The early pregnancy scans are performed before 12 weeks gestation.
Reasons for scan:
· Dating (irregular menstrual cycle or unknown last period)
· History of previous miscarriage
· History of ectopic pregnancy
· Bleeding/ pain in early pregnancy
· Excessive nausea (hyperemesis)
· Suboptimal or excessive BHCG (pregnancy hormone) levels
Early Ultrasound benefits:
· Confirm viable pregnancy and location (heartbeat seen from approximately 6 weeks)
· May exclude ectopic pregnancy
· Assess dates
· Presence of ovarian cysts or uterine fibroid
How scan is performed:
At 8 weeks of pregnancy an embryo can often be seen well by assessing the lower abdomen with a full bladder (transabdominal scan).
Earlier than 8 weeks or if not well visualised an internal (transvaginal) scan may be performed to achieve optimal visualisation.
Timing of scan:
The timing of TVS scan will depend on the reason it is being performed. Patients with pain or bleeding will be seen urgently. If reassurance is required 7 to 8 weeks is ideal as more information can be obtained from the scan.
· 5 weeks – pregnancy sac
· 6 weeks – embryo
· Fetal heart, usually visualised when embryo 4 mm
Dating is most accurately performed between 7 and 11 weeks. Measurement of the embryo (crown-rump length) is accurate to 3 days.