Smartphone Apps More Accurate Than Gestational Age Wheels

Tinker Ready

September 20, 2013

Electronic gestational age calculating apps downloaded to iPhones were more accurate than commonly used paper calculating wheels, according to a study published online September 13 in the American Journal of Obstetrics and Gynecology.

The accuracy of gestational age is important for decisions about induction of labor and interventions at the limits of fetal viability, write Linda R. Chambliss, MD, MPH, from the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, St. Joseph’s Hospital and Medical Center, and the Department of Obstetrics and Gynecology, Creighton University School of Medicine, Phoenix, and Steven L. Clark, MD, from the Hospital Corporation of America, Nashville, Tennessee. In addition, it is a factor in the use of corticosteroids for fetal lung maturation and of magnesium sulfate for neuroprotection of preterm infants.

Therefore, the researchers collected 31 gestational calculator wheels from attending obstetricians, residents, and nurses at St. Joseph's Hospital in Phoenix, Arizona l. Each wheel was set to produce a due date based on a last menstrual period occurring January 1, 2013. The researchers repeated the exercise using 20 electronic gestational age calculators (apps) downloaded to an iPhone. They also compared the 2 types of calculators using the last menstrual period of January 1, 2012, to test the wheels' capacity to make adjustments for a leap year.

Only 10 wheels (32.3%) calculated dates consistent with the standard pregnancy duration of 280 days. The variation in estimated due date calculated by the paper wheels ranged from 1 to 7 days.

In contrast, all 20 electronic gestational age calculators gave a due date of October 8, consistent with standard pregnancy duration of 280 days.

In addition, although none of the paper gestational wheels corrected for a leap year, all of the apps did.

The authors note that the clinical benefit of certain therapies and diagnostic tests may depend on gestational age. In addition, the risk of some interventions, such as elective delivery before 39 weeks' gestation, are also linked to gestation age. They note that elective induction of labor before 39 weeks has been linked to increased morbidity in infants.

"[W]e recommend re-calculation of gestational age using any of the commonly available electronic programs, or Apps prior to decision making in which an error of just a few days could alter the clinical approach," the authors conclude. "Ultimately, the use of paper wheels should be eliminated."

The authors have disclosed no relevant financial relationships.

Am J Obstet Gyn. Published online September 13, 2013. Abstract

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