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Part 1: Normal Labour HANGZHOU WOMENS HOSPITAL International Undergraduate Course, 2011

5 1. Glossary of terms 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.

6 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.

7 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 .

8 Mechanism of normal labour
“Powers” “Passenger” “Passages”

9 Female Male



12 Levator ani OI atla IC PC Vagina Rectum

13 Changes to the uterus during labour

14 Uterine contractions * Retraction
* Rhythm: increase in frequency and duration in labor。 * Symmetry and polarity * Retraction

15 Symmetry and Polarity The intensity of the upper segment of the uterus is the most strong.

16 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.

17 Changes to the cervix during labour

18 Lie, presentation, position, attitude of the fetus in labour

19 Engagement and station of the fetus in labour

20 Mechanism of normal labour





25 PROGRESS IN LABOUR Descent Internal rotation Extension





30 PARTOGRAM - Friedman


32 EPISIOTOMY – midline v mediolateral
PERINEAL TEAR – first to fourth degree

33 Third stage of Labour



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