A first-trimester ultrasound is usually done 7 to 8 weeks from the first day of your last menstrual period, says Rebecca Jackson, MD, assistant professor of obstetrics and gynecology at the Sidney Kimmel Medical College at Thomas Jefferson University in Philadelphia, PA. “The main thing is to confirm pregnancy dating to make sure we have an accurate due date, to make sure that we’re able to see the baby’s heartbeat, and to see if there’s one, or more than one, fetus.”
Your doctor can also use this test to screen for genetic problems, as well as to find any issues with your uterus or cervix. If you’re anxious to learn the baby’s sex, you’ll have to wait a bit longer. The gender reveal, as well as more info about your baby’s anatomy, will come at your next ultrasound, which happens between weeks 18 and 22 of your pregnancy.
A prenatal ultrasound can be done in one of two ways — transabdominally (over your belly) or transvaginally (into your vagina). You may get a transvaginal ultrasound if it’s very early in your pregnancy, because it produces a more accurate image of your still tiny baby.
For a transabdominal ultrasound, you’ll come in with a full bladder. A full bladder tilts your uterus up and moves your intestines out of the way for easier viewing.
Having an ultrasound during your pregnancy is important, because it can give your doctor a lot of information about your baby quickly. “It’s very safe in pregnancy,” Jackson says. “There’s no risk.” If the technician discovers any problems, you may need to come back for a second ultrasound or other tests.
By the Numbers
1958: The year doctors performed the first ultrasound.
2: Number of ultrasounds, on average, women in the United States get during the course of their pregnancies.
120 to 160 beats per minute: A normal fetal heart rate.
75%: How accurate ultrasound is at determining the baby’s sex in the first trimester.
100%: How accurate ultrasound is at determining the baby’s sex in the second trimester.