One of the subjects Arabic astrologers dealt with in the medieval era was the animodar of conception, which used lunar cycles to determine gestation times and to verify the degree of an ascendant, in accordance with one of the principles of Pseudo-Ptolemy's Centiloquium. This paper investigates Ibn al-Kammād's treatise on the animodar of conception edited and translated from Arabic manuscript 939 at the Real Biblioteca del Monasterio, San Lorenzo de El Escorial, Madrid. The special significance attached to the animodar by later astrologers had two consequences for Ibn al-Kammād's treatise. First, the treatise, which was initially one of several parts of a book, has arrived to us as a self-contained piece, probably because it was already regarded as such in medieval times. Second, the initial contents in Ibn al-Kammād's treatise gradually underwent a transformation due to the addition of a number of materials associated with the animodar. Keywords: Ibn al-Kammād, Ibn Hilāl, Pseudo-Ptolemy, Vettius Valens, periods of gestation, lunar cycles, ascendant, animodar of conception.