Normal Labor and Delivery

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Normal Labor and Delivery



Initial Evaluation

Maternal Pelvis

Fetal Position

Managing Early Labor

Electronic Fetal Heart Monitoring

Pain Relief

Second Stage Labor


Delivery of the baby

Delivery of the Placenta

Post Partum Care


Labor consists of regular, frequent, uterine contractions which lead to progressive dilatation of the cervix.

The diagnosis of labor may not be obvious for several reasons:

  • Braxton-Hicks contractions are uterine contractions occurring prior to the onset of labor. They are normal and can be demonstrated with fetal monitoring techniques early in the middle trimester of pregnancy. These innocent contractions can be painful, regular, and frequent, although they usually are not.

  • While the uterine contractions of labor are usually painful, they are sometimes only mildly painful, particularly in the early stages of labor. Occasionally, they are painless.

  • Cervical dilatation alone does not confirm labor, since many women will demonstrate some dilatation (1-3 cm) for weeks or months prior to the onset of true labor.

Thus, in other than obvious circumstances, true labor will usually be determined by observing the patient over time and demonstrating progressive cervical changes, in the presence of regular, frequent, painful uterine contractions. False labor is everything else.

The cause of labor is not known but may include both maternal and fetal factors.

Latent Phase Labor

The first stage of labor is that portion leading up to complete dilatation. The first stage can be divided functionally into two phases: the latent phase and the active phase.

Latent phase labor (also known as prodromal labor) precedes the active phase of labor. Women in latent phase labor:

  • Are less than 4 cm dilated.

  • Have regular, frequent contractions that may or may not be painful.

  • May find their contractions wax and wane

  • Dilate only very slowly

  • Can usually talk or laugh during their contractions

  • May find this phase of labor lasting hours to days or longer.

Active Phase Labor

Active phase labor is a time of rapid change in cervical dilatation, effacement, and station.

Active phase labor lasts until the cervix is completely dilated. Women in active phase labor:

  • Are at least 4 cm dilated.

  • Have regular, frequent contractions that are usually moderately painful.

  • Demonstrate progressive cervical dilatation of at least 1.2-1.5 cm per hour.

  • Usually are not comfortable with talking or laughing during their contractions.

Progress of Labor

For a woman experiencing her first baby, labor usually lasts about 12-14 hours. If she has delivered a baby in the past, labor is generally quicker, lasting about 6-8 hours. These averages are only approximate, and there is considerable variation from one woman to the next, and from one labor to the next.

During labor, the cervix dilates (opens) and effaces (thins). This process has been likened to the process of pulling a turtleneck sweater over your head. The collar opens (dilates) to allow your head to pass through, and also thins (effaces) as your head passes through.

The process of dilatation and effacement occurs for both mechanical reasons and biochemical reasons.

The force of the contracting uterus naturally seeks to dilate and thin the cervix. However, for the cervix to be able to respond to these forces requires it to be "ready." The process of readying the cervix on a cellular level usually takes place over days to weeks preceding the onset of labor.

Labor should be progressive. Serial vaginal examinations are used to plot the course of labor, detect abnormalities and allow for intervention. While there are no set time intervals for performing pelvic examinations, the cervix should progressively dilate during active phase labor at a rate of no less than 1.2 cm/hour (for first babies) to 1.5 cm/hour (for subsequent babies).


Descent means that the fetal head descends through the birth canal. The "station" of the fetal head describes how far it has descended through the birth canal.

This station is determined relative to the maternal ischial spines, bony prominences on each side of the maternal pelvic sidewalls.

"0 Station" ("Zero Station") means that the top of the fetal head has descended through the birth canal just to the level of the maternal ischial spines.

This usually means that the fetal head is "fully" engaged (or "completely engaged"), because the widest portion of the fetal head has entered the opening of the birth canal (the pelvic inlet).

If the fetal head has not reached the ischial spines, this is indicated by negative numbers, such as -2 (meaning the top of the fetal head is still 2 cm above the ischial spines).

If the fetal head has descended further than the ischial spines, this is indicated by positive numbers, such as +2 (meaning the top of the head is now 2 cm below the ischial spines).

Negative numbers above -3 indicate the fetal head is unengaged (floating). Positive numbers beyond +3 (such as +4 or +5) indicate that the fetal head is crowning and about to deliver.

