How many ultrasound scans do you need during pregnancy?

A pregnancy ultrasound is a scan where a wand is pressed against the mother’s abdomen that transmits high-frequency sound waves that are above the range of human hearing.  The echoes of these sound waves are picked up by the wand and used to construct a fuzzy picture of the fetus and surrounding internal organs¹. Ultrasound sensors have many applications in everyday life. Ships use a form of ultrasound called sonar to navigate at sea, and your automobile uses ultrasound proximity sensors to warn you when you are backing into another car².

Different mothers will have different numbers of ultrasound exams during their pregnancies, and sometimes this depends on your doctor’s preferences. This can lead to some confusion about how many scans is an expectant mother supposed to have?

At minimum, the American College of Obstetricians and Gynecologists (ACOG) recommends that all expectant moms have at least one ultrasound scan in their second trimester of pregnancy^3,4. However, the standard practice for most obstetricians in the United States is to perform two routine ultrasounds during uncomplicated, low-risk pregnancies⁵.

• The first trimester scan, also called the Dating Scan, can be conducted between 8 and 13 weeks gestation. The primary purpose of this scan is to confirm the pregnancy and estimate the due date. Many providers prefer a later time window for this scan in order to get more accurate results. This scan can also detect if the pregnancy has multiple babies or if the fetus is implanted in an abnormal location.

• The second trimester scan is called the Anatomy Scan. The recommended time window for this scan is between 18 and 22 weeks gestation. The anatomy scan is a longer test to check that the baby’s physical development is on track, and also to check that the mother’s body is doing a good job of supporting the pregnancy.

There are many reasons why your obstetrician might request additional scans. Moms are followed more closely if their pregnancy is considered to have elevated risk^6,7. In these cases, the ultrasound becomes a monitoring tool rather than a one-time check. Repeated imaging lets the care team see if a problem is developing, and gives them time to intervene. The professional society of obstetricians, ACOG, recommends that the frequency of ultrasounds should be indication-driven^8,9. That is to say, the ultrasound should be performed to check on something specific, and not just as a routine screen or because the mom wants an ultrasound.

There is no risk to having repeated ultrasounds during pregnancy. The high-frequency sound waves used in pregnancy ultrasounds can cause a slight temperature increase to internal organs, but this is under 2°C, and there are no documented reports of this causing harm to mother or baby⁹.

Some obstetricians do like to conduct ultrasounds more frequently, even for uncomplicated pregnancies¹⁰. While this is harmless, make sure you have clearly understood whether your doctor considers you to have elevated risk factors, and make sure that your health insurance is covering the scans.

References

1. Siemens Healthineers. Ultrasound explained: how does it work? YouTube. Published 2023-06-21
2. Maestre S. What is the difference between sonar and ultrasonic sensors? CircuitBread. Published 2022-04-07
3. Findlay S, Redhead T. How Many Ultrasounds Should I Have During Pregnancy? Healthline. Published 2025-05-12
4. American College of Obstetricians and Gynecologists (ACOG). How many ultrasound exams will I have during my pregnancy? ACOG FAQS Ultrasound exams. Last reviewed: 2025-10
5. UPMC Magee-Womens Hospital in Pittsburgh. What Is the Typical Pregnancy Ultrasound Schedule? UPMC Health Beat. Published 2023-05-08
6. Haeri S. The High-Risk Pregnancy Ultrasound: What Extra Monitoring Looks Like. Ouma Health. Published 2026-04-08
7. Lauring J. An ob-gyn explains what it means for your prenatal care and birth. ACOG Expert View. Last reviewed: 2025-03-15
8. American College of Obstetricians and Gynecologists (ACOG). Ultrasound in Pregnancy. Practice Bulletin No. 175. Published 2016-12
9. American College of Obstetricians and Gynecologists (ACOG). Guidelines for Diagnostic Imaging During Pregnancy and Lactation. Committee Opinion No.723 Published 2017-10
10. What to Expect When You're Expecting. Ultrasound once a month - why? Community Forum. Posted 2023-05-17