Normal Labor, Fetal Skull, and Female Pelvis Practice Flashcards

Comprehensive practice flashcards covering normal labor stages, fetal skull anatomy, pelvic diameters, and malpresentations based on the clinical lecture transcript.

How is 'Labor' defined in the lecture?

A series of events that take place in the genital organs in an effort to expel the viable fetus out of the uterus through the vagina into the outer world.

What is the definition of 'Delivery'?

The expulsion or extraction of the viable fetus out of the uterus.

What are the criteria for 'Normal Labor'?

Spontaneous delivery, single, full term, living, presenting by vertex, through the birth canal, within reasonable time, without interference, and without complication.

Name the theories concerning the onset of labor mentioned in the notes.

Uterine distension theory, stretch of lower uterine segment, fetal suprarenal theory, prostaglandin theory, progesterone withdrawal theory, estrogen-progesterone theory, and estrogen-oxytocin theory.

What is the 'Lightening' phenomenon in the prodroma of labor?

A decrease in fundal height as engagement occurs, allowing the mother to breathe more easily and reducing pressure on the diaphragm and stomach.

What is 'The Show' in the context of labor?

The passage of the cervical mucus plug, which may be bloody, as an alarming sign of labor onset or preterm labor.

How are Braxton-Hicks contractions distinguished from true labor pain?

They are irregular, do not increase in frequency or intensity, and do not cause cervical dilatation or effacement.

What are the three core 'P' components that determine normal labor?

Passage (maternal pelvis), Power (uterine contractions), and Passenger (fetus).

Define 'Fetal attitude'.

The relation of fetal parts to each other; normally, this is a flexed attitude.

Define 'Fetal lie'.

The relation between the longitudinal axis of the fetus to that of the mother, which can be longitudinal or transverse.

Define 'Presentation' in obstetrics.

The first part of the fetus which meets the pelvic brim and is first felt by vaginal examination.

What is the 'Denominator' for vertex presentation?

The occipit.

What is the 'Denominator' for breech presentation?

The sacrum.

What is the 'Denominator' for face presentation?

The mentum.

What is the most common fetal head position?

LOA (Left Occiput Anterior).

Why is the LOA position the most common?

Better accommodation between the concavity of the front of the fetus and the convexity of the mother's lumbar spine.

What are the characteristics of true labor pain?

Involuntary, regular, increasing frequency, increasing intensity, increasing duration, low back pain, cervical dilatation/effacement, and passage of show.

Define the First Stage of labor.

The period from true labor pain to full cervical dilatation.

Define the Second Stage of labor.

The period from full cervical dilatation to the delivery of the fetus.

Define the Third Stage of labor.

The period after the delivery of the fetus until the delivery of the placenta.

Define the Fourth Stage of labor.

The stage of observation for at least one hour after the delivery of the placenta.

What is the duration of the first stage of labor in a primigravida?

$12-16$ hours.

What is the duration of the first stage of labor in a multipara?

$6-8$ hours.

What is 'Fergusson's reflex'?

A stretch reflex where receptors in the cervix/vagina trigger oxytocin release during labor.

What is the range for full cervical dilatation?

$0$ to $10\,cm$.

In which type of patient does cervical effacement typically occur before dilatation?

Primipara.

According to the Friedman curve, what is the extent of the Latent Phase?

Up to $3-4\,cm$ of dilatation, lasting up to $8-12-24$ hours.

What occurs during the Second Stage mechanism regarding fetal head movement?

Descent, engagement, increased flexion, internal rotation, extension, restitution, and external rotation.

Define 'Engagement' of the fetal head.

The passage of the widest transverse diameter of the fetus (biparietal diameter) through the pelvic inlet.

What is the 'Two-armed theory' used to explain?

Increased flexion when the occiput meets the resistance of the pelvic floor.

What defines the 'Internal rotation' step in the mechanism of labor?

The occiput rotates $1/8$ of a circle anteriorly to become opposite to the symphysis pubis.

What is 'Restitution'?

The rotation of the occiput $1/8$ of a circle in the opposite direction of internal rotation to undo the twist of the neck.

What causes the 'External rotation' of the fetal head?

The rotation of the shoulders entering the opposite oblique diameter of the pelvis.

What is the surest sign of placental separation?

Cord lengthening.

Describe the Shultz mechanism of placental delivery.

The most common type ($80\%$) where separation starts at the center of the placenta.

