Physical activity and energy balance in relation to birth outcomes during pregnancy in the Tlokwe municipality area: a longitudinal study

Abstract

The high prevalence of obesity in South-African women poses a significant health risk for mother and offspring during pregnancy. Obesity and excessive gestational weight gain during pregnancy are associated with an increased risk of adverse birth outcomes. The high levels of obesity in South-African women contribute to the potential exacerbated health risk. Energy balance dictates gestational weight gain and is also associated with birth weight. Energy imbalances, such as excessive energy intake and decreased energy expenditure, may explain changes in body composition and can negatively affect birth outcomes. This study investigated the relationship between physical activity and energy balance with regards to birth outcomes during pregnancy in the Tlokwe municipal area. A longitudinal observational cohort study design – the Habitual Activity Patterns during PregnancY (HAPPY)-study - measured 41 pregnant women in their first- (1st) (9 – 12 weeks), second- (2nd) (20 – 22 weeks) and third (3rd) trimester (28 – 32 weeks). Energy intake and macronutrient intake was determined by a semi-quantitative food frequency questionnaire while resting energy expenditure was measured applying gas exchange analyses with the Fitmate®. Active energy expenditure and diet-induced thermogenesis were objectively determined using a combined heart rate reading and accelerometer – the ActiHeart®. Body composition measurements of height, weight, and fat mass using skinfolds were taken. Birth outcomes (birth weight, gestational age at birth, abdominal and head circumference) were obtained from medical records. The study is presented in the format of three manuscripts. Results indicated that energy intake increased slightly from the 1st trimester (8841 ± 3456 kJ/day) to the 2nd trimester (9134 ± 3046 kJ/day) and then decreased in the 3rd trimester (8171 ± 3017 kJ/day). Energy expenditure decreased from 1st trimester (10234 ± 2314 kJ/day) to the 2nd trimester (9423 ± 2732 kJ/day) and increased slightly during the 3rd trimester (9535 ± 2326 kJ/day). Energy balance was negative in the 1st trimester (- 1337 ± 4548 kJ/day), positive in the 2nd trimester (381 ± 4213 kJ/day) and negative again in the 3rd trimester (- 1331 ± 3732 kJ/day). The change in both energy intake (p = 0.66) and energy expenditure (p = 0.31) from the 1st to the 3rd trimester was not statistically significant. The change in resting energy expenditure, adjusted for body weight, was statistically significantly related to the change in body mass index (r = 0.59, p = 0.02), gestational weight gain (r = 0.55, p = 0.03) and change in fat mass (r = 0.54, p = 0.03) from the 2nd to the 3rd trimester. Consequently, changes in body composition variables significantly predicted changes in resting energy expenditure, adjusted for weight, from the 2nd to 3rd (R2 = 0.93, p < 0.01), but not from the 1st to the 2nd trimester (R2 = 0.22, p = 0.37). Energy intake and energy expenditure throughout all trimesters as related to birth outcomes were not statistically significant, except for energy expenditure in the 3rd trimester which was significantly negatively associated with head circumference (r = -0.94, p = 0.02) and birth weight (r = -0.68, p = 0.05). It can be concluded that energy expenditure and energy intake did not change significantly during pregnancy. The various components of energy expenditure did, however, change to regulate overall energy balance. A decrease in physical activity throughout pregnancy led to a decrease in active energy expenditure. Resting energy expenditure was significantly associated with body composition variables in late pregnancy. A negative energy balance had a positive association with delivering an appropriate for gestational age infant.. Healthy dietary behaviours and physical activity during pregnancy can assist with the regulation of energy balance that will contribute to optimal birth outcomes.