Operative vaginal delivery (OVD) is birth accomplished with assistance from forceps or a vacuum-cup device. Once these are applied to the fetal head, outward traction generates forces that augment maternal pushing to deliver the fetus.
INCIDENCE AND INDICATIONS
From national data, forceps or vacuum-assisted vaginal delivery aided 3.1 percent of births in the United States in 2015. This is a decline from 9 percent in 1990 (Martin, 2017). For these procedures, a vacuum is disproportionately selected, and the vacuum-to-forceps delivery ratio approximates 4:1 (Yeomans, 2010). Most of these procedures are successful in effecting vaginal birth. From 2006 United States data, only 0.4 percent of forceps trials and 0.8 percent of vacuum extraction attempts failed to result in vaginal birth (Osterman, 2009). In the specific group of nulliparas with term gestations, higher failure rates of 4.4 and 6.4 percent, respectively, were found in a study of 25 academic hospitals (Bailit, 2016).
If technically safe, termination of second-stage labor by OVD is considered for any condition that threatens the mother or fetus and that is likely to be relieved by delivery. Of maternal indications, the most common are maternal exhaustion and prolonged second-stage labor. However, a specific, maximum second-stage length beyond which all women should be considered for OVD has not been defined (American College of Obstetricians and Gynecologists, 2019). Other maternal reasons are preexisting or intrapartum conditions that limit effective pushing or warrant expedited delivery. Severe or acute pulmonary compromise, decompensation from intrapartum infection, neurological disease, and serious cardiac disorders are examples. Frequent fetal indications include nonreassuring fetal heart rate and premature placental separation (Schuit, 2012).
CLASSIFICATION AND PREREQUISITES
Classification of OVD is summarized in Table 29-1. It emphasizes that station and rotation are the two most important discriminators of risk for both mother and neonate. Station is measured by the number of centimeters, either above or below, an anatomical zero station, which is a line drawn between the ischial spines. Stations range from –5 to 0 to +5. Procedures are categorized as outlet, low, and midpelvic, and most are low or outlet deliveries. High forceps, in which instruments are applied above 0 station, have no place in current obstetrics.
TABLE 29-1Operative Vaginal Delivery Prerequisites and Classification According to Station and Rotationa ||Download (.pdf) TABLE 29-1Operative Vaginal Delivery Prerequisites and Classification According to Station and Rotationa
|Procedure ||Criteria || |
|Outlet forceps ||Scalp is visible at the introitus without separating the labia |
Fetal skull has reached pelvic floor
Fetal head is at or on perineum
Head is OA or OP or
Head is right or left OA or OP position but rotation ≤45 degrees
|Low forceps |
|Fetal station is ≥+2 cm but not on the pelvic floor, and:|
(a) Rotation ≤45 ...