OB/GYN
A commonly used abbreviation.
OB is short for obstetrics or for an obstetrician, a physician who delivers babies.
GYN is short for gynecology or for a gynecologist, a physician who specializes in treating diseases of the female reproductive organs.
The word 'gynecology' comes from the Greek gyno, gynaikos meaning woman + logia meaning study, so gynecology literally is the study of women.
These days gynecology is focused largely on disorders of the female reproductive organs.
An obstetrician/gynecologist (OB/GYN) is therefore a physician who both delivers babies and treats diseases of the female reproductive organs