The first stage of labour, poor progression of labour, and augmentation of labour

The presentation is on normal labour, stages and mechanisms, physiological basis of labour, abnormal labour, diagnosis and managment

1.  The first stage of labour, poor progression of labour, and augmentation of labour Dr Indunil Piyadigama

2. Labour Labour is a physiologic process during which the products of conception ( ie , the fetus , membranes, umbilical cord, and placenta) are expelled outside of the uterus. Labour is achieved with gradual effacement and dilatation of the uterine cervix as a result of rhythmic uterine contractions of sufficient frequency, intensity, and duration

3. Mechanism of labour

4. Pelvis (passage) The true pelvis is shallow anteriorly, formed by the symphysis pubis (4–5 cm), and deep posteriorly, formed by the sacrum and coccyx (10 cm). It is divided into three parts – inlet, cavity and outlet The pelvic inlet has a wide transverse diameter – approximately 13 cm, the midcavity of the pelvis is round, whilst the outlet has a wide anterior posterior diameter.

5. Uterine activity (power) The uterine contraction is characterized by its intensity, frequency, and duration. Quantitative assessment of intrauterine pressure to measure the strength of uterine contraction is done by placement of an intrauterine catheter. This is measured in Montevideo units (MVU). Uterine activity varies in different stages of labour: latent phase approximately 100 MVUs active phase of labour 175 MVUs 250 MVUs during the second stage

6. Fetus (passenger) For a successful outcome, the fetal skull, shoulders, trunk and buttocks should pass through maternal pelvis. Several variables in the fetus influence its journey through the birth canal Fetal size  Can be estimated by palpation, ultrasound scan and customized growth chart but all of these methods are subjected to large degree of error.

7. S tages of labour First stage of labour Begins with regular uterine contractions and ends with complete cervical dilatation at 10 cm Divided into a latent phase and an active phase The latent phase begins with mild, irregular uterine contractions that soften and shorten the cervix Contractions become progressively more rhythmic and stronger The active phase usually begins at about 3-4 cm of cervical dilation and is characterized by rapid cervical dilation and descent of the presenting fetal part For a nullipara the first stage of labor this lasts on average 8–18 hours In multiparous women it is between 5 and 12 hours

8. Second stage of labour Begins with complete cervical dilatation and ends with the delivery of the fetus Birth is expected within 3 hours of the start of active second stage in most nulliparous and within 2 hours in most multiparous women

9. Third stage of labour The period between the delivery of the fetus and the delivery of the placenta and fetal membranes Delivery of the placenta often takes less than 10 minutes, but the third stage may last as long as 30 minutes

10. Labour mechanism

11. Physiology CRH CRH is both a hypothalamic and placental peptide. It is produced in varying concentrations throughout pregnancy and labour, but is known to increase exponentially near term. CRH acts on targets within the fetal adrenal pituitary axis, placenta and myometrial smooth muscle, and is thought to play a part in the initiation of labour. Prostaglandin Induce remodelling of the cervical extracellular matrix protein, and cell apoptosis by stimulating matrix metalloproteinase (MMP) activity This leading eventually to fetal membrane rupture. Softening the cervix PGF2ɑ, PGHS-2 and PGE2 receptors augment myometrial responsiveness to contractile agonists PGF2ɑ, also contributes to placental separation Progesterone Inhibit myometrial contractility Suppresses oxytocin-induced prostaglandin production and the myometrial response to oxytocin Progesterone withdrawal is a key component in the facilitation of parturition.

12. Oestrogen Rise in late pregnancy oestrogen enhances oxytocin receptor expression Oxytocin Oxytocin receptor concentration increases significantly as term approaches Binds to receptor and opens calcium activated channel Oxytocin has both direct and indirect actions. Acts directly on the myometrium to produce regular, effective contractions, and Indirectly on the decidua to increase production of prostaglandins.

13. Diagnosis of labour

14. Partogrm

15. Partogram

16. Prolonged 1st stage of labour

17. Prolonged 2nd stage

18. Causes of prolonged labour Inadequate uterine contractions Malposition of the fetal head OP position Extended fetal head – Brow/ face presentation Cephalopelvic disproportion Excessive sedation in the latent phase Epidural – Controversial. No evidence to show prolonged labour. However, second stage can be delayed

19. Further managment Assess uterine activity Can be infrequent (< 3-4 for 10 mins) Inadequate strength Short Incordinated Fetal size, presentation, position and attitude Pelvic assessment Look for signs of obstruction – Excessive caput/ moulding General well being of the mother Hydration Pain relief Position

20. Augmentation of labour Augmentation of labour is the process of stimulating the uterus to increase the frequency, duration and intensity of contractions after the onset of spontaneous labour Coordination of the contraction from fundus of the uterus towards the cervix Can correct malpositions and malpresentations (flex head, rotate) Interventions may not be successful unless maternal wellbeing is improved

21. Amniotomy Amniotic sac is deliberately ruptured so as to cause the release of amniotic fluid Reduces duration of labour by 1hr Do not necessarily improve the clinical outcomes No effect on analgesics or CS rate Discouraged because of 10% chance of false labour

22. Oxytocin Oxytocin in delayed 1 st stage r educe the time to delivery Does not alter the mode of delivery No change in neonatal outcome Different protocols used at different units. Using mU /min rather than ml/min in these protocols are recommended Half life is 3 minutes Uterine overactivity can occur Water intoxication and hyponatremia If boluses given leads to hypotension

23. Prostaglandin Misoprostol 20 mic g have been observed to have same effects as IV oxytocin No difference in side effects

24. Upright posture

25. Other interventions

26. Thank you