Final answer:
The best place to locate information on the menstrual history, number of pregnancies, and number of living children for each OB patient is the postpartum record.
Step-by-step explanation:
The best place in the record to find information on the menstrual history, number of pregnancies, and number of living children for each OB patient is the postpartum record. The postpartum record includes information about the patient's health and progress after childbirth, including details about their reproductive history and any previous pregnancies. It provides a comprehensive overview of the patient's obstetrical history, making it the most suitable place to locate this information.