Vaginal Birth and Maternity Nursing Lecture Notes

Fundamental Obstetric Definitions and Fetal Positioning

• Lie: Defined as the relationship of the long axis of the fetus to the long axis of the uterus. In late stages of pregnancy, this should be longitudinal.

• Attitude: The relationship of the fetal head and limbs to the fetal trunk. Examples include being flexed, deflexed, and partially or completely extended.

• Presentation: Identifies the part of the fetus lying in the lower segment of the uterus. At the $32^{nd}$ week, the position is typically cephalic.

• Denominator: A fixed point on the presenting part used to describe the position.

  • In a cephalic presentation, the denominator is the occiput.

  • In a breech presentation, the denominator is the bottom.

  • In a face presentation, the denominator is the mentum (referred to as "men tongue" in source).

• Position: The relationship of a denominator to the quadrant of the maternal pelvis (e.g., Left Occipito-Anterior or "left osictoanterior").

• Engagement: Occurs when the largest diameter of the presenting part has passed through the pelvic brim. The pelvic brim is widest from side to side at the level of the ischial spines. On the station scale, $0$ equals engagement.

• Station: Refers to the level of the presenting part in relationship to the maternal ischial spines. These spines represented the narrowest diameter through which the fetus must pass. Plus stations ($+1$, $+2$, etc.) indicate that the presenting part has descended past the ischial spines.

• Mechanisms of Labor: The passive movement of the fetus as it passes through the birth canal, adapting to the shape of the maternal pelvis.

• Normal Labor: A process by which the fetus, placenta, and membranes are expelled through the birth canal. It begins spontaneously without intervention, features a vertex presentation, and lasts between $4$ to $24$ hours.

• Preterm Labor: The onset of labor occurring before $37$ weeks ($7$ weeks according to initial mention) of pregnancy.

• Antenatal Period: The duration from the time of conception until the onset of labor.

• Postpartum or Puerperium (Suroperium): The period taken for the reproductive organs to return to the pre-gravid state, usually lasting $6$ weeks following childbirth.

• Maternal Morbidity: Illness or injury occurring from the time of conception until the end of the puerperium, attributed to childbirth.

• Maternal Mortality: Death occurring from the time of conception until the completion of the puerperium, attributed to childbirth.

• Viable: Defined as being capable of independent life.

• Neonatal Period: Pertains to the first $4$ weeks ($28$ days) after birth.

Maternal Status and Parity Terminology

• Gravida: A term for a pregnant woman.

• Para: Describes a woman who has produced one or more living children.

• Paros (Pares): A woman who has born one or more viable offspring.

• Premi Gravida (Primigravida): A woman pregnant for the first time.

• Multi Gravida (Multigravida): A pregnant woman who has previously had more than one pregnancy.

• Grande Multi Gravida (Grand Multigravida): A woman in her fourth or subsequent pregnancy, though she has not necessarily born live children previously.

• Premi Parra (Primiptera): A woman who has given birth to a viable infant, whether living or stillborn.

• Nolipara (Noliptera): A woman who has never given birth to a viable child but may have been pregnant.

• Maltipara (Meltiptera): A woman who has born more than one viable infant.

• Gran Maltipara (Grandmultipara): A woman of high parity, usually one who has born $4$ or more children.

Uterine Physiology and Dynamics during Labor

• Upper Uterine Segment: The upper part of the uterus during pregnancy, developed from the body of the uterus.

• Lower Uterine Segment: The lower part of the uterus during pregnancy, developed from the isthmus and cervix.

• Braxton Hicks Contractions: Painless contractions occurring in the uterus during pregnancy.

• Retraction: The process of permanent and progressive shortening of the uterine muscles. This accompanies contractions to dilate the cervix, expel the fetus, membranes, and placenta, and control bleeding.

• Physiological Retraction Ring: The line of demarcation that develops at the junction of the upper and lower uterine segments during normal labor.

• Polarity: The coordination between the upper and lower uterine segments during normal labor.

• Favorable or Ripe Cervix: A condition where the cervix is soft and considered ready for labor.

• Effacement: The thinning of the cervix in preparation for birth, expressed as a percentage ($0$ to $100\%$). A woman needs to be $100\%$ effaced to be able to push.

• Dilatation: The extent to which the cervix has opened as a result of uterine contractions. Full dilatation is defined as $10\,\text{cm}$.

• Fundal Dominance: The greatest strength of contractions occurs in the fundus of the uterus and moves down to the upper segment with diminishing strength.

• Fetal Axis Pressure: The force of the fundal contraction transmitted to the upper pole of the fetus and down its long axis.

• Secondary Powers: The use of the abdominal muscles and the diaphragm to push during the second stage of labor.

Liquor and Fetal Landmarks

• Liquor: Amniotic fluid.

• Forewaters: The bag of membranes and liquor located in front of the presenting part.

• Hindwaters: The liquor contained within the uterus behind the presenting part.

• Molding: Alterations in the shape and diameters of the fetal head during labor to facilitate passage through the birth canal.

