Induction: Indication & Methods

Question 1

What is induction?

Answer 1

• stimulation of uterine contractions to accomplish delivery PRIOR to the onset of spontaneous labor.

Question 2

What is augmentation?

Answer 2

• treatment of abnormal labor (i.e. contractions/labor is present).

Question 3

What are the indications for induction?

Answer 3

• OBSTETRICAL and MEDICAL induction= delivery before the onset of labor is indicated, when the maternal/fetal risks associated with continuing the pregnancy are thought to be greater than the maternal/fetal risks associated with an early delivery.
• ELECTIVE at term= induction at patient request (no longer before 39 weeks).

Question 4

What are the obstetrical and medical indications?

Answer 4

• post-term pregnancy
• premature rupture of membranes (PROM)
• preeclampsia, eclampsia, HELLP syndrome
• fetal demise
• maternal diabetes
• fetal growth restriction
• twins
• abruptio placentae

Question 5

What are the contraindications of induction?

Answer 5

• prior high risk cesarean incision.
• prior uterine rupture
• prior transmural uterine incision entering the uterine cavity.
• active genital herpes infection.
• placenta previa or vasa previa
• umbilical cord prolapse or persistent funic presentation
• transverse fetal lie
• invasive cervical cancer
• category III fetal heart rate tracing

Question 6

What is the problem with elective induction at term?

Answer 6

• COST to health care! EXPENSIVE

Question 7

What things must we assess when considering induction?

Answer 7

• gestational age (at least 39 weeks)
• fetal weight (4500 g in DM or 5000 g in non-diabetic moms).
• presentation (vasa previa…)
• cervical assessment
• fetal heart rate pattern
• review of pregnancy and medical hx

Question 8

How do we confirm term gestation?

Answer 8

• US at less than 20 weeks gestation supports gestational age of 39 weeks or greater.
• fetal heart tones present for 30 weeks by doppler US.
• it has been 36 weeks since a positive serum or urine hCG result

Question 9

What criteria must be met to confirm gestational date with US?

Answer 9

• consistent if within 5 days by crown-rump length (CRL) if obtained at 6-14 weeks (1st trimester).
• within 7 days if obtained at 14-20 weeks gestation (2nd trimester)

Question 10

Does mean diameter of gestational sac help in determining gestational age?

Answer 10

NO

Question 11

*** What is the gestational week terminology for preterm, term or post term?

Answer 11

• preterm= 20-37 weeks
• term= 39- 41 weeks (BEST TIME TO DELIVER)
• post term= after 41 and 6/7 weeks

Question 12

*** What is late preterm?

Answer 12

• 34-37 weeks

Question 13

*** What is early term?

Answer 13

• 37-39 weeks

* we don’t encourage early labor induction here anymore.

Question 14

How much does fetal brain cortex volume increase between 34 and 40 weeks gestation?

Answer 14

50%

Question 15

Must the cervix be ripened before we induce labor?

Answer 15

YES

Question 16

How do we know if the cervix is ripened?

Answer 16

Bishop scoring system:

• dilation
• effacement
• station (where the leading edge of skull is located in relation to the ischial spines).
• cervical consistency
• position of cervix
• based on -3 to +3 scale

Question 17

What is considered a good score to induce labor using the Bishop scoring system?

Answer 17

• 5 or higher

Question 18

What are some home remedies for induction?

Answer 18

• castor oil
• black cohosh
• pirmrose oil
• acupuncture
• sex
• walking

Question 19

What happens with cervical ripening?

Answer 19

• collagen breakdown leading to weaker and softer stroma.

- increase in prostaglandins

Question 20

What prostaglandins are used for cervical ripening?

Answer 20

• Misoprostol (prostaglandin E1)= not FDA approved for labor induction or cervical ripening, but CHEAP.
• higher rate of vaginal delivery w/o need for oxytocin.
• Cerividil and Prepidil (prostaglandin E2)= more expensive
• higher rate of need for oxytocin and tachysytole.

Question 21

What are 2 mechanical methods for cervical ripening?

Answer 21

1. cook catheter
2. foley catheter
   * low cost, removable, and easy to use, but possible risk of infection.

Question 22

If we already have a ripe cervix, how then can we proceed with induction?

Answer 22

• oxytocin
• membrane stripping
• amniotomy
• prostaglandins

Question 23

What are the 2 protocols for oxytocin use?

Answer 23

• LOW DOSE protocol= start at 1-2 munits/min and increase by 1-2 munits/min every 115-40 minutes.
• HIGH DOSE protocol= start at 6 munits/min and increase by 3-6 munits/min every 15-40 minutes (not done as much).
• remember this is given at a rate to mimic the pulsatile fashion of the pituitary. Reaches steady state at 40 mins and half-life is 1-6 mins (don’t exceed 40 munits/ml).

Question 24

What are the advantages of oxytocin?

Answer 24

• cheap, easy to titrate, easily reversible (since it has a short half life) and it is bioidentical to natural oxytocin in the body.

Question 25

What are some disadvantages of oxytocin?

Answer 25

- one of the most potent uterotonic agents known. - uterine tachysystole/hyperstimulation - uterine rupture - amniotic fluid embolism - hyponatremia, pulmonary edema and generalized edema (due to similarity to ADH/vasopressin).