title: Cardiovascular function in pregnancy: effects of posture.
abstract: OBJECTIVE
  To evaluate the cardiovascular response to active postural changes in pregnancy.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Outpatient Clinic, Fetal Maternity Unit.
  
  
  METHODS
  Sixteen healthy women referred prior to pregnancy.
  
  
  METHODS
  Heart rate, arterial pressure, echocardiographic end-diastolic and end-systolic left ventricular volumes (Teichholz' s formula) were measured in the three months before pregnancy, at the end of the first and second trimester, at mid third trimester, and six months after delivery in the supine and standing position, in thirteen women (mean age 33, range 25-38 years).
  
  
  RESULTS
  Cardiac output (supine position) significantly increased (28%): it reached its maximum at the second trimester, remained steadily elevated in the mid third trimester, and returned to baseline after delivery. Cardiac output increased during pregnancy also in the active orthostatic position, the percentage increase being greater (70%) since the standing pre-conception value was lower. The postural stress induced similar changes in heart rate, arterial pressure and left ventricular ejection fraction before, during and after pregnancy. However, the reduction in cardiac output associated with early standing attenuated significantly at the second trimester and it was absent at mid third trimester (F = 3.13, P = 0.021). This was due to the interplay between the significantly lesser increase in systemic vascular resistance, occurring since the first trimester, and the significantly lesser decrease in left ventricular end-diastolic volume which was observed in the mid third trimester.
  
  
  CONCLUSIONS
  These data indicate that the elevated cardiac output is adequately maintained in pregnancy during the postural challenge, due to optimisation of the responses of preload and afterload.
authors: Cardiovascular Echography Section, Careggi Hospital, Italy.
authors: R
authors: R
authors: Del Bene
authors: G
authors: G
authors: Barletta
authors: G
authors: G
authors: Mello
authors: C
authors: C
authors: Lazzeri
authors: F
authors: F
authors: Mecacci
authors: E
authors: E
authors: Parretti
authors: E
authors: E
authors: Martini
authors: S
authors: S
authors: Vecchiarino
authors: F
authors: F
authors: Franchi
authors: G
authors: G
authors: La Villa
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D011187:Posture / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology*; D011446:Prospective Studies; D013318:Stroke Volume / Q000502:physiology; D016683:Supine Position