• Caput Succidaneum: Edema ("Oudmar") that occurs on the fetal scalp resulting from obstructed venous return and pressure on the birth canal.

• Lightening: Occurs when the presenting part enters the pelvis, usually after the $36^{th}$ week.

• Partograph: A graphical record of the progression of labor, specifically cervical dilatation. It allows for assessment of progress based on visual patterns of dilatation and descent in conjunction with maternal and fetal well-being records.

• Involution: The return of the uterus to its pre-pregnant state.

• Crowning: The point during birth when the baby's head has passed through the birth canal and the top (crown) remains visible at the vaginal opening without receding.

Anatomy of the Pelvis

• Bones of the Pelvis:

  • Two innominate hip bones (comprising the ilium, ischium, and pubic bone).

  • One sacrum.

  • One coccyx.

• Key Landmarks:

  • Ischial Tuberosity: The large prominence upon which the body rests when sitting.

  • Ischial Spines: Inward projections lying above the ischial tuberosity; the situation of the fetal head is estimated in centimeters relative to these spines.

• Joints of the Pelvis:

  • $1$ Symphysis pubis.

  • $2$ Sacroiliac joints.

  • $1$ Sacrococcygeal joint.

• Ligaments of the Pelvis: Interpubic, sacroiliac, sacrococcygeal, sacrotuberous, and sacrospinus.

• Functions of Pelvic Floor Muscles: Holds pelvic organs in place, maintains intra-abdominal pressure, provides voluntary control of defecation, facilitates fetal movement during childbirth, and enables flexion of the coccyx and sacrum.

Pelvic Types and Dimensions

• Pelvic Types:

  • Gnocoid (Gynecoid): Ideal for childbearing; features a rounded brim, generous fore-pelvis, shallow cavity, and blunt ischial spines.

  • Android: Male-type pelvis, least favorable for childbirth. Features a heart-shaped brim and straight sacrum; cannot easily accommodate the biparietal diameter.

  • Anthropoid: Long oval brim; doesn't usually cause problems but may favor occipito-posterior positions.

  • Platypeloid (Plateaumannoid): Kidney-shaped brim; increased risk of obstruction.

• Dimensions (in cm):

  • Brim: Anterior-Posterior = $11$, Oblique = $12$, Transverse = $13$.

  • Cavity: Anterior-Posterior = $12$, Oblique = $12$, Transverse = $12$.

  • Outlet: Anterior-Posterior = $13$, Oblique = $12$, Transverse = $13$.

Monitoring: Cardiotocography (CTG)

• CTG Components: A trace of the fetal heart rate (FHR) and maternal contractions.

• Baseline FHR: The mean level of the FHR at rest. Normal range is $110$ to $160\,\text{BPM}$.

• Variability: Minor fluctuations in the baseline FHR, normally $5$ to $25\,\text{BPM}$ in amplitude. It indicates interaction between the parasympathetic and sympathetic nervous systems and adequate fetal perfusion.

  • Decreased Variability Causes: CNS depression, deep fetal sleep, drugs, prematurity, or hypoxia.

• Accelerations: Transient increases in FHR of $15\,\text{BPM}$ or more above baseline, lasting at least $15\,\text{seconds}$.

• Decelerations: Decreases in FHR below the baseline of more than $15\,\text{BPM}$ lasting at least $15\,\text{seconds}$. These may be categorized as early, variable, prolonged, or late.

The Abdominal Examination

• Preparation: Explanation to the mother, informed consent, ensuring an empty bladder, providing privacy, and using clean, warm hands.

• Aims: Observe signs of pregnancy, assess fetal size/growth, assess fetal health, locate fetal parts, and detect deviations from normal.

• Components of Examination:

  • Inspection: Uterine size, shape, and skin changes.

  • Palpation:

    • Fundal Height: Distance between the top of the uterus and the upper border of the symphysis pubis.

    • Lateral Palpation: Hands are placed on either side of the uterus at the umbilicus to identify the fetal back (greater resistance).

    • Pelvic Palpation: Identification of fetal poles (head vs. bottom).

    • Pollux Palpation: Grasping the lower pole between fingers and thumb to identify if the pole is fixed (engaged).

  • Auscultation: Monitoring the Fetal Heart Rate (FHR).

Stages and Phases of Labor

• First Stage of Labor: From the onset of labor until complete dilatation ($10\,\text{cm}$).

  • Latent Phase: Beginning of effective labor; effacement and dilatation up to $3\,\text{cm}$. Characterized by irregular contractions (Braxton Hicks) or early labor symptoms.

  • Active Phase: Cervix dilates from $3\,\text{cm}$ to $8\,\text{cm}$. Contractions are regular, stronger, and closer together.

  • Transition Phase: From $8\,\text{cm}$ to $10\,\text{cm}$ dilatation. Characterized by a "bloody show," restlessness, and full effacement.

• Second Stage of Labor: From complete dilatation until the birth of the infant.

