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NORMAL & ABNORMAL LABOUR
Part 1: Normal Labour
HANGZHOU WOMENS HOSPITAL
International Undergraduate Course, 2011
1. Glossary of terms
1.
Cervical effacement is shortening of the cervical canal (from a length of 3 cm to a circular aperture.
2.
A “show” results from loosening of the mucus plug in the cervix as a result of effacement and
dilatation of the cervix.
3.
First stage of labor is from onset of labor to full dilatation of the cervix.
Second stage of labor is from full dilatation to delivery of the baby.
Third stage of labor is from delivery to delivery of the placenta.
4.
The birth canal is fully formed at the end of the second stage of labor. Its axis changes through 90
degrees (curve of Carus).
5.
The lie of the baby is the relationship between the longitudinal axis of the baby and the longitudinal
axis of the baby i.e. longitudinal, transverse, oblique.
6.
The presentation of the baby is that part of its anatomy that is lowest in the birth canal i.e. cephalic,
breech, face, shoulder, etc
7.
The position of the baby is the relationship of the presenting part to the right or left side of the pelvis
i.e. LOA, LOP, LOT, OP, OA, ROA, ROP, ROT.
8.
The attitude describes the posture of the fetus i.e. flexion, deflexion, extension.
9.
The denominator is an arbitrary part of the presentation that enables its description during labor. e.g.
occiput in a vertex presentation, sacrum in breech presentation, mentum (chin) in a face presentation.
Definition： Labour
is the process by which
contractions of the gravid uterus expel the fetus
and the other products of conception after 24
weeks from the last menstrual period.
Term Delivery：A term delivery occurs
between 37 and 42 weeks from the last menstrual
period.
Preterm labour：Preterm labor is that
occurring before 37 weeks of gestational age.
Premature ROM: Rupture of the amnotic sac
prior to the onset of labour
Postdate pregnancy：Postdate pregnancy
occurs after 42 weeks .
Mechanism of normal labour
“Powers”
“Passenger”
“Passages”
Female
Male
Levator ani
OI
atla
PC
Vagina
Rectum
IC
Changes to the uterus during labour
Uterine contractions
Rhythm: increase in frequency and duration in labor。
* Symmetry and polarity
* Retraction
*
Symmetry and Polarity
The intensity of the upper segment of
the uterus is the most strong.
Retraction:
The myometrium of the upper uterine
segment does not relax to its original
length after contractions; rather, it
becomes relative fixed at a shorter
length.
Changes to the cervix during labour
Lie, presentation, position, attitude of the fetus in labour
Engagement and station of the fetus in labour
Mechanism of normal labour
PROGRESS IN LABOUR
Descent
Internal rotation
Extension
PROGRESS IN LABOUR
PARTOGRAM - Friedman
CAPUT SUCCEDANEUM
EPISIOTOMY – midline v mediolateral
PERINEAL TEAR – first to fourth degree
Third stage of Labour