Some very recent research suggested that dummies don't reduce Breastfeeding rates;
"Drs. Kair and Phillipi analyzed feeding data on 2,249 infants born between June 2010 and August 2011. Results showed that the rate of exclusive breastfeeding on the mother-baby unit decreased significantly after pacifiers were restricted — from 79 percent of infants in July to November 2010 to 68 percent in January to August 2011.
In addition, the proportion of breastfed infants receiving supplemental formula increased from 18 percent before the policy was changed to 28 percent afterward. The percentage of infants fed only formula remained statistically unchanged during the study period."