The proposed 2-year study will use a longitudinal, comparative, mixed method design to explore the impact of a Very Low Birth Weight (VLBW) (≤33 weeks gestational age) infant on mother-sibling interactions and sibling adjustment. A comparison group of full term infants (≥38 weeks gestational age) will be included to elucidate sibling adjustment problems that are typical to having a new baby in the home and sibling adjustment problems that are associated with the unique stress of having to care for a VLBW infant. Participants will be fifty mothers and siblings of VLBW infants and fifty mothers and siblings of full term infants. Data collection will take place within one week of infant discharge from the hospital (enrollment), and at 1 month and 6 months post infant discharge using self-report measures, qualitative interviews, and mother-sibling interaction observation. Variables of interest include mother's worry, anxiety, depression, and post-traumatic stress; mother-sibling interactions including uninvolvement, positive affect, negative affect, talk, looking and playing; internalizing and externalizing behaviors, sleep/somatic problems, and growth in siblings of VLBW and in siblings of the comparison group with full term infants. Mixed modeling and Ordinary Least Squares (OLS) regression modeling will be conducted to identify factors that make siblings vulnerable to psychological and emotional adjustment problems in response to having a VLBW infant in the home. There are no anticipated risks for the infant participants of the study aside from the small risk of violating confidentiality of infant participants and their mothers. No risks for siblings are anticipated aside from the small risk of violating confidentiality.