Influence of Maternal Prenatal Vitamin D Status on Infant Oral Health

Since endogenous synthesis <strong>of</strong> vitamin D in northern regions <strong>of</strong> the United States and
Canada is only possible between the months <strong>of</strong> May and October, an additional variable
was created categorizing months <strong>of</strong> the year into a dichotomous variable called season.
The winter season included months where there is no endogenous 25(OH)D synthesis
(i.e. November to April). Results from t test analysis appear in Table 4.2.
Table 4.1 – Relationship between maternal 25(OH)D levels and month <strong>of</strong> measurement
Month Number Mean ± S.D.
P value
(nmol/L)
January 16 43.2 ± 25.6
< .0001
February 13 40.9 ± 33.1
March 12 34.3 ± 10.1
April 8 25.7 ± 19.1 *
May 10 47.9 ± 12.9
June 15 47.9 ± 24.0
July 20 57.5 ± 20.7
August 24 69.7 ± 29.5 †
September 27 52.3 ± 20.5
October 24 46.6 ± 22.1
November 23 38.4 ± 16.0
December 8 44.1 ± 21.1
* Significantly differs from July
† Significantly differs from January, February, March, April, October, November
Table 4.2 – Relationship between maternal 25(OH)D levels and season <strong>of</strong> measurement
Season Number Mean ± S.D.
P value
(nmol/L)
Winter
80 38.4 ± 21.8