Risk of intestinal failure in the study population after adjusting for potential confounding variables
| Variable | Univariable model* | Multivariable model† | ||
| Category | HR | 95% CI | HR | 95% CI |
| History of NEC | ||||
| No | Reference | 1.0 | Reference | 1.0 |
| Yes | 15.9 | 9.0 to 28.3 | 7.2 | 3.7 to 14.0 |
| Sex | ||||
| Male | Reference | 1.0 | Reference | 1.0 |
| Female | 1.2 | 0.7 to 1.9 | 1.0 | 0.6 to 1.7 |
| Degree of prematurity (gestational weeks)‡ | ||||
| 32–42 | Reference | 1.0 | Reference | 1.0 |
| 28–31 | 2.0 | 1.0 to 4.3 | 1.2 | 0.5 to 2.5 |
| <28 | 4.5 | 2.3 to 8.8 | 1.9 | 1.0 to 3.9 |
| Size in relation to gestational age (GA)§ | ||||
| LGA and AGA | Reference | 1.0 | Reference | 1.0 |
| SGA | 4.0 | 2.4 to 6.7 | 3.0 | 1.7 to 5.0 |
| Perinatal asphyxia¶ | ||||
| No | Reference | 1.0 | N/A | N/A |
| Yes | 1.5 | 0.7 to 2.9 | ||
| Abdominal surgery** | ||||
| No | Reference | 1.0 | Reference | 1.0 |
| Yes | 18.9 | 11.3 to 31.5 | 6.2 | 3.4 to 11.3 |
| Maternal smoking | ||||
| No | Reference | 1.0 | N/A | N/A |
| Yes | 0.5 | 0.2 to 1.1 | ||
| Birth cohort (year)†† | ||||
| 1987–2001 | Reference | 1.0 | Reference | 1.0 |
| 1994–2001 | 0.9 | 0.2 to 4.2 | 0.7 | 0.2 to 3.1 |
| 2002–2006 | 4.2 | 1.4 to 12.5 | 3.4 | 1.1 to 10.2 |
| 2007–2009 | 11.0 | 3.9 to 30.8 | 8.0 | 2.8 to 23.1 |
| Region in Sweden | ||||
| Rest of Sweden | Reference | 1.0 | N/A | N/A |
| Stockholm county | 1.7 | 1.0 to 2.9 | ||
*Adjusted for each variable, one by one.
†Adjusted for gender, degree of prematurity, intrauterine growth restriction (LGA/AGA vs SGA), study period, previous abdominal surgery and history of NEC.
‡NEC, necrotising enterocolitis.
‡GA in weeks.
§Size in relation to GA: LGA or AGA, and SGA.
¶Apgar <7 at or more than 5 min.
**Defined by International Classification of Disease Codes and Related Health Problems codes versions 9 and 10.
††Based on infant’s birth year.
AGA, appropriate for GA; LGA, large for GA; NEC, necrotising enterocolitis; SGA, small for GA.