Indiana University-Purdue University Indianapolis (IUPUI) / Pregnant and postpartum women with substance use disorders (SUDs) are likely to experience adverse health care encounters that contribute to poor health outcomes for them and their infants. The purpose of this dissertation is to describe the health care encounters of pregnant and postpartum women with SUDs. This dissertation includes two studies. The first study is a metasynthesis of published qualitative studies using a metasummary approach to classify the types of health care encounters experienced by pregnant and postpartum women with SUDs. A taxonomy of health care encounters was developed. Five types of adverse encounters were identified and labeled as (a) judgmental, (b) disparaging, (c) scrutinizing, (d) disempowering, and (e) deficient care. Three types of beneficial encounters were identified and labeled as (a) recovery-based, (b) accepting, and (c) effective care. The second study was a qualitative descriptive study conducted to describe factors that influence the formation of trusting relationships between maternity nurses and pregnant and postpartum women with SUDs. Interviews with 15 maternity nurses and 10 pregnant and postpartum women with SUDs were conducted. Content analysis of the participant narratives revealed a number of characteristics of maternity nurses and pregnant and postpartum women with SUDs that helped or hindered trusting relationships. Six characteristics of maternity nurses were identified and labeled as (a) rapport-building with women, (b) demeanor toward women, (c) provision of care, (d) provision of information, (e) attitude toward substance use, and (f) addiction expertise. Five characteristics of the women were identified and labeled as (a) engagement with nurses, (b) demeanor toward nurses, (c) acceptance of care, (d) investment in recovery, and (e) bonding with infant. Adverse encounters were often associated with provider stigma related to substance use during pregnancy and limited provider knowledge related to addiction. The findings will contribute to the development of strategies to improve the health care encounters of this population by promoting stigma awareness and communication skills training.