Measuring the placenta is quick, easy, inexpensive and noninvasive with EPV.

 

Three simple measurements taken during a standard prenatal ultrasound produce an Estimated Placental Volume (EPV) when input into the free app, Merwin’s EPV Calculator, links below.

The health care provider measures the placenta’s width, height, and thickness. EPV measurements can begin at 20 weeks and continue every 3-4 weeks, similar to fetal growth scans.

The app displays the Estimated Placental Volume in cc units, relative to the range for a baby’s gestational age, highlighting whether the measurement is within the standard range, below 10th percentile or above 90th percentile.

Providers: EPV video tutorials ● Guide and manual

Further questions on how to use EPV can be directed to Dr. Harvey Kliman, at harvey.kliman@yale.edu, who, with his father Merwin Kliman, created the complex polynomial which uses width, height and thickness to calculate volume of a spherical cap.

Measure the Placenta with
Merwin’s EPV Calculator

Calculates the volume of a spherical cap, placed against a normative curve for placenta size by gestational age.

No smartphone? Use the simple EPV Web Calculator.

Another app, Merwins Desktop Calculator, enables calculation of EPV and sharing, printing, etc., from a Mac desktop computer. Useful for a doctor's office.

The remarkable equation behind Merwin's Calculator was developed by mathematician and engineer Merwin Kliman and his son, Dr. Harvey Kliman. The equation enables a 3D curved object to be measured in 2D, using the sizes of the placenta's width, height and thickness. The method calculates the volume of a spherical cap from an imaginary cross section through the middle of the cap.

Published peer-reviewed validation:
“Determination of placental weight using two-dimensional sonography and volumetric mathematic modeling.” Azpurua HJ, Funai EF, Coraluzzi L, Sasson I, Doherty L, Kliman M, Kliman HJ. Am J Perinatology, 27: 151-155, 2010. (Link - free full PDF)

“Utilizing 2-Dimensional Ultrasound to Develop Normative Curves for Estimated Placental Volume (EPV).” Arleo EK, Troiano RN, da Silva R, Greenbaum D, Kliman HJ. Am J Perinatology. 2013 Oct 9. [Link - Epub ahead of print]

“Estimated placental volume and gestational age.” Isakov KMM, Emerson JW, Campbell KH, Galerneau F, Anders AM, Lee YK, Roberts AE, Kliman HJ. (2018) American Journal of Perinatology, 35:748-57, 2018; doi: 10.1055/s-0037-1615285. (Link - free full PDF)

Other Ways to Measure the Placenta

Measure the Placenta recommends Estimated Placental Volume because it is quick, easy, and cost-effective to perform during a standard 2D ultrasound and shown to be effective by multiple research studies.  Right now in peer-reviewed literature there's good evidence that small placentas increase the risk of a stillbirth and EPV can detect small placentas. However, we support all ongoing research efforts to measure placentas during prenatal care, and want to see various forms of placenta measurements integrated into prenatal care. Other ways to measure the placenta found in peer-reviewed literature include:

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