2nd stage labour, its physiology & management
- 1. SECOND STAGE OF LABOUR
- 2. Second stage of labor • From the full dilatation of the cervix and the ends with expulsion of the fetus from the birth canal. Two phases: a. Propulsive phases- starts from full dilatation up to the descent of the presenting part to the pelvic floor. b. Expulsive phase-is distinguished by maternal bearing down efforts and ends with delivery of the baby.
- 3. • Its average duration is 2hrs in primigravida and 30minutes in multipara. • Period typically characterized by • maternal restlessness • Discomfort • desire for pain relief • a feeling that the process is never ending • demands to birth attendants to get the birth process over as quickly as possible.
- 4. Principles • To assist in the natural expulsion of the fetus slowly and steadily • To prevent perineal injuries.
- 5. Physiology of second stage of labour The physiological changes result from a continuation of the some forces which have been at work desiring the first stage of labour. • Descend • Uterine action • Rupture of membrane • Soft tissue displacement
- 6. DESCENT • Descent of fetal presenting part which began during the first stage of labour and reaches its maximum speed toward the end of the first stage of labour,continues its rapid pace through the second stage of labour until the pelvic floor • The average maximum rate of descend is 1.6cm/hr in multiparae • 5.4cm/hr in nullipara.
- 7. Physiology of second stage of labor • UTERINE ACTION: contractions become stronger and longer but may be less frequent, allowing both mother and fetus to rest in between contractions. • They are strong in intensity and become expulsive in nature. • In natural course of labour there is often a lull or quiet period between first and second stage . • The woman rests and may even nap • The fetal head descends through the pelvis the contractions become more forceful and the woman begins to voluntarily bear down with expiratory, grunty short pushes.
- 8. • Pressure from the presenting part stimulates nerve receptors in the pelvic floor (ferguson reflex) and the women experiences the urge to push. • The reflex may initially be controlled to a limited extent but becomes increasingly compulsive, overwhelming and involuntary during each contraction. EXPULSIVE ACTION OF ABDOMINAL MUSCLES & DIAPHARGM • The mother then employs her secondary powers of expulsion i.e. the abdominal muscles and diaphragm to push out the baby. • Contraction of abdominal muscle & diaphragm known as bearing down or pushing
- 9. The membrane • often rupture spontaneously towards the end of the first stage during transition to the second stage. • The consequent drainage of liquor allows the fetal head to be directly applied to the cervix, this pressure aids distension.
- 10. • FETAL AXIS PRESSURE Fetal axis pressure increases flexion of the head, which results in smaller presenting diameters, more rapid progress and less trauma to both mother and fetus.
- 11. SOFT TISSUE DISPLACEMENT: • The descending fetal head displaces the soft tissues of the pelvis. • Anteriorly, the bladder is pushed upwards into the abdominal cavity where it is at less risk of injury during fetal descent. • This results in the stretching and thinning of the urethra Posteriorly, the rectum becomes flattened into the sacral curve and the pressure of the advancing head expels any residual faecal matter. • The levatoani muscles dilate, thin out and are displaced laterally and the perineal body is flattened, stretched and thinned. • The fetal head becomes visible at the vulva, advancing with each contraction and receding between contractions until crowning takes place.
- 12. • . Levatoani muscle • 12. Perineal body
- 13. Expulsion of fetus: The head is then born and the shoulders and body follow with the contraction accompanied by a gush amniotic fluid and sometimes blood. • The second stage culminates in the birth of the baby.
- 14. Recognition of the commencement of the second stage • Not clinically apparent. • Several of the signs are presumptive and can only be confirmed by vaginal examination. These include: • Expulsion uterine contractions: Although this is usually a sign that the cervix is fully dilated, it is possible for the women to feel the urge to push before full dilatation occurs e.g. when rectum is full, etc..
- 15. • Appearance of the presenting part: Although this is usually definitive, it is important to be aware that excessive moulding may result in the formation of a large caput succedaneum, which can protrude through the cervix prior to full dilatation. Similarly, a breech presentation may be visible when the cervix is not fully dilated.
- 16. Rupture of forewaters: This may occur at anytime during labor but physiologically, it occurs at the end of 1st stage when cervix is fully dilated and can no longer support the bag of waters. Dilatation & gaping of the anus: As the fetal head descends and touches the pelvic floor, there’s increased pressure especially on the rectum. This results in dilation and gaping of the anus and may result in discharge of faecal matter.
- 17. • MOULDING OF THE HEAD CAPUT SUCCEDANEUM • Show: loss of blood stained mucus which often accompanies rapid dilatation towards the end of 1st stage of labor. It must be distinguished from frank fresh blood loss caused by partial separation of the placenta, or that caused by ruptured vasa previa. • Congestion of the vulva: the pressure of the fetal head on the vulva results in venous congestion, however, premature pushing may also cause this.
