A first trimester ultrasound is an examination you have during the first 13 weeks of pregnancy.
Due to the size of the developing structures and embryo, it is uncommon to perform an ultrasound before 5 weeks gestation (5 weeks after the start of your last menstrual period). Ultrasound is not consistently able to confirm viability and fetal heart activity before 6 weeks gestation, so unless there is an urgent need to have a scan earlier, most of these ultrasounds are performed after 6 weeks and ideally at 8 weeks for dating purposes. Urgent cases may still be performed earlier; please discuss this with your referring doctor.
Common reasons to have a first trimester ultrasound include:
- To confirmation of dates of pregnancy/gestational age
- To confirm an intrauterine location or ectopic pregnancy (a pregnancy outside the uterus)
- Previous miscarriage
- To determine the number of embryos.
Your ultrasound may be performed transabdominally (on the skin of the abdomen) or transvaginally. Transvaginal ultrasound involves placing a thin transducer (slightly thicker than a tampon) into the vagina. The transvaginal ultrasound gives more detail to the examination as the ultrasound probe comes into closer proximity to the uterus (womb). A transvaginal scan is optional for all patients, and it is your decision whether to proceed with that part of the examination.
Ultrasound, both transabdominal and transvaginal, is considered to be safe during the first trimester of pregnancy.
Your examination will be done by a sonographer who will introduce themselves and confirm your identity and the procedure you are having. A clear gel is applied to the skin over the abdomen so the ultrasound probe can move easily over the surface of your skin.
Once images have been obtained externally over the abdomen, the transvaginal scan may be offered, and you will be asked to empty your bladder and change into a gown or be appropriately covered. The transvaginal transducer is disinfected before use, and a protective cover is placed over the transducer each time it is used, so there is no risk of infection. The probe is then lubricated with gel prior to insertion into the vagina and then moved gently to visualise the pelvic structures. This part generally takes 10-15 minutes. During both parts of the scan, the sonographer may be required to mildly push, but this should not cause pain. If at any time the examination is causing excessive discomfort or you wish the examination to end, tell the sonographer immediately.
If appropriate and available, you will be able to obtain some images at the end of your examination in accordance with the Jones Radiology multimedia policy.
Before your Scan
If possible, please wear comfortable, loose-fitting clothing for easy access to your abdomen, so two-piece clothing is ideal (separate upper/lower garments).
Transabdominal: A full bladder is required. Drink one litre of water finishing one hour before your appointment and do not empty your bladder. Distension (expansion) of your bladder provides a clearer view of your pelvic organs and compresses your bowel out of the way. Your bladder does not need to be overly full – if it causes you pain or distress, please tell reception staff on arrival.
Transvaginal: The transvaginal imaging is done with an empty bladder, and as a result, many women may find it more comfortable.
Preparation details will be confirmed when you make your appointment.
Approximately 15 – 30 minutes.
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