ParturitionStages of Labor Methodius Tuuli MD MPH Division

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

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Objectives 1. Describe physiology of labor 2. Define stages of labor 3. Discuss concepts of normal labor progress – Traditional (Friedman’s) – Contemporary (Zhang’s) – Custom labor curve (Cahill/Tuuli)

PARTURITION 4

Parturition • Early Pregnancy – Uterine quiescence – Closed cervix Fetus • Parturition – Coordinated uterine activity – Cervical remodelling – Progressive cervical dilation Placenta Membranes Mother 5

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 6

Initiation of Labor • Fetus – Sheep • Fetal ACTH and cortisol – Placental 17 α hydroxylase – Estradiol – Progesterone – Placental production of oxytocin, PGF 2 α – Humans • Fetal increased DHEA – Placental conversion to estradiol – Increased decidual PGF 2 and gap junctions – Increased oxytocin and PG receptors – Changes in progesterone receptors 7

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 8

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

LABOR 10

Labor Regular uterine contractions and Progressive cervical dilatation 11

Labor • Cervical effacement • Cervical dilatation 12

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

Passage 14

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

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

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 17

LABOR PROGRESS 18

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) 19

Labor Curve 20

First Stage • Latent phase – onset to rapid cervical change • Active phase – rapid cervical change to complete dilatation • Traditional standards Nulliparous 95 th Mean % tile Latent phase Active phase Multiparous 95 th Mean %tile 7. 3 -8. 6 hr 17 -20 hr 4. 1 -5. 3 hr 12 -14 hr 1. 5 cm/hr 1. 2 cm/hr 21

Second Stage • Traditional standards No epidural Epidural Nulliparous 95 th Mean % tile Multiparous 95 th Mean %tile 53 -57 min 79 min 17 -19 min 45 min 122 -147 min 185 min 57 -61 min 131 min • Immediate versus delayed pushing • Spontaneous versus coached pushing 22

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

CHANGING LABOR STANDARDS 24

Why concern? l Too many cesarean

Why concern?

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. ”

Traditional labor curve: Friedman’s 28

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

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 (95 th tile) • Contemporary sample

2002: Zhang’s Labor Curve

2002: Zhang’s Labor Standard

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

TOWARDS CUSTOM LABOR STANDARDS 34

Does one size fit all? : Fetal Size

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. e 1 -5.

Does one size fit all? Maternal Race

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.

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. e 1 -7.

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.

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

Custom Labor Curve: the Holy Grail

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

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 44

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 45

Questions