Normal Labor And Delivery Flashcards
What is labor?
Progressive cervical dilation resulting from regular uterine contractions that occur at least every 5 mins and last 30-60 seconds
What is false labor?
Braxton-Hicks contractions; irregular contractions without cervical change
What is the suboccipitobregmatic diameter?
9.5cm; head well flexed
What is the occipitofrontal diameter?
11cm; head deflexed; occiput posterior position
What is the supraoccipitomental diameter?
13.5cm; brow presentation; is the longest anterioposterior diameter of the head
What is the submentobregmatic diameter?
9.5cm; face presentations
What is the average circumference of a term fetal head measured in the occipitofrontal plane?
34.5cm
What are the difference pelvic shapes?
Gynecoid, android, anthropoid, platypelloid
What are the characteristics of a gynecoid pelvis shape?
Classic female type of pelvis; round at the inlet, wide transverse diameter and wide suprapubic arch
What are the characteristics of an android pelvis shape?
Classic male type of pelvis; widest transverse diameter closer to the sacrum, prominent ischial spines, narrow pubic arch; fetal head forces to be in OP position (restricts space and arrest of descent can occur)
What are the characteristics of an anthropoid pelvis shape?
Resembles ape pelvis (20% of females); much larger AP than transverse diameter, creates a long narrow oval shape, narrow pubic arch;
What are the characteristics of a platypelloid pelvis shape?
Described as flattened gynecoid pelvis; short AP and wide transverse diameter, wide bispinous diameter and suprapubic arch
Which pelvis shapes have a poor prognosis for delivery?
Platypelloid and android
Which pelvis shapes have a good prognosis for delivery?
Gynecoid and anthropoid
How is clinical pelvimetry assessed?
Diagonal conjugate, obstetric conjugate, palpate, measuring the ischial tuberosities and pubic arch, radiographically via MRI or CT
What is the diagonal conjugate?
Is approximated by measuring from the inferior portion of the pubic symphysis to the sacral promontory; if >11.5cm the AP diameter of pelvic inlet is adequate
What is the obstetric conjugate?
Estimated by subtracting 2cm from the diagonal conjugate; is the narrowest fixed distance thru which the fetal bead must pass thru during vaginal delivery
Which structures should be palpated when assessing clinical pelvimetry?
Anterior surface of the sacrum which is usually concave; ischial spines to assess prominence
How is the pelvic outlet assessed?
By measuring the ischial tuberosities (8.5cm distance is considered adequate transverse diameter) and pubic arch (>90 degrees infrapubic angle is good)
When should pelvimetry be assessed via MRI or CT?
If clinical or obstetrical hx suggestive of pelvic abnormalities or hx of pelvic trauma; rarely performed
What components are a part of the obstetric exam?
Fetal lie, fetal presentation, cervical exam
What is fetal lie?
Reference is maternal spine to fetus spine; determines if infant is longitudinal, transverse or oblique
What is fetal presentation?
Presenting part to the pelvis (vertex, breech, transverse or compound)
What is assessed during a cervical exam?
Dilation, effacement, station, position, consistency
What is the first Leopold maneuver?
Palpate the fundus; fetal head vs buttocks vs transverse position
What is the 2nd Leopold maneuver?
Palpate for spine and fetal small parts
What is the 3rd Leopold maneuver?
Palpate what is presenting in the pelvis with suprapubic palpation
What is the 4th Leopold maneuver?
Palpate for cephalic prominence; can feel chin or occipital protuberance if head is not deep in pelvis
How dilation assessed during a cervical exam?
Check at level of internal os; range from closed to completely dilated at 10cm
What is effacement?
Thinning of the cervix occurs and is reported as a % of change in length; normal cervical length is 3-5cm; range is thick to 100% effaced
What is the station component of a cervical exam?
Degree of descent of the presenting part of the fetus; measured in cm from presenting part to ischial spines; range -5 to +5cm
When is the station considered to be zero?
when the bony portion of the head reaches the level of the ischial spines
What is commonly used to calculate bishop score?
Consistency and position
What is the duration of the first stage of labor?
