The Meaning of No Fetal Heartbeat on an Early Ultrasound

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? You may wonder whether this indicates a miscarriage. Learn what to expect next.

Before looking into the possible reasons for the absence of a heartbeat on ultrasound, it is important to look at three factors. It could simply be that it is too early in your pregnancy for a heartbeat to be heard. When this is the case, and if you have no other symptoms, rechecking an ultrasound in a week is the most common recommendation.

• Type of ultrasound: A transvaginal ultrasound (an ultrasound in which an ultrasound probe is inserted into your vagina to get better access to your uterus) is generally much more accurate 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 but 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.
• The accuracy of your dates: If you believe you are at least seven weeks along and have had a transvaginal ultrasound, consider whether your dates could be wrong. In early pregnancy, being off by a few days with your estimated last menstrual period or having an irregular ovulation pattern can make a difference in whether or not you see a heartbeat on an early ultrasound. 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, even if it has been seven weeks since your last menstrual period.

Having a follow-up ultrasound after a week and detecting no change (still no heartbeat) raises the likelihood of miscarriage, but it may still be too early in your pregnancy. If your periods were irregular, even though it is seven weeks from your last menstrual period you may have been four weeks along in gestational age and still only five weeks along at a second ultrasound.

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.

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

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

Organizations have adopted different criteria as to when ultrasound findings indicate a miscarriage. 

The Society of Obstetrics and Gynecology of Canada criteria include:

• There is no heartbeat in an embryo larger than 5 millimeters.
• Gestational sac is larger than 8 millimeters and has no yolk sac.
• Gestational sac is larger than 16 millimeters and has no embryo.

The American College of Obstetrics and Gynecology extend these guidelines to reduce false positives to zero as compared with the Canadian criteria. These are definite signs of a miscarriage:

• The absence of embryonic cardiac activity with a crown-rump length (CRL) cutoff of 5.3 millimeters.
• The gestational sac of an average diameter of 21 millimeters without embryo (whether or not there is a yolk sac)
• If a gestational sac is empty on initial scan, the continued absence of a yolk sac or embryo on a repeat seven or more days later is always associated with pregnancy loss.

The guidelines listed above can be confusing for anyone. What is important is that you understand how and why your physician has come to the conclusion she has, and feel confident that she is correct. You need to feel at peace with your decision one way or the other, and you do not want to be second-guessing your choices years from now.

If your physician is recommending treatment for a miscarriage after one ultrasound (or even after two) and you are not 100 percent sure that treatment is the right choice, you should 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. Please remember that there's nothing wrong with getting the advice of another physician if you are in doubt.

Having to wait for word on whether you're miscarrying is understandably difficult and may be one of the hardest weeks of your life—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 the medical professionals you work with, miscarriages are daily occurrences, but for you, they are not. In losing a pregnancy you are not only losing a child (a child that many people are already attached to) but the hopes and dreams that went with that child.

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. As with other losses, 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.

_Sources

Doubilet P, Benson C, Bourne T, et al. Diagnostic Criteria for Nonviable Pregnancy Early in the First Trimester. The New England Journal of Medicine. 2013. 369(15):1443-51.

Morin L, Cargill Y, Glanc P. Ultrasound Evaluation of First Trimester Complications of Pregnancy. Journal of Obstetrics and Gynecology Canada. 2016. 38(10):982-988.

Preisler J, Kopeika J, Ismail L, et al. Defining Safe Criteria to Diagnose Miscarriage: Prospective Observational Multicentre Study. BMJ. 2015. 351:h4579.