324 - Seasonal Variation in Maternal and Cord Blood Vitamin D Levels: Strong Correlation and Winter Deficiency

Publication Number: 3313.324

RONELLA MAROM, Tel aviv Medical Center, Tel Aviv, Tel Aviv, Israel; Ayelet Dangot, sourasky medical center, Tel Aviv, Tel Aviv, Israel; Laurence Mangel, Tel Aviv Medical Center, Tel Aviv, HaMerkaz, Israel; Anat Schwartz, Tel Aviv Medical Center, London, England, United Kingdom; Roy Segal, Tel aviv sourasky medical center, Tel aviv, Tel Aviv, Israel; Dror Mandel, Dana Dwek Children's Hospital, Tel Aviv Medical Center, Tel Aviv, Tel Aviv, Israel; Shlomi Cohen, Dana Dwek Children’s Hospital, Tel Aviv, Tel Aviv, Israel; Francis B. Mimouni, Tel aviv university, Tel Aviv, HaMerkaz, Israel

Background: Vitamin D plays a crucial role in calcium homeostasis, bone mineralization, and numerous metabolic and immunological functions. During pregnancy, maternal vitamin D status directly determines fetal stores, as the vitamin crosses the placenta. Despite this dependence, vitamin D deficiency remains common among pregnant women worldwide. Environmental factors, particularly limited sunlight exposure during winter months, are major contributors to seasonal fluctuations in both maternal and neonatal vitamin D concentrations.

Objective: To assess seasonal variation in maternal and neonatal (cord) vitamin D concentrations, evaluate the correlation between maternal and cord blood levels, and examine the relationship between vitamin D concentrations and gestational age at delivery.

Design/Methods: In this IRB-approved prospective study, mothers were recruited prior to delivery during two defined seasonal periods: winter (January 5–March 5) and summer (July 5–September 5). Paired maternal venous and umbilical cord blood samples were obtained for vitamin D measurement. Gestational age at delivery was recorded and analyzed in relation to vitamin D levels.

Results: A total of 91 maternal–cord pairs were analyzed (30 winter, 61 summer). Mean maternal and cord vitamin D concentrations were significantly lower in winter (mean differences –5.3 and –6.5 ng/mL, respectively; both p < 0.001), demonstrating a clear seasonal effect. Vitamin D deficiency was more frequent in winter (maternal 73.3%, cord 66.7%) than in summer (34.4% and 27.9%; both p = 0.002). When categorized dichotomously, deficiency remained higher in winter for both maternal (100% vs. 85.2%; p = 0.027) and cord (96.7% vs. 73.8%; p = 0.008) samples. Maternal and cord vitamin D concentrations were strongly correlated in both seasons (r = 0.91 winter; r = 0.90 summer; both p < 0.001). No significant correlation was observed between gestational age and vitamin D levels.

Conclusion(s): Maternal and neonatal vitamin D levels exhibit significant seasonal variation, with marked deficiency in winter. The strong maternal–cord correlation underscores the pivotal role of maternal vitamin D status in determining neonatal sufficiency. Gestational age was not associated with vitamin D levels, suggesting that seasonal and maternal factors play a more dominant role in influencing perinatal vitamin D status.

Figure 1: Maternal and cord blood vitamin D levels by season
Figure 1 Maternal and cord blood vitamin D levels by season.pdf

Figure 2: Maternal and neonatal vitamin D status by season.
Figure 2 Maternal and neonatal vitamin D status by season.pdf