What No Fetal Heartbeat on an Early Ultrasound Means

Seeing your baby's heartbeat on an early pregnancy ultrasound is one of the surest indicators that a pregnancy is progressing as it should. In general, the risk of miscarriage is much lower once a fetal heartbeat has been detected.

Sadly, the reverse is also true. If no fetal heartbeat is detected on an ultrasound, there's a greater likelihood that the pregnancy will not be carried to term. Miscarriage is one explanation for no fetal heartbeat. However, your doctor might not write the pregnancy off just yet, as other reasons could be behind no heartbeat in a healthy fetus.

Learn more about why you might not hear a heartbeat at your early ultrasound, and whether or not you should be concerned.

Why Fetal Heartbeat May Not Be Detected

If your provider doesn't hear a heartbeat, they'll assess you for other possible miscarriage symptoms. If they don't find any, rechecking with another ultrasound after seven to 10 days is the most common recommendation.

The following are a few possible reasons for the absence of a fetal heartbeat on ultrasound.

The type of ultrasound

Early in pregnancy, a standard abdominal ultrasound won't give your doctor a clear view of your fetus. Instead, they'll most likely do a transvaginal ultrasound, which involves a probe inserted into your vagina to get better access to your uterus. For this reason, transvaginal ultrasound is more accurate than abdominal ultrasound in detecting fetal heartbeat.

Gestational age

If you're less than five or six weeks pregnant, it's unlikely to find a heartbeat by ultrasound. For this reason, many providers won't see pregnant patients until they've passed this gestational age. Keep in mind that, if you're not sure exactly when you conceived, you might not know exactly how far along you are.

Accuracy of your dates

If you believe you're at least seven weeks along and you've had a transvaginal ultrasound that didn't detect a fetal heartbeat, consider whether your dates could be wrong. In early pregnancy, being off by a few days or having an irregular ovulation pattern can make a difference.

For example, if you didn't ovulate exactly two weeks after your menstrual period, there's a chance you're not really "seven weeks pregnant" in gestational age. This is true even if it's been seven weeks since your last menstrual period.

If you're not sure when you conceived, your health care provider will be able to give you an accurate estimate based on your fetus's measurements.

No Heartbeat on Follow-Up Ultrasound

If you don't show any other signs of miscarriage, your health care provider will most likely ask you to return for a follow-up ultrasound. But if there's still no heartbeat, you might need to prepare yourself for a miscarriage.

When No Fetal Heartbeat Indicates Miscarriage

Sometimes the lack of a fetal heartbeat does indicate a miscarriage. If you saw a heartbeat at an earlier ultrasound but not at the next, that's a pretty clear indication that something isn't right. The heartbeat should be getting easier to detect, rather than more difficult.

Your health care provider will also assess possible miscarriage through ultrasound measurements,  which give an estimate of gestational age. If you're still not detecting a heartbeat after your fetus reaches a certain size, you can be fairly certain that you'll lose this pregnancy.

Falling hCG levels are another clue that miscarriage is imminent. Your provider may measure your hCG levels if you have certain risk factors, such as prior miscarriages.

Guidelines for Diagnosing a Miscarriage by Ultrasound

Organizations have adopted different criteria to determine when ultrasound findings indicate a miscarriage. Research shows that a heartbeat should be detected in embryos larger than 7 millimeters.

Other criteria that indicate a miscarriage include:

• Absence of an embryo with a heartbeat at least 11 days after an ultrasound of a gestational sac with a yolk sac
• Absence of an embryo with a heartbeat at least two weeks after an ultrasound of a gestational sac with no yolk sac
  
• Gestational sac larger than 8 millimeters without a yolk sac

If you're experiencing a miscarriage, ask questions so you're comfortable with your treatment plan. Also, give yourself grace as you process and cope with this news.