Combined estrogen/progestin contraceptive methods have a negative effect on breastfeeding duration when compared to progestin-only methods, non-hormonal methods or using no method. These results suggest that combined hormonal methods should not be recommended to breastfeeding women. This is consistent with current CDC recommendations and strengthens the evidence on which they're founded because this study is recent, US-based, examined current contraceptive options, and controlled for confounding using up-to-date statistical approaches. No effect of progestin-only contraceptive use on breastfeeding duration was found when compared to either non-hormonal methods of birth control or using no method. These results are limited by the lack of information on the timing of initiation of use; in particular, we were not able to distinguish early use, i.e., immediate postpartum, from later use. Consequently, these results should not be interpreted to mean that progestin-only methods are compatible with breastfeeding, but rather that good information about the timing of use will be necessary to clarify the relationship between progestin-only contraceptive use and breastfeeding outcomes. Postpartum contraceptive use by women who initiated breastfeeding was found to be associated with maternal age, maternal educational attainment, race/ethnicity, first birth, infant NICU stay, and the number of breastfeeding-related hospital practices experienced by the mother. Differences in contraception use correspond to breastfeeding rates, suggesting that the issues may be related either with common etiology or by direct effects between them. Pregnancy prevention may outweigh breastfeeding protection in a mother's use of contraception after birth. If so, accurate and available information about the impact of hormonal contraception on breastfeeding is need by these women, as well as having access to reliable and attractive contraceptive methods which are compatible with breastfeeding. Overall, these results highlight the importance of labor and delivery practices that allow and enable immediate breastfeeding initiation for long-term breastfeeding success. These results support the importance of the Ten Steps to Successful Breastfeeding for breastfeeding duration, and suggest that greater adoption of and adherence to this standard could improve breastfeeding outcomes.