We conducted a longitudinal study on serum levels of peptides encoded by the calcitonin gene before conception, every month during pregnancy, and 24 h and 5 days after delivery in 26 healthy women. Only subjects fulfilling optimality criteria according to the literature were included. Blood samples for ionized calcium, total (tCT) and extractable (exCT) calcitonin, katacalcin, and calcitonin gene-related peptide (CGRP) were collected. We found no significant changes of ionized calcium, tCT, exCT, and katacalcin levels, while CGRP serum levels showed a significant increase during pregnancy and a fall to preconceptional values after delivery. Since variations of calcitonin levels did not occur in our selected pregnant women, we conclude that thyroidal C cell secretion is not increased during pregnancy. Our data suggest that calcitonin is not involved in the modifications of mineral homeostasis occurring in pregnancy. In addition, the variations of CGRP serum levels we found suggest that such a hormone participates in circulation modifications of pregnant women.