MODULE 2 LESSON 1 - the birthing process

The Birthing Process

The series of events that occur from the onset of labor until the birth of the baby and placenta.

Labor

The process by which regular uterine contractions bring about cervical effacement

Maternal Factors of Labor Onset

Factors in the mother that help trigger the beginning of labor.

Uterine Muscle Stretching

Causes the release of prostaglandins that help stimulate uterine contractions.

Pressure on the Cervix

Stimulates the release of oxytocin from the maternal posterior pituitary gland.

Oxytocin

Hormone that increases significantly during labor and works with prostaglandins to stimulate uterine contractions.

Prostaglandins

Hormones that promote uterine contractions and cervical ripening.

Increase in Estrogen to Progesterone Ratio

As term approaches progesterone availability decreases while estrogen increases making the uterus more excitable.

Progesterone

Hormone that relaxes smooth muscle and helps maintain pregnancy.

Estrogen

Hormone that increases uterine excitability near term leading to contractions.

Fetal Factors of Labor Onset

Factors originating from the fetus that contribute to the initiation of labor.

Placental Aging

Deterioration of the placenta that may trigger contractions.

Fetal Cortisol

Increases near term causing decreased placental progesterone production and increased prostaglandin release.

Fetal Membranes

Produce prostaglandins that stimulate uterine contractions.

5 P's of Labor

The five critical factors that influence the progress of labor and birth.

Powers

Physiological forces responsible for labor including uterine contractions and maternal pushing efforts.

Passageway

The maternal pelvis and soft tissues through which the fetus passes.

Passenger

The fetus and placenta.

Passenger-Passageway Relationship

The relationship between the fetus and maternal pelvis including engagement attitude and position.

Psychosocial Influences

Previous experiences emotional status and psychological factors affecting labor.

Primary Force of Labor

Uterine contractions.

Secondary Force of Labor

Maternal pushing efforts using the abdominal muscles.

Uterine Contractions

Primary physiological force that causes cervical effacement dilation and fetal descent.

Frequency of Contractions

Time measured from the beginning of one contraction to the beginning of the next.

Duration of Contractions

Time measured from the start to the end of one contraction.

Intensity of Contractions

Strength of contractions usually described as mild moderate or strong.

Increment

The building phase of a uterine contraction.

Acme

The peak or strongest point of a contraction.

Decrement

The decreasing phase of a uterine contraction.

Maternal Pushing Efforts

Involuntary bearing-down sensation and voluntary abdominal muscle contractions that aid fetal expulsion.

Requirement Before Pushing

The cervix must be fully dilated before the woman is encouraged to push.

Effacement

The shortening and thinning of the cervix during labor.

Effacement Measurement

Expressed as a percentage from 0% to 100%.

Complete Effacement

100% thinning of the cervix.

Dilation

The opening and enlargement of the cervix during labor.

Dilation Measurement

Measured in centimeters.

Complete Dilation

Approximately 10 cm.

Passageway

Consists of the maternal pelvis and soft tissues.

Three Sections of the Bony Pelvis

Pelvic inlet midpelvis and pelvic outlet.

Pelvic Inlet

Upper opening of the pelvis where the fetus enters.

Midpelvis

Also called the pelvic cavity through which the fetus descends.

Pelvic Outlet

Lower opening of the pelvis through which the fetus is delivered.

Four Types of Female Pelvis

Gynecoid Android Anthropoid and Platypelloid.

Gynecoid Pelvis

Wide rounded pelvis considered the most favorable for vaginal birth.

Reason Gynecoid is Best for Vaginal Birth

Wide open shape provides more room for fetal passage.

Android Pelvis

Heart-shaped narrow pelvis resembling the male pelvis.

Effect of Android Pelvis

May cause slow labor and increase the likelihood of cesarean delivery.

Anthropoid Pelvis

Narrow deep pelvis resembling an upright oval.

Effect of Anthropoid Pelvis

Vaginal birth is possible but labor may be longer.

Platypelloid Pelvis

Flat wide shallow pelvis resembling an oval lying on its side.

Effect of Platypelloid Pelvis

Vaginal birth may be difficult and cesarean section is often required.

Passenger

Refers to the fetus and fetal membranes.

Most Common Fetal Presentation

Head-first presentation occurring in approximately 96% of pregnancies.

Fetal Skull

Largest and least flexible part of the fetus.

Importance of Sutures and Fontanels

Allow flexibility of the fetal skull during labor.

Molding

Overlapping or overriding of the fetal cranial bones during labor.

Components of the Fetal Skull

Face base of the skull and vault of the cranium.

Fontanels

Membrane-filled spaces where fetal skull sutures meet.

Anterior Fontanel

Diamond-shaped fontanel located at the intersection of the sagittal frontal and coronal sutures.

Anterior Fontanel Closure

Closes at approximately 18 months of age.

Posterior Fontanel

Triangular fontanel located at the intersection of the lambdoidal and sagittal sutures.

Posterior Fontanel Closure

Closes approximately 6 to 8 weeks after birth.

Sagittal Suture

Suture running between the two parietal bones.

Coronal Suture

Suture between the frontal bone and parietal bones.

Frontal Suture

Suture associated with the anterior portion of the fetal skull.

Lambdoidal Suture

Suture located between the occipital bone and parietal bones.

Importance of Molding

Allows the fetal head to adapt to the maternal pelvis during labor.

Purpose of Effacement

Prepares the cervix for dilation and birth.

Purpose of Dilation

Allows passage of the fetus through the birth canal.

Purpose of Uterine Contractions

Cause cervical changes and fetal descent.

Purpose of Maternal Pushing

Assists in expelling the fetus after full cervical dilation.

Most Favorable Pelvis for Vaginal Birth

Gynecoid pelvis.

Least Common Pelvis Type

Platypelloid pelvis.

Pelvis Most Similar to Male Pelvis

Android pelvis.

Deep Narrow Pelvis

Anthropoid pelvis.

Flat Shallow Pelvis

Platypelloid pelvis.

Percentage of Head-First Presentation

Approximately 96%.

Normal Complete Cervical Dilation

10 centimeters.

Normal Complete Cervical Effacement

100 percent.

Three Characteristics of Uterine Contractions

Frequency duration and intensity.

Three Phases of a Contraction

Increment acme and decrement.

Primary Hormone Released Due to Cervical Pressure

Oxytocin.

Hormone Released by Uterine Stretching and Fetal Membranes

Prostaglandins.

Function of Estrogen Near Labor

Increases uterine excitability.

Function of Progesterone During Pregnancy

Relaxes smooth muscle and helps maintain pregnancy.