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Fetal aortic stenosis
Fetal aortic stenosis is a disorder that occurs when the fetus’ aortic valve does not fully open during development.〔Marshall, A. (2010). Aortic Valve Stenosis. Retrieved from: http://www.childrenshospital.org/health-topics/conditions/aortic-valve-stenosis〕 The aortic valve is a one way valve that is located between the left ventricle and the aorta, keeping blood from leaking back into the ventricle.〔 It has three leaflets that separate when the ventricle contracts to allow blood to move from the ventricle to the aorta.〔 These leaflets come together when the ventricle relaxes.
Since the valve does not open properly in aortic stenosis, there is a decrease in the forward movement of blood into the aorta. Fetal aortic stenosis impairs left ventricular development, which can lead to hypoplastic left heart syndrome.〔Barron, D.J., Kilby, M.D., Davies, B., Wright, J.G.C., Jones, T. J., Brawn, W.J. (2009). Hypoplastic left heart syndrome" ''The Lancet'' 374 (9689), 15-21. Retrieved from: http://www.sciencedirect.com/science/article/pii/S0140673609605638〕 If untreated, HLHS is lethal,〔Tworetzky, W., Wilkins-Haug, L., Jennings, R.W., van der Velde, M.E., Marshall, A.C., Marx, G.R., Colan, S.D., Benson, C.B., Lock, J.E., Perry, S.B. (2004). Balloon Dilation of Severe Aortic Stenosis in the Fetus: Potential for Prevention of Hypoplastic Left Heart Syndrome: Candidate Selection, Technique, and Results of Successful Intervention. The Journal of Circulation, 110, 2125-2131.Retrieved from: http://circ.ahajournals.org/content/110/15/2125.long〕 as a result of the inability of the left heart to pump enough blood to sustain normal organ function.〔Levine, J.C., Tworetzky, W. (2006). Intervention for severe aortic stenosis in the fetus: Altering the progression of left sided heart disease. Progress in Pediatric Cardiology, 22, 71-78. Retrieved from: http://journals1.scholarsportal.info.subzero.lib.uoguelph.ca/pdf/10589813/v22i0001/71_ifsasipolshd.xml〕 In fetal life, this is condition is manageable because the ductus arteriosus acts as a bypass, and supports the delivery of oxygenated blood to the systemic circulation.〔 However, the ductus arteriosus closes during the first few days of life, resulting in systemic circulation failure in babies born with aortic valve stenosis.〔
==Diagnosis==
Fetal aortic valve stenosis can be diagnosed by echocardiography before birth.〔Maxwell, D., Allan, L., Tynan, M.J. (1991). Balloon dilation of the aortic valve in the fetus: a report of two cases" ''British Medical Journal'' 65, 256-258. Retrieved from: http://heart.bmj.com/content/65/5/256.full.pdf+html〕 The diagnostic features include a poorly contracting left ventricle, aortic valve thickening/restriction, a varying degree of left ventricular hypertrophy and abnormal Doppler flow characteristics in the left heart.〔 There may be little or no detectable flow into or out of the left side of the heart.〔
There are two screening periods, one during the first trimester and the other during the second trimester. Fetal aortic stenosis is typically detected between 18 and 24 weeks gestation.〔 This early detection is important because it allows for parents to be counseled in a timely and rational manner, allowing for discussion of prognosis and possible outcomes.〔 Another reason for this crucial early detection is because it allows for postnatal management planning.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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