Identification of early pregnancy landmarks by transvaginal sonography: Analysis by logistic regression

Academic Article


  • Objective: To assess the feasibility of logistic regression analysis for determining the gestational ages at which detection of early pregnancy landmarks first can be observed. Design: Retrospective analysis. Setting: University-based tertiary care clinic. Patient(s): Eighty-two women with viable singleton pregnancies in whom ovulation had been achieved by an injection of hCG. Intervention(s): Two hundred fifteen transvaginal sonographic scans. Main Outcome Measure(s): Logistic regression was used to estimate the probability of detection of Sonographic findings as a function of gestational age. Result(s): We found that the likelihood of visualization of a gestational sac or fetal heart motion could be represented accurately by logistic equations. Gestational age at which there was 95% probability of visualization was 35.5 days for the gestational sac and 44.5 days for fetal cardiac activity. The probability of detecting fetal cardiac activity was 95% when the mean gestational sac diameter was 1.6 cm and was 99% at 1.9 cm. Conclusion(s): The sonographic appearance of developmental landmarks in early pregnancy occurs within well-defined gestational time periods, and the probabilities for visualization can be closely approximated using a logistic model. Our results suggest that the number of sonographic examinations required to document infertility treatment success can be minimized by surveillance at standardized gestational ages.
  • Published In

    Digital Object Identifier (doi)

    Author List

  • Steinkampf MP; Guzick DS; Hammond KR; Blackwell RE
  • Start Page

  • 168
  • End Page

  • 170
  • Volume

  • 68
  • Issue

  • 1