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Overdiagnosis of Dystocia
Today, expressions such as cephalopelvic disproportion and failure to progress often are used to describe ineffective labors.
The expression cephalopelvic disproportion came into use prior to the 20th century to describe obstructed labor resulting from disparity between the dimensions of the fetal head and maternal pelvis such as to preclude vaginal delivery. This term, however, originated at a time when the main indication for cesarean delivery was overt pelvic contracture due to rickets (Olah and Neilson, 1994). Such true disproportion is now rare, and most disproportions are the result of malposition of the fetal head within the pelvis (asynclitism) or of ineffective uterine contractions. True cephalopelvic disproportion is a tenuous diagnosis because two thirds or more of women diagnosed as having this disorder and delivered by cesarean subsequently deliver even larger newborns vaginally (see Chap. 26, Indication for Prior Cesarean Delivery).
Failure to progress in either spontaneous or stimulated labor has become an increasingly popular description of ineffectual labor. This term is used to include lack of progressive cervical dilatation or lack of fetal descent.
As previously stated, dystocia is the most common current indication for primary cesarean delivery. Gifford and colleagues (2000) reported that lack of progress in labor was the reason for 68 percent of unplanned cesarean deliveries for cephalic-presenting fetuses. Notzon and associates (1994) found that 12 percent of American women without prior cesarean delivery were diagnosed as having dystocia requiring abdominal delivery in 1990, and the rate had increased from 7 percent in 1980. A similar change also was reported in the United Kingdom (Leitch and Walker, 1998). Because many women with a primary cesarean delivery for dystocia undergo repeat cesarean delivery in subsequent pregnancies, an estimated 50 to 60 percent of all cesarean deliveries in the United States may be attributable to this diagnosis.
It is generally agreed that dystocia leading to cesarean delivery is overdiagnosed in the United States and elsewhere. Factors leading to increased use of cesarean delivery for dystocia, however, are controversial. Those implicated have included incorrect diagnosis of dystocia, epidural analgesia, fear of litigation, and even clinician convenience (Lieberman and co-workers, 1996; Savage and Francome, 1994; Thorp and colleagues, 1993a).
Variability in the criteria for diagnosis is a major determinant of this increase. For example, Gifford and colleagues (2000) found that almost 25 percent of the cesarean deliveries performed annually in the United States for lack of progress were in women with cervical dilatation of only 0 to 3 cm (Fig. 20–1). According to Stephenson (2000), this practice is contrary to recommendations of the American College of Obstetricians and Gynecologists (1995a) that the cervix be dilated to 4 cm or more before a diagnosis is made. Thus, the diagnosis often is made before the active phase of labor and therefore, before an adequate trial of labor. Another factor implicated is insufficient oxytocin stimulation of labor in women with slow labor (Rouse and colleagues, 1999). King (1993) found that cesarean deliveries for dystocia in private patients in the United Kingdom were related to office hours and surgery schedules, whereas the timing of procedures for fetal distress were evenly distributed throughout the day.
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Dystocia in Nulliparous Women
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