The present invention provides a gene-containing composition including a gene and a transporter, the transporter being capable of transporting the gene from a pregnant body to fetal cells. When this composition is administered to a pregnant body, birth of offsprings with gene deficiency can be prevented, and gene deficiency can be treated during pregnancy. In animal experiments, when an unknown gene is introduced to animals during their embryogenic stage, the function of the gene in ontogenesis can be elucidated. Moreover, the composition can be used for breeding animals such as pets, industrial animals and cattle.
