Validity of Objective and Subjective Physical Activity Measurement During Pregnancy

Background: Pregnancy researchers use various physical activity (PA) measurement techniques. However, few studies have evaluated the validity of these techniques in free-living environments, and there is little agreement regarding which may be the best to use. Consensus on this issue would be valuable to future researchers wishing to compare results across studies.

Purpose: To determine the validity of the SenseWear Armband (SA; kcal/kg/hr), Omron pedometer (PED; steps/day/hr) and Pregnancy Physical Activity Questionnaire (PPAQ; MET.min/week) during pregnancy and postpartum, using two placements of the ActiGraph accelerometer (hip (ActH; counts/ hr) and ankle (ActA; counts/hr)) as criterion measures.

Methods: The ActH, ActA, SA, and PED were worn by participants (n=20) in a free-living environment for two consecutive weeks (average of the two weeks used in analysis) at ~20 and 32 weeks gestation, and 12 weeks postpartum. Participants also completed the PPAQ at each time point. Pearson correlations were also used to determine validity (r) of the SA, PED, and PPAQ using both ActH and ActA as criterion measures. The relationship between PA measured at the ActH and ActA locations was evaluated at all time points via Pearson correlations.

Results: Moderate correlation was found between the two ActiGraph locations at 20 weeks pregnancy (r=0.53; p<0.05) and 12 weeks PP (r=0.45; p<0.05) but not 32 weeks pregnancy (r=0.05). PED was significantly related to both ActH (r=0.71-0.81; p<0.05) and ActA (r=0.52-0.70; p<0.05), except at 32 weeks gestation, where there was no relationship with ActH (r=0.30). In contrast, neither SA nor PPAQ were related to the ActiGraphs at any time point (r=0.01-0.20).

Conclusion: Assuming that the ActiGraph is an appropriate criterion measure, the Omron pedometer was the only device tested that showed adequate validity when measuring free living PA during pregnancy and postpartum periods. However, placement of ActiGraph on ankle should be encouraged when measuring PA late in pregnancy.