Your Baby Today: Ask the Experts: OB/GYN: Ultrasound

Roy Pitkin, M.D., is a professor of obstetrics and gynecology and is the former chair of the ob/gyn department at the University of California, Los Angeles School of Medicine. He is a frequent advisor to national health agencies on women's health issues and has received numerous international honors for this work.

Q: When is an ultrasound typically done during a pregnancy, and what is the technician looking for when it is done?

A: Timing of an ultrasound will depend on the reason it's being done. In the first two or three months of pregnancy, it can be used to confirm the existence of pregnancy or to count the number of babies in a multiple pregnancy. Halfway through a pregnancy, ultrasound can establish a baseline for later monitoring of fetal growth, to assess the baby's development. Toward the end, the doctor might want to check the position of the baby, the location of the placenta, or the amount of amniotic fluid.