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The most important function of forceps is traction exercised for the purpose of drawing the head through the genital tract. In not a few cases, however, particularly in occipito-posterior presentations, its employment as a rotator is attended by most happy results.
—J. Whitridge Williams (1903)
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Operative deliveries are vaginal deliveries accomplished with the use of forceps or a vacuum device. Once either is applied to the fetal head, outward traction generates forces that augment maternal pushing to deliver the fetus vaginally. The most important function of both devices is traction. In addition, forceps may also be used for rotation, particularly from occiput transverse and posterior positions.
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According to the birth certificate data from the National Vital Statistics Report, forceps- or vacuum-assisted vaginal delivery was used for 3.2 percent of births in the United States in 2014. This is a decline from 9.0 percent in 1990 (Hamilton, 2015). For these deliveries, a vacuum is disproportionately selected, and the vacuum-to-forceps delivery ratio is nearly 5:1 (Merriam, 2017). In general, most of these attempts are successful. In 2006, only 0.4 percent of forceps trials in the United States and 0.8 percent of vacuum extraction attempts failed to result in vaginal delivery (Osterman, 2009).
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If it is technically feasible and can be safely accomplished, termination of second-stage labor by traction instruments is indicated in any condition threatening the mother or fetus that is likely to be relieved by delivery. Some fetal indications include nonreassuring fetal heart rate pattern and premature placental separation (Schuit, 2012). In the past, forceps delivery was believed to be somewhat protective of the fragile preterm infant head. However, outcomes for neonates who weigh 500 to 1500 g do not significantly differ if delivered spontaneously or by outlet forceps (Fairweather, 1981; Schwartz, 1983).
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Some maternal indications include heart disease, pulmonary compromise, intrapartum infection, and certain neurological conditions. The most common are exhaustion and prolonged second-stage labor. However, a specific maximum length beyond which all women should be considered for operative vaginal delivery has not been identified (American College of Obstetricians and Gynecologists, 2016).
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Operative delivery is generally performed from either a low or outlet station. Additionally, forceps or vacuum delivery should not be used electively until the criteria for an outlet delivery have been met. In these circumstances, operative delivery is a simple and safe operation, although with some risk of maternal lower reproductive tract injury (Yancey, 1999).
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CLASSIFICATION AND PREREQUISITES
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Classification for operative vaginal delivery is summarized in Table 29-1. It emphasizes that the two most important discriminators of risk for both mother and neonate are station and rotation. Station is measured in centimeters, –5 to 0 to +5. Zero station reflects a line drawn between the ischial spines. Deliveries ...