When to get an ultrasound
Many practitioners recommend an ultrasound at six to nine weeks. However, others will only do an ultrasound during the first trimester if miscarriage or ectopic pregnancy are suspected. If you have any abnormal bleeding, aren't sure of the date of your last period or had fertility treatments, your doctor will also order a ultrasound around the second month of pregnancy. At this point, the doctor will try to determine where the embryo is. If it's not in the uterus (ectopic pregnancy) or if there is an abnormal placenta (molar pregnancy), your practitioner likely will be able to identify the issue on the ultrasound at this point. Some practitioners will choose to order an ultrasound around nine to 13 weeks of pregnancy to look for the signs of Down syndrome or other development issues. This ultrasound is often done in conjunction with blood work.
What happens during an ultrasound
If you have never had an ultrasound for other reasons, it can seem intimidating. However, it's a very simple and safe (no radiation is used) procedure. After you lay down on the exam table, a small amount of gel is applied to the skin of your abdomen. A device (called a transducer) is applied to your skin, sending high-frequency sound waves into your body that reflect back off internal structures. The echoes are received by the transducer and transformed into a picture on the screen. The pictures are usually printed out (or sometimes recorded on video) for you and the doctor. The ultrasound takes approximately 30 minutes and isn't uncomfortable or painful at all. Some doctors will ask you to drink several glasses of water before the test. A full bladder will help view the baby better.
The baby's heartbeat should be visible on the ultrasound by six weeks of pregnancy. Seeing the heartbeat is very emotional for many women (and their partners) as it's the point when the pregnancy starts to feel "real." If you are pregnant with multiples, your doctor will be able to tell from seeing/hearing two or more heartbeats. If the heartbeat isn't identified at this point, your doctor will schedule another ultrasound in a week or so.
The due date
All fetuses are approximately the same size in the early weeks of pregnancy. Therefore, your doctor can usually approximate you due date by taking certain measurements during the ultrasound. If you have your sonogram between weeks seven and 13, measuring from the crown of the head to the rump will allow the doctor to determine the baby's age (and your due date) within about three days.