Women having their first baby often demonstrate deep engagement (0 or +1) for days to weeks prior to the onset of labor.

Women having their second or third baby may not engage below -2 or -3 until they are in labor, and nearly completely dilated.

Mechanism of Normal Labor

There are five classical steps in the normal mechanism of labor. They are:

  • Descent

  • Flexion

  • Internal Rotation

  • Extension

  • External Rotation

Usually, labor progresses in this fashion, if the fetus is of average size, with a normally positioned head, in a normal labor pattern in a woman whose pelvis is of average size and gynecoid in shape.

There is overlap of these mechanisms. The fetal head, for example, may continue to flex or increase its flexion while it is also internally rotating and descending.

Descent: As the fetal head engages and descends, it assumes an occiput transverse position because that is the widest pelvic diameter available for the widest part of the fetal head.

Flexion: While descending through the pelvis, the fetal head flexes so that the fetal chin is touching the fetal chest. This functionally creates a smaller structure to pass through the maternal pelvis. When flexion occurs, the occipital (posterior) fontanel slides into the center of the birth canal and the anterior fontanel becomes more remote and difficult to feel. The fetal position remains occiput transverse.

Internal Rotation: With further descent, the occiput rotates anteriorly and the fetal head assumes an oblique orientation. In some cases, the head may rotate completely to the occiput anterior position.

Extension: The curve of the hollow of the sacrum favors extension of the fetal head as further descent occurs. This means that the fetal chin is no longer touching the fetal chest.

External Rotation: The shoulders rotate into an oblique or frankly anterior-posterior orientation with further descent. This encourages the fetal head to return to its transverse position. This is also known as restitution.





Pelvic Evaluation

There are four basic pelvic shapes:

  • Gynecoid

  • Android

  • Anthropoid

  • Platypoid

A gynecoid pelvis is oval at the inlet, has a generous capacity and wide subpubic arch. This is the classical female pelvis.

A platypoid pelvis is flattened at the inlet and has a prominent sacrum. The subpubic arch is generally wide but the ischial spines are prominent. This pelvis favors transverse presentations.

An anthropoid pelvis is, like the gynecoid pelvis, basically oval at the inlet, but the long axis is oriented vertically rather than side to side.Subpubic arch may be slightly narrowed. This pelvis favors occiput posterior presentations.

An android pelvis is more triangular in shape at the inlet, with a narrowed subpubic arch. Larger babies have difficulty traversing this pelvis as the normal areas for fetal rotation and extension are blocked by boney prominences. Smaller babies still squeeze through.

Initial Evaluation

Most labors and deliveries are safe, spontaneous processes, requiring little or no intervention, and result in a healthy mother and healthy baby. Some are not so safe and may not have the same good outcome. The two purposes of L&D management are:

  • Monitoring the mother and baby for abnormalities which, through detection and treatment, will lead to a happy outcome for both.

  • Applying knowledge and skills to improve on the quality of the experience or outcome which nature would otherwise provide. This would include such areas as pain relief, prevention or repair of lacerations, reducing fatigue, anemia, risk of infection, and injury to the mother and baby.

Initial Evaluation of a Woman in Labor

An initial evaluation is performed to:

  • Evaluate the current health status of the mother and baby,

  • Identify risk factors which could influence the course or management of labor, and

  • Determine the labor status of the mother.


Interview the patient as soon as she arrives.

Certain key questions will provide considerable insight into the patient's pregnancy and current status:

  • What brought you in to see me?

  • Are you contracting? When did they start?

  • Are you having any pain?

  • Are you leaking any fluid or blood? When did that begin?

  • Have there been any problems with your pregnancy?

  • Has the baby been moving normally?

  • When did you last eat? What did you have?

  • Are you allergic to any medication?

  • Do you normally take any medication?

  • Have you ever been hospitalized for any reason?

Risk Factors

For some women, there is a greater chance of problems during labor than for other women. Various factors have been identified to try to predict those women who will experience problems and those who will not. These are called risk factors. Some are more significant than others. While most women with any of these factors will experience good outcomes, they may benefit from increased surveillance or additional resources.

