A non-comparative study was conducted to examine the effects of 80,000 IU vitamin D given in a single dose to 59 pregnant women from northern or southern France between their 27th and 32nd week of gestation during the winter season. Serum levels of 25 hydroxy-vitamin D (25 OH D), intact Parathyroid Hormone (iPTH), calcium, phosphates, proteins were measured at the inclusion, at delivery (mother and arterial cord) and in the newborn between the 3rd and the 5th day of life. The mothers' sun exposure and their vitamin D dietary intakes were evaluated with scores at the inclusion and at delivery. Before vitamin D supplementation, 34% of the women had a 25 OH D concentration below 10 ng/ml and 32% had hypocalcemia. At delivery, only one woman had a low 25 OH D concentration, whereas 15% of the women showed hypocalcemia. No neonatal hypocalcemia was observed and no vitamin D overdose was recorded in this study. The mothers' vitamin D dietary intakes were quite high; the lack of sun exposure during last summer appeared as a major vitamin D deficiency risk. A single dose of 80,000 IU vitamin D, taken between the 27th and the 32nd amenorrhoea weeks in winter, seems to be a good compromise between efficacy and tolerance.