Placental thickness
Citation, DOI & article data
- Thickness of the placenta
Placental thickness tends to gradually increase with gestational age in a linear fashion. Sonographically, this can be seen to be approximately 1 mm per week and the thickness of the placenta can be used to approximate gestational age:
- approximate gestational age (in weeks) = placental thickness +/- 10 mm
The maximum thickness of a normal placenta at any point during pregnancy is often considered to be 4 cm. Anterior placentas are ~0.7 cm thinner than posterior placentas and maximum thickness for an anterior placenta is ~3.3 cm 7.
Increased thickness
An abnormally increased placental thickness falls under the spectrum of placentomegaly. This can happen with a number of conditions and is associated with increased risk of placental insufficiency. Causes include:
- upper limit of normal variation
- fetal macrosomia
- fetal hydrops
- TORCH infections
- maternal medical conditions
- maternal anemia
- maternal diabetes
If the placenta is thickened and contains cysts, then other entities should be considered:
Mimics
An important mimic for a thickened placenta is an isoechoic abruption. A transient myometrial contraction can also mimic a thickened placenta.
Decreased thickness
An abnormally decreased placental thickness can be seen with:
- pre-eclampsia
- intrauterine growth restriction (IUGR)
- placenta membranacea (extremely rare)
References
- 1. Tongsong T, Boonyanurak P. Placental thickness in the first half of pregnancy. J Clin Ultrasound. 2004;32 (5): 231-4. doi:10.1002/jcu.20023 - Pubmed citation
- 2. Elchalal U, Ezra Y, Levi Y et-al. Sonographically thick placenta: a marker for increased perinatal risk--a prospective cross-sectional study. Placenta. 21 (2-3): 268-72. doi:10.1053/plac.1999.0466 - Pubmed citation
- 3. Hoddick WK, Mahony BS, Callen PW et-al. Placental thickness. J Ultrasound Med. 1985;4 (9): 479-82. J Ultrasound Med (abstract) - Pubmed citation
- 4. Kay H, Nelson DM, MD et-al. The Placenta, From Development to Disease. Wiley-Blackwell. (2011) ISBN:1444333666. Read it at Google Books - Find it at Amazon
- 5. Kurjak A. Donald School textbook of ultrasound in obstetrics and gynecology. Jaypee Brothers Publishers. (2008) ISBN:8184482027. Read it at Google Books - Find it at Amazon
- 6. Avni EF, Avni FE. Perinatal imaging, from ultrasound to MR imaging. Springer Verlag. (2002) ISBN:354067327X. Read it at Google Books - Find it at Amazon
- 7. Lee AJ, Bethune M, Hiscock RJ. Placental thickness in the second trimester: a pilot study to determine the normal range. Journal of ultrasound in medicine : official journal of the American Institute of Ultrasound in Medicine. 31 (2): 213-8. Pubmed
- 8. Fadl S, Moshiri M, Fligner CL, Katz DS, Dighe M. Placental Imaging: Normal Appearance with Review of Pathologic Findings. Radiographics : a review publication of the Radiological Society of North America, Inc. 37 (3): 979-998. doi:10.1148/rg.2017160155 - Pubmed
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