How active are pregnant women? Measuring the methods

Posted by Louise Hayes and Cath McParlin 

Louise and Cath are presenting on the subject of physical activity in pregnancy at the Fuse Phyical Activity Workshop tomorrow (15 May) at Sunderland University.

So we all know we should move a bit more to be more healthy and reduce our risk of getting diseases like diabetes. For a long time pregnancy was seen as a time when a woman could put her feet up, take it easy and ‘eat for two’. But not any longer! Guidance published over the last few years recommends no ‘pregnant pause’, but rather that pregnant women should aim to achieve at least 30 minutes of activity of at least moderate intensity activity on most days of the week - just like the rest of us.

Part of the justification for this is that physical activity might help to reduce the risk of gestational diabetes (GDM) – that’s a type of diabetes that is diagnosed in pregnancy and (usually) resolves after the pregnancy. However, to some extent, the jury’s still out on whether or not being active when you’re pregnant really does reduce GDM.

Partly this is because we don’t really know how to measure physical activity accurately in pregnant women. The more precisely we can measure physical activity, the more accurately we can establish the relationship between it and GDM and other health outcomes.

Physical activity measurement is fraught with difficulty in any circumstances – it’s a challenge to measure such a complex and multi-faceted behaviour. Pregnancy brings additional challenges. With the development (and increasing affordability) of numerous objective methods for measuring physical activity – pedometers, heart rate monitors, accelerometers - objective measurement of physical activity in epidemiology is increasingly common. For pregnant women, however, the validity and acceptability of these methods remains unclear.

We have agonised over how best to measure physical activity in a pregnant population. What effect does the increasing size of the ‘bump’ have on the validity of waist-worn monitors? How good are monitors at recording low-level activity, common in pregnant women? What are appropriate cut-offs for different activity intensities in pregnant women?

The choice of measurement method has a huge influence on conclusions we draw about how active women are during pregnancy. We have compared questionnaire methods and accelerometry using different criteria to define activity intensity and found that, depending on the method used, we identify anything from 12% to 65% of pregnant women to be meeting the current guideline (30 minutes of at least moderate activity per day) in the first half of pregnancy.

We’re looking forward to discussing the whys and wherefores of different methods of assessing physical activity with the experts attending the Fuse PA Group Workshop at Sunderland University tomorrow (Friday 15 May).