Medication Summary
A protocol called active management of labor can be applied to nulliparous women with singleton cephalic presentations at term. This method involves the use of high-dose oxytocin, with a starting rate of 6 mU/min and increasing by 6 mU/min every 15 min to a maximum of 42 mU/min. This is in contrast to the most common oxytocin algorithms used in hospitals in the United States, which typically involve increasing the oxytocin dose 1-2 mU/min every 30-40 minutes. Either way, the goal is to have no more than 7 uterine contractions per 15 min. Under this higher dose protocol, cesarean delivery is performed if vaginal delivery has not occurred or is not imminent 12 hours after admission or for fetal compromise. Initially, cesarean delivery rates were quoted at 4.8%, but it has since doubled, which is attributed to widespread use of epidural anesthesia. Other studies using the active management protocol describe cesarean delivery rates similar to that of the low-dose protocol. Randomized clinical trials have shown that the high-dose oxytocin regimens result in shorter labors than low-dose regimens without adverse effects for the fetus. [31]
A study by Brüggemann et al in term nulliparous women found that the rate of cesarean section was highest in women with labor dystocia that required initiation of oxytocin at 5 cm or less of cervical dilatation. The researchers suggest that oxytocin augmentation before 6 cm of cervical dilatation may fail to reduce the need for cesarean section. [32]
Dinoprostone and misoprostol are prostaglandin analogs used to stimulate cervical dilation and uterine contractions; they are pharmacologic alternatives to using laminaria or placing a Foley bulb in the cervix. Using prostaglandin analogs with a scarred uterus (eg, from prior cesarean or myomectomy) for labor induction is absolutely contraindicated due to the significant risk for uterine rupture.
A randomized clinical trial testing the safety and efficacy of prostaglandin E2 (PgE2) as a treatment for dystocia in spontaneous labor revealed that a single 1-mg dose of PgE2 vaginal gel is more effective than placebo in resolving dystocia without increasing uterine hyperstimulation, but it may be associated with an increase in the incidence of second stage cesarean delivery. [33]
Oxytocics
Class Summary
Oxytocin is the only US Food and Drug Administration (FDA)–approved medication recommended for labor augmentation. Other options include dinoprostone and misoprostol.
Oxytocin (Pitocin)
Produces rhythmic uterine contractions and can stimulate the gravid uterus. Has vasopressive and antidiuretic effects. Can also control postpartum bleeding or hemorrhage. Has a half-life of 3-5 min, and reaches steady state in approximately 40 min.
Beta-adrenergic blocking agents
Class Summary
Another option for abnormal labor secondary to inadequate uterine contractility is a beta-blocker.
Propranolol (Inderal)
Nonselective beta-adrenergic receptor blocker.
-
Labor curve for nulliparas.
-
Labor curve for nulliparas versus multiparas.
-
Abnormal labor curve.
-
Average labor curves by parity in singleton term pregnancies with spontaneous onset of labor. Reprinted from Seminars in Perinatology, Vol 36(5), El-Sayed YY, Diagnosis and Management of Arrest Disorders: Duration to Wait, pgs 374-8, Oct 2012, with permission from Elsevier.
-
The 95th percentiles of cumulative duration of labor from admission among singleton term nulliparous women with spontaneous onset of labor, vaginal delivery, and normal neonatal outcomes. Reprinted from Seminars in Perinatology, Vol 36(5), El-Sayed YY, Diagnosis and Management of Arrest Disorders: Duration to Wait, pgs 374-8, Oct 2012, with permission from Elsevier.
Tables
Indication |
Nullipara |
Multipara |
Prolonged latent phase |
>20 h |
>14 h |
Average second stage |
50 min |
20 min |
Prolonged second stage without (with) epidural |
>2 h (>3 h) |
>1 h (>2 h) |
Protracted dilation |
< 1.2 cm/h |
< 1.5 cm/h |
Protracted descent |
< 1 cm/h |
< 2 cm/h |
Arrest of dilation* |
>2 h |
>2 h |
Arrest of descent* |
>2 h |
>1 h |
Prolonged third stage |
>30 min |
>30 min |
*Adequate contractions >200 Montevideo units [MVU] per 10 minutes for 2 hours. (Please refer to the Pathophysiology for information regarding adequate contractions.) |
||
