Repro: Normal Labor And Delivery

Front 1

Parturition and Phases

Back 1

Partuirition - physiologic process of labor and bringing forth of young

Phase 0 - Quiescence - prelude to parturition - uterine quiescence is 95% of pregnancy. Smooth muscle contractions inhibited, unresponsive to stimuli. Cervical structure maintained with no dilation or thinning

Phase 1 - Preparation for Labor - uterine activation; last 6-8 weeks of pregnancy related to changes in OXYTOCIN RECEPTORS and increases contraction-associated proteins and gap proteins.
a) Cervical Changes - collagen breakdown, increased cytokine release, thinning, softening and relaxation. slight dilation
b) Myometrium changes - increased responsiveness to uterotonins, increased number of oxytocin receptors in myometrium related to painless, frequent uterine contractions ("fake labor" or Braxton Hicks contractions). Formation of lower uterine segment for fetal head

Phase 2 - Labor - 1st stage with latent phase of cervical dilation (2-8hr), Active phase is rapid. 2nd stage of delivery, 3rd stage of placenta delivery

Phase 3 - Puerperium - immediately after delivery, myometrial contraction to close large vessels and prevent post-partum hemorrhage; lactogenesis, uterine inovulation occurs over 4-6 weeks, reinstitution of ovulatoin if not nursing (prolactin inh.)

Front 2

Labor Process Theoretical Physioloigic Changes

Back 2

1) Retreat from pregnancy maintenance - withdrawal of progesterone can institute labor and giving progesterone injections can lengthen pregancy if preterm

2) Uterotonin induction of parturition

3) Fetus likely is source of initial signal - fetal DHEAS may induce more maternal estrogens, prostaglandins and oxytocin response

Uterine smooth muscle responds to Ca++ increase to contract, decreases relax. cAMP and cGMP may play a role, BUT research shows Ca++ channel blockers may lengthen pregnancy.

Oxytocin receptors increase 50x and oxytocin can induce pregnancy and prostaglandin release and helps prevent post partum hemorrhage

Front 3

Stages of Labor

Back 3

First Stage - onset of labor (painful, regular uterine contractions, cirvical dilation and effacement at full dilation of 10cm. Occurs in Latent phase 0-4cm over 8 hrs to 2 weeks and Active phase >4cm

Second Stage - From 10cm cervical dilation to delivery

Third Stage - Placenta delivery

Fourth Stage - Immediate 1-2hr postpartum - contraction of myometrium and lactogenesis initiation

Front 4

Dilation speed Nulliparous vs multiparous

Back 4

Nulliparous - 1.2cm/hr on average
Multiparous - 1.5cm/hr on average. FASTER

Front 5

Hormones needed at each stage of Labior

Back 5

Phase 0 - Quisence - progesterone, prostacyclin, relaxin, NO

Phase 1 - Activation - Estrogen, progesterone, uterine stretch

Phase 2 - Stimulation - prostaglandins, oxytocin

Phase 3 - Oxytocin

Front 6

Mechanism of Labor

Back 6

Movements have to take place in order for fetus to present normally and for mother to be able to push baby

Fetal occiput rotates anteriorly to just under pubic symphysis, allows fetal extension for delivery of fetal head, then baby undergoes restitution, external rotation to right or left depending on anterior shoulder. Restitution KEY to delivery of shoulders

Front 7

Management of Delivery

Back 7

Controlled delivery of head - as see fetal crowning, support perineum to allow controlled delivery, aspirate nose and mouth after delivery of head

One hand on either side of head, pull straight down to deliver anterior shoulder until it is visible under pubic symphysis. Then pull straight up to deliver posterior shoulder.

Gentle traction on cord while holding uterus in place allows placental delivery (3rd stage).

Front 8

Intrapartum Fetal Surveillance

Back 8

Internal and External Electronic Fetal Monitoring

External monitor - one transducer for fetal heart valves and one for uterine contractions. Tells when contractions occur and time but NOT STRENGTH. HR monitor only good for normal HR

Internal monitor - bipolar technology, fetal scalp electrode and second fluid electrode. EKG trace for fetal HR, R-R wave for baseline HR and variability. Used if can't distinguish maternal and fetal rhythms. Intrauterine Pressure Catheter tells strength of contractions

Front 9

Fetal HR variability in intrapartum fetal surveillance

Accelerations

15 x 15

Reactive Tracings

Decelerations

Decrease in FHR

Early verses Late

Back 9

Related to variations around baseline HR and needs baseline (internal monitor)

Flatline = BAD, need some variability or suggests fetal distress and hypoxemia

Acceleration = 15bpm up lasting at least 15 sec (15x15 RULE)

Reactive tracing - two accelerations within 20 min and suggests good fetal health

Decelerations - decrease below baseline. Categorized by time to nadir. Slow decline in fetal heart rate due to vagal n. stimulation due to head compression.

Early deceleratoin is OK and is >30 sec to nadir. Associated with uterine contractions (inverse). Should check on pts though

Late deceleration is bad b/c means FETAL HYPOXIA or ACIDEMIA. Not inversely associated with contraction

Variable decelerations - due to umbilical cord compression or nuchal cord compression. Can mean membrane ruptures, amniotic fluid loss, etc. re-position patient to eliminate or consider C-section

Front 10

Late deceleration with loss of variability

Back 10

IMMEDIATE C-section

Front 11

What usually causes fetal tachycardia

Back 11

meds or infection

Front 12

Abnormal Labor, evaluation of dystocia

Back 12

3 P's: Power, Passenger, Passage

Power - Strength, Duration, Frequency. Contractions can only report strength with IUPC. >200 MVU in 10 min window can proceed with labor, involves maternal effort

Passenger - Fetal weight >4000g can affect normal labor, head down or cephalic vertex presentation is ideal as is anterior occiput. Posterior occiput, breach and transverse may require C-section. Fetal anomalies (hydrocephalus, abdominal wall defects, spina bifida) can also affect

Passage - Bony passage (measure with pelvimetry), Soft tissue (distended bladder, stool in rectum, fibroids, ovarian masses). Anesthesia can inhibit cardinal movements if applied early by altering pelvic floor