Supplementary Material for: Sex-Specific Long-Term Trends in Length of Hospital Stay, Postmenstrual Age at Discharge, and Survival in Very Low Birth Weight Infants

Introduction: In very low birth weight (Methods: This is a single-center retrospective cohort analysis based on quality assurance data of VLBW infants born from 1978 to 2018. Estimation of sex-specific LOHS over time was based on infants discharged home from neonatal care or deceased. Estimation of sex-specific PAD over time was based on infants discharged home exclusively. Analysis of in-hospital survival was performed for all VLBW infants. Results: In 4,336 of 4,499 VLBW infants admitted from 1978 to 2018 with complete data (96.4%), survival rates improved between 1978–1982 and 1993–1997 (70.8 vs. 88.3%; hazard ratio (HR) 0.20, 95% confidence interval 0.14, 0.30) and remained stable thereafter. Boys had consistently higher mortality rates than girls (15 vs. 12%, HR 1.23 [1.05, 1.45]). Nonsurviving boys died later compared to nonsurviving girls (adjusted mean survival time 23.0 [18.0, 27.9] vs. 20.7 [15.0, 26.3] days). LOHS and PAD assessed in 3,166 survivors displayed a continuous decrease over time (1978–1982 vs. 2013–2018: LOHS days 82.9 [79.3, 86.5] vs. 60.3 [58.4, 62.1] days); PAD 40.4 (39.9, 40.9) vs. 37.4 [37.1, 37.6] weeks). Girls had shorter LOHS than boys (69.4 [68.0, 70.8] vs. 73.0 [71.6, 74.4] days) and were discharged with lower PAD (38.6 [38.4, 38.8] vs. 39.2 [39.0, 39.4] weeks). Discussion/Conclusions: LOHS and PAD decreased over the last 40 years, while survival rates improved. Male sex was associated with longer LOHS, higher PAD, and higher mortality rates.