Aims Two markers show a constant positive association with infant birth weight: maternal pre-pregnancy weight for height and weight gain during pregnancy. Both are dependent on a positive energy balance in pregnancy where nutritional calorific intake is greater than energy expended.

Our pilot study used the Actiheart accelerometer device that measures continuous ambulatory activity and heart rate to calculate ‘free-living’ energy expenditure in third trimester pregnant women in rural Nepal.

Methods Three-week time limited study. Sixteen third trimester rural women from Jumla district Nepal were selected to wear the Actiheart device for 24 h. Participants were recruited by moving house to house in small village communities. All participants were agricultural labourers responsible for small marginal farms and household chores.

A Nepali nurse gathered informed verbal consent from the women, measured BMI and assessed their trimester by questioning.

The Actiheart device has been validated against the doubly labelled water method as the gold standard of energy expenditure measurement.

Participants were excluded from the study if the Actiheart device was worn for <20 h or if heart rate trace was <80% complete. Data was analysed using Actiheart software.

Results 16 participants were measured during the three-week period and five were excluded from the sample due to insufficient heart rate trace or time wearing the Actiheart.

Physical activity level (PAL) category boundaries stated by the WHO, showed 4/11 women had a ‘light’ PAL (1.40–1.69), 3/11 ‘moderate’ PAL (1.70–1.99) and 4/11 ‘vigorous’ activity level (>2).

The sample average PAL was 1.85, significantly higher than that reported in studies of pregnant women in developed countries such as the UK (1.62) and Sweden (1.65).

8/11 participants were estimated to be in negative energy balance when using the total daily energy intake of 2140kcal reported in pregnant women in the nearby area of Tamang.

Conclusion Pregnant women in rural Nepal have heavy workloads and high physical activity levels in the third trimester. High maternal energy expenditure and poor nutrition may result in a negative energy balance leading to weight loss, low birth weight and poor maternal and neonatal outcomes.