Definition of labor

The course and conduct The course and conduct of normal labor and deliveryof normal labor and delivery

Song WeiweiSong WeiweiOB&GY Department of Shengjing OB&GY Department of Shengjing

HospitalHospital

Definition of laborDefinition of labor

Labor is strictly defined as regular Labor is strictly defined as regular

uterine contractions with resultant change of uterine contractions with resultant change of

cervical effacement and dilatation and cervical effacement and dilatation and

extrusion of the products conception.extrusion of the products conception.

Types of deliveryTypes of delivery

Premature delivery:Premature delivery:28w28w~36w~36w+6+6

Term delivery:37~41wTerm delivery:37~41w+6+6

Postterm delivery:>42w

Why and when the labor initiated?Why and when the labor initiated?

Mechanical theory Mechanical theory Endocrine regulating theoryEndocrine regulating theory

Neurohumone theoryNeurohumone theory

No exact course has been found that can initiate the onset of labor.

expulsive force birth canal fetal factors psychological factors(3 Ps: powers, passage and passenger)

Four factors that determineFour factors that determine a normal labora normal labor

Expulsive forceExpulsive force

----- uterine contraction

Characteristics of uterine contraction

rhythmicity

symmetry

polarity

retraction

----- uterine contraction

Characteristics of uterine contraction

rhythmicity

symmetry

polarity

retraction

rhythmicity

symmetry

polarity

retraction

Birth canal (passage)

bone canal

pelvis: size \shape\ inclination of pelvisinclination of pelvis

soft canal

vagina 、 cervix 、 low segment of uterine

cervical effacement :2~3cm before labor

cervical dilatation: closed to 10cm open

FetusFetus

LieLie- relationship between the long axis - relationship between the long axis of the fetus and that of the mother of the fetus and that of the mother (longitudinal, transverse or oblique).(longitudinal, transverse or oblique).

PresentationPresentation- the fetal part that lies - the fetal part that lies closest to the pelvic inlet (cephalic - closest to the pelvic inlet (cephalic - vertex, face; breech; shoulder).vertex, face; breech; shoulder).

PositionPosition- relationship of the fetal parts - relationship of the fetal parts to maternal parts.to maternal parts.

frank breech

presentation

complete breech presentation

incomplete breech presentation

FetusFetus

Body weight of fetus Diameters of fetal skull

BPD:9.3cm Occipito frontal diameter ： 11.3cm Occipito bregmatic diameter ： 9.5cmOccipito mental diameter ： 12.5cm

Fetal positionFetal anomality: hydrocephalus, conjoined twins.

Body weight of fetus Diameters of fetal skull

BPD:9.3cm Occipito frontal diameter ： 11.3cm Occipito bregmatic diameter ： 9.5cmOccipito mental diameter ： 12.5cm

Fetal positionFetal anomality: hydrocephalus, conjoined twins.

What signs might the patient report What signs might the patient report to herald the onset of true labor?to herald the onset of true labor?

Bloody show:Bloody show: the release from the cervix of the the release from the cervix of the protective mucous plug intermixed with a small protective mucous plug intermixed with a small amount of blood as a result of cervical amount of blood as a result of cervical effacement.effacement.

Regular contractionsRegular contractions: contractions occurring at : contractions occurring at regular intervals (such as every five minute) regular intervals (such as every five minute) suggest true labor. The contractions are felt in suggest true labor. The contractions are felt in the lower abdomen and back, and are noted to the lower abdomen and back, and are noted to increase in intensity over time. increase in intensity over time.

Rupture of membranes (ROM)Rupture of membranes (ROM) : a gush of clear : a gush of clear fluid (break your water) is felt coming from the fluid (break your water) is felt coming from the vagina. The fluid may otherwise leak slowly but vagina. The fluid may otherwise leak slowly but steadily out of the vagina.steadily out of the vagina.

What is a Bishop score?What is a Bishop score?-----evaluate the condition of cervix-----evaluate the condition of cervix This system is used to grade the cervix in terms of

readiness for delivery. Each factor is given a score of 0 to 3. the factors graded are dilation, effacement, station, consistency and position.

Station refers to the level of descent of the presenting part (usually the head) of the fetus. The preferred method is in relationship to the ischial spines. Above the spines one uses -5 to -1 cm (-5 being most superior). Zero station is at the level of the ischial spines. Similarly, +1 to +5 cm describes the presenting part below the level of the ischial spines (+5 being at the introitus).

A cervix that is ready (ripe) for delivery is considered favorable. A score of 5 or greater strongly suggests an advancing cervix.

What are the stages of labor?What are the stages of labor?

Stage 1: onset of labor ~ full dilation of the cervix. Stage 1: onset of labor ~ full dilation of the cervix.

latent phaselatent phase: in which early cervical effacement : in which early cervical effacement and dilation occur:0~3cm.and dilation occur:0~3cm.

active phaseactive phase: cervical dilation becomes more : cervical dilation becomes more rapid (approximately 3 to 4 cm to full dilation of rapid (approximately 3 to 4 cm to full dilation of 10cm).10cm).

Stage 2 : complete cervical dilation~ delivery of Stage 2 : complete cervical dilation~ delivery of the infant. the infant.

Stage 3: after delivery of the infant ~ delivery of Stage 3: after delivery of the infant ~ delivery of the placenta.the placenta.

