Obstetrics is the branch of medical science that specializes in the care of females during pregnancy, childbirth, and the subsequent recovery period following delivery. Those who practice this form of medicine are 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 expanded his personal database to include obstetrics and pediatrics. As a result, he put together a prenatal enrichment program for B'Elanna, which would eventually expand into parenting class both both her and Tom. (VOY: "Lineage")