Having a new baby in the home is viewed as one of the five most stressful life events for young children. [1] The day-to-day routines and structure are altered, including peer-play activities, family activities, and eating and bedtime routines. For many children, the interruptions in routine come at a critical point in their social development. A child's reliance on predictable structure during the toddler and preschool years is marked [2] and a change in routine may lead to greater vulnerability to maladjustment. [3] Social development and health problems may be magnified when the newborn is a very low birth weight (VLBW) infant (less than 1500g) and requires additional attention from the mother. Many VLBW infants experience some degree of cognitive, motor, and language delays, [4-7] and 5-10% develop cerebral palsy.[8, 9] Parents look forward to the discharge of a VLBW from the hospital, but at the same time they are apprehensive about the complicated care that is required once the VLBW infant is home. [10, 11] An impressive amount of research has been conducted on mothers'response to having a VLBW infant in the home.[12-14] However, little research has explored the effects on other members of the family, such as older siblings. The proposed 2-year study will use a longitudinal, comparative, mixed method design to explore the impact of a VLBW (d33 weeks gestational age) infant on the mother-sibling interactions and sibling adjustment. A comparison group of full term infants (e38 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;and 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 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. The findings will provide the foundations for developing tailored nursing interventions and services suited to optimize mother and sibling adjustment during the critical transition period after an infant comes home. PUBLIC HEALTH RELEVANCE: Research is needed to identify factors related to the adjustment of siblings of VLBW infants. After discharge, many VLBW infants have chronic medical conditions that require close attention in the home for several months, resulting in extensive changes in day-to-day routines for siblings. A child's reliance on predictable structure during the toddler and preschool years is marked, and a change in routine may lead to greater vulnerability to psychological, emotional, and physical health problems. This research will be the first to longitudinally explore sibling adjustment following VLBW infant homecoming, with scientific relevance regarding the psychological, emotional, and physical health of siblings. The proposed study is germane to the goal of identifying factors to promote the health of young children, particularly those who are at risk for maladjustment due to having a sibling with a chronic medical condition.