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First Trimester UltrasoundFirst Trimester 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?
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
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
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
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
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
The Early Gestational SacThe Early Gestational Sac
Early EmbryoEarly Embryo
The Crown-Rump LengthThe Crown-Rump Length
Late 1Late 1stst Trimester—10 week Trimester—10 week
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
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
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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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)
Multifetal GestationMultifetal Gestation
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
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
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
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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?
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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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