Amniotic fluid in the first trimester

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Amniotic fluid in the first trimester has been estimated from weeks 7~~-13~~-12. Although the amniotic fluid index (AFI) is calculated in the second trimester, one can get an idea of whether the amount of amniotic fluid is too much or too little at an earlier time point.

Generally, the problem is that there is too little amniotic fluid in the first trimester, and this is most commonly estimated with the difference between the mean sac diameter and the crown rump length. A difference between mean sac diameter and crown-rump length of < 5 mm is suspicious for, but not diagnostic of early pregnancy failure.

The amniotic fluid volume is related to, but different than the mean sac diameter. Although the first trimester amniotic fluid volume is not currently one of the criteria for pregnancy failure, an abnormal amount of fluid has may indicate a poor outcome.

Radiographic features

Ultrasound

Estimated amniotic fluid volume (mean +/- standard deviation) ²

week 7: 1.0 ml +/- 1.4
week 8: 2.9 ml +/- 1.4
week 9: 7.2 ml +/- 4.0
week 10: 24.7 ml +/- 9.5
week 11: 45.4 ml +/- 12.6
week 12: 80.6 ml +/- 12.3

This is different than the gestational sac volume ²

week 7: 8.3 ml +/- 4.3
week 8: 16.2 ml +/- 6.8
week 9: 26.0 ml +/- 10.8
week 10: 47.1 ml +/- 19.6
week 11: 67.9 ml +/- 20.9
week 12: 90.8 ml +/- 14.3

-<p><strong>Amniotic fluid in first trimester</strong> has been estimated from weeks 7-13. Although the <a href="/articles/amniotic-fluid-index">amniotic fluid index (AFI)</a> is calculated in the second trimester, one can get an idea of whether the amount of amniotic fluid is too much or too little at an earlier time point.</p><p>Generally, the problem is that there is too little amniotic fluid in the first trimester, and this is most commonly estimated with the difference between the mean sac diameter and the crown rump length. A difference between mean sac diameter and crown-rump length of < 5 mm is suspicious for, but not diagnostic of <a href="/articles/missed-miscarriage-2">early pregnancy failure</a>.</p><h4><strong>Radiographic features</strong></h4><h5><strong>Ultrasound</strong></h5><p>Estimated amniotic fluid volume (mean +/- standard deviation) <sup>2</sup></p><ul>
+<p><strong>Amniotic fluid in the first trimester</strong> has been estimated from weeks 7-12. Although the <a href="/articles/amniotic-fluid-index">amniotic fluid index (AFI)</a> is calculated in the second trimester, one can get an idea of whether the amount of amniotic fluid is too much or too little at an earlier time point.</p><p>Generally, the problem is that there is too little amniotic fluid in the first trimester, and this is most commonly estimated with the difference between the mean sac diameter and the crown rump length. A difference between mean sac diameter and crown-rump length of < 5 mm is suspicious for, but not diagnostic of <a title="Failed early pregnancy" href="/articles/failed-early-pregnancy">early pregnancy failure</a>.</p><p>The amniotic fluid volume is related to, but different than the <a href="/articles/mean-sac-diameter">mean sac diameter</a>. Although the first trimester amniotic fluid volume is not currently one of the criteria for pregnancy failure, an abnormal amount of fluid has may indicate a poor outcome.</p><h4><strong>Radiographic features</strong></h4><h5><strong>Ultrasound</strong></h5><p>Estimated amniotic fluid volume (mean +/- standard deviation) <sup>2</sup></p><ul>

References changed:

1. Weissman A, Itskovitz-Eldor J, Jakobi P. Sonographic measurement of amniotic fluid volume in the first trimester of pregnancy. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 15 (11): 771-4. <a href="https://www.ncbi.nlm.nih.gov/pubmed/8908588">Pubmed</a> <span class="ref_v4"></span>
2. Odeh M, Hirsh Y, Degani S, Grinin V, Ofir E, Bornstein J. Three-dimensional sonographic volumetry of the gestational sac and the amniotic sac in the first trimester. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 27 (3): 373-8. <a href="https://www.ncbi.nlm.nih.gov/pubmed/18314515">Pubmed</a> <span class="ref_v4"></span>
3. Bronshtein M, Blumenfeld Z. First- and early second-trimester oligohydramnios-a predictor of poor fetal outcome except in iatrogenic oligohydramnios post chorionic villus biopsy. Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 1 (4): 245-9. <a href="https://doi.org/10.1046/j.1469-0705.1991.01040245.x">doi:10.1046/j.1469-0705.1991.01040245.x</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/12797052">Pubmed</a> <span class="ref_v4"></span>

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