The Meaning of No Fetal Heartbeat on an Early Ultrasound

Fetal heartbeat not detected on early ultrasound

 Verywell / Colleen Tighe

Seeing your baby's heartbeat on an early pregnancy ultrasound is one of the surest indicators that a pregnancy is proceeding as it should. In general, the risk of miscarriage is much lower once the pregnancy has reached this point. But what does it mean if you go in for an ultrasound, and there is no fetal heartbeat?

Why Fetal Heartbeat May Not Be Detected

There are a few possible reasons for the absence of a heartbeat on ultrasound. If you have no other symptoms, rechecking with another an ultrasound test in a week is the most common recommendation.

Type of Ultrasound

A transvaginal ultrasound (an ultrasound in which a probe is inserted into your vagina to get better access to your uterus) is generally much more accurate than an abdominal ultrasound in early pregnancy. Prior to eight weeks gestation, a transvaginal ultrasound provides by far the best results.

Finding a fetal heartbeat on a handheld doppler can take even longer. You may be able to hear a fetal heartbeat with these devices at seven to eight weeks. Or you may not hear a heartbeat until you are 12 weeks along.

Gestational Age

If you are less than seven weeks pregnant, it's unlikely to find a heartbeat by ultrasound. Using a transvaginal ultrasound, a developing baby's heartbeat should be clearly visible by the time a woman is seven weeks pregnant. Abdominal ultrasound is considerably less sensitive, so it can take longer for the heartbeat to become visible.

Accuracy of Your Dates

If you believe you are at least seven weeks along and have had a transvaginal ultrasound that did not 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 did not ovulate exactly two weeks after your menstrual period started, there is a chance you are not really "seven weeks pregnant" in gestational age. This is true even if it has been seven weeks since your last menstrual period.

No Heartbeat on Follow-Up Ultrasound

If you have a follow-up ultrasound after a week and there is no change (still no heartbeat), the likelihood of miscarriage is greater. But it may still be too early in your pregnancy for a heartbeat to be found. If your periods were irregular, even though it is seven weeks from your last menstrual period, you may still be only five weeks along at a second ultrasound.

No Fetal Heartbeat After Seven Weeks Gestation

If you are past seven weeks pregnant, seeing no heartbeat may be a sign of miscarriage. But there are many exceptions to the "heartbeat by seven weeks" rule. You've likely heard of people who were certain they had miscarried or were not pregnant, and then went on to have a normal pregnancy.

Since there can be exceptions and the approach you take next is extremely important, medical authorities have developed guidelines as to when you can be fairly certain you have had a miscarriage.

Lack of a Fetal Heartbeat Indicating Miscarriage

Sometimes a lack of a fetal heartbeat does indicate a definite miscarriage. These situations include:

  • Having previously seen the heartbeat but finding no heartbeat on a subsequent ultrasound
  • Seeing no heartbeat and having falling hCG levels
  • Having ultrasound measurements that indicate a heartbeat should definitely be present

Guidelines for Diagnosing a Miscarriage by Ultrasound

Organizations have adopted different criteria as to when ultrasound findings indicate a miscarriage. The Society of Obstetrics and Gynecology of Canada criteria include:

  • No heartbeat in an embryo larger than 5 millimeters
  • Gestational sac larger than 8 millimeters without a yolk sac
  • Gestational sac larger than 16 millimeters without an embryo

ACOG Definite Signs of Miscarriage

The American College of Obstetrics and Gynecology (ACOG) extends the Canadian guidelines to reduce false positives to zero.

  • Absence of embryonic cardiac activity (heartbeat) with a crown-rump length (CRL) cutoff of 5.3 millimeters
  • Gestational sac of an average diameter of 21 millimeters without embryo (whether or not there is a yolk sac)
  • Continued absence of a yolk sac or embryo on a repeat scan if a gestational sac is empty on initial scan

If You're Told You Have Miscarried

The guidelines listed above can be confusing. What is important is that you understand how and why your physician has come to this conclusion, and feel confident that it is correct. You do not want to be second-guessing your choices years from now.

If your physician recommends treatment for a miscarriage after one ultrasound (or even after two) and you are not 100% sure that treatment is the right choice, discuss the matter with your physician and possibly ask for a follow-up ultrasound. Most of the time there is no significant risk associated with waiting a few more days, as long as there is no indication of problems such as an ectopic pregnancy.

Alternatively, you can always get a second opinion from another OB-GYN. Remember that there's nothing wrong with getting the advice of another physician if you are in doubt.

A Word from Verywell

Having to wait for word on whether you're miscarrying is very difficult, but it is definitely better to be absolutely sure before getting a diagnosis. Be your own advocate for your care. Ask as many questions as you need, and expect to receive clear and compassionate answers.

For medical professionals, miscarriages are daily occurrences, but for you, they are not. It is normal to grieve, whether it is the anticipatory grief that comes with wondering about the absence of a heartbeat or the grief of loss if you miscarry. People go through stages of grief after​ a miscarriage and everyone responds differently. Honor yourself and grieve in the way that is best for you and your partner.

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