Normal Labor ,Delivery and the Puerperium

Department of Obstetrics and Gynecology , The general hospital of Tian Jin medical university

Zhang Xuhong

Four major factors determined labor and delivery

The powerThe pelvisThe fetusPsychological factors

The power: The characteristics of myometrial muscle are unique which compared with s

keletal muscle The degree of shortening of smooth muscle

cells with contractions may be greater Forces can be exerted in smooth muscles in

any direction Smooth muscle is organized in different

manners Multidirectional force generation permits

versatility in expulsive force directionality

An important ancillary force in expulsion of the fetus is that produced by increased maternal intra-abdominal pressure.

Pelvic Planes The pelvis is divided into 3 planes: The plane of the pelvic inlet: The fetal head e

nters the pelvis through this plane in the transverse position.

The midplane: is the most important. Because most instances of arrest of descent occur at this level.

The plane of the pelvic outlet: is formed by two triangular planes with a commom base at the level of the ischial tuberosities.This plane is the site of a low pelvic arrest.

Main pelvic diametersPelvic inlet: anteroposterior;

transvers;left and right obliqueMidplane: bispinous diameterPelvic outlet: bituberous diamete

r; posterior sagittle diameter; subpubic angle

Cervical Effacement

Prior to the onset of parturitionBecome soft and thin frequentlyTake up into the lower uterine segmentMucous plug releasedBloody show

Psychological factors :recent research has shown that it act an important role in labor.because of fearing labor pain,a considerable number of women suffered dystocia.

Labor Is a physiologic process that permits a

series of extensive physiologic changes in the mother.

Allow for the delivery of the fetus through the birth canal.

It is defined as progressive cervical effacement and dilatation, resulting from the regular uterine contractions.

What is the regular

contraction?

The regular contraction: Occurs at least every 5 minutes and last 30 to 60 seconds,with greater intensity.

The contractions appear to arise in the upper coronal regions of the uterus,

then near the fundus,spread to the lower pole progressively.

Preparation for laborLightening: two or more weeks before la

bor,fetal head in most primigravid women settles into the brim of the pelvis.

False labor: during last 4~8 weeks of pregnancy,the uterus undergoes irregular contractions.

Cervical effacement.These are not associated with progressi

ve cervical dilatation.

EngagementEngagement occurs when the widest di

ameter of the fetal presenting part has passed through the pelvic inlet. (in cephalic presentations, the widest diameter is occipitofrontal diameter)

When the fetal head has engaged, that means the bony presenting part is at the level of the ischial spine.

The station of the presenting part in the pelvic canal is defined as its level above or below the plane of the ischial spine.

The level of the ischial spines assigned as “zero”(S-0), each centimeter above or below this level is given a minus or plus designation(S-1; S+2…

…).

When the presenting is out of the pelvis, it is freely movable, it is considered to be floating.

When it has passed through the plane of the inlet ,but is not yet engaged, it is considered to be dipping.

Labor is divided into three stagesFirst stage : From the onset of regular

contraction of uterine to complete dilation of the cervix.(10cm)

It consists of two phases: The latent phase: onset of true labor to cervical effacement and early dilation.(3cm); The active phase: the cervical dilation is more rapid occurs.(4cm~10cm).

Second stage : From complete dilation of the cervix to the birth of the baby.

Third stage :is from the birth of the baby to the delivery of placenta and membrances.

Length of stagesprimipara multipara

Duration of the first stage

11~12 hours 6~8 hours

Rate of cervical dilatation during active phase

1.2cm/hour 1.5cm/hour

Duration of second stage

1~2hours 5~30min

Duration of third stage

5~15min 5~15min

Management of first stage Drawing picture of stages of labor(partogram). Record maternal pulse rate,BP,respiratory rate,te

mperature ,urine output every 1~2 hours; descent of the fetal head.

Auscultate the fetal heart rate(FHR) every 30 minutes

Monitor the uterine contraction every 30 minutes for frequency,duration,intensity

Do vaginal examination every 2 hours to determine the progress of labor.

