Normal Labor and Delivery Midwifery Division Department of OB/GYN University of North Carolina School of Medicine.

Normal Labor and Delivery

Midwifery Division Department of OB/GYN

University of North CarolinaSchool of Medicine

OBJECTIVES

• Describe the maternal factors in birth

• List the various fetal positions and presentations

• Review the 7 Cardinal Movements

• Define the 4 stages of labor

• Describe a normal fetal heart rate pattern

• Discuss the factors affecting the US C/S rate and VBAC rate.

NORMAL LABOR & DELIVERYDefinitions

• Labor: progressive dilatation of the cervix in association with uterine contractions

• Term : > 37 weeks gestation• Preterm: < 37 weeks gestation

– 11% of all US births in 1997– 80% of preterm births between 34 - 36 weeks– Preterm delivery < 35 weeks: 3.5%

Obstetrical Pelvic Exam

• Dilation (dilatation): patency of the internal cervical os – 0 = “closed”– 10 cm = “complete”

• Effacement: shortening of the cervical length – 0% = “thick”– 100% = “fully effaced”

Obstetrical Pelvic Exam

• Station: level of presenting part (bony portion) in relation to the maternal ischial spines– Ischial spines = O station

– Above spines: -5 to -1

–Below spines: +1 to +5

Obstetrical Pelvic Exam

• Presentation: fetal part closet to pelvic inlet– vertex– brow– face– breech – shoulder

• Position: relationship of particular point on the presenting part of the fetus and the vertical and horizontal planes of the maternal pelvis– Vertex: occiput for orientation– Breech: sacrum– Face: mentum

Vertex Parietal Brow Face

Obstetrical Pelvic Exam• Lie: relationship between the long axis

of the fetus and the mother– Longitudinal– Transverse

• Asynclitism: anterior or posterior parietal bone precedes the sagittal suture– Anterior – Posterior

Cardinal Movements of Labor

1. Engagement: descent of biparietal diameter to the level of the ischial spines (0 station)

– Often occurs before onset of labor in nulliparous patients

2. Descent 3. Flexion: presenting diameters of fetal head

presenting to maternal pelvis are optimized

Cardinal Movements of Labor

4. Internal rotation: fetal occiput rotates from transverse to AP

5. Extension: head rotates under symphysis pubis

6. External rotation (restitution): occiput and spine assume same position

7. Expulsion: fetal body delivers

NORMAL LABOR & DELIVERYStages of Labor

• First stage: Onset of labor to full dilation (10m cm)

• Second stage: Full cervical dilation to delivery of infant

• Third stage: Delivery of infant to delivery of placenta

• Fourth stage: First hour after birth

Ritgen Maneuver

Erb’s palsey

NORMAL LABOR & DELIVERYPhases of Labor

• Latent phase: onset of contractions until active phase

• Active phase: 3 cm dilation in nulliparas; 4 cm dilation in multiparas to deceleration phase

• Deceleration phase: 8 – 9 cm dilation to complete dilation

POST PARTUM HEMORRHAGE

• Not a diagnosis but a consequence of an event– Atony of the uterus– Placenta problem– Laceration

Defined as greater than 500 ml.

Estimated as 5 % of vaginal births.

Average EBL with C/S = 1000ml.

TREATMENT FOR PPH

• Find the cause and treat promptly• Active management of the third stage• Med: Pitocin Cytotec Methergine Hemabate

Repair lacerations promptly

Abnormal Latent Phase of Labor

• > 20 hours in nulliparas• > 14 hours in multiparas• Treatment

– Therapeutic rest• Morphine (10- 20 mg)• Hypnotic (Ambien)

– 85% proceed into active phase of labor– 10% - no contractions– 5% - may need oxytocin

Primary Dysfunctional Labor

Slow rate of dilation in the active phase of labor– < 1.2 cm/hr in nulliparas

– < 1.5 cm/hr in multiparas

Disorders of the Active Phase

• Secondary Arrest: cessation of previously normal rate of dilation for two hours

• Combined Disorder: cessation of dilation when patient has previously exhibited a primary dysfunctional labor

Disorders of the Second Stage

• Protracted Descent: – < 1 cm/hr in nulliparas

– < 2 cm/hr in multiparas

• Prolonged: – Nulliparas

• With epidural – 3 hours

• No epidural – 2 hours

– Multiparas• With epidural – 2 hours

• No epidural – 1 hour

Abnormalities of Labor THE 5 “P”

