Cord serum vitamin D in a South China birth cohort.

Background And Objectives: Vitamin D deficiency during pregnancy has been associated with many adverse pregnancy and birth outcomes. Low serum 25-hydroxyvitamin D (25OHD) levels (<30 nmol/L) increases the risk of nutritional rickets. This study aimed to investigate the concentration of cord serum 25OHD in a birth cohort in Guangzhou, China and determine whether maternal lifestyle factors had any effect on these levels.

Methods And Study Design: A total of 854 pregnant women giving birth between Dec 2016 and Dec 2017 were recruited to this study. Basic information was obtained from the clinical database. A voluntary retrospective pregnancy lifestyle questionnaire was completed by 388 participants. The concentration of serum 25OHD, calcium, phosphorus, and alkaline phosphatase (ALP) were measured in umbilical cord blood.

Results: The mean (SD) of cord serum 25OHD was 44.7 (16.7) nmol/L. The prevalence of cord 25OHD <30 nmol/L was 22.2% and 70.4% had levels <50 nmol/L. The prevalence of vitamin D deficiency is higher in infants born in winter months (31% <30 nmol/L and 76% <50 nmol/L), compared to those born in the summer (12% <30 nmol/L and 64% <50 nmol/L). Infants born to women taking a vitamin D containing supplement had approximately 10 nmol/L higher levels of 25OHD than those who did not supplement their diets.

Conclusions: Summer born infants have higher serum 25OHD levels at birth, but there are still infants being born with vitamin D deficiency. Vitamin D containing supplement use during pregnancy was effective in raising cord serum vitamin D levels.