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 bleedingReview measurements and how they apply to dating criteriaDiscuss how to document a first trimester ultrasound in the medical record
4 Indications Dating of pregnancy Size vs dates discrepancy; multiple gestation determination *(1st Trimester)*Vaginal bleedingAbdominal 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 studyEarly dating is the most accurate (+/- 5-7d or 8%)Better defines timing for later testing and interventionsTriple/Quad testTocolysis/SteroidsReduces the incidence of induction for postdates
6 Measurements Mean Sac Diameter Embryonic Crown-Rump Length (CRL) Should be measured in 3 dimensionsMay be all that is visible at the discriminatory zone; IUP best confirmed with some fetal element, such as a yolk sacEmbryonic Crown-Rump Length (CRL)Measurement of a CRL with fetal cardiac activity is the best measurement for dating purposes
7 Typical MeasurementsThere are tables for determining gestational age based on:Gestational Sac MeasurementCrown-Rump LengthAll 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 Gestational Age (weeks)Sac Size(mm)CRL43561472782915933211031114112511371
13 Early Pregnancy Failure Failure of appropriate interval growth by u/s of embryoFetal 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 suspicionEven more so in the face of risk factorsThree primary tools for evaluationPhysical examQuantitative β HCGUltrasound
15 Lab and UltrasoundDiscriminatory Zone—the quant β-hCG level at which one would expect to be able to identify an intrauterine pregnancyFor vaginal sonography— ( per ACOG)For abdominal sonography—If the quant β-hCG is at or above the discriminatory zone, AND no IUP can be identified, the pregnancy may be ectopic
19 Other applications Evaluation of gynecologic structures Uterus—position, fibroidsAdnexae—masses, corpus luteumEarly screen for chromosomal anomaliesNuchal translucency measurements
20 DocumentationWhether 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 possibleFetal numberPresence or absence of fetal cardiac activityCrown-rump lengthEvaluation of uterus and adnexal structures and presence of free fluid
21 Final Pearls Do not include the yolk sac with the CRL Practice, practice, practiceAbdominal and VaginalIf you are not sure it is an IUP, get help
22 What Measurement is the most accurate for ultrasound dating? Crown Rump Length – Up to the 12th week of life.
23 In what order do fetal structures appear? Gestational sac – 4 to 5 weeksYolk sac – 5 to 6 weeksFetal pole - 6 to 7 weeksCardiac Activity - 6 to 7 weeks.
24 What organ, what anatomic view? Normal or abnormal?