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New Methods of Intrapartum Management

LABOR STIMULATION

The stimulation of uterine contractions may be characterized as labor induction or labor augmentation. Induction of labor implies stimulation of uterine contractions in their prior absence, with or without ruptured fetal membranes. Labor induction may be elective or indicated. Elective induction of labor is defined as the initiation of labor solely for convenience. In general, elective induction is not recommended. Augmentation refers to stimulation of uterine contractions when spontaneous contractions have failed.

Common Indications for Labor Stimulation with Oxytocin

Induction

Postterm gestation

Hypertensive disease

Maternal medical problems (eg, diabetes mellitus, renal disease)

Fetal abnormalities (eg, growth restriction, isoimmunization)

Augmentation

Slow progress in labor secondary to uterine hypocontractility

Techniques for induction of labor may be divided into surgical or medical. Surgical techniques include stripping of membranes or amniotomy. Stripping of fetal membranes involves bluntly separating.

Once amniotomy is performed, the patient is committed to delivery. Induction of labor in a woman with a favorable cervix by amniotomy or a combination of amniotomy and oxytocin is widely accepted and used. Many obstetricians will perform amniotomy only after regular contractions are established.

The state of the cervix is related to the success of labor induction. A cervical scoring system designed by Bishop has been used by many to predict inducibility, with a score of 4 or less considered unfavorable. In a patient with an unfavorable cervix, many advocate the use of cervical-ripening agents, including extraovular catheters, osmotic dilators, prostaglandins (E1, E2, F2a), and locally applied hormones such as relaxin or estrogens. Prostaglandins have been shown to enhance cervical effacement and dilatation; increase the chance of successful induction; and reduce the time, dose, and need for intrapartum management.

Prostaglandin

Prostaglandin E2 (PGE2) and PGF2a are as effective as oxytocin for the induction of labor at term and even more effective in early and midpregnancy, when the uterus is more refractory to oxytocin. Prostaglandin E2 can be given intravaginally as suppositories or a gel. Side effects are few and include fever, vomiting, and diarrhea. There is a risk of uterine rupture when prostaglandins are used after 28 weeks of gestation.

Prostaglandin is the preferred agent for preinduction cervical ripening. Prostaglandin given for cervical ripening reduces the rates of failed induction, cesarean birth, and instrumental vaginal delivery.

Commercially available preparations are PGE2 gel preparations in doses of 0.5 mg and PGE2 vaginal suppositories. The gel preparations and the vaginal suppositories are used in clinical practice to ripen the cervix. Both intracervical and intravaginal instillations of PGE2 have been used to ripen the cervix. The dose of PGE2 gel given intracervically is usually 0.5 mg (range 0.25 to 1.0 mg), repeated in 6-12 hours if induction of labor is desired. The intravaginal dose is 3 mg (2.5-4 mg), repeated in 4-6 hours if labor is not initiated. With an unfavorable cervix (Bishop score of 3 or less), 0.5 mg of intracervical PGE2 is more effective than 4 mg of intravaginal PGE2. However, both routes are equally effective if the cervix is favorable.

Prostaglandin Ripening Agents

Agent

Dose

Route

Dinoprostone (prostaglandin F2)

0.5 mg in 2.5-mL gel

Intracervical

Dinoprostone

10 mg in suppository (0.3 mg/h)

Intravaginal

Prostaglandin E2

2 to 5-mg gel

Intravaginal

Misoprostol (prostaglandin El)

25 mcg

Intravaginal

Oxytocin

Oxytocin is the primary agent for labor induction. Factors affecting the dose response to oxytocin include cervical dilation, parity, and gestational age. Higher doses of oxytocin are generally required in a preterm nullipara with an unfavorable cervix. The goal of oxytocin administration is to effect uterine activity that is sufficient to produce cervical change and fetal descent while avoiding fetal distress.

INTRAPARTUM FETAL HEART RATE MONITORING

The goal of intrapartum FHR monitoring is to detect signs of fetal jeopardy in time to intervene before irreversible fetal damage occurs. Despite the liberal use of continuous electronic fetal monitoring and operative delivery, there has been no consistent decrease in the frequency of cerebral palsy.

Vaginal Breech Delivery

The rate of cesarean delivery for fetuses with intrapartum breech presentation exceeds 90%. Of the remaining 10%, some are delivered vaginally before cesarean delivery can be performed. Only a small percentage of patients elect to undergo a trial vaginal breech delivery.

External Cephalic Version

External cephalic version results a reduction in the incidence of both intrapartum breech presentation and cesarean delivery rate.

Shoulder Dystocia

Shoulder dystocia is defined as the inability to deliver the fetal shoulders with normal obstetric maneuvers after delivery of the fetal head. Typically, delivery of the fetal head is followed by retraction of the head onto the perineum (turtle sign) during spontaneous or instrumental vaginal delivery. This retraction occurs because the fetal shoulder girdle occupies an anteroposterior position.