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First Trimester Ultrasound

First Trimester Ultrasound. Questions. What Measurement is the most accurate for ultrasound dating? In what order do fetal structures appear? What are the 7 items to document in 1 st trimester ultrasounds?. Objectives. Review the indications for first trimester ultrasound

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First Trimester Ultrasound

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  1. First Trimester Ultrasound

  2. Questions • What Measurement is the most accurate for ultrasound dating? • In what order do fetal structures appear? • What are the 7 items to document in 1st trimester ultrasounds?

  3. Objectives • Review the indications for first trimester ultrasound • Discuss utilization of ultrasound and laboratory data in the evaluation of first trimester bleeding • Review measurements and how they apply to dating criteria • Discuss how to document a first trimester ultrasound inthe medical record

  4. Indications • Dating of pregnancy • Size vs dates discrepancy; multiple gestation determination *(1st Trimester)* • Vaginal bleeding • Abdominal or pelvic pain: rule out ectopic pregnancy/ torsion/ heterotopic pregnancy/ ovarian cyst ***Not credentialed to do*** • To confirm viability

  5. Pregnancy Dating with 1st trimester ultrasound • The only utility for “routine” ultrasound as determined by the RADIUS study • Early dating is the most accurate (+/- 5-7d or 8%) • Better defines timing for later testing and interventions • Triple/Quad test • Tocolysis/Steroids • Reduces the incidence of induction for postdates

  6. Measurements • Mean Sac Diameter • Should be measured in 3 dimensions • May be all that is visible at the discriminatory zone; IUP best confirmed with some fetal element, such as a yolk sac • Embryonic Crown-Rump Length (CRL) • Measurement of a CRL with fetal cardiac activity is the best measurement for dating purposes

  7. Typical Measurements • There are tables for determining gestational age based on: • Gestational Sac Measurement • Crown-Rump Length • All of the U/S machines at NHP contain software which perform these calculations. The measurements will trigger the gestational age determination.

  8. Determination of Gestational Age

  9. The Early Gestational Sac

  10. Early Embryo

  11. The Crown-Rump Length

  12. Late 1st Trimester—10 week

  13. Early Pregnancy Failure • Failure of appropriate interval growth by u/s of embryo • Fetal pole/yolk sac should be seen by the time the MSD is 20 mm (not as accurate as FCA though) • Fetal Cardiac Activity should be seen by the time the CRL is 4mm (5mm per AIUM) • If not, may repeat the u/s in one week

  14. Rule out ectopic • Classic triad—amenorrhea, vaginal bleeding, pain • Must have a high index of suspicion • Even more so in the face of risk factors • Three primary tools for evaluation • Physical exam • Quantitative β HCG • Ultrasound

  15. Lab and Ultrasound • Discriminatory Zone—the quant β-hCG level at which one would expect to be able to identify an intrauterine pregnancy • For vaginal sonography—1200-1500 (1000-2000 per ACOG) • For abdominal sonography—3000-4000 • If the quant β-hCG is at or above the discriminatory zone, AND no IUP can be identified, the pregnancy may be ectopic

  16. Rapidly Rising Quant β HCG • Identifying multifetal gestation • Identifying gestational trophoblastic disease • Don’t forget lab error (i.e. normal pregnancy in your differential)

  17. Multifetal Gestation

  18. Other applications • Evaluation of gynecologic structures • Uterus—position, fibroids • Adnexae—masses, corpus luteum • Early screen for chromosomal anomalies • Nuchal translucency measurements

  19. Documentation • Whether obtained abdominally or vaginally, the following information should be obtained and documented: • Presence or absence of IU gestational sac and identification of an embryo if possible • Fetal number • Presence or absence of fetal cardiac activity • Crown-rump length • Evaluation of uterus and adnexal structures and presence of free fluid

  20. Final Pearls • Do not include the yolk sac with the CRL • Practice, practice, practice • Abdominal and Vaginal • If you are not sure it is an IUP, get help

  21. What Measurement is the most accurate for ultrasound dating? • Crown Rump Length – Up to the 12th week of life.

  22. In what order do fetal structures appear? • Gestational sac – 4 to 5 weeks • Yolk sac – 5 to 6 weeks • Fetal pole - 6 to 7 weeks • Cardiac Activity - 6 to 7 weeks.

  23. What organ, what anatomic view? Normal or abnormal?

  24. What organ, what view? Normal or abnormal?

  25. What are the “lucky #7” components of a first trimester ultrasound again?

  26. Components of documentation of a first trimester ultrasound • #1: IUP or no IUP • #2: how many fetuses • #3: FCA or no FCA • #4: CRL • #5: uterine masses • #6: adnexal masses • #7: free fluid 27

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