RESULTS
Of the 303 women who were enrolled, 237 had complete mother/umbilical
cord blood data. 138 (47.7%) women had vitamin D deficiency
(< 50nmol/L) at delivery whereas only 34 (13.8%) of the
cord-blood samples showed levels under the recommended cut-off for
newborns (< 30nmol/L) (10). The mean difference between
maternal venous blood and cord blood 25(OH)D was negative (higher levels
in the cord blood compared to the maternal blood) in 91% of cases
(-16.27nmol/L, SD=13.36), Fig 1. The difference was not significantly
associated with maternal 25(OH)D level, placenta weight or delivery mode
(p > 0.493). After dividing the women into three
groups, <25nmol/L (n=64), 25-49.9nmol/l (n=74) and ≥50nmol/L
(n=151) we did not find significant difference in maternal age,
gestational age at delivery, fetal weight, level of ionized calcium
(Ca2+) in the cord blood, maternal body-mass-index
(BMI), nationality, exposure to sunlight, frequency of diabetes or
delivery mode, Table 1. Multiple regression with maternal 25(OH)D as the
dependent variable and supplementation dose, age, BMI, nationality,
education, exposure to sunlight, diabetes as independent variables
showed that only the dose of supplementation (p <0.001)
had a significant influence on maternal 25(OH)D, Table not shown.
The correlation between maternal and umbilical cord 25(OH)D was for the
whole cohort 0.906 (p < 0.001). Subdivision into
different levels of maternal 25(OH)D, delivery mode, diabetes and BMI
showed a lower correlation coefficient for all three subgroups of
maternal levels. For all other calculations the correlation was
excellent (Table 2). There was no correlation between placenta weight or
hematocrit to the umbilical cord level of 25(OH)D (r = 0.193, p =
0.180, respectively r = -0.063, p = 0.353).
The correlation between maternal and umbilical cord 25(OH)D was not to a
clinical point of view affected by the supplementation dose (none
supplementation n = 18, r = 0.948; 10.000UI/week n = 73, r = 0.853;
20.000UI/week n = 38, r = 0.805; all P values < 0.000). For
those without information about supplementation (n = 106) the
correlation coefficient was 0.938 (P < 0.000). The correlation
between umbilical cord Ca2+ and supplementation dose
was non-significant (n = 141, r = 0.000, p = 0.997).
The risk for preterm labor (OR 1.725, 95%CI: 0.808-3.683) preterm
rupture of membranes (OR 1.538, 95%CI: 0.678-3.491), low AS (3.465,
95%CI 0.310-38.777) with 25(OH)D levels < 50nmol/L was not
increased whereas the risk for diabetes was significantly decreased (OR
0.470, 95 CI 0.252-0.879).