First trimester dating ultrasound

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Gestational sac size may be determined by measuring the largest diameter, or the mean of three diameters.

These differences rarely effect gestational age dating by more than a day or two.

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.

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.

Technique First trimester scanning can be performed using either an abdominal approach or a vaginal approach.

Abdominal scanning is performed with a full maternal bladder, provides a wider field of view, and provides the greatest depth of view.

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.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.Vaginal scanning is best performed with the bladder empty, gives a much greater resolution with greater crispness of fine detail.In circumstances where both approaches are readily available, the greater detail provided by transvaginal scans usually outweighs other considerations, and is preferred.In order to use Medscape, your browser must be set to accept cookies delivered by the Medscape site.

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