Induction of Labor
According to ACOG (The American College of Obstetricians and Gynecologists) "More than 22% of all gravid women undergo induction of labor in the United States." This number has more than doubled between 1990 and 2006. Inductions of labor can be elective (done by preference) or medically indicated.
Elective inductions
Timing
Although full-term is defined as 37 weeks to 41 weeks of gestation, we do not electively induce labor before 39 weeks by good dating criteria. This is because some babies between 37 and 39 weeks can have issues such as of hyperbilirubinemia (Jaundice), or trouble with temperature regulation. Additionally, by waiting until 39 weeks to induce labor, it builds in a margin of security if the dates are not what they seem. Finally, by waiting until 39 weeks weeks, it more likely that the patient will enter spontaneous labor by herself.
Dating
It is harder than most people appreciate to determine the exact dating of a pregnancy. If patient has a regular 28 day interval menstrual cycle, it is helpful. Early ultrasound definitely establishes accurate dating criteria. Most generally it is a combination of such things that enable us to accurately determine the length of the pregnancy. If we do not know with reasonable accuracy the gestational age of pregnancy then we cannot confidently proceed with elective inductions of labor.
Cervical favorability
Elective inductions or any inductions for that matter are best done in the presence of a favorable cervix. Well before labor, a cervix is closed thick and firm and the presenting part of the baby is high and not pressing down on the pelvis. Once the patient nears full-term the cervix normally begins to soften, thin (efface) and dilate. We use a scoring system called the Bishops score to determine cervical favorability. If the score is higher and the cervix is more favorable then the likelihood of successful induction is higher. Think about it this way: if the uterus is made to contract against a cervix which is closed and firm, the likelihood of it opening is less. If instead uterus is pushing against a soft partially open cervix, progress will be made much more quickly. The strength of the contractions needed to open a soft cervix is less, and that makes for a smaller chance of complications.
Indications for elective induction of labor
Most women do not request elective induction simply because they are TOBP or "tired of being pregnant". Indications that I have considered include the following:
Living far from hospital with concern for rapid progress
Spouse or relatives who are only in town for a limited period of time
Painful nuisances like varicose veins
Medically indicated inductions
Sometimes complications of pregnancy develop before labor does. In this case, inductions of labor can be indicated. If delivery is necessary, we always prefer to deliver vaginally, if it is safe, and thus we attempt induction .
Examples of maternal or fetal conditions that may be indications for induction of labor:
abruption (premature separation of the placenta)
chorioamnionitis
fetal demise
preeclampsia
premature rupture of membranes (PROM)
posterm, aka postdates pregnancy (being overdue )
maternal medical complications, e.g., diabetes, high blood pressure.
fetal complications, i.e. growth restriction of low fluid (oligohydramnios)
Methods of Induction
Not uncommonly when medical inductions are indicated, the cervix is not favorable. Methods of induction differ depending on whether the cervix is favorable or unfavorable. If the cervix is unfavorable, we say we have to " ripen " it. This means we use medicinal or mechanical methods to dilate, soften and thin it.
Methods of cervical ripening
A class of medicines call prostaglandins have been shown to ripen the cervix. Most notable of these is Misoprostol, or Cytotec. This is best given as a vaginal suppository at low dose, about every 4 hours as needed. The FDA (Food and Drug Administration) acknowledges its use as a cervical ripening agent though initially its purpose was prevention of peptic ulcers.
The safest and most effective method of mechanical cervical ripening is the use of a foley catheter into the cervix. A foley is commonly used to drain urine, but in this case a sterile foley is inserted into the opening of the cervix and it's balloon inflated.
Both these methods have been properly studied and show a high rate of effectiveness and a low rate of complications.
Induction with pitocin
Pitocin is the synthetic twin of oxytocin made by our own pituitary to start labor. It is given in the IV and produces a gradual increase in contractions. When we use pitocin, our goal is to mimic the gradual natural phases of labor and not to produce a faster or harder labor. It is a fallacy that induced labor is more painful than spontaneous labor.
Many labors begin with cervical ripening and continue with pitocin, once contractions are establish and the cervix begins to open. Artificial rupture of membranes may be performed at a strategic interval to help labor along.
Consent for induction of labor
Induction is a procedure, and as such, requires your informed consent. Induction, like any medical procedure, is not without risks. First of all, it may not work. If it does, it may take 2-3 days. Or, induction may be effective, but you may end up needing a C section for reasons unrelated to the induction. It is worth noting that inductions are associated, especially in those with an unfavorable cervix or medical complications, with a higher chance of C section, compared with spontaneous labor. Having said all this, the big picture is that most inductions are safe and effective.
Reference: Adapted from ACOG Practice Bulletin Number 107 August 2009