Parturition/Stages of Labor

1. Parturition/Stages of Labor Methodius Tuuli, MD, MPH Division of Maternal-Fetal Medicine

3. Objectives • Describe physiology of labor • Define stages of labor • Discuss concepts of normal labor progress • Traditional (Friedman’s) • Contemporary (Zhang’s) • Custom labor curve (Cahill/Tuuli)

4. PARTURITION

5. Parturition • Early Pregnancy • Uterine quiescence • Closed cervix • Parturition • Coordinated uterine activity • Cervical remodelling • Progressive cervical dilation

6. Mediators of Uterine Activity • Inhibitors • Progesterone • Prostacycline • Relaxin • Nitric Oxide • Parathyroid hormone-related peptide • CRH • HPL • Quiescence • Uterotrophins • Estrogen • Progesterone • Prostaglandins • CRH • Activation Uterotonins Prostaglandins Oxytocin Stimulation • Involution • Oxytocin • Thrombin • Involution

7. Initiation of Labor • Fetus • Sheep • Fetal ACTH and cortisol • Placental 17 α hydroxylase •  Estradiol •  Progesterone • Placental production of oxytocin, PGF2 α • Humans • Fetal increased DHEA • Placental conversion to estradiol • Increased decidual PGF2 and gap junctions • Increased oxytocin and PG receptors • Changes in progesterone receptors

8. Initiation of Labor • Oxytocin • Peptide hormone • Hypothalamus-posterior pituitary • Oxytocin receptors • Fundal location • 100-200 x during pregnancy • Actions • Stimulate uterine contractions • Stimulate PG production from amnion/decidua

9. Oxytocin receptor Extracellular Calcium channel Intracellular Phospholipase C cAMP Ca+ MLCK Ca store + Oxytocin + Prostaglandin Uterine contractions

10. Labor

11. Labor Regular uterine contractions and Progressive cervical dilatation

12. Labor • Cervical effacement • Cervical dilatation

13. Labor: the three “P’s” • Passage • Passenger • Powers

14. Passage

15. Passenger • Size • Estimated fetal weight • Lie • Longitudinal • Transverse/oblique • Presentation • Vertex 95% • Non-vertex 5% • Station • Position

16. Passenger: cardinal movements of labor • Descent • Flexion • Internal rotation • Extension • External rotation • Expulsion

17. Powers • Uterine contractions • Duration 30-60 seconds • 3-5 contractions / 10 minutes • Montevedeo units (intrauterine catheter) • Baseline to peak • Sum over 10 minutes • Adequate: >200-250 MVU

18. Labor Progress

19. Stages of Labor • First stage – onset of labor to complete dilatation • Latent phase • Active phase • Second stage– complete cervical dilation to expulsion of fetus • Third stage– expulsion of fetus to expulsion of placenta • (Fourth Stage– First hour after expulsion of placenta)

20. Labor Curve

21. First Stage • Latent phase – onset to rapid cervical change • Active phase – rapid cervical change to complete dilatation • Traditional standards

22. Second Stage • Traditional standards • Immediate versus delayed pushing • Spontaneous versus coached pushing

23. Third Stage • Standards • Mean – 6 minute • 97th% tile – 30 minutes • Active versus passive

24. CHANGING LABOR STANDARDS

25. Why concern? • Too many cesarean

26. Why concern?

27. 1955: Friedman’s Labor Curve • Convenience sample • 622 consecutive nullips • 500 with adequate data • Cervical dilation (Y) plotted against time (X) • Major advance in his day “…..introduces a new dimension to us. Evaluation of progress, previously synonymous with nebulous degree of change, becomes available to us in terms of specific change.”

28. Traditional labor curve: Friedman’s

29. Limitations of Friedman’s Curve • Non-representative sample • More ‘graphical’ than ‘statistical’ • Did not take into account special characteristics of labor data • Adopted without complete context • Subject characteristics • Interventions

30. 2002: Zhang’s Labor Curve • Took into account the unique features of labor data • Left censored • Interval censored • Repeated measures • Log-normal distribution • ‘Appropriate’ analytical tools • Repeat ed measures regression curves • Interval censored regression models medians (95th tile) • Contemporary sample

31. 2002: Zhang’s Labor Curve

32. 2002: Zhang’s Labor Standard

33. Zhang’s curve: key concepts • Transition to active labor after 6cm dilation; not 4cm. • No deceleration phase • Traverse times • much longer in latent phase • much shorter in active phase

34. TOWARDS CUSTOM LABOR STANDARDS

35. Does one size fit all?: Fetal Size

36. Does one size fit all?: Fetal Sex Cahill AG, Roehl KA, Odibo AO, Zhao Q, Macones GA. Am J Obstet Gynecol. 2012 Apr;206(4):335.e1-5.

37. Does one size fit all? Maternal Race

38. Does one size fit all? Induced labor Harper LM, Caughey AB, Odibo AO, Roehl KA, Zhao Q, Cahill AG. Obstet Gynecol. 2012 Jun;119(6):1113-8.

39. Does one size fit all? Induction method Tuuli MG, Keegan MB, Odibo AO, Roehl K, Macones GA, Cahill AG. Am J Obstet Gynecol. 2013 Sep;209(3):237.e1-7.

40. Does one size fit all?: Maternal Obesity Norman SM, Tuuli MG, Odibo AO, Caughey AB, Roehl KA, Cahill AG. Obstet Gynecol. 2012 Jul;120(1):130-5.

41. Custom Labor Curve: the Holy Grail Seeks to incorporate the multiplicity of individual patient factors in estimating expected labor progress • Has been methodologically challenging • Recent progress • N=5000 • Detailed labor data • Collaboration with statisticians • Mathematical model incorporating • Parity • Epidural • BMI • Labor type

42. Custom Labor Curve: the Holy Grail

43. Custom Labor Curve: the Holy Grail • Next steps • Validate in independent data set (N=4000) • Refine model to include time variable factors • Software development • RCT to assess impact on cesarean rate

44. Summary • Labor involves transition of the uterus from a quiescent state to regular contractions and cervical dilation resulting in delivery of the fetus and placenta • Initiation of labor in humans is incompletely understood, but involves maternal-fetal-placental interactions

45. Summary • Clinical management of labor requires understanding of the normal progress • Our understanding of normal progress of labor is evolving towards more ‘customized’ individualized standards

46. Questions