P1.168: Delayed Cord Clamping: Its Potential Effect on Bilirubin-Induced Visuocortical Dysfunction During Infancy

Background: Delayed cord clamping (DCC) benefits preterm newborns by increasing their red blood cell (RBC) volume and their hematocrit. However, an increased rate of RBC turnover may lead to an excessive bilirubin load. We have reported that elevated total serum bilirubin (TSB) levels in preterm neonates are associated with bilirubin-induced visuocortical dysfunction that persists during infancy and may be mediated by effects on the extrastriate visual cortex that manifest as impaired sweep visual evoked potentials (sVEPs).1 We hypothesized that an elevated bilirubin load due to DCC may lead to subtle visuocortical dysfunction.

Methods: This study is a sub-analysis of infants who participated in a prospective cohort study investigating the effects of bilirubin on visuocortical function.1 The cohort was divided into 3 groups based on umbilical cord management: (1) immediate cord clamping (ICC), ( < 30 seconds, n=25); (2) standard DCC (30-60 seconds, n=30); and (3) prolonged DCC (60-120 seconds, n=7). At 12-months corrected age, Vernier acuity, contrast sensitivity, and grating acuity were measured using sVEPs and compared. Peak TSB during the first week of life and first hematocrit documented during hospitalization were also recorded.

Results: Values are presented as mean ± standard deviation (SD), and range. Across all three study groups, the peak TSB levels was 10.6 ± 3.6 mg/dL, (range, 4.1-24.1). By group, peak TSB levels were 9.9 ± 2.6 mg/dL (6.3-13.9) for ICC, 10.3 ± 3.1 mg/dL (4.1-18.2) for standard DCC, and 13.8 ± 6.3 mg/dL (9.1-24.1) for prolonged DCC. Peak TSB levels in the prolonged DCC group were significantly higher than those in both the ICC group (p = 0.049) and standard DCC group (p = 0.037). Higher TSB levels and longer DCC duration were positively correlated with impaired Vernier acuity and contrast sensitivity, as measured by sVEPs (Figure 1). There were no significant differences in grating acuity between the groups.

Conclusion: Longer DCC, thereby presumed higher hematocrit, and elevated bilirubin load (consequent higher peak TSB level) during neonatal life can impact visuocortical integrity at 12-months corrected age. These findings of persistent impaired visual perturbations during infancy are concerning and necessitate longer term follow-up assessment of extrastriate visual cortex integrity and its potential impact on childhood executive function.

References:
1. Good WV, Wong RJ, Norcia AM, Hou C, Cellucci J, McGovern MQ, et al. Effect of bilirubin on visuocortical development in preterm infants. J Perinatol. Published online February 5, 2025. doi:10.1038/s41372-025-02213-4