This study was undertaken to determine the longitudinal changes of serum 1,25-dihydroxyvitamin D (1,25-(OH)(2)D) and insulin like growth factor I (IGF-I) levels at 20.7, 27.6, and 35.5 week periods of gestation in 40 pregnant women who remained normotensive (NT) and in 10 women who developed preeclampsia (PE). As compared with the first period, significant increases (P < 0.01) in maternal serum 1,25-(OH)(2)D and IGF-I were observed in the NT group. In the PE group, a similar increase in serum 1,25-(OH)(2)D was observed. In contrast, significant (P < 0.05) lower IGF-I levels were observed in the PE group at the moment of diagnosis. In addition a high incidence of subjects with low increase in IGF-I levels (<percentile 10) was found in the PE group (30% versus 5%, P = 0.02). In conclusion, circulating levels of 1,25-(OH)(2)D were not alterated in women before they developed PE. In the opposite, the high percentage of PE women with low increase in circulating IGF-I levels between the 20th and 35th week of pregnancy suggests early alterations of IGF-I synthesis in women developing PE.