- 18. COMFIRMATORY EVIDENCE Done by vaginal examination which reveals no cervix and it is done to: • Ensure the women is not pushing too early before the cervix is fully dilated. • To provide a baseline for timing the length of 2nd stage of labor.
- 19. Mechanism of labor • Definition: The series of movement that occur on the head in the process of adaptation, during its journey through the pelvis is called mechanism of labor. At the onset of labor, Most common presentation - vertex Most common position- either left or right occipitoanterior
- 20. In this instance: • The lie is longitudinal. • The presentation is cephalic. • The position is right or left occipito-anterior • The attitude is one of good flexion • The denominator is the occiput • The presenting part is the posterior part of the anterior parietal bone.
- 21. Principles of mechanism of labor • Descent takes place throughout the labor. • Whichever part leads and first meet the resistance of the pelvic floor will rotate until it comes under the symphysis pubis. • Whatever emerges from the pelvis will pivot around the pubic bone.
- 22. Main movement of fetus • Engagement • Descent • Flexion • Internal rotation • Crowning • Extension of the head • Restitution • External rotation • Birth of the shoulder and trunk
- 23. Engagement • When the bi-parietal diameter of the head passes the pelvic inlet, the head is said to be engaged. • In the most nulliparous pregnancies this occurs before the onset of active labor because the firmer abdominal muscle directs the presenting part into the pelvis. • In multiparous pregnancies, in which the abdominal musculature is more relaxed, the head often remains freely movable above the pelvic brim until labor is established.
- 26. Descent • In fact descent is a continuous process occurring throughout the labor till the head is born. • Descent of the fetal head into the pelvis often begins before the onset of labor. For a primigravida women this usually occurs during the later weeks of pregnancy. • In multigravida women muscle tone is often more lax and therefore descent of the fetal head and engagement of the fetal may not occur until labor actually begins. • Throughout the first stage of labor the contraction and retraction of the uterine muscles allow less room in the uterus, exerting pressure on the fetus to descend further.
- 28. Flexion • As soon as head meets resistance from the cervix, pelvic wall or pelvic floor during descent, full flexion is achieved. • Flexion is essential for descent, since it reduces the shape and size of the plane of the advancing diameter of the head.
- 30. Internal rotation: occiput rotates anteriorly and the fetal head assumes an oblique orientation. • It is a movement of great importance without which there will be no further descent. • It is probably due to slope of pelvic floor which determines the direction of rotation, pelvic shape and inequalities in flexibility of component parts of the fetus. • The muscles are hammock shaped & slope down anteriorly so which ever part fetus first meets the lateral half of this slope will directed forward & towards the centre • Torsion of the neck is an inevitable phenomenon during internal rotation of head. • There is no movement of the shoulders from the oblique diameter as the neck sustains a torsion of only 1/8th of a circle. • The AP diameter of head now lies in widest AP diameter of pelvic outlet
- 32. Crowning After internal rotation of the head, further descent occurs until the sub- occiput lies underneath the pubic arch. At this stage, the maximum diameter of the head (bi-parietal) stretches the vulval outlet without any recession of the head even after the contraction is over called crowning of the head.
- 34. Extension of the head Once crowning has occurred the fetal head can extend, pivoting on the sub-occipital region around the pubic bone. This releases the sinciput, face, and chin, which sweep the perineum, and then are born by a movement of extension.
- 36. Restitution The twist in the neck of the fetus which resulted from internal rotation is now corrected by a slight untwisting movement. The occiput moves 1/8 of a circle towards the side from which it started.
- 38. External rotation Movement of rotation of the head visible externally due to internal rotation of the shoulders. As the anterior shoulder rotates toward the symphysis pubis from the oblique diameter, it carries the head in a movement of external rotation through 1/8th of a circle in the same direction as restitution.
- 40. Birth of shoulder and trunk • After the shoulders are positioned in anteroposterior diameter of the outlet, further descent takes place until anterior shoulder escapes below the symphysis pubis first, by a movement of lateral flexion of the spine, the posterior shoulder sweeps over the perineum. • Rest of the trunk is then expelled out by lateral flexion
- 42. THIRD STAGE LABOUR • Placental separation:Central separation,Marginal separation • Descent of placenta • Expulsion of placenta
- 43. SIGNS • Uterus become globular in shape & firmer • Lengthening of cord • Gush of blood • Uterus rises in abdomen
Editor's Notes
- #7: Lasting for 60-90 sec
- #10: Intensified contractile power of uterus –force is transmitted through
- #24: Occiput –lt iliopectinal eminence,sinciput at rt sacroiliac jt & sagittal suture on rt oblique diameter of pelvis
- #25: ANT-Nagele’s obliquity,post-Litzman’s
- #26: Head reach pelvic floor when cx is fully dilated
- #28: SOF-10CM,SOB-9.5
- #41: Modified ritgen maneuver-exert forward pressure on fetal chin through the perineal skin just in front of anus ,other hand erts pressure against occiput
- #42: Placental stage