Version 1.18
April 29, 2020

Perform Gestational Age and Amniotic Fluid Index calculations.

You asked. We listened. We’ve just released a dedicated measurement package containing obstetric calculations to determine EFW, EDD, and AFI.

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Assess fetal health.

Butterfly iQ now provides an easy-to-use interface for collecting and processing multi-image fetal biometry to generate estimated date of delivery (EDD), estimated fetal weight (EFW) after 12 weeks gestation and amniotic fluid index (AFI).

EDD is an important metric for planning obstetrical care. While EDD can be estimated from the last menstrual period (LMP), ultrasound provides a standardized way for these estimates to be calculated, especially in IVF cases or when the LMP is unknown.

The standard four biometric values are:

  • Biparietal diameter (BPD)
  • Head circumference (HCC)
  • Abdominal circumference (AC)
  • Femur length (FL)

While a single measurement can provide an EDD, it gets more accurate as more measurements are made. In order to generate the fetal health parameters, the standard Hadlock table is used.

The amniotic fluid index (AFI) is a quantitative estimate of amniotic fluid and an indicator of fetal health. The AFI is a score (expressed in cm) attributed to the amount of amniotic fluid visualized. Guidelines for minimum and maximum values exist to support a diagnosis of polyhydramnios or oligohydramnios in a growing fetus. AFI is a standard part of a fetal biophysical profile obstetric exam.

Getting started with OB calculations on the Butterfly iQ.

Adding the first measurement.

Open the Butterfly iQ app, and select the Obstetric preset. Select Fetal Biometrics (or Amniotic Fluid Index) under the Actions menu.

How measurements are recorded.

Scan in real-time and Freeze the image featuring the biometric value (BPD, HC, AC or FL) you wish to record. Choose the corresponding label, and place calipers.

Adding a second measurement.

Follow the steps above to add additional measurements. The accuracy of the measurement will update with every new biometric that is added.

Watch reports build in real-time.

Access your report by selecting AUA. See the measurements and calculations of EDD and EFW.

Frequently asked questions.

Do measurements need to be acquired in a fixed order? 

Measurements may be acquired in any order.

Do all 4 biometric measurements need to be acquired for an EDD to be calculated? 

No. As more measurements are added, the EDD calculation becomes more accurate. However, a single measurement can produce the EDD. 

Is the EDD result displayed in real-time?  

As you adjust the measurement calipers on a frozen image, the values for EDD/GA update in real-time. This allows for immediate biometric feedback.

What are the 4 biometric inputs in the OB Calc package? 

BPD (Biparietal diameter), HC (Head circumference), AC (Abdominal circumference), FL (Femur length). 

What are the outputs from the OB Calc package? 

GA (gestational age), EDD (estimated date of delivery), EFW (estimated fetal weight).

What are the major formulas used? 

For calculations, the NICHD and Hadlock tables are used. 

Why are we only given the option for one measurement instead of averaging them? 

Butterfly has opted for a one measurement technique in response to customer requests, in accordance with industry guidelines, such as those released by BMUS.

Will first trimester measurements be added to the OB Calc package?

First trimester measurements are in active development.  The initial offering includes OB calculations that are best suited for transabdominal imaging. Stay tuned for more updates.