Management of Normal and Abnormal Labors

Overview Gross & molecular structure of the myometrium and cervix Biochemical aspects of uterine contractions Birth canal Stages of labor Diagnosis, causes, & management of abnormal labor

Gross & molecular structure of the myometrium and smooth muscle surrounded by collagen and glycoaminoglycans cervix to fundus muscle component increases

o contractions strongest in fundus blood vessel course in between muscle fibers

o blood flow decreases during contractions fetal oxygenation post partum hemorrhage

Early Pregnancy few cellular contacts uncoordinated contractions

Late Pregnancy Placental estriol increases

o gap junctionso electrical communications o coordinated contractions

Cervix less smooth muscle collagen feels firm

Physiology of cervical ripening collagen fibers fractures

o proteolytic enzymeso hyaluronic acid replaces glycosaminoglycanso water content increaseso cervix softens, effacement begins, dilates

Regulators of cervical ripening Inhibitor

o progesterone Promoters

o estriol - oxytocin receptorso relaxin

o oxytocino PGE1 and 2

o Laminaria rods

Physiology of uterine contractions

Inhibition of Uterine Contractions

Promotors of uterine contractions

oxytocin PGF2

o release of calcium from sarcoplasmic reticulum influx of calcium from Ca channels

Characteristics of the maternal birth canal Inlet

o sacral promontoryo linea terminaliso posterior symphysis

Conjugates True - superior symphysis to sacral promontory

o not relevant to child birth Diagonal - inferior symphysis to sacral promontory

o clinical estimate of obstetrical conjugate (-1.5cm) Obstetrical - posterior symphysis to sacral promontory

o what the fetus passes through

Mid-pelvis sacrum

o hollow lateral

o ischial spines A-P = sagittal line

o inferior symphysis through bispinous diameter to sacrumo anterior sagittalo posterior sagittal

Outlet diamond shape

o mid symphysiso 2 ischial tuberositieso coccyx

Gynecoid pelvis round inlet hollow sacrum spines not prominent

o anterior sagittal > posterior occiput anterior presentations gentle curved symphysis most common type and best prognosis

Anthropoid pelvis African Americans oval inlet (A-P > transverse) spines rotated anteriorly anterior sagittal < posterior occiput posterior good prognosis (2nd stage longer)

Android whites heart-shaped inlet funnel shaped canal converging side walls straight sacrum prominent spines narrow symphysis poorest prognosis

Platyploid all planes are flat and oval Southeast Asians baby delivers transverse prognosis poor unless baby is small

7 cardinal fetal movements engagement descent flexion internal rotation extension external rotation expulsion

Stages of labor 1st stage - onset of regular contractions to full dilation

o latent phaseo active phase

Latent phase 0 to 4cm average = 14hr (Gravida 0), 8hrs (>Gravida 0) prolongation disorder = > 20hrs, 14hrs

Active phase 4cm to complete dilation phase of maximum rate of dilation

average = 1.2 cm/hr, 1.5 cm/hr arrest disorder = no dilation in 2 hrs protracton disorder = slower than normal dilation

2nd stage full dilation to delivery descent disorder - presenting part does not descend prolonged 2nd stage

o without regional anesthesia > 2hrs, 1hrs

o with regional anesthesia > 3hrs, 2 hrs

Causes of abnormal labor poor uterine contractions

o 3-5 contractions every 10 mino length of contractions = 60-90 seco strength = 25-100mmHg (requires pressure catheter)o Montevideo units

sum of all contractions in a 10 minutes period 150-220 considered adequate

Treatment = oxytocin (Pitocin)

Cephalopelvic disproportion (CPD) small pelvis fetal macrosomia (>4000 gm) abnormal fetal position

o occiput posterioro militaryo browo face (mentum posterior)o non vertex presentation

fetal anomalies (hydrocephaly, ascites)

Treatment of CPD Cesarean delivery

Putting it all together Active labor > 4cm Check every 2 hours in labor No progress of slow progress, evaluate contractions

o Palpationo Pressure catheter

o Trial of oxytocin Prolonged 2nd stage

o > 2-3 hours Delivery options

o Operative vaginal (forceps or vacuum)o Cesarean section

Watch for shoulder dystocia

Miscellaneous issue Neonatal group B Strep prophylaxis

o Penicillin G 5 million loading, 2.5 million q 4hro GBBS carriero Prolonged rupture of membranes (> 18hr)o Maternal fever (> 380 C, 100.40F)o Previous GBS infected baby