Q&A: I am 18 weeks pregnant and have concers about the saftey of an ultrasound.

There is no evidence that routine ultrasound at 18 to 20 weeks causes any damage to the baby, and no reason to believe so. Even in complicated pregnancies where moms get ultrasounds at frequent intervals, multiple ultrasounds have not been found to cause any problems. One ultrasound will not hurt your little one.

In my mind, the greatest downside to ultrasound is that sometimes they find things with unclear implications. For example, a choroid plexus cyst is a small cyst in the baby's brain that is very common, but it is more common in fetuses with trisomy 21 (Down syndrome) than in typical fetuses. It is usually gone within a few months, and doesn't mean that anything is wrong with the baby's brain—it is just found more commonly with some chromosomal conditions. If this sort of finding is seen when you have your ultrasound, it may give you things to worry about that you wouldn't know about if you didn't have the scan. On the other hand, if you want to know about the chance of a problem with the baby's anatomy, like a heart defect or spina bifida, you will only get that information if you have a scan.

Talk to your doctor about why he wants you to have the ultrasound. Is he unsure of your due date? Are you measuring surprisingly big or small? Do you have risk factors for problems that can be identified by ultrasound and treated during pregnancy? Or does he just order ultrasound routinely? You may just want to go with the flow, and follow your doctor's routines. If you choose not to get the scan now, you can probably get one later on if questions arise.