Generally, these techniques are only used when the cervix is unfavorable because the catheter tends to come out as the cervix opens. It is suitable for women with intact or ruptured membranes. In most cases, a Foley catheter is placed through the internal cervical os, and downward tension is created by taping the catheter to the thigh (Mei-Dan, 2014). A modification of this-extraamnionic saline inusion (EASI}-adds a constant saline infusion through the catheter into the space between the internal os and placental membranes (Fig. 26-2). Karjane and coworkers (2006) reported that chorioamnionitis was signiicantly less frequent when infusion was done compared with no infusion-6 versus 16 percent. Similarly, in a large metaanalysis, trans cervical catheters were not associated with higher rates of maternal or fetal infection (McMaster, 2015).
As discussed above, transcervical catheters do not reduce the cesarean delivery rate compared with prostaglandins. The PROBAAT trials (-I, -P, -M, and II), in which cervical ripening with a Foley catheter was compared with vaginal dinoprostone gel, dinoprostone vaginal inserts, and vaginal or oral misoprostol, reported similar outcomes between the mechanical technique and the prostaglandin agents. Also, fewer overall cases of cardiotocographic changes were seen in the mechanical technique group Qozwiak, 2011, 2013, 2014; Ten Eikelder, 2016).
FIGURE 26-2 Extraamnionic saline infusion (EASI) through a 26F Foley catheter that is placed through the cervix. The 30-mL balloon is inflated with saline and pulled snugly against the internal os, and the catheter is taped to the thigh. Room-temperature normal saline is infused through the catheter port of the Foley at 30 or 40 mUhour by intravenous infusion pump.
Similar cesarean delivery rate results are found in other comparison studies. Schoen and coworkers (2017) observed that concurrent oxytocin with a transcervical Foley catheter shortened the median time-to-delivery compared with a Foley catheter followed by oxytocin. However, rates of cesarean delivery were unchanged. Connolly and associates (2016) reported similar findings for women within intact membranes undergoing labor induction. Amorosa and colleagues (2017) found no beneit for transcervical catheter coupled with oxytocin compared against oxytocin alone for women with ruptured membranes. Other studies of concurrent misoprostol reported reduced timeto-delivery without afecting cesarean delivey rates (Carbone, 2013; Levine, 2016). Finally, the concurrent addition of tension does not appear to enhance catheter eicacy. Fruhman and coworkers (2017) randomized 140 women to trans cervical Foley catheter with and without tension, and reported similar vaginal delivery rates within 24 hours or overall.
Cervical dilation can be accomplished using hygroscopic osmotic cervical dilators, as described for early pregnancy termination (Chap. 18, p. 358). Intuitive concerns of ascending infection have not been veriied, and their use appears to be safe. Placement generally requires a speculum and positioning of the woman on an examination table. Several studies performed in the 1990s compared hygroscopic cervical dilators and prostaglandins and found few benefits of this mechanical technique. And, more recent studies veriied these conclusions (Maier, 2017).