Induction of Labor Quick Facts PB107
Cervical Ripening – facilitate cervical softening/thinning to reduce the rate of failed induction (causes collagen breakdown/reorganization, changes in glycosaminoglycans, increased cytokine production, WBC infiltration…i.e. cervical remodeling)
1. Mechanical: hygroscopic dilators, osmotic dilators (laminaria), Foley catheters with 30-80 cc, double-balloon devices…associated with decreased C/S rate when compared to oxytocin alone, increase likelihood of delivery w/in 24 hours, lower risk of tachysystole compared to PGEs *can be safely used outpatient in appropriately selected pts
a. Hygroscopic dilators & laminaria: increased infections
b. Balloons: displacement of presenting part, bleeding, ROM, febrile morbidity (adding Oxytocin doesn’t further shorten labor, what about adding prostaglandin?)
2. Pharmacologic: prostaglandin E1 (Misoprostol tablets) or E2 (Dinoprostone, either gel or vaginal insert)…NOT associated with decreased C/S rate when compared to oxytocin alone, increase likelihood of delivery w/in 24 hours, increase risk of tachysystole (as well as uterine rupture in 3rd trimester in pts with h/o C/S or myomectomy, so don’t use)
*patient should remain recumbent for 30+ minutes, continuous EFM for 0.5-2 hours and longer if patient is having regular uterine contractions
a. Misoprostol: 25 mcg vaginally every 3-6h, wait 4h after last dose to start Pitocin
b. Dinoprostone (insert): 0.5 mg every 6-12h (max 1.5 mg over 24h period), wait 30-60 minutes after removal to start Pitocin
1. Prostaglandins – Vaginal misoprostol is the most efficient prior to 28 weeks.
2. Oxytocin – onset w/in 3-5 minutes and steady state w/in 40 minutes, gradual increase in receptor sensitivity from 20-34 weeks -> plateau from 34 weeks until term -> then further increase, predictors of success = BMI, dilation, parity, GA
a. Low-dose: start at 0.5-2 mU/min, increase by 1-2 mU/min every 15-40 minutes
b. High-dose: start at 6 mU/min, increase by 306 mU/min every 15-40 minutes
c. NO maximum dose established! (hypotension/hyponatremia with rapid infusions)
3. Amniotomy – insufficient evidence to support amniotomy alone for IOL, adding AROM to Pitocin shortens induction-to-delivery interval, no evidence to guide timing in GBS+ mothers
4. Nipple stimulation – useful in women with favorable cervices, decreases PPH risk, trend towards increased perinatal death when unmonitored
5. Membrane stripping – increases phospholipase A2 and prostaglandin F2-alpha, increases likelihood of delivery w/in 48 hours & decreases likelihood of requiring other induction methods, may or may not increase risk of PROM, insufficient data re: use in GBS+ mothers
Indications for Induction: abruption, chorio, fetal demise, gHTN, cHTN, PreE, PROM, post-term pregnancy, DM, renal disease, pulmonary disease, APLS, growth restriction, isoimmunization, oligo, etc. (logistic reasons - risk of rapid labor, distance from hospital, psychosocial issues - are also acceptable) *success rate similar to spontaneous labor if Bishop score 8+
- Must confirm term gestation if IOL being done for logistic/psychosocial reasons
o Ultrasound prior to 20 weeks supports GA >39 weeks
o FHTs have been present for 30+ weeks
o It has been 36+ weeks since +UPT/SPT
- Must discuss risks of induction
o In primigravidas with unfavorable cervix, there is a 2-fold increase in C/S rate
o Labor progress/curve will be slower
- Special cases
o PROM: Oxytocin reduced interval between ROM and delivery, reduced chorio, reduced post-partum febrile morbility, reduced neonatal antibiotics…no increase in C/S. Can also use prostaglandins. Insufficient evidence re: mechanical dilators.
o IUFD: Before 28 weeks, vaginal misoprostol 200-400 mcg q4-12h is preferred (even in women with h/o C/S), but high-dose Pitocin is also acceptable. After 28 weeks, management is based on Bishop score (use Foley if cervical ripening is needed and patient has a h/o C/S).
Contraindications to Induction: previa, transverse lie, cord prolapse, prior classical C/S or myomectomy that entered the cavity, active HSV, etc.