How Soon Can an Ultrasound Show a Baby's Heartbeat?

pregnant woman getting ultrasound

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While the heart of a fetus is still developing, it may be detectable by ultrasound as early as 6 weeks gestation. Technically, it is not a fetus at this point but an embryo, and the baby's heartbeat is only visible on an ultrasound, not audible this early in pregnancy. 

How the Fetal Heart Develops

The baby's heart develops from two tubes that join together in the middle to create a chamber with four tubes extending from it. It starts to beat between 5 and 6 weeks gestation and may be detected via ultrasound around this time as well. The heart of the embryo continues to develop over the next several weeks. It is fully formed around 10 weeks gestation.

Seeing a Fetal Heartbeat With Ultrasound

There are two types of ultrasounds that are generally used to visualize a pregnancy: a transvaginal ultrasound, in which a probe is inserted into the vagina to gain proximity to the womb, and an abdominal ultrasound, which is placed on the mother's abdomen. Both are useful procedures for various circumstances at different points in pregnancy. Transvaginal ultrasounds can see the growing embryo earlier than abdominal ultrasounds can. 

Abdominal ultrasounds are generally very effective after 8 weeks gestation to detect a fetal heartbeat but not before that time. So, if you are having an ultrasound prior to 8 weeks from your last menstrual period, it will most likely be a transvaginal ultrasound. 

In the early weeks of pregnancy, the fetal heartbeat looks like a rhythmic flickering of light.

What You Can See

Transvaginal ultrasounds produce clear images of the fetus, uterus, and surrounding structures, all of which help doctors confirm pregnancy, establish a pregnancy timeline, and gain insight into the health of the pregnancy.

In addition, an ultrasound is helpful for: 

  • Checking the health of your pelvic organs
  • Determining the number of fetuses you are carrying
  • Identifying your risk of miscarriage
  • Pinpointing the location of the pregnancy (normal or ectopic pregnancy)

When They Are Used

Not all women will have an early pregnancy ultrasound. Whether or not you have one will depend on your doctor's preference and the particulars of your pregnancy and medical history. For example, if you have experienced vaginal bleeding, a miscarriage in a previous pregnancy, or other circumstances that make you or your healthcare provider more alert to potential problems, you may be referred for an early pregnancy ultrasound.

You're more likely to get one in a higher risk pregnancy, such as if you have a chronic medical condition, or when using fertility treatments. Some doctors use ultrasound to confirm pregnancy, others rely on other diagnostic techniques, such as blood tests.

If a Heartbeat Can’t Be Detected

A transvaginal or abdominal ultrasound showing no fetal heartbeat means that either the pregnancy is too early along for the heartbeat to be detected (which is possible if gestational age is 7 weeks or earlier), or a pregnancy loss has occurred.

Sadly, if an ultrasound fails to find a fetal heartbeat after one has previously been seen, the doctor may conclusively diagnose miscarriage. In addition, when there is no heartbeat detected in a pregnancy that is definitely far enough along that the heartbeat should be visible, this also indicates a miscarriage has occurred.

Hearing a Fetal Heartbeat

A stethescope or handheld doppler devices may be used to hear the heartbeat beginning around 8 weeks. However, it may take until 10 to 12 weeks or so to be audible.

A Word From Verywell

Seeing and/or hearing a heartbeat early in pregnancy is a very positive sign that your pregnancy is developing as expected. Know that most likely your pregnancy will progress normally but sometimes complications or pregnancy loss do occur, particularly in the first trimester. So, aim to monitor yourself for signs of miscarriage in the early weeks, and call your health care provider with any questions or concerns. 

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Article Sources
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  1. Herbst MK, Shanahan MM. Obstetric Ultrasound. [Updated 2019 Jun 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-.

  2. Condous G. Ultrasound diagnosis of miscarriage: new guidelines to prevent harm. Australas J Ultrasound Med. 2011;14(4):2. doi:10.1002/j.2205-0140.2011.tb00127.x

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