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PHYSIOLOGY OF NORMAL LABOUR

PHYSIOLOGY OF NORMAL LABOUR. DEFINITION. Series of events that take place in the genital organs in an effort to expel the viable products of conception out of the womb through the vagina in to the outer world. Parturient is the patient in labour

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PHYSIOLOGY OF NORMAL LABOUR

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  1. PHYSIOLOGY OF NORMAL LABOUR

  2. DEFINITION • Series of events that take place in the genital organs in an effort to expel the viable products of conception out of the womb through the vagina in to the outer world. • Parturient is the patient in labour • Parturition is the physiological process involved in birthing.

  3. DEFINITION • EUTOCIA means normal labour. • DYSTOCIA means abnormal labour.

  4. Criteria for Normal Labour • Spontaneous in onset and at term. • With vertex presentation. • Without undue prolongation. • Natural termination with minimal aids. • Without having any complication affecting the health of the mother and/or the baby. • 53% of women with singleton cephalic presentations at term had a spontaneous labour and delivery.

  5. Causes for onset of Labour

  6. STAGES OF LABOUR • FIRST STAGE- From the onset of true labour to complete dilatation of the cervix (6 to 18 hours in primigravida and 2 to 10 hours in a multipara). • SECOND STAGE- From complete dilatation of cervix to the birth of the baby (30 min to 3 hours in a primigravida, 5 to 30 min in multipara)

  7. STAGES OF LABOUR • THIRD STAGE – From the birth of the baby to delivery of the placenta ( 5 to 30 min) • FOURTH STAGE – From the delivery of the placenta until the postpartum condition of the patient has become stabilized.

  8. TRUE vs FALSE LABOUR • TRUE LABOUR • Contractions occur at regular intervals • Intervals gradually shorten • Intensity gradually increases • Discomfort is in the back and abdomen • Cervix dilates • Discomfort is not stopped by sedation • “Show” • Formation of “bag of waters”

  9. TRUE vs FALSE LABOUR • FALSE LABOUR • Contractions occur at irregular intervals • Intervals remain long • Intensity remains unchanged • Discomfort is chiefly in the lower abdomen • Cervix does not dilate • Discomfort is relieved by sedation

  10. EVENTS IN THE FIRST STAGE • UTERINE CONTRACTION AND RETRACTION • FORMATION OF DISTINCT LOWER AND UPPER SEGMENTS • CHANGE IN UTERINE SHAPE • CERVICAL DILATATION AND EFFACEMENT

  11. Uterine contraction and retraction • Contraction is temporary reduction in length of the fibres, which attain full length on relaxation . • Retraction - permanent shortening of uterine muscle fibres • Initially come at varying intervals of 15-30 min for about 30 sec and in late first stage at intervals of 3-5 min lasting for 45 sec • Mechanical stretching of cervix enhances uterine activity FERGUSON REFLEX

  12. CHARACTERISTICS OF UTERINE CONTRACTIONS • good synchronization of the contraction waves • Fundal dominance with gradual diminishing contraction wave through the mid zone to lower segment • Waves of contraction follow a regular pattern • Intra-amniotic pressure rises beyond 20mmHg with onset of true labour pains during contraction • Good relaxation occurs in between contractions

  13. FORMATION OF DISTINCT LOWER AND UPPER SEGMENTS • Upper segment(active) - contracts, retracts & expels the fetus • Lower segment (passive) - thins & stretches • Physiological retraction ring is formed

  14. CHANGES IN UTERINE SHAPE • With contractions produces elongation of uterine ovoid with decrease in horizontal diameter • Elongation of uterine ovoid causes the longitudinal muscles to taut and helps in cervical dilatation and formation of LUS • Decrease in horizontal diameter causes straightening of fetal vertebral column and exerts Fetal Axis Pressure.

  15. CERVICAL DILATATION AND EFFACEMENT • Longitudinal muscle fibers of upper segment attached circular muscle fiber of lower segment & upper part of cervix in bucket holding fashion. • Polarity of Uterus- Co ordination between fundal contraction & cervical dilatation • Bag of membranes- Uterine contractions exert hydrostatic pressure through fetal membrane against cervix & lower uterine segment • Fetal axis pressure

  16. Bag of membranes-

  17. PHASES OF FIRST STAGE • The Latent Phase • Up to 3 cm dilatation • Dilatation averaging 0.39 cm/hour • Average latent phase lasts 8.6hrs in nulliparas and 5.3 hrs in multiparas • Upper limit is 20 hours in primigravidas and 14 hours in multiparas

  18. PHASES OF FIRST STAGE • The Active Phase • Beyond 3cm dilatation • 1.2cm/hr for primigravida & 1.5cm/hr for multiparas • Average length of 5.8hrs in primigravida & 2.5 hrs in multiparas • Upper limit of 12 hrs for primigravida & 6hrs for multiparas

  19. EVENTS IN THE SECOND STAGE • This stage is concerned with decent and delivery of the fetus • Contractions come at the intervals of 2-3min and last for about 1 to 1 ½ min • Expulsive forces of uterine contractions is added by voluntary contraction of abdominal muscles- Bearing Down Efforts

  20. Evolution of dilatation and Decent curve

  21. EVENTS IN THE THIRD STAGE • Comprises of placental separation, its decent and expulsion • Two ways of placental separation • Central (Schultze) • Marginal(Mathews-Duncan)

  22. Two ways of placental separation

  23. THANK YOU

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