Duration of the laborDuration of the labor

I stage II stage III stage

Nullipara 9-15 hr 1-2 hr 15-30min

Multipara 7-9 hr 0.5-1 hr 5-15 min

Mechanisms of laborMechanisms of labor

The special labor mechanisms is due to The special labor mechanisms is due to asymmetry of the shape of both the asymmetry of the shape of both the fetal head and maternal pelvis.fetal head and maternal pelvis.

Changes in the position of the fetal head Changes in the position of the fetal head are required for the average size fetus are required for the average size fetus to accomplish passage through the to accomplish passage through the birth canal. birth canal.

The rotations are accomplished by the The rotations are accomplished by the propulsive force of uterine activity.propulsive force of uterine activity.

Cardinal movements of laborCardinal movements of labor

engagementengagement

descentdescent

1. flexion1. flexion

2. internal rotation2. internal rotation

3. extension3. extension

4. external rotation4. external rotation

expulsionexpulsion

movements movements of the headof the head

EngagementEngagement

It is the descent of the largest It is the descent of the largest

transverse diameter of fetal head transverse diameter of fetal head

(BPD) to a level below the plane of (BPD) to a level below the plane of

the pelvic inlet.the pelvic inlet.

Then the head is engaged. Then the head is engaged.

Flexion (IFlexion (I movement of the head) movement of the head)

- placement of the fetal chin on the thorax - placement of the fetal chin on the thorax

(fetus takes a chin-to-chest posture)(fetus takes a chin-to-chest posture)

Internal rotation (IIInternal rotation (II movement) movement)

- the occiput rotates toward the mother’s - the occiput rotates toward the mother’s

pubic symphysis.pubic symphysis.

Extension - III Extension - III movement movement

Begins at the level of maternal vulvaBegins at the level of maternal vulva

The fetal head is delivered by extension The fetal head is delivered by extension

from the flexed to the extended position from the flexed to the extended position

rotating around the symphysis pubis ( the rotating around the symphysis pubis ( the

occiput arches toward the fetal back).occiput arches toward the fetal back).

External rotation - IV External rotation - IV movement movement

After delivery of the head the forces After delivery of the head the forces exerted on the head by the maternal exerted on the head by the maternal pelvic musculature are relived and pelvic musculature are relived and the fetus resumes its normal face-the fetus resumes its normal face-forward position.forward position.

Its face begins to „look” at one of Its face begins to „look” at one of mother’s leg.mother’s leg.

ExpulsionExpulsion

Delivery of the shoulders - first the Delivery of the shoulders - first the

anterior one (under the symphysis anterior one (under the symphysis

pubis) and then the posterior one. pubis) and then the posterior one.

The rest of the body is usually quickly The rest of the body is usually quickly

delivered.delivered.

How are uterine contractions How are uterine contractions monitored?monitored?

Uterine contractions may be monitored by an internal or external pressure monitor (tocometer). Internal monitoring with an intrauterine pressure catheter (IUPC) confirms the adequacy of contractions. The unit of measure for the IUCP is called the Montevideo unit.

Uterine contraction can also be evaluated by the palpation of abdomen.

How is fetal heart rate monitored?How is fetal heart rate monitored?

Intermittent Doppler ultrasound or (rarely) fetal stethoscope

Continuous electronic monitoring via an external monitor or internally via a fetal scalp electrode

What are the types of episiotomy What are the types of episiotomy and their indication?and their indication? Sometimes episiotomy is considered

necessary to facilitate delivery of the fetus or to avoid a spontaneous tear or tears during a forceps delivery. It is an incision in either the midline or in the mediolateral position of the perineum.

EpisiotomyEpisiotomy

A lateral incision of perineum before A lateral incision of perineum before delivery of the headdelivery of the head

Why?Why?– to enlarge the area of the outlet to enlarge the area of the outlet easier easier

delivery of the head delivery of the head prevention of prevention of intraventricular hemorrhageintraventricular hemorrhage

– prevention of lacerationsprevention of lacerations– prevention of late complications - relaxation of prevention of late complications - relaxation of

pelvic muscles and urine incontinencepelvic muscles and urine incontinence

EpisiotomyEpisiotomy

Prophylactic - nulliparas, some Prophylactic - nulliparas, some

multiparas multiparas

MandatoryMandatory

– in instrumental delivery, like forceps or in instrumental delivery, like forceps or

vacuum extractorvacuum extractor

– in abnormal presentations, like breechin abnormal presentations, like breech

– in preterm deliveriesin preterm deliveries

Median episiotomyMedian episiotomy

How is pain controlled?How is pain controlled?

The most common form of pain control by far is the epidural. This allows a woman to receive analgesia while maintaining enough sensation to push during the delivery. Alternatively, narcotic analgesics are sometimes used. Spinal anesthetics are sometimes used, delivered into the same area as an epidural but in a single dose. Local blocks, such as a pudendal block, may be given for perineal anesthesia. A local is also given before repair of a tear or episiotomy.

What is VBAC?What is VBAC?

VBAC stands for vaginal birth after cesarean. This is a trial of labor for a patient who has previously undergone a C-section with a low transverse uterine incision. The patient should have had no more than two prior sections, an adequate pelvis, and no history of other uterine incision or rupture. VBAC is contraindicated in patients who have had a prior classical cesarean section due to the increased risk of uterine rupture.