• Passageway: maternal pelvis

• Powers: uterine contractions

• Passenger: fetus

• Placenta: profusion

• Psyche: mother’s readiness

Uterine Contractions

• External tocodynamometry–Less accurate

– 3-5 contractions/10 minutes

• Internal tocodynamometry–Measures mm Hg

– 180 – 220 Montevido units/10 minutes

INDUCTION OF LABOROxytocin

• Peptide from posterior pituitary• Usually given IV; can be given IM• IV bolus = hypotension• 10 units/ml; dilute in 1000 cc LR• Routine dose: Start at 2mu/min, 2 mu/min every 15-30 minutes to 36 IU/min• Active management of labor: start at 6 mu/min,

by 6 mu/min every 15 minutes to 36 mu/min• High doses – ADH effect = water intoxication

INDUCTION OF LABORBishop Score

0 1 2 3

Dilation Closed 1 - 2 3 – 4 > 5

Effacement 0 – 30 40 – 50 60 – 70 > 80

Station -3 -2 -1 +1, +2

Consistency Firm Medium Soft

Position Posterior Mid Anterior

INDUCTION OF LABORMisoprostol (Cytotec®)

• PO tablet FDA approved to prevent gastric ulceration in patients taking NSAID’s

• PGE1

• 25 mcg (1/4 of 100mcg tablet) in vagina Q 4 hours X 4 doses

• Wait 6 hours after last dose to start oxytocin

• Contraindicated with uterine eschar

NORMAL LABOR & DELIVERYFoley Bulb

• Place special foley through cervix and inflate balloon to 30 cc

• Tape to thigh – remove by 12 hours

• Used when Cytotec contraindicated – uterine eschar

• Mechanism: mechanical/local release of prostaglandins

• Frequently used with pitocin

NORMAL LABOR & DELIVERYAnesthesia

• Cesarean section– Spinal– Epidural– General (more risky in obstetrics)

• Vaginal delivery– Local– Pudendal– Epidural– Combined spinal/epidural

Pudendal Block

NORMAL LABOR & DELIVERYLacerations

• Cervical (use clock to describe location)• Vaginal (left or right)• Periurethrael• Clitoral• Perineal

– 1st degree: skin only involved– 2nd degree: skin and subcutaneous tissue– 3rd degree: external rectal sphincter– 4th degree: rectal mucosa not intact

NORMAL LABOR & DELIVERYEpisiotomy

• Types– Midline– Mediolateral– Proctoepisiotomy

• Originally thought to protect perineum• Now thought to result in more 3rd and

4th degree extensions• More perineal pain• At UNC less that 3% of patients

First degree

Third degree

Second degree

External sphincter

External sphincter

NORMAL LABOR & DELIVERYCesarean Delivery

• Skin incisions– Vertical – Pfannensteil

• Uterine incisions– Low cervical transverse (Kerr)– Low vertical or “T” shaped– Classical

NORMAL LABOR & DELIVERYCesarean Delivery

Breech12%

Fetal Distress

9%

Repeat C/S35%

Dystocia30%

Other14%

USA TRENDS

VBAC/Trial of Labor

• One previous LUT incision (1% rate of rupture)

• Two previous LUT incisions (2% rupture)

• Unknown incision (up to 7% rupture)• Success of TOLAC = VBAC (vaginal

birth after cesarean section): 60 – 80%

Frank breech Complete breech

Incomplete breech

BREECH

NORMAL LABOR & DELIVERYBreech Presentation

• 37 weeks gestation – external cephalic version (50% success)– Ultrasound– Non-stress test– IV/subcut terbutaline for tocolysis– Ultrasound monitoring– Repeat non-stress test/– K-B stain prn

• Cesarean section vs vaginal birth

Multiple Gestation• Twins

– Vertex/vertex – vaginal delivery– Vertex/breech or transverse lie – breech

extraction of 2nd twin– Breech/other – Csection (locked twins)

• Triplets or higher order gestation – Cesarean delivery indicated

GBS Epidemiology

• 10-30% of pregnant women colonized• Vertical transmission may occur• Neonatal invasive GBS infection

decreased 21% from 1993 to 1998. • In 2000 rate was .23 per 1000 live births• Early onset infection

