While some practitioners will only perform first-trimester ultrasounds on a pregnant woman if she is experiencing bleeding or abdominal pain, ultrasounds have also in many places become so routine that many women will have more than one ultrasound during the early stages of their gestation. Most proponents of routine first-trimester ultrasounds will suggest waiting until the eighth week of pregnancy before undergoing an ultrasound scan unless the expectant mother experiences worrying symptoms.
For newly pregnant women, ultrasound scans can be an exciting opportunity to get to see their baby, and to receive reassurance that their baby is developing normally. However, when an ultrasound scan reveals a lack of a fetal heartbeat, that excitement can quickly turn into dread.
How accurate are early-pregnancy ultrasounds really, and if you had an ultrasound during which your baby's heartbeat was not picked up, could there have been a mistake?
Transvaginal Ultrasound Scans During Early Pregnancy
Before the eighth week of pregnancy and in some cases up to week 12, your healthcare provider may choose to perform a transvaginal ultrasound. Your baby will be so small and low down in your abdomen at this stage that transabdominal ultrasound scans will not give your provider accurate information. During a transvaginal scan, or TVS, the ultrasound transducer is placed into your vagina to get a good picture of what is going on inside your uterus.
If you have a TVS between six and eight weeks gestation, your provider will pick up your baby and the sac. A heartbeat may be detected at this stage, but it is also not unusual for that not to happen. If no heartbeat is seen, you will most likely simply be asked to return in a few weeks.
The fetal heartbeat will usually be easily detected after the eighth week of pregnancy and especially after the tenth. If no heartbeat is detected at this stage, this is a reliable indicator that your baby has passed away, and you will go on to have a miscarriage or a D&C.
A transabdominal ultrasound, an ultrasound scan during which the transducer is placed on your abdomen, can accurately detect a fetal heartbeat between around seven weeks and eight weeks gestation.
Should your provider not be able to detect a fetal heartbeat using a transabdominal scan after the seventh week, it is possible that your pregnancy is less far along than you initially thought and that the heartbeat is not strong enough to be picked up in this way. In case the gestational age of your pregnancy is not in question or a fetal heartbeat was already detected before but is now absent, a lack of fetal heartbeat is a reliable sign of impending miscarriage.
Should your dates not be quite clear and a transabdominal ultrasound fails to detect a fetal heartbeat, your provider will suggest you have a transvaginal scan, which should clarify the status of your baby's heartbeat.
Note: A Doppler may not accurately detect fetal heartbeat until after the first trimester has passed.
No Fetal Heartbeat: What Now?
If your provider failed to detect a fetal heartbeat, here is what may happen next:
- If you are not sure when you conceived and you are not having other miscarriage symptoms, you will most likely be asked to return in a week or two for another scan.
- If a fetal heartbeat was already detected on a previous ultrasound scan, or fetal measurements confirm your gestational dates, a miscarriage will be diagnosed. In some cases, your hCG levels will be tested to confirm this.
You may either be advised to wait for a miscarriage to start naturally, or your provider will suggest a dilation and curettage. In the latter case, if you are not sure of your dates or you would prefer to miscarry naturally, you can ask for a wait and see approach. Most miscarriages can complete on their own without any complications, and the decision to have a D&C is yours alone unless signs of infection are present.
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