Am J Perinatol 2024; 41(06): 722-729
DOI: 10.1055/a-1730-8536
Original Article

Cord-Blood Derived Chemistry Reference Values in Preterm Infants for Sodium, Chloride, Potassium, Glucose, and Creatinine

1   Section of Neonatology, Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Canada
2   Libin Cardiovascular Institute of Alberta, University of Calgary, Alberta, Canada
3   Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
Rana Ismail
1   Section of Neonatology, Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Canada
M. Sarah Rose
4   Research Excellence Support Team, Alberta Health Services, Calgary, Calgary, Canada
Andrew W. Lyon
5   Pathology and Laboratory Medicine, Saint Pauls Hospital Laboratory, Saskatoon, Saskatchewan, Canada
Tanis R. Fenton
3   Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
6   Community Health Sciences, University of Calgary, Calgary, Canada
7   Nutrition Services, Alberta Health Services, Calgary, Canada
› Author Affiliations
Funding A previous study on which this analysis is based received a grant for $24,933 from the Laboratory Services Health Services Research Funding Competition in 2002.


Objective International guidelines recommend that preterm infants should be supported to maintain their serum electrolytes within “normal” ranges. In term babies, cord blood values differed in pathological pregnancies from healthy ones.

Study Design We examined cord blood sodium, chloride, potassium, glucose, and creatinine to derive maturity-related reference intervals. We examined associations with gestational age, delivery mode, singleton versus multiple, and prenatal maternal adverse conditions. We compared preterm cord values to term, and to adult reference ranges.

Results There were 591 infants, 537 preterm and 54 term. Preterm cord glucose levels were steady (3.7 ± 1.1 mmol/L), while sodium, chloride, and creatinine increased over GA by 0.17, 0.14 mmol/L/week, and 1.07 µmol/L/week, respectively (p < 0.003). Average preterm cord potassium and chloride were higher than the term (p < 0.05). Compared with adult reference intervals, cord preterm reference intervals were higher for chloride (100–111 vs. 98–106 mmol/L), lower for creatinine (29–84 vs. 62–115 µmol/L), and more variable for potassium (2.7–7.9 vs. 3.5–5.0 mmol/L) and sodium (130–141 vs. 136–145 mmol/L). Cesarean section was associated with higher potassium and lower glucose, multiple births with higher chloride and creatinine and lower glucose, and SGA with lower glucose.

Conclusion Cord blood values varied across the GA range with increases in sodium, chloride, and creatinine, while glucose remained steady. Average preterm reference values were higher than term values for potassium and chloride. Preterm reference values differed from published adults' reference values. The changes across GA and by delivery mode, SGA, and being a multiple, which may have direct implications for neonatal care and fluid management.

Key Points

  • Cord blood electrolyte, creatinine, and glucose values vary across neonatal gestational age.

  • Average preterm cord values of potassium and chloride were higher than term values.

  • Cord reference values differ by delivery mode, growth, and multiple impacting neonatal care decisions.

Authors' Contribution

A.S. conceived the idea, developed the protocol, interpreted the data, wrote the first draft, reviewed edits, and approved the final version. R.I. contributed to the protocol, interpreted the data, critically reviewed and edited the manuscript, and approved the final version. M.S.R. analyzed the data, critically reviewed and edited the manuscript, and approved the final version. A.W.L. was part of the original research grant, edited the revision and addressed reviewers' comments. T.R. F. received the original grant to conduct the research, conceived the idea, developed the protocol, interpreted the data, reviewed edits, and approved the final version. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

Publication History

Received: 30 June 2021

Accepted: 20 December 2021

Accepted Manuscript online:
04 January 2022

Article published online:
07 February 2022

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