This document discusses cervical ripening and labor induction. It provides indications and contraindications for labor induction, as well as factors that predict success. Methods for cervical ripening include prostaglandins and mechanical/alternative methods. Oxytocin and prostaglandins like misoprostol are common agents for labor induction, but they carry risks like uterine hyperstimulation and abnormal fetal heart rate patterns. Careful dosing and monitoring are important when inducing labor.

1. Getting Things Started… Cervical Ripening and Labor Induction Jennifer Frank MD Fox Valley FMR Program

2. The best teachers… Are our patients. Case 1: 36 yo G2P1 at 39 weeks for social induction. VBAC Cytotec for cervical ripening Case 2: 29 yo G1 at 40 +2 weeks for social induction Cytotec for cervical ripening

3. Take home points (or learning objectives) Cervical ripening, labor induction, and labor augmentation carry risks that are potentially serious to mom and baby and must be weighed by the potential benefit. There is good evidence to direct the safe use of cervical ripening agents and agents used for labor induction and labor augmentation. There are clinical indications when labor induction (+/- cervical ripening) is appropriate.

4. Indications for Labor Induction Maternal and fetal indications Placental abruption Chorioamnionitis Fetal demise Gestational hypertension, preeclampsia, eclampsia Premature ROM Postterm pregnancy Maternal medical indications Fetal compromise (e.g. IUGR)

5. Indications for Induction Other types of indications Risk of rapid labor Distance from hospital Psychosocial indications ACOG Practice Guideline No. 10. Induction of labor.

6. Contraindications to Labor Induction Vasa previa Complete placenta previa Transverse fetal lie Umbilical cord prolapse Previous transfundal uterine surgery ACOG Practice Guideline No. 10. Induction of labor.

7. Additional Contraindications Absolute Pelvic structural abnormality Active genital herpes infection Invasive cervical cancer Relative Abnormal FHT Breech presentation Maternal heart disease Multifetal pregnancy Polyhydramnios Presenting part above pelvic inlet Severe maternal hypertension Harman JH, Kim A. Current trends in cervical ripening and labor induction. AFP 1999;60:477-84.

8. Successful Labor Induction Different definitions of success Achieve vaginal delivery in specified time (12-24 hours) Achieve active labor within a specified time Achieve active labor

9. Factors Predicting Success Cervical status Traditional Bishop score > 9 Favorable score varies from > 5 to > 8 Inverse relationship b/w cervical score and length of latent phase of labor Increased risk of cesarean delivery with “unfavorable” cervix (generally < 5) Crane JM. Factors predicting labor induction success: A critical analysis 2006; Clin Obstet Gynecol 49;573-84.

10. Maternal Factors Maternal characteristics Parity Variable evidence for the weight this has on predicting delivery within 24 hours Height Association between taller women and increased chance of vaginal delivery within 12-24 hours of starting labor induction Weight Lower weight – more likely to be successful Age Younger women are more likely to be successful

11. Fetal Factors Higher birth weights (>3.5 kg) associated with increased risk for failed induction (lower rate of vaginal delivery within 24 hours) Increasing gestational age associate with increased likelihood of labor induction success

12. Fetal maturity Criteria for establishing fetal maturity Fetal heart tones documented for at least 20 weeks by nonelectronic fetoscope or for 30 weeks by Doppler At least 36 weeks since a positive HCG (serum or urine) At least 39 weeks' gestation based on crown-rump length performed at 6–11 weeks' gestation At least 39 weeks' gestation based on ultrasound measurement at 12–20 weeks' gestation Sanchez-Ramos L. Induction of labor. Obstet Gynecol Clin North Am - 01-JUN-2005; 32(2): 181-200, viii

13. Cervical Ripening Softening, effacement, dilation preceding active labor Prostaglandins play an unknown role in mediating cervical ripening When is it needed? “Unripe cervix” based on cervical score (usually < 6 on Bishop score)

14. Bishop score ___ Soft Med Firm Consistency ___ Anter Mid Post Position +1 to +2 -1 or 0 -2 -3 Station 80 60-70 40-50 0-30 Effacement (%) 5-6 3-4 1-2 0 Dilation 3 2 1 0 Factor

15. Assessing Cervix TVUS More objective Not superior to Bishop score in meta-analysis Fetal fibronectin May bind placenta and membranes to decidua Presence associated with preterm birth Not superior to Bishop score Insulin-like growth factor binding protein-1 Synthesized by maternal decidua, may be released with cervical ripening and fetal membrane separating from decidua May indicate cervical “ripeness”

16. Methods of cervical ripening Low dose oxytocin < 4 mU/minute Dinoprostone (PGE 2 ) Intravaginal or intracervical FDA approved for cervical ripening Pt needs to be recumbent for 30 minutes and should be monitored for 1-4 hours Onset of contractions usu. within 1 st hour, peak at 4 hours

17. Methods of cervical ripening continued Misoprostol: PGE 1 Not FDA approved for this indication Oral or vaginal administration* 3x systemic bioavailability of vaginal vs. oral As or more effective than other methods Increased risk of tachysystole Has not equated with worse overall outcomes Hyperstimulation occurs in 1-10% of patients Cheaper and more convenient Recommend informed consent