– Antibiotics in labor will reduce– Prevents 225 newborn deaths per year

• Late onset infection

GBS Protocol

• Routine culture at 35-37 weeks

• Culture lower 1/4 vaginal and peri anal area

• Culture stable up to 96 hours in Amies transport media

• If patient allergic to penicillin, get suscepibility testing

GBS Protocol

• Treat with intravenous penicillin

• Attempt to achieve 2 doses to prevent invasive evaluation of neonate

• PCN 6 million units IV load, then 3 million units q 4 hours

GBS ProtocolPenicillin allergy:

- Kefzol 2 grams IV load, then 1 gram q 8 hrs if not at high risk of anaphylaxis– Clindamycin – 900 mg IV q 8 hrs

• 15-20% of isolates resistant– Vancomycin – 1 gram IV q 12 hours, doses

given over 30 minutes

Hager et al. Obstet Gynecol 2000;96:141-5.

NORMAL LABOR & DELIVERYEstimated Fetal Weight

• Leopold’s maneuvers (palpation of the maternal abdomen)

• Ultrasound estimate of fetal weight (error of 10 – 15%)

• Maternal estimate of fetal weight (best)

Forceps Assisted Vaginal Delivery

• Outlet forceps: – Scalp visible at the introitus w/o parting the labia– Sagittal suture < 45 degrees

• Low forceps:– Leading point of skull at +2 or below

• < 45 degrees

• > 45 degrees

• Mid-forceps:– Head is engaged but presenting part is above +2 station– Rarely done

Mitivac vacuum

NORMAL LABOR & DELIVERYVacuum vs Forceps

• Forceps– More maternal trauma– Minimal fetal trauma (bruising)

• Vacuum– Less maternal trauma– Potential for increased fetal trauma

(subgaleal bleeding)

UnderstandingFetal Monitoring (Parameters)

• Baseline rate

• Variability

• Presence of accelerations

• Presence of decelerations

• Changes or trends of FHR patterns over time

Fetal Heart Rate Baseline

• 10 minute window

• Duration: at least 2 minutes

• Bradycardia: < 110 bpm

• Tachycardia: > 170 bpm

Fetal Monitoring (Variability)

• Concept of long-term variability dropped

• Absent: undetectable

• Minimal: undetectable - < 5 bpm

• Moderate: 6 - 25 bpm

• Marked: > 25 bpm

Fetal Monitoring (Accelerations)

• Onset to peak: < 30 seconds

• > 32 weeks: >15 bpm X >15 secs

• < 32 weeks: > 10 bpm X > 10 secs

• > 2 minutes in duration: prolonged

• > 10 minutes in duration: change in baseline

DECELERATIONSFetal Monitoring (Variables)

• Onset to nadir < 30 secs

• > 15 bpm below baseline

• Duration: > 15 seconds

• < 2 minutes from onset to return to baseline

DECELERATIONSFetal Monitoring (Variables)

Treatment• Pelvic exam (rule out prolapsed cord)

• Maternal oxygen

• Change maternal position

• Stop pushing

• Amnioinfusion

Fetal Monitoring (Early Decelerations)

• Onset to nadir > 30 secs

• Coincident in timing with UC

• Nadir occurring simultaneously with the peak of the contraction

Fetal Monitoring (Late Decelerations)

• Onset to nadir > 30 secs

• Delayed in timing

• Nadir occurring after the peak of the contraction

• Reoccuring can be ominous

Fetal Monitoring(Late Decelerations)

Treatment• Correct hypotension or other maternal

conditions

• Maternal oxygen

• Scalp stimulation

• Cesarean delivery if repetitive

Cord Blood Gases

• Defensive medicine (not used clinically)

• Clamp cord segment at all deliveries

• Obtain arterial sample for 5 minute Apgar score < 7

NORMAL LABOR & DELIVERYCord Blood Gases

Umbilical artery (No labor)

• Acidemia: pH < 7.15

• Metabolic: base excess > -11 mmol/L and pCO2 < 65 mm

• Respiratory: base excess < 11 mmol/L and pCO2 > 65 mm

• Mixed: base excess > -11 mmol/L and pCO2 > 65 mm

NORMAL LABOR & DELIVERYCord Blood Gases

Umbilical artery (No labor)

Clinically significant acidemia is probably represented by an umbilical arterial pH of < 7.0