Objective: To summarize current evidence on the association between infant pacifier use and breastfeeding.

Data Source: MEDLINE, CINAHL, the Cochrane Library, EMBASE, POPLINE, and bibliographies of identified articles.

Study Selection: A search for English-language records (from January 1950 through August 2006) containing the Medical Subject Heading terms pacifiers and breastfeeding was conducted, resulting in 1098 reports. Duplicate and irrelevant studies were excluded, yielding 29 studies that fit inclusion criteria for the review (4 randomized controlled trials, 20 cohort studies, and 5 cross-sectional studies). Two independent reviewers abstracted data and scored these studies for quality; disagreements were settled through consensus with a third investigator.

Main Exposure: Pacifier use.

Main Outcome Measures: Breastfeeding duration or exclusivity.

Results: Results from 4 randomized controlled trials revealed no difference in breastfeeding outcomes with different pacifier interventions (pacifier use during tube feeds, pacifier use at any time after delivery, an educational program for mothers emphasizing avoidance of pacifiers, and a UNICEF (United Nations Children’s Fund)/World Health Organization Baby Friendly Hospital environment. Most observational studies reported an association between pacifier use and shortened duration of breastfeeding.

Conclusion: The highest level of evidence does not support an adverse relationship between pacifier use and breastfeeding duration or exclusivity. The association between shortened duration of breastfeeding and pacifier use in observational studies likely reflects a number of other complex factors, such as breastfeeding difficulties or intent to wean. Ongoing quantitative and qualitative research is needed to better understand the relationship between pacifier use and breastfeeding.

Comment: Given current American Academy of Pediatrics guidelines to consider offering a pacifier to all infants at bedtime to reduce the risk of SIDS, the potential impact of pacifiers on breastfeeding is increasingly important to understand. Even small deleterious effects on breastfeeding duration or exclusivity could have significant public health implications. At the same time, the potential reduction in SIDS with pacifier use at the initiation of sleep is compelling. This systematic review demonstrates that the relationship between pacifier use and breastfeeding is complex and poses challenges for study.

Randomized controlled trials provide stronger evidence than cohort or cross-sectional studies. Thus, the failure of the RCTs in this review to demonstrate any deleterious effect of pacifiers on breastfeeding duration or exclusivity is significant and important.

Two of the RCTs showed that pacifier use is high even among those who were instructed not to use them. In the study by Kramer and colleagues, 61.4% of infants in the intervention group (nonuser group) used pacifiers (vs 84.0% in the control group); 40.8% of infants in the intervention group used pacifiers daily (vs 55.7% in the control group). In the study by Collins and co-authors, infants in the control group were not supposed to receive a pacifier in the hospital, but 31% received a pacifier at some point before discharge.  Data on actual pacifier use were not reported in the remaining RCTs.

Two of the 4 RCTs controlled for pacifier use in the hospital only. We do not know whether the intervention and control groups differed in pacifier use at later times; it may be that mothers offer pacifiers to their infants after discharge independent of hospital practices or educational interventions.

Conversely, most observational studies demonstrated a negative association between pacifiers and breastfeeding duration or exclusivity. However, unlinked randomized trials, observational studies cannot prove the direction of causality and it is not known in these studies whether pacifier use led to decreased breastfeeding or if decreased breastfeeding (eg, during weaning) led to increased pacifier use. As a case in point, when Kramer and colleagues analyzed the results of their RCT ignoring randomization they found a strong observational association between daily pacifier use and weaning by 3 months (25.0% vs 12.9% of the exposed vs unexposed groups; RR, 1.9%;95% CI, 1.1-3.3). They argue that breastfeeding and pacifier use are complex behaviors influenced by factors that are difficult to measure and therefore difficult to control for in observational studies. These factors are likely to lead to residual confounding and reverse causality bias, suggesting that valid assessment of the effects of behavioral interventions on behavioral outcomes require randomized trails. In addition, the same child-rearing beliefs that motivate women to breastfeed exclusively may discourage pacifier use for infant soothing.

Pacifier use may be a marker for breastfeeding problems; mothers might resort to pacifiers for fussy infants when breastfeeding is going poorly. In support of this, one of the cohort studies selected a subsample of Brazilian women for an ethnographic study consisting of indepth interviews and observation. These researchers found that pacifier use is widely regarded by mothers as a positive behavior. Furthermore, mothers reported using pacifiers to take their infants off of their breasts and to lengthen the interval between feedings. Pacifiers may represent an implicit form of weaning when mothers are ambivalent about breastfeeding. Further research is needed to understand the social and cultural factors that influence a mother’s decision to use a pacifier.

Despite the comprehensive nature of the literature search performed, this systematic review may be limited by its inclusion of English-language reports only. This inclusion criterion could have restricted the type of reports included and is a potential source of bias.

The American Academy of Pediatrics guideline on SIDS suggests an important paradigm that our systematic review was unable to address. None of the studies looked at pacifier use only at nap time or bedtime, which would more directly assess the impact of the American Academy of Pediatrics recommendation that pacifiers be offered at the initiation of sleep. This recommendation was based on the results of case-control studies that found stronger evidence for SIDS risk reduction when pacifiers were use at “last sleep” than at other times. Future research should examine if pacifiers have an effect on breastfeeding when used in this specific capacity.

In conclusion, the strongest current evidence on pacifiers and breastfeeding indicates that pacifier use is not detrimental to breastfeeding outcomes. Ongoing quantitative and qualitative research is needed to confirm these finding and more fully understand the complex relationships between pacifier use, breastfeeding and SIDS, including the optimal timing for pacifier introduction.