Induction of labor is the chemical or mechanical initiation of uterine contractions before their spontaneous onset for the purpose of bringing about birth. Chemical, mechanical, physical, and alternative methods are used to induce labor. IV oxytocin (Pitocin) and amniotomy are the most common methods.

Labor may be induced for indicated reasons, including:

• Risk of continuing the pregnancy becomes more dangerous for either the mother or the fetus

• No contraindications for artificial rupture of the membranes (amniotomy)

• No contraindication for augmenting uterine contractions with oxytocin

Elective induction is when labor is initiated without a medical indication. To prevent iatrogenic prematurity, elective induction of labor should not be initiated until the woman reaches at least 39 completed weeks to ensure adequate fetal lung maturity.  

Oxytocin is a hormone normally produced by the posterior pituitary gland. It stimulates uterine contractions and aids in milk ejection (let-down).  Synthetic oxytocin (Pitocin) may be used either to induce labor or to augment labor. However, it can present hazards to the mother and fetus. The goal of oxytocin use is to produce contractions of normal intensity, duration, and frequency using the lowest dose of medication possible.  

Oxytocin is given intravenously and begins at a small dose, increasing every 15-30 minutes until labor is occurring.  Typical dosing involves:

• Starting dose of 1-2mu/min, increasing by 1-2 mu/min every 15 minutes to a maximum of 20mu/min

Some physicians advocate active management of labor-augmentation to establish efficient labor with the aggressive use of oxytocin so that the woman gives birth within 12 hours of admission to the labor unit.  This involves:

• Starting dose of 4-6 mu/min, increaing by 6mu/min every 15 minutes to a maximum of 36mu/min

Maternal hazards of any uterotonic medication include:

• Placental abruption

• Uterine rupture

• Unnecessary cesarean birth because of abnormal FHR and pattern

• Postpartum hemorrhage

• Infection

Caution and Interventions While Caring for Women With Tachysystole due to Medications

Uterine Tachysystole with Oxytocin (Pitocin) Infusion

Signs of uterine tachysystole include:

• More than five contractions in 10 minutes or

• A series of single contractions lasting greater than 2 minutes or

• Contractions of normal duration occurring within 1 minute of each other.

Interventions (with normal [category I] FHR tracing):

• Reposition or maintain woman in side-lying position (either side).

• Administer IV fluid bolus with 500 ml of lactated Ringers solution.

• If uterine activity has not returned to normal after 10 min, decrease the oxytocin dose by at least half.

• If uterine activity has not returned to normal after another 10 min, discontinue the oxytocin infusion until fewer than five contractions occur in 10 min.

Interventions (with indeterminate [category Ⅱ] or abnormal [category Ⅲ] FHR tracing):

• Discontinue oxytocin infusion immediately.

• Reposition or maintain woman in side-lying position (either side).

• Administer IV fluid bolus with 500 ml of lactated Ringers solution.

• Consider giving oxygen at 10 L/min via nonrebreather face mask if the above interventions do not resolve the indeterminate or abnormal (category Ⅱ or category Ⅲ) FHR tracing.

• If still no response, consider giving 0.25 mg terbutaline subcutaneously according to unit protocol or standing orders.

• Notify obstetric health care provider of actions taken and maternal and fetal response.

Resumption of oxytocin after resolution of tachysystole:

• If the oxytocin infusion has been discontinued for less than 20–30 min, resume at no more than one-half the rate that caused the tachysystole.

• If the oxytocin infusion has been discontinued for more than 30–40 min, resume at the initial starting dose.

Amniotomy

Amniotomy (the artificial rupture of membranes, or AROM) can be used to induce labor when the condition of the cervix is favorable (ripe) or to augment labor if progress begins to slow. Labor usually begins within 12 hours of AROM.