physiological changes during 1st stage of labor
TRANSCRIPT
-
7/23/2019 Physiological Changes During 1st Stage of Labor
1/18
Physiological changes during first stage of labor
The first stage is chiefly concern with the preparation of
the birth canal so as to facilitate expulsion of the fetus in
the 2nd stage. During first stage of labor, following
physiological changes are occurs.
1. Uterine action
I. Contraction and retraction of uterine muscles
-
7/23/2019 Physiological Changes During 1st Stage of Labor
2/18
Uterine contractionare involuntary, they are controlled
by the nervous system and endocrine influence.
Normally the uterus begins to contract effectively 280
days after the !". #ontraction consists of regular,
painful with hardening of uterus. The patient experiences
pain, which is situated more on the hypogastric region,
often radiating to the thighs. "robable causes of pain aremyometrial hypoxia during contractions, stretching of
the peritoneum over the fundus, stretching of the cervix
during dilatation and compression of the nerve ganglion.
$t earlier the contractions are often wee% and may beimperceptible to the mother but it becomes more
powerful at last.
-
7/23/2019 Physiological Changes During 1st Stage of Labor
3/18
The feature of uterine contraction:
Frequency: &t is the interval of each contraction. &n the early
stage of labor, the contractions come at intervals of ten to
fifteen minutes. The intervals gradually shorten with
advancement of labor until in the second stage, when it comes
every two or three minutes.
Duration: &t is length of each contraction. &n the first stage, the
contractions last for about '0 seconds initially but gradually
increase in duration with the progress of labor. Thus in second
stage, the contractions last longer then in the first stage.
-
7/23/2019 Physiological Changes During 1st Stage of Labor
4/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
5/18
Retraction is a phenomenon of the uterus in labor in which the muscle
fibers are permanently shorted. #ontraction is a temporary reduction in
length of the fibers, which attain their full length during relaxation. &n
contrast, retraction results in permanent shortening and the fibers are
shorted once and for all. etraction is a specially a property of upper
uterine segment. &t ma%es upper segment of uterus gradually shorter and
thic%er in progressive nature after each contraction and cavity diminishes
which %eeps place with the gradual descent of the presenting part.
The effects of retraction which is essential in normal labor are-
ormation of upper and lower uterine segment.
Dilatation and effacement of up of the cervix.
educe the surface area of the uterus favoring separation of placenta.
!aintain the advancement of presenting part and help in expulsion of
fetus.
-
7/23/2019 Physiological Changes During 1st Stage of Labor
6/18
II. Fundal dominance:
/terine contraction that is strongest at the top of the
uterus and wea%est in the lower uterine segment. ach
uterine contraction starts in the fundus near one of the
cornua and spreads across and downwards. Thecontraction lasts longest in the fundus where it is also
most intense, but the pea% is reached simultaneously over
the whole uterus and the contraction fades from all parts
together. This pattern permits the cervix to dilate and the
strongly contracting fundus to expel the fetus.
-
7/23/2019 Physiological Changes During 1st Stage of Labor
7/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
8/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
9/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
10/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
11/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
12/18
II. Cer$ical dilatation:
Dilatation of cervix is the process of enlargement of the
os uteri from a tightly closed aperture to an openinglarge enough to permit passage of the fetal head.
Dilatation is measured in centimeters and full dilatation
at e;uates to about +0cm.
Dilatation occurs as a result of uterine action and the
counter pressure applied by the bag of membranes and
the presenting part. $ well )flexed fetal head closely
applied to the cervix favors efficient dilatation. "ressureapplied evenly to the cervix causes the uterine fundus to
respond by contraction.
-
7/23/2019 Physiological Changes During 1st Stage of Labor
13/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
14/18
III. Presentation of (ho":
&t is the bloodstain mucoid discharged seen a few hours
before, or with in a few hours after labor has started.
During pregnancy a woman
-
7/23/2019 Physiological Changes During 1st Stage of Labor
15/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
16/18
II. +eneral fluid !ressure
7hile the membranes remain intact, the pressure of
uterine contractions is exerted on the fluid and as fluid is
not compressible, the pressure is e;uali4ed through out the
uterus and over the fetal body and is %nown as general
fluid pressure. 7hen the membrane ruptures and ;uantity
of fluid emerges, the placenta is compressed between the
uterine wall and the fetus during contractions and theoxygen supply to the fetus is thereby diminished and there
is ris% of fetal hypoxia during uterine contraction.
-
7/23/2019 Physiological Changes During 1st Stage of Labor
17/18
-
7/23/2019 Physiological Changes During 1st Stage of Labor
18/18
I. Fetal a%is !ressure
During each contraction the uterus rears forward
and the force of the fundal contraction is
transmitted to the upper pole of the uterus, down
the long axis of the fetus and is applied by the
presenting part to the cervix. This is %nown as fetal
axis pressure and becomes much more significant
after rupture of the membranes and during the
second stage of labor.