Moderate increase in risk

More than moderate increase in risk

  • Age < 16 or > 35

  • 2 spontaneous or induced abortions

  • < 8th grade education

  • > 5 deliveries

  • Abnormal presentation

  • Active TB

  • Anemia (Hgb <10, Hct <30%)

  • Chronic pulmonary disease

  • Cigarette smoking

  • Endocrinopathy

  • Epilepsy

  • Heart disease class I or II

  • Infertility

  • Infants > 4,000 gm

  • Isoimmunization (ABO)

  • Multiple pregnancy (at term)

  • Poor weight gain

  • Post-term pregnancy

  • Pregnancy without family support

  • Preterm labor (34-37 weeks)

  • Previous hemorrhage

  • Previous pre-eclampsia

  • Previous preterm or SGA infant

  • Pyelonephritis

  • Rh negative

  • Second pregnancy in 9 months

  • Small pelvis

  • Thrombophlebitis

  • Uterine scar or malformation

  • Venereal disease

  • Age >40

  • Bleeding in the 2nd or 3rd TM

  • Diabetes

  • Chronic renal disease

  • Congenital anomaly

  • Fetal growth retardation

  • Heart disease class III or IV

  • Hemoglobinopathy

  • Herpes

  • Hypertension

  • Incompetent cervix

  • Isoimmunization (Rh)

  • Multiple pregnancy (pre-term)

  • > 2 spontaneous abortions

  • Polyhydramnios

  • Premature rupture of membranes

  • Pre-term labor (<34 weeks)

  • Prior perinatal death

  • Prior neurologically damaged infant

  • Severe pre-eclampsia

  • Significant social problems

  • Substance abuse

Vital Signs

Obtain a set of vital signs from the mother, including BP, pulse and temperature.

  • Elevated BP suggests the presence of pre-eclampsia.

  • Elevated BP may be defined as a persistently greater than 140 systolic or 90 diastolic. Usually, if one is elevated, both are elevated.

  • Elevated temperature suggests the possible presence of infection.

  • Many pregnant women normally have oral temperatures of as much as 99+. These mild elevations can also be an early sign of infection.

  • While a pregnant pulse of up to 100 BPM or greater may be normal, rapid pulse may also indicate hypovolemia.


Check the frequency and duration of any uterine contractions.

In some cases, the patient will have been timing the contractions. Placing your hand on the maternal abdomen, you will be able to feel each contraction as the normally soft uterus becomes firm and rises out of the abdomen. Time the contractions from the beginning of one to the beginning of the next one. Also note the duration of the contractions and their relative intensity (mild, mild-to-moderate, moderate, severe).

Contractions can also be followed by use of an electronic fetal monitor. In this case, the paper channel will show the rhythmic peaks that correspond to a uterine contraction.

Fetal Heart Rate

Record the fetal heart rate.

This can be done with a fetal Doppler device, and electronic fetal monitor, ultrasound visualization of the fetal heart, or a DeLee type stethoscope.

Normal rates are between 120 and 160 BPM at full term. Post term babies may sometimes normally have rates as low as 110 BPM.

The fetal heart rhythm should be regular, without any skipped beats or compensatory pauses.

Urine for Protein and Glucose
Check the urine for protein and glucose.

The presence of protein (1+ or greater) can suggest the presence of pre-eclampsia. This level of 1+ on a random urine sample corresponds to about a:

  • 30 mg/dL concentration

  • 300-999 mg in a 24-hour urine sample

The presence of glucosuria (1+ to 2+ or greater) can suggest the presence of diabetes.

Estimated Fetal Weight

Estimate the fetal weight. An average baby at full term weighs 7 to 7 1/2 pounds.

By feeling the maternal abdomen, an experienced examiner can often predict within a pound the actual birthweight. A woman who has delivered a baby in the past can often do about as well in predicting her current baby's weight if you ask her, "Is this baby bigger or smaller than your last?"

Significant landmarks are:

  • 500 gm: Lower limit of viability

  • 1000 gm: Probable survival

  • 1500 gm: Likely survival

  • 2500 gm: Traditional limit of prematurity

  • 3100 gm: Average female at full term

  • 3400 gm: Average male at full term

  • 4000 gm: Macrosomia in diabetic pregnancies

  • 4500 gm: Typical definition of macrosomia

Gestational Age (Weeks)

10th %ile

50th %ile

90th %ile





































































































Pounds/Grams Conversion Table



1000 grams (1 kg) is 2.2 pounds.