Describe the Duncan mechanism of placental delivery.

Occurs in $20\%$ of cases where separation starts at the lower pole of the placenta.

Name the bones comprising the fetal vault.

$2$ frontal bones, $2$ parietal bones, $2$ temporal bones, and $1$ occipital bone.

What is the 'Frontal suture'?

The suture between the two frontal bones.

What is the 'Sagittal suture'?

The suture between the two parietal bones.

Describe the Anterior Fontanelle (Bregma).

Large, lozenge-shaped, surrounded by $4$ bones ($2$ frontal, $2$ parietal), and ossifies at $1.5-2$ years after birth.

Describe the Posterior Fontanelle (Lambda).

Small, triangular, surrounded by $3$ bones ($2$ parietal, $1$ occipital), and ossifies at $1.5$ months after birth.

What is the measurement of the Biparietal diameter (BPD)?

$9.5\,cm$.

What is the measurement of the Bitemporal diameter?

$8.5\,cm$.

What is the measurement of the Bimastoid diameter?

$7.5\,cm$.

Which fetal head diameter is associated with a fully flexed head and vertex presentation?

Suboccipito-bregmatic (SOB) at $9.5\,cm$.

Which diameter engages when the head is in a deflexed/military attitude?

Occipito-frontal (OF) at $11.5\,cm$.

Which diameter engages in a brow presentation?

Mento-vertical (MV) at $13.5\,cm$.

Which diameter engages in a face presentation with a fully extended head?

Submento-bregmatic (SMB) at $9.5\,cm$.

What is 'Molding' or 'Moulding'?

The adaptation of the fetal head to the pelvic cavity by slightly overriding bones at sutures to reduce head circumference.

What does '3rd degree moulding' indicate?

Parietal bones have overlapped and are irreducible; a sign of relative or absolute cephalopelvic disproportion (CPD).

Define 'Asynclitism'.

A lateral inclination of the fetal head where the sagittal suture is directed toward the symphysis pubis or sacrum, making one parietal bone lower than the other.

Contrast Caput Succedaneum and Cephalhematoma base on suture lines.

Caput succedaneum crosses suture lines; Cephalhematoma is limited by the periosteum and does not cross sutures.

What is 'Caput Succedaneum'?

Diffuse scalp edema due to venous congestion resulting from prolonged pressure by the cervix or pelvic bones.

What is 'Cephalhematoma'?

A sub-periosteal hemorrhage that appears within $2-3$ days after labor and is limited by a single bone's periosteum.

What divides the female bony pelvis into the false and true pelvis?

The pelvic brim (arcuate line or linea terminalis).

What is the 'False Pelvis'?

The part of the bony pelvis above the pelvic brim that supports the gravid uterus but has no importance in labor.

Name the four bones that compose the pelvis.

$2$ innominate bones (ilium, ischium, pubis), the sacrum, and the coccyx.

What is the 'Obstetric Conjugate' of the pelvic inlet?

The shortest AP diameter through which the fetus must pass, measuring $10.5\,cm$, from the sacral promontory to the most bulging point of the symphysis pubis.

How is the 'Diagonal Conjugate' measured and what is its value?

Measured clinically via vaginal exam from the sacral promontory to the inferior border of the symphysis pubis; value is approximately $12.5\,cm$.

What is the 11-12-13 rule for AP diameters in the True Pelvis?

Inlet AP = $11\,cm$, Cavity AP = $12\,cm$, Outlet AP = $13\,cm$.

What is the 11-12-13 rule for Transverse diameters in the True Pelvis?

Inlet Transverse = $13\,cm$, Cavity Transverse = $12\,cm$, Outlet Transverse = $11\,cm$.

What is the 'Plane of least pelvic dimensions'?

The obstetric mid-pelvis bounded by the lower border of the SP, ischial spines, and the junction of the $4th$ and $5th$ sacral pieces.

Define 'Thom's dictum' for the pelvic outlet.

The sum of the bituberous and posterior sagittal diameters must be $> 15\,cm$ to allow an average-sized head to pass.

Define 'Arnell & Irvin dictum' for the mid-pelvis.

The sum of the bispinous diameter and posterior sagittal diameter of the mid-pelvis must be $\ge 13.5\,cm$.

Describe a 'Gynecoid' pelvis.

The typical female pelvis ($50\%$ incidence) with a slightly transverse oval inlet and wide subpubic angle, ideal for vaginal delivery.

Describe an 'Android' pelvis.

