Abstract: OBJECTIVE:Identify perinatal risk factors associated with SIP STUDY DESIGN:This was a retrospective case-control study of SIP in infants born at ≤28 weeks of gestation and admitted between 1995 and 2016 at a tertiary care NICU. Infants with NEC or other GI abnormalities were excluded. Cases of SIP were matched with gestational age-matched controls with the closest birth date. Maternal, infant and birth related factors were evaluated using univariate analyses and significant factors were evaluated using multiple logistic regression. RESULT:25 cases of SIP were matched with 25 controls. No maternal factors reached statistical significance. Being one of twins increased the odds of SIP 29-fold. Birth-order or weight-discrepancy in twin had no association of SIP within twin pairs. CONCLUSION:Twins are at significantly higher risk for SIP. The association of SIP and twin gestation was independent of previously reported risk factors of perinatal indomethacin or magnesium sulfate and merits further study.