Primiparas typically 6-18 hours; multiparas typically 2-10 hours
What is the rate of cervical dilation for a female who is primiparas?*
1.2cm per hour
What is the rate of cervical dilation for a woman who is multiparas?
1.5cm per hour
What are the 7 cardinal movements of labor?
Engagement, descent, flexion, internal rotation, extension, external rotation and expulsion
What is engagement (1st cardinal movement)?
Defined as presenting part at zero station
What is descent (2nd cardinal movement)?
Brought about by the force of uterine contractions and maternal valsalva efforts
What is flexion (3rd cardinal movement)?
OA- baby’s chin to chest thus changing the presenting part from occipitofrontal to the smaller suboccipitobregmatic
What is internal rotation (4th cardinal movement)?
Occurs usually at the ischial spines; fetal head enters pelvis in transverse diameter, rotates so the occiput turns anteriorly or posteriorly toward the pubic symphysis
What is extension (5th cardinal movement)?
Crowning occurs when the largest diameter of the fetal head is encircled by the vaginal introitus; station is +5; head is born by rapid extension
What is external rotation (6th cardinal movement)?
The delivered head now returns to its original position at the time of engagement to align itself with the fetal back and shoulders
What is expulsion (7th cardinal movement)?
The anterior shoulder then delivers under the pubic symphysis followed by the posterior shoulder and the remainder of the body
What are the indications for an episiotomy?
Likelihood of spontaneous laceration seems high; to expedite delivery by enlarging the vaginal outlet
What are the features of a midline episiotomy?
Most commonly performed; greater risk of extension into 3rd or 4th degree; less postpartum pain
What are the features of a mediolateral episiotomy?
Greater blood loss, more difficult to repair, more postpartum pain and increased risk of dyspareunia
What is the modified Ritgen maneuver?
Fingers of the right hand are used to extend the head while counter pressure is applied to the occiput by the left hand to allow for a more controlled delivery; simple manual support to the perineum may be equally effective
What is a first degree perineal laceration?
A superficial laceration involving the vaginal mucosa and/or the perineal skin
What is a second degree perineal lacerations?
Laceration extending into the muscles of the perineal body but doesn’t involve the anal sphincter
What is a 3rd degree perineal laceration?
Laceration extends into or completely thru the anal sphincter but not into the rectal mucosa
What is a 4th degree perineal laceration?
Involves the rectal mucosa
If induction is indicated and cervix is unfavorable what can be done?
Agents for cervical ripening can be used
What is the goal of cervical ripening?
To facilitate the process of cervical softening, thinning and dilating in hopes to reduce the rate of failed inductions
What is the induction of labor?
The process by which labor is induced by artificial means
What is augmentation?
The artificial stimulation of labor which has already begun
What are some indications for induction?
Abruptio placentae, chorioamnionitis, fetal demise, preeclampsia/eclampsia, gestational HTN, PROM, post term pregnancy, fetal compromise
What are the contraindications to induction?
Unstable fetal presentation, acute fetal distress, placental previa or vasa previa, previous classical C section or transfundal uterine surgery (i.e. myomectomy) or any contraindications to vaginal delivery (HIV with high viral load, active genital HSV outbreak, etc)
What do uterine contractions and cervical dilation result in?
Visceral pain (T10-12 through L1)
Descent of fetal head and pressure from the pelvic floor, vagina and perineum generate somatic pain via which nerve?
The pudendal nerve (S2-4)
What is regional anesthesia?
Partial or complete loss of pain sensation below level of T10
How is dilation, effacement and station recorded?
Ex. 4/50/-2 (4cm dilated/50% effacement/-2cm station)
What are the benefits for amniotomy (AROM)?
Augment labor and allows assessment of meconium status
What are the risks associated with amniotomy (AROM)?
Cord prolapse, prolonged rupture is associated with chorioamnionitis
What are the goals for obstetric anesthesia?
To provide effective pain relief for mother during the course of labor and delivery that is safe for her and her baby
How does obstetric anesthesia affect uterine blood flow?
Regional anesthesia may decrease uterine blood flow if hypotension occurs and is not promptly treated; adequate hydration prior may mitigate the risk for hypotension (if it does occur can give vasopressor)
