Reformed theology unequivocally affirms the virginal conception and birth of Jesus Christ. The Heidelberg Catechism (Q&A 35–36) confesses that the eternal Son of God 'took on him the very nature of man, of the flesh and blood of the virgin Mary, by the operation of the Holy Spirit.' The virgin birth is understood as necessary both to distinguish Christ from ordinary sinful humanity (in Reformed Christology, the absence of a human father helps explain Christ's freedom from original sin) and to signal that salvation comes entirely from God.

Calvin and Reformed orthodoxy treat the virgin birth as an integral article of faith. The Belgic Confession (Article 18) affirms that the Son 'took upon himself the form of a servant... being born of a woman, being truly born.' Reformed Mariology is modest: Mary is honored as the mother of Christ and as a model of faith and obedience, but is not a mediatrix and is not invoked in prayer.