Valerie Hill - Labour and Birthing Process

The 5 P’s Affecting Labour

Passenger (fetus and placenta)

Passage (Birth canal)

Powers (Contractions)

Position of the Laboring Patient

Psychological Response

Passenger

Affected by the fetal head. The fetal skull is composed of two parietal bones, two temporal bones, the frontal bone and the occipital bone. The areas where more than two bones meet are called fontanels which can be examined during vaginal exam after the membranes rupture.

Fontanelles allow the bones of the skull to overlap and shift to allow baby to come out. Normal head shape resumes by 3 days

Anterior Fontanelle (size, shape, location, closure)

• Larger of the two fontanelles. Diamond shaped and lies at the junction of the sagittal coronal and frontal sutures. It closes by 18 months.

Posterior Fontanelle (shape, location, closure)

• Triangular and at the junction of the two parietal and one occipital bones. Closes by 6-8 weeks.

Cephalic/Vertex Presentation

• Occiput is the presenting/closest part to the os of the cervix.

Breech presentation

• Sacrum is the presenting/closest part to the os of the cervix

Shoulder Presentation

• Scapula is the presenting/closest part to the os of the cervix.

Fetal Presentation vs Fetal Lie vs Fetal Attitude

Presentation: The position of the fetus/presenting part

Lie: The relation of the spine of the fetus to the spine of the mother.

Attitude: Flexion

Longitudinal/Vertical Lie

The long axis of the fetus is parallel with the long axis of the mother. Cephalic or breech presentation.

Transverse/Horizontal Lie

The long axis of the fetus is perpendicular to the mothers long axis. Vaginal birth cannot occur unless lie changes.

Oblique: Lie

• The long axis of the fetus lies at an angle to the long axis of mom. 

General Flexion

•  Back rounded. Chin flexed on chest. Thighs flexed on abdomen. Knees flexed. Arms crossed over the chest and umbilical cord between the arms and legs. 

Biparietal Diameter

• : Largest transverse diameter entering the pelvic inlet in a well flexed baby. 

Fetal Position

• The relationship of a reference point on the presenting part to the four quadrants of the mothers pelvis. Detonated by three letter abbreviation. 

• First letter is if the presenting part is on the right or left side denoted by R or L

• The second letter is for the specific presenting part of the fetus. O for occiput, S for sacrum, M for mentum, and Sc for scapula. 

• Third letter for the presenting part in relation to the anterior, posterior or transverse portion of the maternal pelvis. Denoted by A, P or T (which direction it’s facing).

Station

The relationship of the presenting fetal part to an imaginary line drawn between the maternal ischial spines. Measures the degree of descent. If the presenting part (example occiput) is at the level of the spines it’s at a 0. Above the spines it’s at -x and below is at +x. When the presenting part is at +4-5 birth is imminent.

Engagement

Engagement is the term used to indicate that the largest transverse diameter of the presenting part (Commonly biparietal diameter) has passed through the pelvic brim and into the pelvis. Usually occurs in the weeks before labor begins in nulliparas and may occur just before or during labor in multiparas.

Bony Pelvis

• Separated by the brim/inlet into the false and true pelvis. The false pelvis is the part above the rim and plays no part in childbearirng. The true pelvis is the part involved in birth and is divided into the inlet/brim, the midpelvis/cavity and the outlet. In the latter part of pregnancy the coccyx is moveable unless it has been broken and fused to the sacrum during healing.

4 Basic Types of Pelvises

• The 4 basic types of pelvis from most to least common are gynecoid (classic female), android (classic male), anthropoid (resembling anthropoid apes) and platypelloid (flat pelvis)

Soft Tissues

After labor begins the thick and muscular upper segment of the uterus is separated from the thin walled lower segment through a physiological retraction ring. As the upper portion thickens and loses capacity the lower segment stretches to accommodate more of the fetus. Contractions push the fetus against the cervix which effaces and dilates to allow the first fetal portion to descend into the vagina. The pelvic floor is a muscular layer that separates the pelvic cavity from the perineal space below and helps the fetus rotate anteriorly

Primary Powers

Involuntary uterine contractions that signal the beginning of labor. Originate at certain pacemaker points in the thickened muscles of the upper uterine segments and move down.Measured in frequency (time between), duration (time of) and intensity of contraction. Responsible for effacement and dilation. Effacement usually happens before dilation in first time pregnancies and with dilation for subsequent. When the cervix is fully dilated and retracted it can no longer be palpated.

