Changes in the growth of very preterm infants in England 2006-2018

Objective To compare weight gain from birth to term equivalent age in very preterm infants in England born during two eras (2006-2011 and 2014-2018); to assess demographic and care factors influencing weight gain. Methods Data for infants born before 32 weeks of gestation during 2014-2018 in England were obtained (29 687 infants). Weight gain modelled using SuperImposition by Translation And Rotation (SITAR), with infants grouped by gestational week. A cohort from 2006 to 2011 was used for comparison (3288 infants). Multiple linear regression was used to assess factors influencing change in weight SD score from birth to 36 weeks postmenstrual age. Results Weight gain velocity (termed 'intensity' in SITAR models) was greater in the more recent cohort for all gestation groups born before 30 weeks of gestation. After adjustment for gestation, birth weight and other perinatal factors, care elements associated with faster weight gain included delivery in a level 3 unit (0.09 SD less weight gain deficit, 95% CI: 0.07 to 0.10) and parenteral nutrition initiation during the first day of life (0.08 SD, 95% CI: 0.06 to 0.10). Factors associated with slower weight gain included early ventilation (-0.07 SD, 95% CI: -0.08 to -0.05) and less deprived neighbourhood (-0.012 SD per Index of Multiple Deprivation decile, 95% CI: -0.015 to -0.009). Conclusions Weight gain for extremely preterm infants was faster during 2014-2018 than during 2006-2011. Early initiation of parenteral nutrition and birth in a level 3 unit may contribute to faster weight gain.