Increased Parathyroid hormone serum concentrations, [PTH] enhance 1,25-(OH)2D and decrease 24,25-(OH)2D synthesis from 25-hydroxy vitamin D (25-OHD). At term, pregnant women have elevated PTH and infants have low [PTH]. 16 pairs of maternal (M) and umbilical cord (C) venous sera were analyzed for 24,25-(OH)2D, 25-OHD, calcium, magnesium and PTH. Both M 24,25-(OH)2D (2.6±0.5 ng/ml) and C 24,25-(OH)2D (3.0±1.2 ng/ml) were lower than 29 adult normals (5.0±0.6 ng/ml). Normal adult 24,25-(OH)2D is correlated with 25-OHD (R=.40 P<.03) with a 24, 25/25 of .21±.02. C 24,25-(OH)2D was also correlated with C 25-OHD (R=.49 P<.05) with a 24, 25/25 of .21±.10 whereas M 24,25-(OH)2D was not correlated with M 25-OHD (R=.10, N.S.) with a 24,25/25 ratio of .13±.05. Whereas M and C 25-OHD are correlated (R=.71), M and C 24,25(OH)2D were not correlated (R=.26), with the majority of C 24,25(OH)2D higher than M 24,25(OH)2D. C-M differences were 1.79±1.04 mg% calcium and .17±.15 meq/L magnesium. C-M calcium and C-M magnesium was positively correlated (R=.87) as were M calcium and magnesium (R=.81) and C calcium and magnesium (R=.69). No significant correlations were found between C, M, or C-M calcium and magnesium and M or C 24,25-(OH)2D and 25-OHD. The decreased M 24,25-(OH)2D is consistent with the recognized increased M “PTH]. Since C [PTH] is low, the relatively low C 24, 25-(OH)2D suggests little fetal synthesis of this sterol.