Secondary powers

•  Voluntary bearing down efforts by the patient after cervical dilation. These augment the force of the involuntary contractions. When the fetus reaches the pelvic floor, the patient feels an involuntary urge to push

Ferguson Reflex

• In the first and second stages of labor, increased intrauterine pressure caused by contractions forces the fetus to descend. When the fetus reaches the perineal floor, mechanical stretching of the cervix occurs, and stretch receptors in the posterior vagina cause the release of oxytocin that triggers mom to bear down. This is called the ferguson reflex.

7 Signs Preceding Labour

• Lightening/Dropping: The fetus presenting part descends into the true pelvis 2-4 weeks before term in first time pregnancies and during labor for multiparous. Patients usually breathe easier after this but may feel increased bladder pressure and frequency.

• Relaxation of the pelvic joints may cause persistent low back pain. 

• Strong, frequent but irregular contractions may occur. These are called braxton hicks.

• More profuse vaginal mucus

• Bloody Show: Blood tinged or brownish vaginal mucus.

• Loss of 0.5-1.5kg of water weight.

• Surge of energy/nesting.

First Stage of Labor

• Onset of regular uterine contractions to full dilation of the cervix.

• Longest stage.

• Divided into latent/early and active stages of labor.

• During the latent phase there is more cervical effacement and little descent. During the active phase there is more dilation and descent.

• The latent phase is 0-3cm dilated and less than 1cm long in a nulliparous patient, and 0-4 less than 1cm in a multiparous patient.

• Active labour is 4cm in nulliparous and 4-5 in multiparous.

Second Stage of Labour

• Time that the cervix is fully dilated to the birth of the fetus. Composed of two phases. The latent phase, and the active pushing phase. During the latent phase the fetus descends passively and rotates anteriorly. The urge to bear down is not strong. During the active phase the patient has very strong urges to bear down due to stretch receptor activations caused by fetal descent.

Third Stage of Labour

• The third stage of labor lasts from the birth of the fetus until the placenta is delivered. After 3-4 contractions the placenta is separated and after that it can be pushed out in the next contraction. 

The Fourth Stage of Labour

• From delivery of placenta including at the least the first 2 hours after birth.

What are the 7 cardinal movements of labour?

Engagement

Descent

Flexion

Internal Rotation

Extension

Restitution and External Rotation

Expulsion

Engagement

When the biparietal diameter of the head passes the pelvic inlet, the head is said to be engaged in the pelvic inlet. The head usually engages the pelvis in a synclitic position (parallel to the anteroposterior plane of the pelvis). Asynclitism may occur to accommodate the head through the pelvis. Extreme asynclitism can prevent descent due to cephalopelvic disproportion.

Descent

The progress of the presenting part through the pelvis. Depends on four forces. Pressure exerted by amniotic fluid, direct pressure exerted by the contracting fundus on the fetus, force of the contraction of the maternal diaphragm, and extension and straightening of the fetal body.

Flexion

When the fetal head meets resistance at the base of the uterus, the fetal head flexes so that the smaller suboccipitobregmatic diameter (9.5cm) is the presenting part.

Internal Rotation

• In order for the fetus to exit, the head must rotate into the occipitotransverse position such that the back of the head (occiput) is under the pubic bone. This occurs in the pushing stage while the fetus moves between the ischial spines and the lower pelvis. Previous childbirth injury or regional anesthesia may interfere with the levator ani muscles and interfere in this step. 

Extension

: At the perineum, the fetal head emerges by extending. The occiput is presented first followed by the face and chin.

Restitution and External Rotation

After the head is born, it turns back into the sideways position it was in before, which aligns it with the body. The shoulders then rotate, which causes the head to rotate even more. The anterior shoulder is delivered first, and then the posterior shoulder is guided up to be delivered next.

Expulsion

After the birth of the shoulders, the baby’s body is flexed up to deliver the rest of the body. After the baby is fully out, the second stage of labor ends.