Chapter 13: Labor and Birth Process

Vocabulary flashcards covering the initiation, premonitory signs, true versus false labor, stages, and critical factors (the Ps of labor) of the labor and birth process.

Labor

The process by which the birth canal is prepared to allow the fetus to pass from the uterine cavity to the outside world.

Gap Junctions

Proteins that connect cell membranes and facilitate the coordination of uterine contractions and myometrial stretching.

Cervical Dilation

The opening or enlargement of the external cervical os, progressing from closed ($0\,\text{cm}$) to fully open ($10\,\text{cm}$).

Braxton Hicks Contractions

Irregular contractions felt as a tightening or pulling sensation in the abdomen and groin that assist in cervical ripening and softening without causing progressive cervical dilation.

Late Preterm

An infant born between $34\,0/7$ and $36\,6/7$ weeks' gestation who experiences many of the same health issues as other preterm birth infants.

Lightening

The descent of the fetal presenting part into the true pelvis, causing the uterus to lower and move into a more anterior position.

Bloody Show

Pink-tinged secretions resulting from the expulsion of the cervical mucus plug mixed with a small amount of blood from ruptured cervical capillaries.

Prelabor Rupture of Membranes (PROM)

The rupture of amniotic membranes accompanied by the loss of amniotic fluid prior to the onset of labor.

False Labor

A condition occurring during the latter weeks of pregnancy characterized by irregular contractions that do not bring about progressive cervical dilation or effacement.

True Labor

Labor characterized by regular contractions that increase in frequency, duration, and intensity, resulting in progressive cervical dilation and effacement.

First Stage of Labor

The stage of labor that begins with the first true contraction and ends at complete cervical dilation ($10\,\text{cm}$), consisting of the latent and active phases.

Latent Phase

The initial phase of the first stage of labor characterized by slow cervical dilation from $0$ to $6\,\text{cm}$ and effacement from $0\%$ to $40\%$.

Active Phase

The phase of the first stage of labor characterized by rapid cervical dilation progressing from $6\,\text{cm}$ to $10\,\text{cm}$ and effacement from $40\%$ to $100\%$.

Second Stage of Labor

The expulsive stage of labor that begins with complete cervical dilation ($10\,\text{cm}$) and ends with the birth of the newborn.

Crowning

The point during the second stage of labor when the top of the fetal head remains visible at the vaginal opening and no longer regresses between contractions.

Spontaneous Pushing

A natural method of managing the second stage of labor that follows the birthing parent's spontaneous urge and involuntary bearing-down efforts.

Laboring Down

An alternative strategy for second-stage management in patients with epidural analgesia that promotes passive descent of the fetus before initiating active pushing.

Third Stage of Labor

The stage of labor that begins immediately after the newborn is born and ends with the separation and expulsion of the placenta.

Fourth Stage of Labor

The restorative period lasting from $1$ to $4$ hours after birth, during which maternal physiologic stabilization occurs and family attachment begins.

Passageway

The route through which the fetus must travel to be born vaginally, consisting of the maternal pelvis and soft tissues.

Molding

The elongated or changed shape of the fetal skull at birth resulting from the overlapping of pliable cranial bones along suture lines.

Fetal Attitude

The posturing (flexion or extension) of the fetal joints and the spatial relationship of the fetal parts to one another.

Fetal Lie

The relationship of the long axis (spine) of the fetus to the long axis (spine) of the laboring person, classified as longitudinal, transverse, or oblique.

Fetal Presentation

The body part of the fetus that enters the pelvic inlet first and lies over the cervical os (cephalic, breech, or shoulder).

Frank Breech

A breech presentation in which the fetal buttocks present first with both lower extremities extended straight up toward the face.

Complete Breech

A breech presentation in which the fetus sits cross-legged above the cervix with both hips and knees flexed.

Footling Breech

An incomplete breech presentation characterized by one or both fetal feet presenting into the maternal pelvis first.

Shoulder Presentation

An abnormal presentation occurring when the fetus is in a transverse lie with the scapula or acromion process presenting over the pelvic inlet.

Fetal Position

The relationship of a designated landmark on the fetal presenting part (such as occiput, mentum, sacrum, or acromion) to a specific quadrant of the maternal pelvis.

Fetal Station

The relationship of the fetal presenting part to the level of the maternal pelvic ischial spines, measured in centimeters above (minus) or below (plus) the spines.

Zero ($0$) Station

The station designated when the leading portion of the fetal presenting part is directly at the level of the maternal ischial spines.

Fetal Engagement

The entrance of the greatest transverse diameter of the fetal presenting part (the biparietal diameter) into the smallest diameter of the maternal pelvis, typically at $0$ station.

Floating

The clinical term used when engagement has not occurred because the fetal presenting part remains freely movable above the pelvic inlet.

Cardinal Movements of Labor

The sequence of deliberate, precise positional changes undertaken by the fetus through the birth canal: engagement, descent, flexion, internal rotation, extension, external rotation (restitution), and expulsion.

Flexion (Cardinal Movement)

The movement occurring when the fetal head meets tissue resistance, bringing the chin to the thorax and substituting the smaller suboccipitobregmatic diameter ($9.5\,\text{cm}$) as the presenting part.

Internal Rotation

The anterior movement of the fetal head by approximately $45^\circ$ under the pubic symphysis to align the anteroposterior diameter of the head with the anteroposterior diameter of the pelvic outlet.

Restitution (External Rotation)

The untwisting of the fetal head by about $45^\circ$ following delivery to realign its sagittal suture with the shoulders and back in the birth canal.

Cervical Effacement

The progressive thinning and shortening of the cervical canal from $2\,\text{cm}$ in length ($0\%$ effaced) down to a paper-thin structure ($100\%$ effaced).

Contraction Frequency

The parameter quantifying how often uterine contractions occur, measured from the beginning of one contraction to the beginning of the next contraction.

Contraction Duration

The parameter quantifying how long a contraction lasts, measured from the onset of a contraction to the completion of that same contraction.

Contraction Intensity

The strength of a uterine contraction determined by manual palpation of the fundus or quantified in millimeters of mercury using an intrauterine pressure catheter.

Flexible Sacrum Position

An upright maternal position in which body weight is lifted off the sacrum, allowing the pelvic outlet to expand and facilitating flexibility of the sacroiliac joints.