Amniotomy: amniotic fluid; meconium? augment uterine contractility

Second stage of labor----Descent of the fetal headThe mechanism of the labor : six-movements of the baby enable it to adapt to the maternal pelvis. They are:

DescentFlexion Internal rotation ExtensionExternal rotationExpulsion

Descent: Is brought by

※ The force of the uterine contractions

※ Maternal bearing down(Valsalva) efforts

※ Gravity if the patient is upright

Flexion

Partial flexion exists before labor.Further flexion is caused by: (1)resistance from the cervix (2)walls of the pelvis (3)pelvic floorIt can change the presenting diameter fro

m the occipitofrontal to the smaller suboccipitobregmatic.

Internal RotationTransverse or oblique diameter rotates

so that the occiput turns anteriorly toward the symphysis pubis.

It occurs as the fetal head meets the muscular sling of the pelvic floor.

The presenting part reach the lever of the ischial spines.

Extension The vaginal outlet is directed upward and for

ward Bulge of the perinium Crowning: the largest diameter of the fetal he

ad is encircled by the vulvar ring. Episiotomy: mediolateral and midline episioto

my. To reduce perineal resistance and avoid tearing and stretching of perineal tissues.

External Rotation

The delivered head returns to its origional position at the time of engagement(restitution)

Shoulders undergo an internal rotation to anteroposterior position within the pelvis

Expulsion

Anterior shoulder delivers, followed by the posterior shoulder and body of the child

Clinical management of second stage To encourage the patient to hold her breath a

nd to bearing –down with each contractions. Monitor the fetal heart rate every 5 minutes. Vaginal examination every 30 minutes. After delivery, the cord is clamped and cut wit

hin 15~20 seconds. Delayed cord clamping can result in hyperbilirubinemia as additional blood is transferred to the newborn infant.

Clinical management of third stage

After the baby’s delivery,to inspect the cervix and vagina for laceration and surginal repair performed if necessary.

To add 20 units of oxytocin to the intravenous infusion to enforce the contractions to reduce uterine bleeding.

Separation of the placenta occurs within 2~10minutes

Signs of placental separation

A fresh show of blood from the vagina.The umbilical cord lengthens outside th

e vagina natually.The fundus of the uterus rises up.The uterus becomes firm and globular.

Perineal laceration classified as: First degree: a laceration involving the vaginal

epithelium or perineal-skin. Second degree: a laceration extending into the

subepithelial tissues of the vagina or perineum with or without involvement of the muscles of the perineal.

Third degree: a laceration involving the anal sphincter.

Fourth degree: a laceration involving the rectal mucosa.

Puerperium The puerperium : after delivery of the baby an

d placenta to approximately 6 weeks postpartum.During the puerperium ,the reproductive organs and maternal physiology return to the prepregnancy state.

In women who do not nurse, menstrual flow will return by 6~8 weeks. Ovulation may not occur for several months.

lochiaFirst few days after delivery, the uterine

discharge is red.----lochia rubraAfter 3~4 days, the lochia becomes pale

r.---lochia serosa By tenth day, it becomes a white or yell

ow-white color.---- lochia alba.Complete involution of the uterus(about

42 days).

Lactation Two events are instrumental in initiating lacta

tion: (1) the drop in placental hormones (particularly estrogen)allows lactation to occur, (2)Sucking stimulate the release of prolactin and oxytocin. Sucking is thought important for milk production and the ejection.

The second day after delivery, colostrum is secreted.

After about 3~6 days, the colostrum is replaced by mature milk.

Induction and Augmentation of labor The indications and contraindications for

induction and augmentation of labor . (text book P162).

Bishop Score (cervix position, consistency, effacement, dilatation,fetal head station) to assess likelihood of successful induction of labor . If the score >6,the induction may be successful.

Several principles about oxytocin used should be note: Oxytocin must be given intravenously. A dilute infusion must be used. 5%Glucose 5

00ml + oxytocin 2.5U iv. The drug is best infused with calibrated infusi

on pump. The induction of labor should not exceed 72 h

ours. If adequented labor is estabilished, the infusio

n rate and the concentration may be reduced.

Complications of inductionHyperstimulation: case fetal distress fro

m ischemiaRupture of the uterus.Antidiuretic effect: coma.Uterine muscle fatigue,postdelivery uteri

ne atony : to increase the risk of postpartum hemorrhage.