2-4 hours /
week of physical activity (reduction
of 15-16% on risk). However, they
point out that this association must
be seen with caution, since it only
had statistical significance in the
studies of cohort, but not in the ran-
domized and controlled studies. The
other types of physical activity and
activity practice before pregnancy
pointed in the way of risk reduction,
but also without statistical signifi-
cance, which was justified by the
authors because of low power of the
sample.
As far as dose-response is con-
cerned, the authors found evidence
on the decreased risk for PTD with
2 to 4 hours per week of physical
activity but didn’t find higher rates
of reduction of the risk with supe-
rior levels of activity. In this case,
it is important to note that the
number of studied cases involving
superior levels of activity is scarce,
being necessary more studies to be
8 november 2018 www.revdesportiva.pt
possible to withdraw conclusions.
There is, however, scientific evidence
that levels of 5 to 7 hours / week of
physical activity have benefits in
the reduction of pre-eclampsia and
gestational diabetes.
About the limitations, although
most of the studies have adjusted
analyses to several confound-
ers, and the meta-analyze hadn’t
shown heterogeneity among the
studies, the authors assume some
interference of the confounders not
measured, such as the diet. The fact
that the different studies report the
results in different measures turn
the analyze more difficult.
This paper points to some jus-
tifications about the inverse rela-
tionship between physical activ-
ity and PTD, namely the fact that
the practice of physical exercise
is related with a better control of
weight gain. However, this review
demonstrated a significant reduc-
tion of the risk associated solely
with exercise, independently of body
mass index of the pregnant women.
So, it is concluded that the prac-
tice of more physical activity by the
pregnant women is related to the
reduction of the risk for PTD, but
some studies are needed to clarify
the dose-response relationship and
the association with the different
types and intensities of the physical
activity as well. It is always good
to remind that physical exercise
has good evidence for the preven-
tion of the several complications of
pregnancy, is useful and it is recom-
mended to consider the global well-
being of the pregnant woman, that
should keep herself active through-
out pregnancy.
Full text can be red at www.revdesportiva.pt
a. Student of the post-graduation course on
sports medicine. Medical School of Porto
(2018/2019)
1. D Aune, S Schlesinger, T Henriksen,
OD Saugstad, S Tonstad. Physical
activity and the risk of preterm birth: a
systematic review and meta-analysis of
epidemiological studies. BJOG. 2017 Nov;
124(12):1816-1826.
The preterm delivery in Portugal
It is a normal reality that also occurs
in Portugal. A visit to several sites
allows to find out some numbers.
For example, in 2005 there were
in Portugal 109399 live births and
7260 (6.6%) were PTD, this means,
they were born before full 37 weeks
of gestation. The text indicates that
“these percentages have been kept
stable for the last years”, where the
twin pregnancy is the main cause.
In the meanwhile, a news dated
06/2016 referred that “in 2014,
6393 preterm babies were born …
and, of these, 816 (about 1%) were
very premature (<32 weeks), which
have the highest risk. In another
text, it is stated that prematurity
is the main cause of death during
the first year of life, and it is the
2 nd cause before 5 years of age, but
“the technological development
and the differentiation in some
hospitals” caused the increase of
the survival rate. It is added, in this
text, other risk factors: pregnancy
at the extremes of age (<18 and >35
years of age), smoking habits, quick
wear jobs and intense psychologi-
cal stress. BR