gynecology and obstetrics
Induction of Labor
Technique
If the cervix is closed, long, and firm (unfavorable), the goal is to cause the cervix to open and become effaced (favorable). Various pharmacologic or mechanical methods can be used. They include Misoprostol25 mcg vaginally every 2 to 4 hours or 25 to 50 mcg orally every 2 hours Prostaglandin E2 given intracervically (0.5 mg) or as an intravaginal pessary (10 mg [prostaglandins are contraindicated in women with prior cesarean delivery or uterine surgery because these drugs increase the risk of uterine rupture]) Oxytocinin low or high doses Use of laminaria and transcervical balloon catheters, which may be useful when other methods are ineffective or contraindications exist ( Technique reference ) Once the cervix is favorable, labor is induced. Constant IV infusion ofoxytocinis the most commonly used method; it is safe and cost-effective. Low-doseoxytocinis given at 0.5 to 2 milliunits/minute, increased by 1 to 2 milliunits/minute, usually every 15 to 60 minutes. High-doseoxytocinis given at 6 milliunits/minute, increased by 1 to 6 milliunits/minute every 15 to 40 minutes to a maximum of 40 milliunits/minute. With doses>40 milliunits/minute, excessive water retention may lead to water intoxication. Use ofoxytocinmust be supervised to prevent uterine tachysystole (> 5 contractions in 10 minutes averaged over 30 minutes), which may compromise the fetus. External Fetal Monitoring is routine; after amniotomy (deliberate rupture of the membranes), internal monitoring may be indicated if fetal status cannot be assessed externally. Amniotomy can be done to augment labor when the fetal head is applied to a favorable cervix and not ballotable (not floating). 