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Page 1: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

First Trimester UltrasoundFirst Trimester Ultrasound

Page 2: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

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QuestionsQuestions

What Measurement is the most accurate What Measurement is the most accurate for ultrasound dating?for ultrasound dating?

In what order do fetal structures appear?In what order do fetal structures appear?

What are the 7 items to document in 1What are the 7 items to document in 1stst trimester ultrasounds?trimester ultrasounds?

Page 3: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

ObjectivesObjectives

• Review the indications for first Review the indications for first trimester ultrasoundtrimester ultrasound• Discuss utilization of ultrasound and Discuss utilization of ultrasound and

laboratory data in the evaluation of laboratory data in the evaluation of first trimester bleedingfirst trimester bleeding• Review measurements and how they Review measurements and how they

apply to dating criteriaapply to dating criteria• Discuss how to document a first Discuss how to document a first

trimester ultrasound intrimester ultrasound in the medical the medical recordrecord

Page 4: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

IndicationsIndications

• Dating of pregnancyDating of pregnancy

• Size vs dates discrepancy; multiple Size vs dates discrepancy; multiple gestation determination gestation determination **(1(1stst Trimester)* Trimester)*

• Vaginal bleedingVaginal bleeding

• Abdominal or pelvic pain: rule out Abdominal or pelvic pain: rule out ectopic pregnancy/ torsion/ ectopic pregnancy/ torsion/ heterotopic pregnancy/ ovarian cyst heterotopic pregnancy/ ovarian cyst ***Not credentialed to do******Not credentialed to do***

• To confirm viabilityTo confirm viability

Page 5: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Pregnancy Dating with 1Pregnancy Dating with 1stst trimester ultrasoundtrimester ultrasound

• The only utility for “routine” ultrasound as The only utility for “routine” ultrasound as determined by the RADIUS studydetermined by the RADIUS study

• Early dating is the most accurate (+/- 5-7d Early dating is the most accurate (+/- 5-7d or 8%)or 8%)

• Better defines timing for later testing and Better defines timing for later testing and interventionsinterventions– Triple/Quad testTriple/Quad test– Tocolysis/SteroidsTocolysis/Steroids

• Reduces the incidence of induction for Reduces the incidence of induction for postdatespostdates

Page 6: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

MeasurementsMeasurements

• Mean Sac DiameterMean Sac Diameter– Should be measured in 3 dimensionsShould be measured in 3 dimensions– May be all that is visible at the May be all that is visible at the

discriminatory zone; IUP best confirmed discriminatory zone; IUP best confirmed with some fetal element, such as a yolk with some fetal element, such as a yolk sacsac

• Embryonic Crown-Rump Length Embryonic Crown-Rump Length (CRL)(CRL)– Measurement of a CRL with fetal cardiac Measurement of a CRL with fetal cardiac

activity is the activity is the bestbest measurement for measurement for dating purposesdating purposes

Page 7: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Typical MeasurementsTypical Measurements

• There are tables for determining There are tables for determining gestational age based on:gestational age based on:– Gestational Sac MeasurementGestational Sac Measurement– Crown-Rump LengthCrown-Rump Length

• All of the U/S machines at NHP All of the U/S machines at NHP contain software which perform contain software which perform these calculations. The these calculations. The measurements will trigger the measurements will trigger the gestational age determination.gestational age determination.

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Determination of Gestational AgeDetermination of Gestational Age

Gestational Age (weeks)

Sac Size

(mm)

CRL

(mm)

4 3

5 6

6 14

7 27 8

8 29 15

9 33 21

10 31

11 41

12 51

13 71

Page 9: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

The Early Gestational SacThe Early Gestational Sac

Page 10: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Early EmbryoEarly Embryo

Page 11: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

The Crown-Rump LengthThe Crown-Rump Length

Page 12: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Late 1Late 1stst Trimester—10 week Trimester—10 week

Page 13: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Early Pregnancy FailureEarly Pregnancy Failure

• Failure of appropriate interval growth Failure of appropriate interval growth by u/s of embryoby u/s of embryo• Fetal pole/yolk sac should be seen by Fetal pole/yolk sac should be seen by

the time the MSD is 20 mm (not as the time the MSD is 20 mm (not as accurate as FCA though)accurate as FCA though)• Fetal Cardiac Activity should be seen Fetal Cardiac Activity should be seen

by the time the CRL is 4mm (5mm by the time the CRL is 4mm (5mm per AIUM)per AIUM)– If not, may repeat the u/s in one weekIf not, may repeat the u/s in one week

