The overwhelming majority of nipple and breast stimulation research has centered on the efficacy of these methods for use in CSTs.[9–16] Kavanagh et al. investigated breast stimulation for cervical ripening and induction of labor in a 2005 Cochrane review. Six trials of women at term with premature rupture of membranes and no contractions were included in the studies. In the one trial that made the comparison, breast stimulation by a variety of techniques was found to be as effective as oxytocin alone in reducing the number of women not in labor at 72 hours after method initiation (n = 37, 58.8% vs. 25%; relative risk, 2.35; 95% confidence interval, 1.00%–5.54%, one randomized control trial). Overall, the included trials had small study populations and reported limited maternal and fetal outcomes. Kavanagh et al. offered no conclusions on the safety of breast stimulation but suggest further research regarding safety and efficacy as well as maternal satisfaction with the intervention.
Despite the availability of such research, its relevance to labor augmentation is limited. Contraction stress tests may be performed at varying points in gestation and are considered efficacious if three contractions are elicited in a 10-minute window, which is different than active labor contractions capable of producing labor progress. Similarly, success of breast stimulation during labor induction without preexisting contractions differs clinically from labor augmentation once contractions have been established. Dependence on CST and induction studies to understand efficacy and safety of nipple stimulation for labor augmentation is not possible.
Efficacy of Nipple Stimulation versus Oxytocin
Two studies on the use of nipple stimulation for labor augmentation have been published since 1990 (Table 1).[6,18] In their randomized controlled trial, Stein et al. assessed the efficacy of nipple stimulation for labor augmentation as compared with oxytocin use (N = 84). The study populations were similar in terms of maternal age, gestational age, and pelvic examination at study initiation. Women who performed nipple stimulation applied a breast pump unilaterally for 15 minutes and repeated on the alternate breast. Method failure was defined as a contraction frequency of less than one contraction every 3 minutes within 30 minutes of stimulation initiation. The control group, women receiving oxytocin augmentation, received intravenous oxytocin at a rate of 1 mU/min, increased by 1 mU/min every 15 to 30 minutes. Method failure was not defined for the control group. Internal intrauterine pressure catheters measured uterine activity for both study groups. Fifty percent (n = 17) of study participants using nipple stimulation were considered method failures. No statistically or clinically significant difference in cervical dilation (P = .05) was demonstrated between nipple stimulation (rate of 1 cm/h) and oxytocin use (rate of 2 cm/h).
More recently, a 1999 randomized controlled trial by Curtis et al. studied nipple stimulation versus oxytocin infusion in 79 women with prelabor rupture of membranes, or physician-determined "inadequate labor." The intervention protocol included unilateral stimulation via manual compression or electric breast pump performed for 10 minutes, followed by a rest period of 5 minutes; the cycle was repeated a maximum of four times. Method failure was defined as a lack of cervical change or contraction frequency of less than one contraction every 3 minutes within 60 minutes of stimulation initiation. Women in the control group received intravenous oxytocin at a rate of 0.25 mU/min, which was doubled at 10- to 20-minute intervals until "active labor" was achieved. Curtis et al. determined method failure for 65% of women using nipple stimulation (n = 32); these women subsequently received oxytocin augmentation per control group protocol. In the control group, oxytocin method failure ranged from 10% to 25%.
Both studies documented the overall length of labor for study participants. Stein et al. found no statistically significant differences in the length of first- or second-stage labor between the two groups. Curtis et al. went further to explore length of labor with regard to parity. The time interval between augmentation initiation and birth was significantly shorter for both nulliparous and multiparous women receiving oxytocin versus nipple stimulation. Nulliparous women required augmentation for a mean of 6.6 hours in the oxytocin group and 10.5 hours in the breast stimulation group (P = .002), whereas multiparous women required 5 hours in the oxytocin group and 7.6 hours in the breast stimulation group (P = .03). Interestingly, despite this time difference, there was no difference in the overall duration of the first stage of labor in the nipple stimulation and oxytocin groups.
Uterine Tachysystole Both Curtis et al. and Stein et al. cited uterine tachysystole, or hyperstimulation, as a safety concern in nipple stimulation research, but neither offered a standard definition. Similarly, in their meta-analysis of induction studies, Kavanagh et al. found no occurrence of uterine tachysystole with nipple stimulation, yet none of the included trials provided a definition of this phenomenon. Despite the lack of a standard definition, Stein et al. reported zero cases of uterine hyperstimulation among women using nipple stimulation and/or oxytocin. Hyperstimulation was not reported separately from other adverse events by Curtis et al., thus the rate of occurrence in that study is unknown.
The argument that nipple stimulation will yield an uncontrollable dose of oxytocin with potentially adverse consequences was narrowly explored by both Stein et al. and Curtis et al. Stein et al. reported statistically significant differences in contractile intensity between nipple stimulation and oxytocin administration (68 Montevideo units and 101 Montevideo units, respectively, P = .002); both groups achieved similar rates of cervical dilation. These data suggest that less uterine activity can lead to similar progress in labor. One can postulate that less uterine activity may also lead to lower risk of hyperstimulation. Further study and precise definitions of tachysystole are required to understand the precise physiologic aspects of this phenomenon. Conclusions related to the safety of nipple stimulation and its association with uterine tachysystole cannot be made based on this limited data.
Maternal and Fetal Outcomes Curtis et al. reported on the incidence of adverse fetal and maternal events, including decelerations, decreased variability, meconium staining, and uterine tachysystole. They found no difference in these outcomes, except for a decreased risk of meconium staining in nulliparous women who used nipple stimulation compared with oxytocin stimulation (P = .04). Stein et al. reported no adverse fetal effects in either study group.
Stein et al. found no statistically significant differences between the two groups in terms of cesarean birth rate and umbilical artery pH. Though not statistically significant, women using nipple stimulation and oxytocin experienced a 44% cesarean birth rate compared with 18% in the nipple stimulation only group and 27% in the oxytocin only group. Curtis et al. did not find any difference in the cesarean birth rate between study groups. Nulliparous women using nipple stimulation experienced fewer instrumental births (n = 5 vs. n = 10; P = .02) and more spontaneous vaginal births (P = .04) than those women receiving oxytocin.
Both Stein et al. and Curtis et al. conducted an analysis on the subgroup of participants who began nipple stimulation and who were determined to have method failures and were subsequently provided oxytocin. Stein et al. reported a statistically significant rate of cervical dilation of 2 cm/h while using oxytocin augmentation compared with 0 cm/h while using nipple stimulation only in this subgroup (P = .009). Although nipple stimulation followed by oxytocin led to faster cervical dilation and higher uterine activity in this study, the ultimate safety of such practice remains undetermined. Curtis et al. reported 65% of the adverse outcomes occurred in participants who used both augmentation methods. Higher rates of cesarean birth were reported by Stein and higher rates of fetal heart rate decelerations, meconium staining, and uterine hyperstimulation were reported by Curtis for the subgroup of women who used both methods of labor augmentation.
Both Stein and Curtis found no significant differences in Apgar scores at 1 and 5 minutes between nipple stimulation only and oxytocin only methods.[6,18] Although these data are limited, they suggest nipple stimulation does not place the fetus at increased risk for adverse outcomes.
J Midwifery Womens Health. 2010;55(1):65-69. © 2010 Elsevier Science, Inc.
Cite this: Management of Protracted Active Labor with Nipple Stimulation: A Viable Tool for Midwives? - Medscape - Jan 01, 2010.