Mean sac diameter
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Mean sac diameter (MSD) is a sonographic measurement of the gestational sac and is usually first seen at around 3 weeks after conception (5 weeks after the last menstrual period), when it measures 2-3 mm.
MSD = (length + height + width)/3
Normal MSD (in mm) + 30 = days of pregnancy
Important points for a normal intrauterine pregnancy
For an endovaginal scan
- an embryo/fetal pole should be visible when the MSD measures 16 mm
- when the MSD measures 8 mm: a yolk sac should be visible
For a trans-abdominal scan
- when the MSD measures 20 mm: a yolk sac should be visible
- when the MSD measures 25 mm: a fetal pole should be visible
- an MSD of 16-24 mm without an embryo is suspicious for pregnancy failure, but not definitive
For a healthy gestation it is suggested that the mean sac diameter should be at least 5 mm greater than the crown rump length.
The MSD usually increases by about1 mm per day.
See also
-<p><strong>Mean sac diameter (MSD)</strong> is a sonographic measurement of the <a href="/articles/gestational-sac">gestational sac</a> and is usually first seen at around 3 weeks after conception (5 weeks after the last menstrual period), when it measures 2-3 mm.</p><p><strong>MSD = (length + height + width)/3 </strong></p><p>Normal MSD (in mm) + 30 = days of pregnancy</p><h5>Important points for a normal intrauterine pregnancy</h5><h6>For an endovaginal scan</h6><ul>- +<p><strong>Mean sac diameter (MSD)</strong> is a sonographic measurement of the <a href="/articles/gestational-sac">gestational sac</a> and is usually first seen at around 3 weeks after conception (5 weeks after the last menstrual period), when it measures 2-3 mm.</p><p>MSD = (length + height + width)/3</p><p>Normal MSD (in mm) + 30 = days of pregnancy</p><h5>Important points for a normal intrauterine pregnancy</h5><h6>For an endovaginal scan</h6><ul>
-</ul><p>For a healthy gestation it is suggested that the mean sac diameter should be at least 5 mm greater than the <a href="/articles/crown-rump-length">crown rump length</a>.</p><p>The MSD usually increases by about<strong> 1</strong> mm per day.</p>- +</ul><p>For a healthy gestation it is suggested that the mean sac diameter should be at least 5 mm greater than the <a href="/articles/crown-rump-length">crown rump length</a>.</p><p>The MSD usually increases by about<strong> </strong>1 mm per day.</p><h4>See also </h4><ul><li><a title="Small gestational sac size" href="/articles/small-gestational-sac">small gestational sac</a></li></ul><p> </p>
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