Page 14: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Rule out ectopicRule out ectopic

• Classic triad—amenorrhea, vaginal Classic triad—amenorrhea, vaginal bleeding, painbleeding, pain

• Must have a high index of suspicionMust have a high index of suspicion– Even more so in the face of risk factorsEven more so in the face of risk factors

• Three primary tools for evaluationThree primary tools for evaluation– Physical examPhysical exam– Quantitative β HCGQuantitative β HCG– UltrasoundUltrasound

Page 15: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Lab and UltrasoundLab and Ultrasound

• Discriminatory Zone—the quant β-Discriminatory Zone—the quant β-hCG level at which one would expect hCG level at which one would expect to be able to identify an intrauterine to be able to identify an intrauterine pregnancypregnancy• For vaginal sonography—1200-1500 For vaginal sonography—1200-1500

(1000-2000 per ACOG)(1000-2000 per ACOG)• For abdominal sonography—3000-For abdominal sonography—3000-

40004000• If the quant β-hCG is at or above the If the quant β-hCG is at or above the

discriminatory zone, AND no IUP can discriminatory zone, AND no IUP can be identified, the pregnancy may be be identified, the pregnancy may be ectopicectopic

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Page 17: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Rapidly Rising Quant β HCGRapidly Rising Quant β HCG

• Identifying multifetal gestationIdentifying multifetal gestation

• Identifying gestational trophoblastic Identifying gestational trophoblastic diseasedisease

• Don’t forget lab error (i.e. normal Don’t forget lab error (i.e. normal pregnancy in your differential)pregnancy in your differential)

Page 18: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Multifetal GestationMultifetal Gestation

Page 19: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Other applicationsOther applications

• Evaluation of gynecologic structuresEvaluation of gynecologic structures

• Uterus—position, fibroidsUterus—position, fibroids– Adnexae—masses, corpus luteumAdnexae—masses, corpus luteum

• Early screen for chromosomal Early screen for chromosomal anomaliesanomalies– Nuchal translucency measurementsNuchal translucency measurements

Page 20: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

DocumentationDocumentation

• Whether obtained abdominally or Whether obtained abdominally or vaginally, the following information should vaginally, the following information should be obtained and documented:be obtained and documented:– Presence or absence of IU gestational sac Presence or absence of IU gestational sac

and identification of an embryo if and identification of an embryo if possiblepossible

– Fetal numberFetal number– Presence or absence of fetal cardiac Presence or absence of fetal cardiac

activityactivity– Crown-rump lengthCrown-rump length– Evaluation of uterus and adnexal Evaluation of uterus and adnexal

structures and presence of free fluid structures and presence of free fluid

Page 21: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

Final PearlsFinal Pearls

• Do not include the yolk sac with the Do not include the yolk sac with the CRLCRL

• Practice, practice, practicePractice, practice, practice– Abdominal and VaginalAbdominal and Vaginal– If you are not sure it is an IUP, get helpIf you are not sure it is an IUP, get help

Page 22: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

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What Measurement is the most accurate for What Measurement is the most accurate for ultrasound dating?ultrasound dating?

• Crown Rump Length – Up to the 12Crown Rump Length – Up to the 12thth week of life. week of life.

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In what order do fetal structures In what order do fetal structures appear?appear?

• Gestational sac – 4 to 5 weeksGestational sac – 4 to 5 weeks

• Yolk sac – 5 to 6 weeksYolk sac – 5 to 6 weeks

• Fetal pole - 6 to 7 weeksFetal pole - 6 to 7 weeks

• Cardiac Activity - 6 to 7 weeks.Cardiac Activity - 6 to 7 weeks.

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

Page 25: First Trimester Ultrasound. 2 Questions What Measurement is the most accurate for ultrasound dating? What Measurement is the most accurate for ultrasound

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

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

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Components of documentation of a Components of documentation of a first trimester ultrasound first trimester ultrasound

– #1: IUP or no IUP#1: IUP or no IUP– #2: how many fetuses#2: how many fetuses– #3: FCA or no FCA#3: FCA or no FCA– #4: CRL #4: CRL – #5: uterine masses#5: uterine masses– #6: adnexal masses#6: adnexal masses– #7: free fluid#7: free fluid

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The endThe end

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