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Labor and Delivery

Laborà rhythmic contraction and relaxation of the uterine muscles in the process of expelling the POC, the neonate and the placenta.

It is not known exactly how labor begins.

There are theories:

  1. Uterine stretch theory à when the uterus gets too full, it will automatically contract.
  2. Posterior pituitary releases oxytocin as baby descends and this induces labor.
  3. Prostiglandin theory à it stimulates uterine contractions. At time of delivery, motherís blood and amniotic fluid have high levels of prostiglandins.
  4. Progesterone depravation theory à level drops and estrogen increases which cause uterine contractions.

Four Factors is Labor Process

  1. Passageway
  2. Passenger
  3. Powers
  4. Psyche
  1. Passageway.

Refers to the birth canal. Made up of the inlet and the outlet. Pelvis is measured at first prenatal visit called the diagonal conjugate. Should be >11.5. Outlet is also measured, which is the diameter between the ischial spine, which is the transverse measurement. Any problem with these measurements is called CPD or cephalopelvic disproportion.

Three things that cause CPD:

Things that alter the descent into passage:

  1. Full bladder. Must check the bladder especially if she has had an epidural.
  2. Full bowel. May have an enema.
  3. Position of mother.

2. Passenger.

Since the fetal head is the largest part to be delivered, it influences the ease or difficulty of the birth. The head is formed by 8 cranial bones. The 4 that are most important in OB are the 2 parietal (top of head), the occipital (back of head) and the frontal bone. These bones are separated by sutures (membranes that have not ossified). This allows the head to be delivered easily. As a result, the head may be out of shape (molding). As they mold it adapts to the shape of the birth canal. Goes away in a few days. The areas where the sutures comes together, is a fontanel. They are membranes.

  1. Anterior fontanel à should be soft and slightly depressed. If extremely depressed this indicates dehydration. Will close at 18 months. Allows brain to grow. Crying will make it bulge a bit because it causes pressure but if at rest and still bulging this is not good.
  2. Posterior fontanel à will close at 2-3 months.

Fetal lie à position of fetal spine in relationship to the motherís spine. Long axis of fetus to long axis of mother.

Longitudinal and transverse lies are most important.

Longitudinal: spines are parallel.

Transverse: babyís spine is like a right angle. Momís is straight and babyís is horizontal.

Fetal Attitude à relationship of the fetal parts to one another. Most common is the tucked position. Flexion is the fetal position.

Fetal station and engagement à refers to the level of the presenting part to the momís ischial spines. Above this level is (-) numbers, below is (+) numbers. Determined by vaginal exam.

Here is a way to remember:

-3 à floating

-2 à in the right direction

-1 à settling in

  1. à half way there ENGAGEMENT

+1 à inching out

+2 à nearly there

+3 à get the crown (babyís head is visible at perineum)

Fetal presentation à part of the fetus that enters the birth canal first. 95-97% the head enters the birth canal first. Cephalic presentations are vertex and face. Vertex is the most common cephalic presentation. Occipital (O) bone is reference point for vertex. Babyís chin is tucked to the chest. For face presentation (more rare) the occipital bone is extended back and the leading bone is the chin (M).

Can have breech presentation, the buttocks enters first. (S).

Frank breech: legs are straight up.

Full or complete breech: baby sits indian style or tailor position.

Footling breech: one or both feet are presenting.

Most breech are delivered C-section.

Normal to see meconium in amniotic fluid.

Fetal positionà relationship of the fetal presenting part to the momís pelvis. Pelvis is divided into 4 quadrants. Documented by 3 letters.

1st: indicates which side (R or L).

2nd: indicates the presenting part.

3rd: indicates anterior or posterior.

Most common is LOA.

3. Powers.

The primary power of normal labor is uterine contractions. Puts baby in position, causes decent, cervical dilation and effecement. Pressure of the baby descending is the secondary power. Uterine contractions hurt. Contractions are rhythmic and increase in intensity as labor progresses.

DIF: duration, intensity and frequency. Each contraction has 3 parts. Increment, Acme and Decrement.

After a contraction there should always be a period of relaxation. The placenta can only provide oxygen for 90 seconds. If not, then baby will be in distress.

  1. Duration à from beginning to end of the contraction. Measured in seconds. In the 1st stage of labor will start at 15-20 seconds by end of 1st stage can last 60 seconds.
  2. Intensity à how strong it is. Described as mild, moderate of strong. Mild feels like tip of nose. Moderate feels like chin. Strong feels like forehead.
  3. Frequency à how often contractions are occurring from beginning of 1 contraction to the beginning of another. Measured in minutes. Start at 5 then 2-3 minutes apart.

Two points about contractions that are very important:

  1. If the duration of a contraction lasts longer than 90 seconds, it must be reported ASAP. During a contraction there is vasoconstriction that reduces oxygen to the fetus. The placenta can supply sufficient oxygen to fetus for only 90 seconds then it must refresh its supply. Called a Tetanic if longer than 90 seconds.
  2. Contractions that occur less than 1 minute apart do not provide enough rest to the uterine muscles between contractions. Can also mean the uterus can rupture. Called sustained contraction.

Cervical effacement and dilation:

Effacement à softening, thinning and shortening of the cervical canal. When this occurs the internal os becomes shorter and becomes part of the lower segment of the uterus. Usually in primiparas cervical effacement occurs before dilation. Multiparas effacement and dilation occur at same time. Effacement is measured in %. At 100% a rim or edge cannot be felt during a vaginal exam.

Dilation à increase in size of the external os. Must be 10cm to be fully dilated.

Both are determined by palpation with fingertips during SVE.

Force of amniotic sack pushing against cervix will often aid in dilation. After membranes rupture the fetal part help in dilation.

4. Psyche.

  1. Womanís psychological state. Anxiety level may be too high to follow directions. May need to go to classes to prepare. Someone may need to stay with them during labor.
  2. Support system. This role is important and level of anxiety needs to be assessed. Todayís trend is to hire a support person. Monitrice: nurse or midwife that provides physical and emotional support and also does assessment. Doula: professional labor assistant.
  3. Previous coping stategies need to be assessed.

Be aware that as labor progresses, her behavior will change. Early in labor she is excited, maybe aprehensive, communicates well, will follow instructions easily. Do teaching at this time, if she has had no prenatal training. As contractions increase in intensity, she will become more serious and will want you to stay with her. She will have difficulty following instructions. As birth nears, sheíll feel it will never end and questions her ability to cope. Will have trouble following directions.

TRUE labor signs:













This will help you remember when labor is about to start:


W: Weight loss. Often have nausea, diarrhea and indigestion. Not unusual to experience 1-3 pound loss.

O: Observe change sensation. About 10-14 days before labor, lightening occurs. Fetus is settling down into the brim of the pelvis. Will be able to breathe better. Increase in urination and more leg cramps. Back ache typically low and dull. Burst of energy a day or two before, called nesting behaviors.

R: Rupture of membranes. Typically will go into labor. If longer than 24 hours, then at risk for infection. Chance that the cord will drop down with the water. As a nurse, check fetal heart rate after ROM because she can have a prolapsed cord.

L: lightening.

D: Dilation and effacement. Most indicative sign.

S: Show of blood. When cervix dilates the bloody show comes out.