PB#107: Induction of Labor Flashcards
Physiologic goal of cervical ripening
Facilitate process of cervical softening/thinning/dilating
Clinical goals of cervical ripening (2)
Reduction in rate of failed IOL, reduction in IOL-to-delivery time
Observed histologic changes during cervical ripening (4)
Collagen breakdown/rearrangement, changes in glycosaminoglycans, increased cytokine production, WBC infiltration
Bishop score signifying unfavorable cervix
6 or less
Bishop score signifying favorable cervix
8 or more
What a “favorable” cervix indicates
Probability of vaginal delivery after IOL is similar to spontaneous labor
Bishop score points for dilation
Closed = 0; 1-cm = 1; 3-4cm = 2, 5-6cm = 3
Bishop score points for position
Post = 0; mid = 1; ant = 2
Bishop score points for effacement
0-30% = 0; 40-50% = 1; 60-70% = 2; 80+% = 3
Bishop score points for station
-3 = 0; -2 = 1; -1–0 = 2; +1 or more = 3
Bishop score points for consistency
Firm = 0; med = 1; soft = 2
General categories for cervical ripening methods (3)
Mechanical dilators, synthetic PGE1, synthetic PGE2
Mechanical cervical ripening options (5)
Hygroscopic dilators, osmotic dilators (Laminaria japonicum), Foley catheters, double balloon devices, EASI balloon
Typical size and inflation volume of cervical Foley balloon
14-26F, 30-80mL
Routes of administration of miso (3); incremental dosages of miso
Vaginal, PO, sublingual; 25mcg increments
Is intrapartum miso exposure associated w/ long-term adverse fetal consequences?
No (in absence of fetal distress)
Available formulations and dosages of PGE2 (2)
2.5mL syringe containing 0.5mg dinoprostone gel, 10mg dinoprostone vaginal insert
Which formulation of PGE2 releases prostaglandins at a slower rate?
Insert (0.3mg/h) over gel
Effect of vaginal prostaglandins for cervical ripening compared to placebo or pit alone on time to delivery; effect on C/S rate; effect on tachysystole
Increase likelihood of delivery within 24h; do not reduce C/S rate; increase risk of tachysystole w/ associated FHR changes
Time from pit onset to uterine response; time of pit onset to steady level in plasma
3-5 mins; 40 mins
Changes in response to pit by gestational age
Gradual increase from 20-30wga, followed by plateau from 34wga until term, then further increase in sensitivity
Predictors for successful response to pit IOL (4)
Lower BMI, greater cervical dilation, higher parity, greater EGA
Cytokines increases associated w/ membrane stripping (2)
Increase in phospholipase A2 activity, increase in PGF2alpha levels
Clinical benefits of membrane stripping (2)
Increases likelihood of spontaneous labor within 48h, reduces incidence of IOL w/ other methods
Risk associated w/ membrane stripping
Increased risk of PROM
Disadvantage of AROM when used alone for IOL
Can be associated w/ unpredictable and sometimes long intervals before onset of ctxs
Only “natural” method for IOL
Nipple/Unilateral breast stim
Clinical advantage of nipple stim; caveat
Associated w/ significant decrease in pts not in labor at 72h; only in pts w/ favorable cervices
Percentage of pts doing nipple stim who experienced tachysystole w/ or w/o FHR changes
0%
Does nipple stim increase or decrease mec-stained fluid; C/S rates?
No change; no change
PP benefit of breast stim for IOL
Decrease in PPH rates
How to quantify ctxs
Number present in 10-min window, averaged over 30-min period
Normal ctx rate
5 or fewer ctxs in 10 mins, averaged over 30-min period
Tachysystole
> 5 ctxs in 10 mins, averaged over 30-min period
How to qualify tachysystole
Presence or absence of decels
Does tachysystole apply to spontaneous or stimulated labor, or both?
Both
Logistical reasons for IOL (3)
Risk of rapid labor, distance from hospital, psychosocial indications
Methods to confirm gestational age for logistical IOL (3)
US measurement at <20wga supports age of 39+wga, FHT documented as present for 30+ weeks, positive serum/urine hCG pregnancy test 36+ weeks ago
General contraindications to IOL
The same as for spontaneous labor