A male-pattern pelvis ($20\%$ incidence) with a heart-shaped inlet and converging side walls, associated with persistent occipito-posterior (OP) and deep transverse arrest.

Describe an 'Anthropoid' pelvis.

A pelvis with a long oval inlet ($25\%$ incidence) where AP diameters are long and transverse are short; common in face-to-pubis deliveries.

Describe a 'Platypelloid' pelvis.

A flat pelvis ($5\%$ incidence) with a transverse oval inlet (short AP, long transverse), commonly leading to deep transverse arrest.

What is the benchmark clinical 'Zero Station' for fetal head progression?

The level of the ischial spines.

List three importances of the ischial spines in obstetrics.

1. Standard for engagement (station 0); 2. Level where internal rotation occurs; 3. Landmark for pudendal nerve block.

What is 'Naegele's obliquity'?

Posterior asynclitism where the sagittal suture is nearer to the sacral promontory and the anterior parietal bone is lower.

What is 'Litzmann's obliquity'?

Anterior asynclitism where the sagittal suture is nearer to the symphysis pubis and the posterior parietal bone is lower.

Define 'Breech Presentation'.

A longitudinal lie in which the buttocks is the presenting part with or without the lower limbs.

What is a 'Frank Breech'?

A breech with extended legs where the knees are extended while the hips are flexed.

What is a 'Complete Breech'?

A breech where both the hip and knee joints are flexed.

When is 'External Cephalic Version' (ECV) typically performed?

Between $37$ and $38$ weeks of gestation.

Name the condition where the engaging diameter is the Bitrochanteric diameter ($10\,cm$).

Breech presentation.

What maneuver is used to assist shoulder delivery in a breech presentation?

Lovset maneuver.

What is 'Mauriceau-Smellie-Veit' method?

Jaw flexion-shoulder traction used to deliver the after-coming head in breech presentation.

What is 'Burns-Marshall technique'?

A method to deliver the after-coming head by allowing the fetus to hang until the nape appears, then lifting the body towards the mother's abdomen.

Which forceps are specifically mentioned for the after-coming head in breech?

Piper's forceps.

What is the denominator for a Brow presentation?

The frontum (frontal bone).

What is the engaging diameter in a Brow presentation?

Mento-vertical diameter ($13.5\,cm$).

What occurs during the 'External cephalic version' technique to ensure safety?

Hospitalization, evacuation of bladder, Trendelenburg position, and use of fetal monitors before and after.

What is the most common cause of shoulder/transverse lie?

Multiparity ($90\%$ of cases).

What is the management of a persistent shoulder presentation at term?

Cesarean section (CS).

What is the 'Denominator' for a shoulder presentation?

The scapula.

Define 'Synclitism'.

The presence of the sagittal suture midway between the symphysis pubis and the promontory of the sacrum.

What is 'Girdle contact'?

The contact between the fetal head and the cervix or pelvis that causes venous/lymphatic obstruction, leading to caput succedaneum.

What is the commonest fetal head diameter distending the vulva in an OA position if head extension is premature?

Occipito-frontal ($11.5\,cm$ or $11\,cm$ depending on slide).

What is the range for 'normal' pelvic inclination angle?

$40-60$ degrees (average $55$ degrees).

Define 'Obstetric axis' of the pelvis.

A J-shaped curve corresponding to the direction taken by the fetal head, passing down/back then down/forward at the ischial spines.

What does a 'High pelvic inclination' ($> 60$ degrees) signify?

It may delay engagement, favor OP position, and interfere with internal rotation.

Is 'Secondary face presentation' usually developed before or during labor?

During labor, often from extending a deflexed head in an OP position.

In face presentation, which position is considered 'undeliverable' spontaneously?

Persistent Mento-Posterior (DMP).

What is the 'Prague technique'?

A method involving shoulder traction and flexion of the fetal neck by bringing the trunk toward the mother's abdomen to deliver the head as face to pubis.

What is the 'Gold Standard' for diagnosing fetal presentation during pregnancy?

Ultrasonography (US).

What is 'Chignon'?

An artificial caput succedaneum induced by ventouse (vacuum) delivery.

Why is the 2nd stage of labor longer with epidural anesthesia?

The Fergusson reflex is lost as stretch receptors become less sensitive, reducing the oxytocin response.

What is the engaging transverse diameter during asynclitism?

The subparietal-supraparietal diameter ($9\,cm$).