Venous blood was obtained from 100 consecutive and unselected Saudi Arabian mothers and their neonates within 48 h after delivery. Plasma levels of 25-hydroxyvitamin D (25-OHD) and total calcium were measured in paired samples. Fifty-nine mothers and 70 neonates had subnormal (less than 10 ng/ml) 25-OHD levels. Plasma Ca concentrations were low in 61% of the mothers and 59% of the newborns consisting of 10 preterm and 38 full term babies. There were significant correlation between the plasma levels of maternal and neonatal 25-OHD (r= 0.54; P= 0.0001), maternal 25-OHD and Ca (r=− 0.22; P= 0.03), neonatal 25-OHD and Ca (r=− 0.28; P= 0.0009), and maternal and neonatal calcium levels (r= 0.46; P= 0.0001). Nevertheless, maternal 25-OHD was not invariably higher than that in the infant. Normocalcemia was observed in 29 neonates and 26 mothers (20 mother/baby pairs) in the presence of subnormal maternal 25-OHD. Twenty babies and 16 mothers including nine mother/baby pairs had hypocalcemia in the presence of normal levels of 25-OHD. This indicates that vitamin D plays a crucial, but not exclusive, role in calcium homeostasis during pregnancy.