Use the numbers on the right to

move between pounds and grams

as needed in calculating fetal weight.

























Cervical Dilatation and Effacement

Using sterile gloves and lubricant, perform a vaginal exam and determine the dilatation and effacement of the cervix. A small amount of bleeding during the days or hours leading up to the onset of labor is common and called "bloody show."

Dilatation is expressed in centimeters. I have relatively large fingers, and for my hands, I make the following generalizations:

  • 1.5 cm: One finger fits tightly through the cervix and touches the fetal head.

  • 2.0 cm: One finger fits loosely inside the cervix, but I can't fit two fingers in.

  • 3.0 cm: Two fingers fit tightly inside the cervix.

  • 4.0 cm: Two fingers fit loosely inside the cervix.

  • 6.0 cm: There is still 2 cm of cervix still palpable on both sides of the cervix.

  • 8.0 cm: There is only 1 cm of cervix still palpable on both sides of the cervix.

  • 9.0 cm: Not even 1 cm of cervix is left laterally, or there is only an anterior lip of cervix.

  • 10.0 cm: I can't feel any cervix anywhere around the fetal head.

Effacement is easiest to measure in terms of centimeters of thickness, ie., 1 cm thick, 1.5 cm thick, etc. Alternatively, you may express the thickness in percent of an uneffaced, 50%, 90%, etc. This expression presumes a good knowledge of what an uneffaced cervix should feel like.

Status of Fetal Membranes

With a pelvic examination, determine the status of the fetal membranes (intact or ruptured).

A history of a sudden gush of fluid is suggestive, but not convincing evidence of ruptured membranes. Sudden, involuntary loss of urine is a common event in late pregnancy.

Usually, ruptured membranes are confirmed by a continuing, steady leakage of amniotic fluid, pooling of clear, Nitrazine positive fluid in the vagina on speculum exam. Vaginal secretions are normally slightly acid, turning Nitrazine paper yellow. Amniotic fluid, in contrast, is a weak base, and will turn the Nitrazine paper a dark blue.

Dried amniotic fluid forms crystals (ferning) on a microscope slide. Vaginal secretions do not.

Blood Count

Following admission, the hemoglobin or hematocrit may be useful.

Women with significant anemia are more likely to have problems sustaining adequate uterine perfusion during labor. They also have less tolerance for hemorrhage than those with normal blood counts.

Women with no prenatal care should, in addition, have a blood type, Rh factor, and atypical antibody screen performed.

Other tests may be indicated, based on individual history.

Fetal Orientation

By abdominal and pelvic examination, determine the orientation of the fetus.

There are basically 3 alternatives:

  • Cephalic (head first, or vertex)

  • Breech (butt or feet coming first)

  • Transverse lie (side-to-side orientation, with the fetal head on one side and the butt on the other)

Most of the time, the fetus will be head first (vertex).

The easiest way for a relatively inexperienced examiner to determine this presentation is by pelvic exam. The fetal head is hard and bony, while the fetal butt is soft everywhere except right over the fetal pelvic bones.

When the baby is presenting butt first, the presenting part is very soft, but with hard areas within it (sacrum and ischial tuberosities).

If one or both feet are presenting first, you will feel them.

If you don't feel any presenting part (head or butt) on pelvic exam, there is a good chance the baby is in transverse lie (or oblique lie). Then things get a little more complicated.

Transverse lie or oblique lie can be suspected if the fundal height measurement is less than expected and if on abdominal exam, the basic orientation of the fetus is side-to-side.

More experienced examiners can tell much from an abdominal exam.

Making a "V" with their thumb and index finger and pressing down just above the pubic bone,  they can usually feel the hard fetal head at the pelvic inlet.

Leopold's Maneuvers

1. Using two hands and compressing the maternal abdomen, a sense of fetal direction is obtained (vertical or transverse).

2. The sides of the uterus are palpated to determine the position of the fetal back and small parts.

3. The presenting part (head or butt) is palpated above the symphysis and degree of engagement determined

4. The fetal occipital prominence is determined.

Evaluation of the Maternal Pelvis

This is frequently performed prenatally, but can also be done at the initial evaluation of a patient in labor.

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