A first trimester early pregnancy and dating 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 prior to 6 weeks gestation, so unless there is an urgent need to have an early pregnancy and dating 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 indications for conducting a 1st trimester ultrasound include:
- Confirmation of dates/gestational age
- Confirm Intrauterine location or ectopic pregnancy
- Previous miscarriage
- Defining number of embryos
Your ultrasound may be performed transabdominally or transvaginally. Transvaginal ultrasound involves placing a thin transducer (slightly thicker than a tampon) into the vagina. The transvaginal ultrasound can offer extra detail to the examination as it allows the ultrasound probe to come into close 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.
About this Early Pregnancy & Dating Ultrasound
Your examination will be performed by a sonographer. Upon being taken into the examination room the sonographer will introduce themselves, confirm your identity and examination. A clear gel is applied to the skin over the area to be examined. The ultrasound probe is moved over the surface to study the structures below.
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 in to 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 of the examination 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, please advise 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 Dr Jones & Partners multimedia policy.
Before your Scan
It is a good idea to wear comfortable, loose fitting clothing that allows easy access to the area that is being imaged, so two piece clothing is ideal (separate upper/lower garments).
Transabdominal: A full bladder is required. Drink one litre of water finishing one hour prior to your appointment and do not empty your bladder. Distension of your bladder provides a window to view your pelvic organs and compresses bowel out of the way. Your bladder need not be overly full that it causes you pain or distress; please advise reception staff on arrival if this is the case and you will be advised of your options.
Transvaginal: Imaging is performed with an empty bladder and as a result many women may find it more comfortable.
Preparation details for your examination will be confirmed when you make your appointment.
Approximately 15 – 30 minutes.
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