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 3^rd 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

 

Labor Induction

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.