Sedentary time during pregnancy and gestational diabetes risk: a mixed methods approach among women in the UK

Introduction: Sedentary time is associated with increased risk of type 2 diabetes, but the association between sedentary time and gestational diabetes (GDM) has not been tested. The primary aim of this mixed-methods study was to test associations between objectively measured sedentary time during pregnancy, as well as time spent in two specific sedentary behaviours (television time and occupational sitting time), and incident GDM, glucose levels, and other pregnancy-related outcomes. This thesis also aims to explore the social context of sedentary time during pregnancy. Methods: Pregnant women (n=260) with a risk factor for gestational diabetes wore an activPAL accelerometer for one week at 20 weeks’ gestation and reported their usual television time and occupational sitting time in the second trimester. Of these women, 192 provided 4 days of accelerometry data and were included in analyses. GDM diagnoses and glucose levels were measured through standard glucose tolerance tests at 24-28 weeks’ gestation. Further outcomes were extracted from medical records following birth. Semi-structured interviews were conducted with a subsample (n=18) of participants in the third trimester. Results: Objectively measured sedentary time was not associated with the development of GDM (OR 1.003 (95%CI 0.998, 1.008)), but was associated with fasting (β=0.16 (95%CI 0.01, 0.31)) and 2-hour glucose levels (β=0.15 (95%CI 0.01, 0.30)) among women who did not have GDM. Higher television time was associated with increased risk of GDM (OR 3.03 (95%CI 1.21, 7.96)), while higher occupational sitting was associated with decreased risk (OR 0.20 (95%CI 0.06, 0.59)). The main theme that emerged from the interviews was that there is a social expectation for women to sit down and to rest during their pregnancies. Conclusion: Only television time was associated with increased likelihood of developing GDM. However, objectively measured sedentary time was associated with glucose levels during pregnancy. Any interventions designed to reduce sedentary time during pregnancy should aim to address broader social perceptions about the ‘importance of rest’ during pregnancy