Portraits of pregnant women are rare in Catholic Renaissance art. In seventeenth-century Holland, the Catholic rule of Spain had been thrown off and a Protestant Calvinistic republic emerged, freeing Dutch artists to choose an unorthodox subject matter for their paintings. The Golden Age of Holland was characterized by extreme wealth, originating from overseas trade, which fostered a marked interest in philosophy, science, medicine, as well as art. Despite this, portraiture of pregnancy remained uncommon. An exception to this rule was Jan Vermeer of Delft, who lived during the zenith of this era. Jan Vermeer painted fewer than 40 pictures, fathered 15 children, and died bankrupt and little appreciated at the age of 43. Vermeer confined himself almost entirely to images of women in various domestic situations, including three figures of pregnant women. In this framework, pregnancy could be viewed as an icon for fidelity and conformism to social expectations. In this paper we investigate the roots of this unusual icon in Vermeer’s oeuvre, and suggest that the use of pregnancy in his paintings could have been inspired by his Delft-resident contemporaries Antony van Leeuwenhoek and Reinier de Graaf, fathers of well-known and opposing theories of reproduction. These eminent scientists and Vermeer’s pregnant wife, who frequently served as his model, might have made pregnancy less mysterious and more realistic to the painter.