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Abnormalities or difficulties in pregnancy or during labor and delivery can necessitate alternative delivery methods.
Forceps
Delivery and Vacuum Extraction
Forceps
and vacuum extractors are devices applied to the fetal head to extract
the fetus through the birth canal.
Forceps delivery and vacuum extraction have essentially the same indications. Choice depends largely on user preference. Either procedure may be indicated when the 2nd stage of labor (from full cervical dilation until delivery of the fetus) is prolonged—eg, when the woman is exhausted or when epidural anesthesia prevents her from bearing down adequately. Other indications include fetal distress and some abnormal fetal presentations. These procedures are used when the station of the fetal head is low (≥ +2 cm); then, minimal force or rotation is required to deliver the head.
Contraindications for both procedures include a fetal head larger than the pelvic opening, incomplete dilation of the cervix, absence of engagement, and indeterminate fetal presentation or position. Major complications are maternal and fetal injuries, particularly if the operator is inexperienced.
Induction
of Labor
Induction
of labor is stimulation of uterine contractions, usually with oxytocin.
Indications:
Induction of labor can be medically indicated (eg, for preeclampsia or eclampsia) or elective (to determine when delivery occurs). Before elective induction, fetal lung maturity must be assessed; if gestational age is < 39 wk, amniocentesis is done to determine lecithin/sphingomyelin ratio or other indexes of fetal lung maturity. Contraindications to induction include fundal uterine surgery, prior classical cesarean section, and hypertonic uterine dysfunction. Multiple prior uterine scars are a relative contraindication.
Technique:
If the cervix is closed, long, and firm (unfavorable), drugs are given to cause the cervix to open and become effaced (favorable). Misoprostol 25 μg vaginally q 4 to 6 h may be effective. Contraindications to misoprostol include prior uterine surgery and cesarean section. Alternatives include prostaglandin E2 given intracervically (0.5 mg) or as an intravaginal pessary (10 mg).
Once the cervix is favorable, labor is induced. Constant IV infusion of oxytocin is the safest, most effective method. Dose is 0.5 to 2 milliunits/min, increased by 0.5 to 2 milliunits q 15 to 30 min as needed to ensure strong contractions; uncommonly, > 20 milliunits/min is needed. With higher doses (> 40 milliunits/min), excessive water retention may occur. Use of oxytocin must be supervised to prevent hypertonic uterine contractions, which may compromise the fetus. External fetal monitoring is routine, and internal monitoring may begin as soon as the membranes can be safely ruptured—usually, when the cervix is dilated 2 cm and the vertex is engaged.
Cesarean
Section
Cesarean
section is delivery by incision into the uterus.
About 15 to 25% of deliveries in the US are by cesarean section. This rate varies significantly between practices (and is much lower in most other countries). (See also the American College of Obstetricians and Gynecologists practice guideline Vaginal
birth after previous cesarean delivery.)
Indications:
Although morbidity and mortality rates of cesarean section are low, they are still several times higher than those of vaginal delivery; thus, cesarean section should be done only when it is safer for the woman or fetus than vaginal delivery. The most common specific indications are previous cesarean section, protracted labor, fetal dystocia (particularly breech presentation), and a nonreassuring fetal heart rate, which requires rapid delivery.
Many women are interested in elective cesarean section on demand. The rationale includes avoiding damage to the pelvic floor (and subsequent incontinence) and serious intrapartum fetal complications. However, such use is controversial and requires discussion between the woman and her physician. Many cesarean sections are done in women with previous cesarean sections because, for them, vaginal delivery increases risk of uterine rupture; however, risk of rupture with vaginal delivery is only about 1% overall (risk is higher for women who have had multiple cesarean sections or a vertical incision). Vaginal birth is successful in almost 75% of women who have had a single prior cesarean section and should be offered to those who have had a single prior cesarean section by lower uterine transverse incision. (The United Kingdom's National Institute for Clinical Excellence provides detailed guidelines regarding indications and technique in Cesarean
section.) A trial of labor is often impractical because it requires the obstetrician, an anesthesiologist, and a surgical team to be available immediately.
Technique:
During cesarean section, practitioners skilled in neonatal resuscitation should be available. The uterine incision can be classic or lower segment. A classic incision is made longitudinally in the anterior wall of the uterus, ascending to the fundus. This incision results in more blood loss than a lower-segment incision and is usually done only when placenta previa is present, fetal position is transverse, or the lower uterine segment is poorly developed. A lower-segment incision is made transversely or longitudinally in the thinned, elongated lower portion of the uterine body under the bladder reflection. A longitudinal lower-segment incision is used only for certain abnormal presentations and for excessively large fetuses. In such cases, a transverse incision can extend laterally into the uterine arteries, sometimes causing excessive blood loss.
Last full review/revision November 2005
Content last modified November 2005
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