First Stage of Labor Flashcards
Define labor
regular, painful contractions that promote cervical change
Phase 1
quiescence = prelude to parturition.
Contractile unresponsiveness; cervical softening
What inhibits uterine contractions?
1) progesterone
2) prostacyclin
3) relaxin
4) nitric oxide
5) parathyroid hormone-related peptide
6) corticotropin-releasing placental lactogen
Phase 2
activation = preparation for labor
uterine preparedness for labor; cervical ripening
Define uterotropins
1) estrogen
2) prostaglandins
- stimulate upregulation of myometrial receptors for oxytocin and prostaglandins
- activate gap junctions b/w myometrial cells
Phase 3
stimulation = processes of labor
uterine contraction; cervical dilation; fetal and placental expulsion
includes 3 stages of labor
Define uterotonins
promote labor progression
1) prostaglandins
2) oxytocin
Phase 4
involution = parturient recovery
uterine involution; cervical repair; breastfeeding
What promotes involution?
1) oxytocin
2) thrombin
3) prostaglandin
1st clinical stage of labor
begins w/ true labor contractions –> ends with full dilation; comprised of 2 phases
What are the 2 phases of the first stage of clinical labor?
1) latent: contractions become more regular, painful, and frequent BUT little cervical dilation w/ little to no fetal descent
2) active: cervical dilation to completion
Describe receptor changes that stimulate labor
- progesterone binds more readily to PR-A (vs PR-B) –> quiescence ceases
- estrogen stimulates expression of prostaglandin and oxytocin receptors
- myometrial cells develop gap junctions that facilitate direct communication b/w muscle fibers
–> uterine contractions
Goodell’s sign
cervical softening ~4wks after LMP
Chadwick’s sign
increased cervical vascularity ~6wks after LMP (cervix and vaginal walls appear blue)
cervical ripening
rearrangement of collagen prior to and during labor –> become less dense
What are the 4 phases of cervical remodeling?
1) softening
2) ripening
3) dilation
4) postpartum repair
effacement
lengthening of muscle fibers at internal os –> stretches endocervix upward into lower uterine segment
dilation
widening of external os
What promotes dilation?
1) force of contractions
2) hydrostatic action of amniotic fluid
3) pressure of presenting part if ROM
What does passing of mucuos plug indicate?
likely labor w/in 48h
Describe internal rotation
OT/LOA/ROA –> direct OA
How long is the latent phase of the 1st clinical stage of labor?
<20h
What is considered prolonged latent phase?
nullips: >20h
multips: >14h
How dilated are people at the beginning of the active phase?
nullip: ~4cm
multip: ~5cm
How long does the active phase last?
nullip: ~4.4-4.9h w/ 1.2cm dilation/h
multip: ~2.2-2.4h w/ 1.5cm dilation/h
What are the 3 subphases of the active phase?
1) acceleration: little progress in dilation
2) maximum slope: 3.0cm/h (nullip); 5.7cm/h (multip)
3) deceleration: occurs b/w 8-10cm
How else may labor progression be identified beyond a cervical exam?
- fetal station and position
- maternal behavior
- contraction pattern
- s/sx of transition into second stage of labor
- change of location of back pain
- change in location of maximum intensity of FHT
- change in position of FHT
Define transition
change from first to second stage of labor; occurs typically b/w 8-10cm dilation
s/sx of transition
- lull in frequency/intensity of contractions
- presenting part induces maternal urge to bear down
- FHT progressively lower on maternal abdomen
- rectal/perineal bulging
- progressive visibility of fetal head at introitus
- increase in bloody show
premature rupture of membranes (PROM)
occurs >1h before onset of labor
preterm premature rupture of membranes (PPROM)
PROM before 37wks GA
artificial rupture of membranes (AROM)
AKA amniotomy
provider induced ROM
What is criteria for AROM?
1) cephalic presentation
2) engagement in pelvis (0 or +1 station)
What are risks associated w/ AROM?
- cord compression –> FHT deceleration
- cord prolapse
- maternal discomfort
- increased risk infection
- rupture of fetal vessels (RARE)
What is ACOG criteria for labor dystocia?
1) active labor (>/= 6cm)
2) adequate contractions (>/=200 Montevideo units)
3) ROM for at least 4h
What is the effect of labor on gastric emptying time?
prolonged, especially after administration of analgesics
When is fasting recommended?
6-8h before elective C/S or puerperal tubal ligation
How is the risk of gastric content aspiration mitigated?
- clear fluids b/w normal pushing; no solids
- antacids given routinely
- prepped for intubation w/ cricoid pressure
- employ regional anesthesia (vs general) when possible
When are antacids indicated during labor?
before general anesthesia (w/in 1h - give second dose if >1h and anesthesia not yet induced)
What is an example dose of antacids?
Bicitra (sodium citrate + citric acid) 30mL PO
others: nonparticulate antacid; H2-receptor antagonist; metoclopramide
What are indications for IVs during labor?
- potential or actual risk factors
- cannot tolerate PO fluids
- administration of rx (eg abx prophylaxis, analgesics, oxytocin) prior to epidural
What is a recommended IV administration?
isotonic fluids 125-250mL/h
What are indications for measuring I/Os?
- IV fluid administration
- pre-eclampsia/on magnesium = STRICT I/Os!
- concern for pt hydration status (eg dehydration, hyperemesis)
- post-C/S
- during active labor
How often should pt empty bladder during active labor?
q2h
What effect does a distended bladder have on first stage of labor?
- blocks fetal head from descending
- increases lower abdominal pain
What effect does a distended bladder have on second stage of labor?
inhibits contractility of uterine contractions
What effect does a distended bladder have on postpartum state?
- can increase PPH d/t uterine atony
- bladder hypotonicity, stasis, infection risk
What is the effect of labor on WBC count?
peaks –> 20x10^3/mm^3
What is the effect of labor on BP?
increases during contractions; returns to baseline in b/w
What is the effect of labor on cardiac output?
- increases by 10-15% in first stage
- increases up to 50% during second stage d/t increased stroke volume
How often should vitals be checked during labor?
BP, HR, RR: q1h
T: q2-4h w/ membranes intact; q1-2h if abnormal T or ROM
hypotonic uterus
- slow/stalled labor progress d/t acute stress (eg fatigue, pain)
- R/O malpresentation and CPD
hypertonic uterus
- series of contractions each lasting >2mins
OR
- contraction frequency of 5 or more in 10 mins
