Tips for Ultrasound Imaging in First Trimester of Pregnancy

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Published: 12 Dec 2017      

Though ultrasound is used in several types of medical procedure, it’s perhaps most closely associated with pregnancy. As a result, anybody who’s looking for an ultrasound job should have at least a rudimentary knowledge of how to conduct ultrasound procedures on pregnant women.

Beyond the basics, these tips will give you an idea on how to optimise the images that you generate while scanning somebody in the first trimester of pregnancy, thus allowing you to provide more accurate treatment to your patients.

Ensure the Patient has a Full Bladder

While having a full bladder means some discomfort for the patient, it also creates the best acoustic setting for an accurate ultrasound scan. Your machines waves will be better able to penetrate the womb, ovaries, and fallopian tubes, thus creating a better visualisation. The only contradiction to this is when performing trans-vaginal ultrasounds, as these require to close use of a probe near the pelvic organs, which a full bladder can obstruct.

If the patient does not have a full bladder, intravenous hydration is an option.

Choosing Your Probe

The probe you choose depends on what you’re looking for. Generally, a low-frequency probe does the job, as this allows the ultrasound waves to penetrate further, thus providing a more accurate visualisation. Curvilinear probes tend to be favoured, as they provide good image quality and can be switched between obstetrician and gynaecological functions.

Know the Stages of Early Pregnancy

Pregnancies progress quite quickly during the early stages, so you need to know what you’re looking for as each week goes by. This includes the first signs of pregnancy, which are the presence of a gestational sac, detected via a trans-abdominal pelvic scan. You may see a pseudo-sac in the case of an ectopic pregnancy.

From there, you should be able to detect the foetus’ cardiac activity at about the five to six-week mark using trans-vaginal imaging, which includes being able to track its heart rate. You’ll be able to do the same with trans-abdominal imaging within six to seven weeks. Use M-Mode to detect the motion of the foetus’ heart, but avoid using Power Doppler. This transmits a lot of energy, which can potentially damage the heart.

Being able to detect the heart rate accurately is key to assessing the state of the pregnancy.

Don’t Assume One Child

You should also scan for multiple gestations before removing your probe to discuss the results with your patient. After finding a gestational sac, take some time to search for another one before moving forward with your analysis.

Ask About the Conception

As more women look towards in-vitro fertilisation, you need to be aware of how this can change the results of your early ultrasound scans. About 1% of women who have undergone in-vitro fertilisation undergo heterotopic pregnancies. Knowing how the baby was conceived beforehand clues you in on potential early issues to look for that you might otherwise have missed.

Ensure Obstetric Follow-up

This is particularly important in cases where you detect an intrauterine pregnancy with your ultrasound. Encourage the patient to follow up your results with an obstetrician as soon as possible. This is the case regardless of whether you detect any cardiac activity.

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