Effect of cord clamping time on neonatal vitamin B12, folate and urinary iodine concentration.

Objectives: The aim of this randomised study was to investigate whether early or late clamping of the cord influences the status of micro-elements and thyroid hormone levels in newborns.
Material and Methods: The study participants were randomised into two groups: Group 1, in which cord clamping was performed within 10 s (n = 32) and Group 2, in which clamping was performed at the 60th second (n = 28). Sociodemographic parameters were recorded; maternal and neonatal levels of free triiodothyronine (FT3), free thyroxine (FT4), thyroid stimulant hormone (TSH), urinary iodine concentration levels (UIC) folate and vitamin B12 were measured.
Results: Of the maternal and neonatal thyroid hormone values examined, a significant difference was determined between the groups only in respect of the FT4 and FT3 values of the newborns in the first 24 hours (p = 0.037, p = 0.009, respectively). The FT4 values in the first 24 hours were determined to be lower than normal in 15.6% (n: 5) of the newborns in Group 1 and in 0% of Group 2. The FT3 values in the first 24 hours were determined to be lower than normal in 62.5% (n: 20) of the newborns in Group 1 and in 28.5% of Group 2. Vitamin B12 values below the normal limit were determined at a significantly higher rate in Group 1 (p = 0.009). A statistically significant positive correlation was observed between the maternal and neonatal vitamin B12 levels (r: 0.334, p = 0.009).
Conclusions: Late clamping of the umbilical cord may contribute to erythrocyte synthesis by allowing passage of vitamins such as B12 and folic acid to the newborn.