This document defines and describes the physiology of normal labor. Normal labor is defined as spontaneous onset between 37-40 weeks of gestation, with a vertex baby presentation, no complications, and natural termination with minimal aid. The physiology involves two steps - uterine contractions and retraction. Contractions temporarily harden and shorten the uterus, becoming stronger over time. Retraction permanently shortens uterine muscles to facilitate dilation, delivery, and postpartum hemostasis.
2. INTRODUCTION
Labor is a physiologic process during which the
products of conception (ie, the fetus,
membranes, umbilical cord, and placenta) are
expelled outside of the uterus.
3. DEFINITION OF NORMAL LABOUR
Series of events that take place in the genital
organ in an effort to expel the viable(alive)
products of conception out of the womb/uterus
through vagina into outer world is called
Normal Labour.
4. DEFINITION OF NORMAL LABOUR
Labour is defined as the presence of regular
uterine contractions with progressive cervical
dilatation and effacement.
5. CRITERIA/CHARACTERISTICS OF
NORMAL LABOUR
1. Spontaneous in onset and at term ( between 37
-40 weeks of gestation.)
2. With Vertex presentation
3. Without any undue prolongation.
4. Without any complications.
5. Naturally Terminated with minimal aid.
6. PHYSIOLOGY OF NORMAL LABOUR
Physiology of normal labour complete into two
steps -
UTERINE
CONTRACTION
RETRACTION
7. PHYSIOLOGY OF NORMAL LABOUR
1. Uterine contraction :
During contraction, uterus becomes hard and
somewhat pushed anteriorly to make the long axis
of the uterus in the line with that of pelvic axis.
8. PHYSIOLOGY OF NORMAL LABOUR
1. Uterine contraction :
Simultaneously, the patient experiences pain which
is situated more on the
hypogastric region, often radiating to the thighs.
9. PHYSIOLOGY OF NORMAL LABOUR
1. Uterine contraction :
Probable cause of pain are –
a) Myometrial hypoxia during contractions.
b) Stretching of the peritoneum over the fundus.
c) Stretching of the cervix during dilatation.
d) Compression of the nerve ganglion.
The pain of uterine contractions is distributed along the
cutaneous nerve distribution of T10 to L1.
12. PHYSIOLOGY OF NORMAL LABOUR
INTENSITY –
The intensity of uterine contractions describes the
degree of uterine
systole.
The intensity gradually increases with advancement
of labour until it
becomes maximum in the second stage during
delivery of the baby.
Intrauterine pressure is raised to 40-50 mm Hg
during first stage and about 100-120 mm Hg in the
second stage of labour during contractions.
14. PHYSIOLOGY OF NORMAL LABOUR
DURATION
In the first stage, the contractions last
for about 30 second initially but
gradually increases in duration with
the progress of labour.
Thus in the second stage,
the contractions last longer than in the
first stage.
15. PHYSIOLOGY OF NORMAL LABOUR
FREQUENCY
In the early stage of labour, the
contractions come at intervals of ten to
fifteen minutes.
The intervals gradually shorten with
advancement of labour until in
the second stage, when it comes every
two or three minutes.
19. PHYSIOLOGY OF NORMAL LABOUR
Unlike any other muscle of the body,
the uterine
have this property to
muscles
become
shortened once and for all.
20. PHYSIOLOGY OF NORMAL LABOUR
Contraction is a temporary
reduction in length of the fibers, which
attain their full length during relaxation.
In contrast,
retraction results in permanent shortening
and the fibers are shortened once and for
all.
21. PHYSIOLOGY OF NORMAL LABOUR
The net effect of retracton on normal
labour are:- -
Essential property in the formation
of lower uterine segment and
dilatation and
effacement up of the cervix.
23. PHYSIOLOGY OF NORMAL LABOUR
To maintain the advancement of the presenting
part made by the uterine contractions and to
help in ultimate expulsion of the fetus.
To reduce the surface area of the uterus
favouring separation of placenta.
Effective haemostasis after the separation of the
placenta.
