First trimester scanning is useful to identify abnormalities in the early development of a pregnancy, including miscarriage and ectopic pregnancy, and provides the most accurate dating of a pregnancy.
Technique First trimester scanning can be performed using either an abdominal approach or a vaginal approach.
In circumstances where both approaches are readily available, the greater detail provided by transvaginal scans usually outweighs other considerations, and is preferred.
The patient is scanned in the normal examination position (dorsal lithotomy) with her feet secure in stirrups and her perineum even with the end of the examination table.
Place a small amount of ultrasonic coupling gel on the tip of the transvaginal transducer. After lubricating the vaginal opening, gently insert the transducer into the vagina.
Visualize the longitudinal plane of the uterus (sagital section) and evaluate its' size.
It can be measured from the cervix to the fundus, AP diameter, and width.
Normal uterine volume is less than 100 cc (nulliparous patients) and less than 125 cc (multiparous patients).Identify (if present), the gestational sac, yolk sac, fetus (or fetuses), presence or absence of fetal movement and fetal heart beat.After the uterus is evaluated by sweeping up and down and side to side, the ovaries are identified and evaluated.This is most easily accomplished by first identifying the internal iliac vessels.The ovaries are usually located just anterior to the iliac vessels.Document important views and measurements on film or electronically.