Purpose of App Review

  • to review the diversity of due date and gestational age calculations
  • to compare the iPhone app to the similar iPad app


Obstetric wheels provide the prenatal care provider with important information.

By knowing a patient’s estimate gestational age (EGA), her last menstrual period (LMP), or estimated date of confinement/delivery (EDD), you can calculate the other two variables.

Being able to calculate gestational age today is very helpful for appropriate patient care, both in the inpatient and outpatient settings.

Occasionally, it is also important to be able to calculate the EGA on a particular day or calculate the EDD from the gestational age on a given day. The Wheel SP medical app, similar to its iPad cousin–(the Wheel HD, previously reviewed with 9 other obstetric wheel apps–seeks to help prenatal care providers calculate pregnancy-related dates simply and quickly.

User Interface

The Wheel SP medical app leaves the actual wheel behind (it literally disappears behind the rolling menu).

2013-10-01 12.55.00

The home screen is the main and most often used screen of the app. This screen allows you to select the dates for LMP, conception, EDD, as well as travel to different dates.

2013-10-14 02.37.55

Furthermore, you can take the patient’s pregnancy dating information you have and simply select which field you want to control. The rolling month, day, year roulette feature allows you quickly select the appropriate date. As you change one parameter, the others (including EGA) will change to reflect the most recent information on the patient.

2013-10-14 02.37.55

If you are controlling LMP, conception, or EDD, you can then tap the EGA box (simply listed as # weeks # days). In doing so, a new bottom half of the screen appears and gives you an estimated fetal weight (EFW) estimate in grams and pounds/ounces, as well as lists days of pregnancy completed and remaining.

2013-10-01 12.55.21

Comparing the Wheel SP medical apps to its iPad cousin, I had two questions: can I still manipulate the date and EGA to calculate the LMP or EDC? Also, does the Wheel SP include fetal biometry as part of the app?

The answer to my first question is: Yes! This makes the Wheel SP app one of my new best iPhone friends as I had found this feature lacking in most other iPhone-based apps. In order to make these calculations, you select the Today radio button. You can then change the date and time travel to that date as if it was today–the EGA will then change to reflect the new date.

2013-10-14 02.37.55

In real life, though, there are times when all I have is an EGA and the day it was calculated. Since I don’t add weeks and days very well in my head, I would prefer the app to do it for me–the Wheel SP does just that. After selecting the date of interest as today, you can tap the EGA button and change the gestational age (GA). Doing this will then change the LMP, date of conception, and EDDs–viola, problem solved!

2013-10-14 02.38.00

In hunting down the answer to my first question, I discovered the answer to my 2nd question. Hidden in the choose the Today radio button, then the EGA box sequence, you can enter crown rump length (CRL), femur length (FL), and biparietal diameter (BPD) to calculate LMP, conception, EDD, and EGA!

2013-10-14 02.42.42

The final hidden gem is the EFW calculation. You can use abdominal circumference, femur length, head circumference, and biparietal diameter to individually calculate the EFW. Unfortunately, you cannot use all of them together to create a calculation (like an ultrasound machine could). When the EFW is calculated, it lists the calculation formula (by author and year).

2013-10-20 02.36.06 2013-10-20 02.36.19

Evidence and literature used to support app

  • The app does not discuss how it makes the gestational age, EDD, and LMP calculations.
  • Though this may be a weakness, real obstetric wheels do not either and are known to be off from a computer generated calculation by 1-5 days.
  • There are no studies on app-based wheels and calculations. The app does list which EFW formulas (study name and year of publication) it uses for each biometric parameter to calculate EFW.


  • $1.99


  • can calculate EGA for a particular day
  • can use EGA on a date to calculate the EDD
  • incorporates ability to use fetal biometry to calculate EGA
  • almost all features of the Wheel HD for the iPad are included in the Wheel SP (does not tell month or trimester, which the app tells me is not important)


  • cannot save patient EDDs–biggest detractor
  • have to purchase iPhone version separate from iPad version–this is the only wheel I have seen work this way
  • poor form as Apple does not endorse this policy since it is easy to port apps to the iPad
  • biometry used for dating does not carry over to EFW calculations
  • cannot save EDD

Healthcare providers that would benefit from the app

  • Health care providers and students taking care of women who are pregnant (or could be pregnant)


  • The Wheel SP medical app does a great job at compacting almost all of The Wheel HD’s features into the constraints of an iPhone app.
  • I plan on using this as my primary obstetric/pregnancy wheel because of the ability to make standard OB wheel calculations, as well as calculate the EFW by GA and by biometric measurements.
  • As of date of publish, there is no Android version available

iTunes Link

Type of Device used to review app–iPhone 4S
Version of App–1.5

Rating: 4/5

  1. User Interface – 4. Basic features easy to use. Has a few hidden features that require a little more persistence and exploration.
  2. Multimedia usage – 4. Smooth transitions, smooth split screen included. No use of images or video.
  3. Price – 4. $1.99 is pretty affordable, especially for the robust nature of the calculations available.
  4. Real world applicability – 4. As an Obstetrician, I would use it daily/almost daily.

This post does not establish, nor is it intended to establish, a patient physician relationship with anyone. It does not substitute for professional advice, and does not substitute for an in-person evaluation with your health care provider. It does not provide the definitive statement on the subject addressed. Before using these apps please consult with your own physician or health care provider as to the apps validity and accuracy as this post is not intended to affirm the validity or accuracy of the apps in question. The app(s) mentioned in this post should not be used without discussing the app first with your health care provider.