Homologous artificial insemination and fertilization are generally immoral. The Catechism of the Catholic Church specifically defines and addresses these techniques:
Techniques involving only the married couple (homologous artificial insemination and fertilization) are perhaps less reprehensible [than techniques that require the intrusion of a donor or surrogate] yet remain morally unacceptable. They dissociate the sexual act from the procreative act. The act that brings the child into existence is no longer an act by which two persons give themselves to one another but one that "entrusts the life and identity of the embryo into the power of doctors and biologists and establishes the domination of technology over the origin and destiny of the human person. Such a relationship of domination is in itself contrary to the dignity and equality that must be common to parents and children." (CCC 2377; cf. Donum Vitae 5)
That said, the Church does recognize an exception "for those cases in which the technical means is not a substitute for the conjugal act but serves to facilitate and to help so that the act attains its natural purpose" (DV 6).