title: Changes in fetal cardiac axis between 8 and 15 weeks' gestation.
abstract: OBJECTIVE
  To document changes in the normal embryonic/fetal cardiac axis in the late first and early second trimesters of pregnancy.
  
  
  METHODS
  Images from 188 fetal echocardiograms performed prospectively between 8 and 15 weeks' gestation in 166 healthy pregnancies and in 10 pregnancies with severe fetal heart disease were reviewed. For each echocardiogram, three measurements of the cardiac axis were taken in the axial plane at the level of the four-chamber view. Differences in mean embryonic/fetal cardiac axis at different gestational ages in the healthy pregnancies were compared.
  
  
  RESULTS
  The mean ± SD embryonic/fetal cardiac axis was 25.5 ± 11.5° from 8 + 0 to 9 + 6 weeks (Group  1), 40.4 ± 9.2° from 10 + 0 to 11 + 6 weeks (Group  2), 49.2 ± 7.4° from 12 + 0 to 12 + 6 weeks (Group  3), 50.6 ± 5.7° from 13 + 0 to 13 + 6 weeks (Group 4) and 48.6 ± 7.3° from 14 + 0 to 14 + 6 weeks (Group 5). Groups 1 and 2 were significantly different from each other and all other groups (P < 0.05). The results for 22 cases with repeat measurements from 8 + 0 to 11 + 6 and 12 + 0 to 14 + 6 weeks confirmed that the embryonic/fetal cardiac axis increased significantly (P < 0.001). In the cases with severe congenital heart disease, the cardiac axis was > 90th centile in four cases and < 10th centile in two cases.
  
  
  CONCLUSIONS
  The embryonic cardiac axis is relatively midline at 8 weeks and levorotates in the late first trimester. By 12 weeks' gestation, the normal leftward fetal cardiac axis is established and remains stable until at least 14 + 6 weeks. Observation of an abnormal cardiac axis in some cases of severe congenital heart disease prior to 15 weeks' gestation may assist in prenatal detection.
authors.affiliation: Fetal and Neonatal Cardiology Program, Department of Pediatrics, Division of Cardiology, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: A
authors.initials: A
authors.lastname: McBrien
authors.forename: L
authors.initials: L
authors.lastname: Howley
authors.forename: Y
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: D
authors.initials: D
authors.lastname: Hutchinson
authors.forename: A
authors.initials: A
authors.lastname: Hirose
authors.forename: P
authors.initials: P
authors.lastname: Sekar
authors.forename: V
authors.initials: V
authors.lastname: Jain
authors.forename: T
authors.initials: T
authors.lastname: Motan
authors.forename: J
authors.initials: J
authors.lastname: Trines
authors.forename: W
authors.initials: W
authors.lastname: Savard
authors.forename: L K
authors.initials: LK
authors.lastname: Hornberger
mesh_terms: D004452:Echocardiography; D005260:Female; D047109:Fetal Development; D005315:Fetal Diseases / Q000000981:diagnostic imaging; D005318:Fetal Heart / Q000002:abnormalities / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006321:Heart / Q000196:embryology; D006330:Heart Defects, Congenital / Q000000981:diagnostic imaging*; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D016216:Ultrasonography, Prenatal; D054088:Ventricular Septum / Q000000981:diagnostic imaging / Q000196:embryology*
keywords: axis; cardiac development; fetal echocardiography; fetal heart; first trimester; reference values