Obstetrics was the branch of medical science that specialized in the care of females during pregnancy, childbirth, and the subsequent postnatal recovery period. Those who practiced this form of medicine were known as obstetricians or obstetrics specialists. (VOY: "Prototype"; TNG: "Lessons")
In 2377, when The Doctor began to take care of the pregnant B'Elanna Torres, he proceeded to expand his medical database in obstetrics and pediatrics. As a result, he put together a prenatal enrichment program for Torres, which eventually expanded into a parenting class for both her and Tom Paris. (VOY: "Lineage")