On April 21, 1472 Italian physician Paolo Bagellardo (d. 1494) had his treatise on pediatrics, De infantium aegritudinibus et remediis, printed in Padua at the press of Bartholomaeus de Valdezoccho and Martinus de Septem Arboribus.
This was the first medical treatise, and probably also the first scientific treatise, to make its original appearance in printed form rather than having prior circulation in manuscript. It is also one of the two first books published in print by a living author, the other being Valturio's De re militari (1472).
Hook & Norman, The Haskell F. Norman Library of Science and Medicine (1991) no. 102. ISTC no. ib00010000. In November 2013 a digital facsimile was available from the Bayerische Staatsbibliothek at this link.