Early Ultrasounds – Are They Necessary?  

Early Ultrasounds – Are They Necessary?   

Most women, on finding out they are pregnant, are automatically given a referral for an early or ‘dating’ ultrasound.

They book in, have the ultrasound, and feel excited to see their newly-formed baby on the screen.

They’re also slightly scared at just how vulnerable the little cluster of cells is.

Early Ultrasounds – Are They Necessary?

Early pregnancy ultrasounds are part and parcel of the pregnancy package, yet few women really question whether or not they are necessary.

Why Do I Need An Early Ultrasound?

Most women will have an early ultrasound without anyone ever explaining why it is needed, or discussing the risks and benefits of having one performed.

Some given reasons for an early ultrasound are:

  • To confirm the pregnancy by detecting the baby’s heartbeat – usually around 6-7 weeks gestation.
  • To confirm the estimated due date, especially if you have irregular menstrual cycles, or you are uncertain about the date of your last menstrual period. During pregnancy your care provider will check your baby’s growth; having an accurate due date is said to assist this. The estimated due date, calculated by a scan at 7-8 weeks, will be accurate to plus or minus 3-4 days.
  • To confirm the pregnancy is located in the uterus, and is developing normally.
  • To detect how many babies are present, in case you are more likely to have conceived multiples, due to assisted fertility treatments or family history.
  • To identify any potential problems that would increase the risk of miscarriage – e.g. the heart beat is too low, or the pregnancy too small
  • To investigate the cause of vaginal bleeding and pelvic pain.
  • To confirm that pelvic organs are healthy, and there are no signs of fibroids or ovarian cysts.

What Are The Effects Of Ultrasound?

Ultrasound was originally developed during the Second World War, for the detection of enemy submarines. In the 1950s, a Scottish surgeon discovered that body tissues gave off sound wave echo when ultrasound was applied. It very quickly became a diagnostic tool used in pregnancy.

Find out more about Ultrasounds In Pregnancy – Risks and Benefits.

Ultrasound works by introducing energy into the body. A sonar beam heats the tissue being scanned. How high the temperature reaches depends on the tissues being scanned. Bone will heat up more than soft tissue; fluid is less affected than soft tissue.

The level of heating also depends on the length of exposure, the intensity of the ultrasound machine, and whether the transducer (the instrument placed on the stomach) is held in one position, or moved frequently.

During a normal pregnancy, increases in body temperature of up to 2.5 degrees Celsius are assumed to be safe. Research seems to suggest temperature elevations of up to 2.7 degrees, caused by ultrasound, are also safe.

Animal and human studies have shown that increasing normal temperatures can cause birth defects and abnormal development in fetuses. Yet human studies have not yet shown any direct links between pregnancy ultrasound and any adverse effects on babies. It is this lack of evidence that allows ultrasound to be considered perfectly safe.

It is worth noting, however, all human studies were performed before the early 1990s, when ultrasound intensity was much lower than it is today. The upper intensity limits in the US are almost 8 times higher than the limits set in 1992. There is currently no evidence-based research that looks at how babies are affected by ultrasound at this much higher intensity limit.

Another side effect of ultrasound is cavitation. This is when the small pockets of gas found in mammal tissue begin to vibrate, and then collapse. So far, research has not determined whether there is any significance in cavitation effects on human fetal tissue.

Can I Decline The Early Ultrasound?

Most women aren’t aware they can decline the early ultrasound scan, or even that there might be a reason to do so. The early ultrasound has become a pregnancy ‘rite of  passage’, which is expected and looked forward to. Yet there is absolutely no reason to have an early ultrasound, unless there are indications of medical complications.

The United Kingdom’s Royal College of Obstetricians and Gynaecologists (RCOG) published a paper in 2015, advising ultrasound should be performed only in the first 10 weeks of pregnancy, when clinically indicated (if there is suspicion of medical problems which might threaten the health of the mother or baby).

The RCOG paper looks at the issues of ultrasound exposure in the first trimester of pregnancy, which is known as the embryonic period. This is the stage where the embryo is most vulnerable, due to it being so small, and cell division being so rapid.

The paper’s authors urge caution in the use of early ultrasound, in the light of the lack of current human research. They also go further, to say colour and pulsed wave Doppler – both of which have greater intensity and power output than the type used commonly in obstetrics – shouldn’t be used at all during the first trimester.

The choice to have an early ultrasound should be one that women can make freely, while being aware of the potential risks, as well as the presumed benefits. Most women are very cautious of accepting their pregnancy as ‘real’, or anything more than tentative, in the first trimester; they believe an early ultrasound might help them feel reassured.

Whether or not this is the case, women should be aware they have a choice. Each individual situation should be looked at separately. If you choose to have a scan, make sure that the sonographer is highly skilled and experienced. Ask to have the shortest scan possible, which will give you just the information you require.

Recommended Reading:

10 Procedures You May Want To Reject During Pregnancy

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Sam McCulloch Dip CBEd CONTRIBUTOR

Sam McCulloch enjoyed talking so much about birth she decided to become a birth educator and doula, supporting parents in making informed choices about their birth experience. In her spare time she writes novels. She is mother to three beautiful little humans.


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