Am J Obstet Gynecol 17, 1989) Fig 1A A very early, 3-mm mean diameter intrauterine gestational sac at 5 weeks postmenstruation Fig 1B A typical yolk sac.The mean sac diameter of the gestational sac is 10.6 mm.

first trimester dating ultrasound accuracy-86

For United States readers, the website,, of the American Institute of Ultrasound in Medicine will be helpful for guidelines.

Alternatively for international readers, the website,, of The International Society of Ultrasound in Obstetrics and Gynecology should be searched for similar guidelines.

The disadvantages are cost, decreased sensitivity for major anomalies compared to the 20 week exam, and marked increase in training requirements for providers.

The role of the early anatomic survey, when free DNA screening for chromosomal anomalies is being utilized, remains to be determined.

These outliers are not limited to multiple gestations.

In the series by Doubilet and Benson using transvaginal ultrasound , non-visualization of a early intrauterine pregnancy sac, was seen with a β-h CG level as high as 6567 m IU/ml.

A yolk sac is usually seen by 6 menstrual weeks, or by the time the mean diameter of the sac has reached 10 mm (Fig 1B and Fig 1C).

A fetal pole with heart tones is typically seen by the completion of 7 menstrual weeks (Fig 1D).

Their finding is very useful in differentiating early pregnancy sacs from intracavitary fluid.