  • Passive Phase: No maternal urge to push; presenting part is still high.

  • Active Phase: Fetal head is low, triggering the maternal urge to bear down and involuntary pushing.

• Third Stage of Labor: From the birth of the infant until the placenta and membranes are delivered.

Progress and Care During Labor

• The Four Ps (Outcomes of Labor):

  1. Power: Uterine contractions.

  2. Passenger: Fetal size and presentation.

  3. Passage: Cervix, bony pelvis, and soft tissues.

  4. Psyche: Knowledge, expectations, support, and environment.

• Assessing Progress:

  • Contractions: Measured for strength, intensity, length, and frequency over $10$ minutes every half hour.

  • Vaginal Loss: Blood or mucus-stained loss indicates progress (detachment of membranes).

  • Liquor Assessment: Report meconium-stained liquor (fetal distress) or offensive smells (infection).

  • Vaginal Examination (VE): Assesses descent, flexion, rotation, cervical softening, effacement, and dilatation.

• Maternal Risk Assessment: Ongoing monitoring of BP, temperature, pulse (half-hourly), and fluid input/output.

• Signs of Second Stage: No palpable cervix, urge to push, bloody show, bowel pressure, anal pouting, perineal stretching, and grunting.

Mechanisms of Normal Birth (Cardinal Movements)

1. Descent: Progression of the fetal head into the pelvis ($0$ station and beyond).

2. Flexion: Fetal chin flexes to the chest upon meeting resistance from pelvic tissues, presenting the smallest diameter.

3. Internal Rotation: The head rotates to accommodate the pelvic cavity width (widest from front to back).

4. Extension: The head passes under the symphysis pubis, pivoting and extending with maternal effort.

5. Restitution: After the head is born, it rotates briefly to realign with the long axis of the body.

6. External Rotation: The shoulders align with the anterior-posterior diameter, causing the head to turn further to the side.

7. Expulsion: The anterior shoulder moves under the symphysis pubis, followed by the posterior shoulder and the rest of the body.

Third Stage Management and Perineal Care

• Signs of Placental Descent: Firm uterine contraction, decreased fundal size, change in uterine shape/immobility, lengthening of the umbilical cord, and a gush of blood.

• Active Management: Use of oxytocic agents (e.g., Syntemetrine) and Controlled Cord Traction (CCT) to reduce blood loss and shorten the stage.

  • Controlled Cord Traction: Ensure the uterus is contracted, guard the uterus, apply downward continuous steady traction via cord clamp. Move upward once the placenta is visible.

• Physiological Management: No intervention or drugs. Relies on maternal effort, skin-to-skin, or nipple stimulation. Lasts $20$ minutes to $1\,\text{hour}$.

• Perineal Tears:

  • First Degree: Skin, subcutaneous tissue, vaginal mucosa.

  • Second Degree: Superficial and deep perineal muscles and the perineal body.

  • Third Degree: Perineal muscles and the anal sphincter.

  • Fourth Degree: Anal sphincter and anorectal epithelium.

• Episiotomy: An incision made in the perineum to widen the vaginal opening.

Prenatal Physiology and Fetal Development

• Hormones:

  • Progesterone: Acts on smooth muscles, promotes breast development.

  • Human Chorionic Gonotropin (HCG): Secreted by trophoblasts; stimulates corpus luteum to produce progesterone/estrogen ("o s slash prog") until the placenta takes over. High values cause morning sickness and prevent maternal rejection of the fetus.

  • Human Placental Lactogen (HPL): Facilitates growth; begins $5$-$10$ days after implantation. Low levels are associated with miscarriage.

• Signs of Pregnancy:

  • Probable: Nausea, tiredness, amenorrhea, breast soreness.

  • Definite: Ultrasound, fetal parts palpated, fetal heart heard.

• Physiological Changes:

  • Cardiovascular: Increased blood volume, drop in Hb iron stores, increased skin blood flow.

  • Respiratory: Increased BMR and oxygen consumption, rib flaring, raised diaphragm.

  • Renal: Potential for urine stasis due to relaxed smooth muscle.

  • Skeletal: Lordosis, widening of the pelvis.

• Placental Function: Protection, respiration, excretion, endocrine, nutrition, and storage.

• Fetal Circulation: Deoxygenated blood travels to the placenta via $2$ umbilical arteries; oxygenated blood returns via $1$ umbilical vein.

• Teratogen: An agent or influence causing physical defects in a developing fetus.

Fetal Skull Anatomy

• Bones: Occiput, two parietals, and two frontals.

• Sutures:

  • Lamboidal: Between occiput and parietals.

  • Sagittal: Divides the parietal bones.

  • Coronal: Separates parietal and frontal bones.

  • Frontal: Divides the frontal bones.

• Fontanelles:

  • Posterior: Triangular shape at the junction of lamboidal and sagittal sutures. Presence on VE indicates a well-flexed head.

  • Anterior: Diamond shape at sagittal, coronal, and frontal sutures. Presence on VE indicates the head is not well-flexed.