When to have dating ultrasound

The length and the anterior-posterior dimensions of the gestational sac are measured on this sagittal image of this retroverted uterus Fig 1C The third diameter of the gestational sac seen in Figure 1B is measured in this image.

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Intrauterine sacs embryonic structures Warren and associates described the orderly appearance of gestational sac, yolk sac, and embryo with heartbeat at a given number of days from the onset of the last menstrual period (Table 1).

With a transvaginal probe, a 2- to 3-mm gestational sac can usually be seen by 5 weeks from the last menstrual period (Fig 1A).

The β-h CG cut-offs for visualizing a intrauterine pregnancy sac, a yolk sac, and a fetus with heartbeat are guidelines.

These cut-offs are accurate in a high percentage of patients with singleton pregnancies, but are subject to biologic as well single test error.

Fertil Steril 8, 1988) Discriminatory zones The generally accepted β-h CG discriminatory zone of 2000m IU/ml for the appearance of an intrauterine gestational sac is not 100% reliable.

Recent papers by Doubilet and Benson and Ko and Cheung have provided examples of women with titers greater than 2000 m IU/ml, where transvaginal ultrasound did not identify a early intrauterine sac, and a subsequent ultrasound confirmed a viable pregnancy.The double decidual ring sign was 82% sensitive and 97% specific.Confidence intervals for the reviewed studies were not ideal because of the size of the studies. using high resolution ultrasound found a diagnostic sensitivity of 94% and 100% specificity for the double decidual ring in identifying an intrauterine pregnancy.Failure to understand the limitations of diagnostic ultrasound or inadequate training of physicians in this technique can result in grave complications for the patient and liability for health-care providers.The benefits of routine transvaginal ultrasound at 6–7 weeks from the LMP include: The standard of care for performing routine ultrasound examination at 6–7 weeks varies from country to country.We also rescan the patient in 7–10 days to document the appearance of the yolk sac.

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