A mother’s state of health and underlying health issues may influence the detection of her unborn baby’s heartbeat, and further tests will be necessary to determine the cause.
Detecting a fetal heartbeat is a sign that the baby is alive and doing fine, but there are times ultrasound exams produce mixed results that raise concerns for the baby’s health.
A silent scan will shock any mom-to-be as it indicates a missed miscarriage.
No heartbeat and measurements less than normal at the time of the scan generally indicate a missed miscarriage. Still, there have been cases where a heartbeat was later detected, and the pregnancy proceeded normally.
The initial diagnosis of a missed miscarriage should be confirmed before any further medical procedures are considered to terminate the pregnancy.
A fetal heartbeat is proof of life, and not immediately detecting a heartbeat does not necessarily mean that life has expired.
Medicine has progressed almost to the point of certainty based on examination results.
Yet, there are times when a second examination has different results from the first, which is the dilemma we will discuss.
A ground-breaking medical study gives hope
A 2015 medical study was conducted in the United Kingdom on the existing criteria to diagnose miscarriage.
Using embryo crown-rump size, sac diameter, and no heartbeat, the results from 3,192 participants enforced the need for a follow-up ultrasound scan after seven days or more.
The study in question speaks for itself as far as the adoption of standard medical protocols is concerned.
This is evident in the quote below:
“Until relatively recently the American College of Radiology guidance to define miscarriage used a mean gestational sac diameter of ≥16 mm for an empty gestational sac or visualisation of an embryo with a crown-rump length of ≥5 mm and no heartbeat. In contrast, the Royal College of Obstetricians and Gynaecologists used a mean gestational sac diameter of ≥20 mm or an embryo with a crown-rump length of ≥6 mm and no heartbeat. For measurements below these cut-off values, a repeat ultrasound scan after seven or more days was recommended.”
As far back as 2011, evidence was provided in a series of papers stating that the guidelines for miscarriage diagnosis were unsafe.
A subsequent review confirmed that the guidelines indeed lacked adequate information.
As no participants were directly involved in the study, it was difficult to follow through with each participant, but out of 549 initial miscarriage diagnoses, 19 were wrong.
Follow up ultrasound scan two weeks later showed that these pregnancies were viable after all.
This may seem like a small number from so many pregnancies, but saving one pregnancy by diligently following up with additional tests is well worth the effort.
A heartbeat is proof of life
Ultrasound scans are an effective means of monitoring and evaluating a baby in the womb, and the sound of your baby’s heartbeat follows through with a flurry of warm emotions.
Yet, not every expecting mother is greeted with this reassuring “hello from the inside.”
The creation of a baby’s heart begins with two tubes joined together in the middle that create a chamber with four tubes extending from it.
It starts to beat at 5 to 6 weeks gestation, and it is possible to detect using ultrasound at this time.
At this point, your baby is still an embryo, and the heart will only be fully formed at around 10 weeks gestation.
The heartbeat can be monitored using a transvaginal or an abdominal ultrasound, which also gives other vital signs like your baby’s measurements.
It is possible that an ultrasound scan may not detect a fetal heartbeat.
Generally, this would mean the pregnancy is too early or the possibility of a failed pregnancy.
A heartbeat might not be detectable at 7 weeks, and a later scan may be able to confirm the baby’s heartbeat.
No detectable heartbeat after a prior examination is a sign that a miscarriage may have occurred. This becomes more plausible if the pregnancy is far enough along that a heartbeat should be visible.
Ultrasound scans are reliable medical instruments, but expectant mothers should still prepare correctly for the examination.
You may be asked not to eat for a few hours before an abdominal scan, or you may be requested to drink a lot of water to fill your bladder before the scan.
Your doctor will advise you on how to prepare for your ultrasound scan.
What a missed miscarriage means
A missed miscarriage is when the embryo has died, but your body hasn’t expelled it yet, and you do not experience the typical miscarriage symptoms of severe cramping and bleeding.
You may still feel as though your pregnancy is continuing as usual. Still, when an ultrasound scan fails to detect a heartbeat when one should be detectable, the chances are high that it’s a possible missed miscarriage.
The exact reason for a missed miscarriage is not always apparent, but a common reason is a chromosomal issue that makes the fetus incompatible with life.
Most doctors will not confirm a missed miscarriage from a single ultrasound examination, especially in the early days of pregnancy.
The reason is that dating the pregnancy can be off as not all women have an identical cycle.
Some women have a longer cycle that can range between 35 and 45 days and does not measure up to the pregnancy wheel based on a 28-day cycle with ovulation on day 14.
Your doctor will also check the HCG hormone levels produced by the placenta, which will double every 48 to 72 hours in a normal pregnancy.
If the level of HCG is not increasing enough and there is no fetal heartbeat, your doctor will likely diagnose a missed miscarriage.
Signs that indicate a missed miscarriage might be definite include:
- A heartbeat was detected on a previous ultrasound but is not visible on a subsequent scan
- No heartbeat with falling HCG levels.
- Ultrasound measurements that indicate a heartbeat should definitely be present.
These indications require time to properly evaluate, especially when checking HCG levels, but all three results combined do not give a promising outcome.
As seen in the 2015 study, there isn’t 100% confirmation of a missed miscarriage without the two-week window for a final ultrasound scan.
There is a chance, however slight, that the heartbeat might be visible within this mercy window period.
Is waiting for another ultrasound after no heartbeat was detected dangerous?
If you are not 100% sure about your doctor’s diagnosis after one or even two ultrasound scans, you can request a follow-up ultrasound and more hormone tests.
For the most part, there is no significant risk to waiting a few more days as long as there is no indication of an ectopic pregnancy.
You can also get a second opinion from a different doctor, which should confirm your doctor’s diagnosis.
Can being overweight be a cause of not hearing a fetal heartbeat?
Being plus-sized does not affect the scan in any way, as the visuals will still present correct measurements. However, in some cases, it might be more difficult to hear the heartbeat clearly.
What may add to the difficulty of hearing a heartbeat early in pregnancy is a tipped uterus which sits more to the back and rests on the bladder.
Follow-up scans will reveal a more prominent heartbeat as the uterus shifts into the correct position.
A heartbeat is proof of life, and if there is no immediately detected with your first ultrasound scan, it does not necessarily mean bad news. A later scan should reveal that all-important sound to let you know that all is well.
A fetal heartbeat can disappear and reappear in the early stages of pregnancy when conducting an abdominal ultrasound, but this is not very common.
The weight of the mother and uterus position can play a role in suppressing the sound of the heartbeat. In this event, a later ultrasound when the pregnancy has advanced a bit may confirm a normal heartbeat.