sonograms ultrasounds Ahhh, the thrill of the ultrasound while pregnant -- you get to peek at your gorgeous, growing baby! Most of us would probably elect to have them weekly if we could. But our doctor calls the shots -- at least in most instances.

How many ultrasounds you'll have while pregnant is a topic of discussion around here. I spoke to Dr. Eva K. Pressman, Associate Professor of Obstetrics and Gynecology and Director of Obstetrics and Maternal Fetal Medicine at the University of Rochester, about what pregnant moms can expect.

How many sonograms should a woman have while pregnant? What's "normal?"

There is no exact standard for ultrasound evaluation during pregnancy in this country -- a woman can typically expect one or two.

Most patients will have at least one scan at 18 - 20 weeks gestation to evaluate the fetal anatomy. It is also common to have a scan in the first trimester to establish dating for the pregnancy and, if desired, screen for Down syndrome. (This first trimester ultrasound would include the nuchal translucency and is combined with a blood test for a complete "first trimester screen.")

Sonograms done in the third trimester are usually to assess fetal growth if the size of the uterus (as measured by a measuring tape on the maternal abdomen) does not grow as expected.

At what appointment is the first sonogram typically performed?

The most common sonogram is the one done at 18 - 20 weeks (4 - 5 months). If there is bleeding in the first trimester, a question of how far along a patient is, or the patient desires first trimester screening for Down syndrome, the first scan would be done in the first trimester, anywhere from 6 - 13 weeks, depending on the indication.

And after that? Do some women have them at each monthly visit?

Uncomplicated pregnancies in which the uterus grows at the expected rate do not require any additional sonograms. There are very few medical indications that would require a sonogram at each monthly visit.

When is the last sonogram before birth typically performed?

The last scan is often the one done at 18 - 20 weeks, which is the best time to evaluate all of the fetal anatomy.

How much of this simply has to do with your healthcare provider -- his/her philosophy and access to the equipment?

The number of sonograms is affected by the patient's desire to have more scans, the physician's access to equipment, and complications that arise in the pregnancy.

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3D ultrasound technology, sometimes used by parents to take commercial "keepsake" photos, is a different thing altogether -- and the Food and Drug Administration (FDA) cautions against taking prenatal photos when there is no medical need to do so. 3D scans may also be used by a practitioner if he detects a problem with the baby.

Talk to your doctor with any questions you have about ultrasounds.

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What about you? How many ultrasounds have you had? Only the typical one or two, or have you had more?