18. Nonpharmacologic methods for cervical ripening Stripping or sweeping the membranes Causes an increase in prostaglandins Insert finger through internal cervical os and move in a circular direction to detach the inferior part of the membranes from the lower uterine segment Risks: infection, bleeding, accidental amniotomy, discomfort Alone is not effective but may reduce dose of oxytocin needed Important note: Strippingmembranes.com is for sale

19. Nonpharmacologic methods for cervical ripening continued Mechanical dilators – local pressure stimulating release of prostaglandins and dilating cervix Hygroscopic (osmotic) dilators Balloon devices (Foley bulb) Method & materials Effective for cervical ripening (compared to misoprostol, PGE 2 ) Amniotomy Increases production/release of prostaglandins Evidence does not support use for labor induction

20. Alternative methods for cervical ripening Evening primrose oil, Black Haw, Black and blue cohosh, red raspberry leaves All have uncertain role Castor oil, hot baths, enemas No evidence to support use Sexual intercourse – stimulation of oxytocin release and prostaglandins Uncertain role, but fun to try. Breast stimulation May be helpful but no good evidence Acupuncture/transcutaneous nerve stimulation May have benefit, need better studies Tenore, JL. Methods for cervical ripening and induction of labor. AFP 2003.

21. Labor Induction Stimulating uterine contractions to promote delivery prior to the onset of spontaneous active labor Rate is > 20% and increasing Most common indication is postterm pregnancy

22. Risks of Labor Induction Operative vaginal delivery Cesarean delivery Excessive uterine activity with abnormal FHR patterns (uterine hyperstimulation) Delivery of preterm infant

23. Labor Induction - ACOG PGE analogues are effective for both cervical ripening and labor induction (Level A) Cytotec at doses of 25 micrograms every 3-6 hours are effective for cervical ripening and labor induction (Level A) With term PROM, may induce labor with prostaglandins (Level A) Increased complications with doses of cytotec > 50 mcg (Level B) Avoid cytotec in VBAC (Level B)

24. Methods of Labor Induction Oxytocin Oxytocin receptors in the uterus increase starting at 32 weeks IV administration of solution of 10 Units to 1 Liter of isotonic solution = 10 mU/1mL Continuous infusion vs. pulsed dosing Continuous usually start at 0.5 to 2.5 mU/min increased by same increment every 15-60 minutes Effect within 3-5 minutes, steady state by 15-30 min. No clearly superior regimen – great variability in response

25. Methods of Labor Induction PGE 1 PGE 2 Oxytocin

26. Oxytocin continued Oxytocin is good… It is potent May titrate Short half-life Well tolerated

27. Oxytocin for labor induction Low-dose Start at 0.5-2 mU/min Increase by 1-2 mU/min every 15-40 minutes High-dose Start at 6-8 mU/min Increase by 6 mU/min every 15-40 minutes High-dose results in shorter labor, decreased intra-amniotic infections, and decreased rates of c/section for dystocia but higher risk of hyperstimulation Sanchez-Ramos L. Induction of labor. Obstet Gynecol Clin North Am - 01-JUN-2005; 32(2): 181-200, viii

28. Dosing of Oxytocin Commonly accepted practice is to increase by 1-2 mU/min every 40 minutes May optimize pharmacokinetics by not increasing dose before steady-state is reached Lower risk of hyperstimulation May result in longer labor for oxytocin-insensitive women May result in lower overall dose of oxytocin required Usual dose More than 90% of women will respond to 16 mU/min or less Rare for women to require 20-40 mU/min

29. Potential Risks Stripping membranes Bleeding from undiagnosed placenta previa or low-lying placenta Accidental amniotomy Nipple stimulation Uterine hyperactivity FHR decels Amniotomy Unpredictable length of time until onset of contractions Cord prolapse Chorioamnionitis Cord compression Vasa previa rupture Laminaria Increased maternal/fetal infections ACOG Practice Guideline No. 10. Induction of labor.

30. Potential Risks cont’d Misoprostol (cytotec) Tachysystole, hyperstimulation Uterine rupture Increase in meconium staining of AF Abnl FHR tracing Likely dose and route dependent Intravaginal/intracervical PGE 2 1-5% rate of uterine hyperstimulation Fever, vomiting, diarrhea Uterine rupture secondary to hyperstimulation Oxytocin Dose related Hyperstimulation FHR decels Placental abruption/uterine rupture secondary to hyperstim Water intoxication Antidiuretic effect and hypotension with large/rapid IV administration ACOG Practice Guideline No. 10. Induction of labor.

31. Questions & Comments

32. References ACOG Practice Bulletin No 10 Induction of Labor, 1999. Crane JM. Factors predicting labor induction success: A critical analysis 2006; Clin Obstet Gynecol 49;573-84. Harman JH, Kim A. Current trends in cervical ripening and labor induction. AFP 1999;60:477-84. Tenore JL. Methods for cervical ripening and induction of labor. AFP 2003;67:2123-8. Weeks A. Oral misoprostol administration for labor induction. Clin Obstet Gynecol 2006;49:658-71.