Objective: The investigators aim to conduct a prospective cohort study using state-of-the-art, noninvasive measurement of sedentary behavior in n=130 pregnant women during each trimester of their first pregnancy. We will link sedentary behavior to gestational weight gain, blood pressure, and potential determinants such as demographics, health conditions and behaviors, psychosocial factors, perceptions/beliefs, and the environment.
Specific Aims:
Aim 1: Objectively measure sedentary behavior across pregnancy trimesters Aim 2: Relate objectively-measured sedentary behavior to blood pressure and gestational weight gain across pregnancy Aim 3: Characterize correlates and determinants of sedentary behavior during pregnancy
1.3 Background: Cardiovacular disease (CVD) remains the leading cause of death in women with minimal declines over the past 30 years among women \<55 years old. Stagnant rates of CVD mortality in younger women have occurred alongside notable declines in men and older adults and are thought to be due, in part, to high rates of obesity and elevated blood pressure (BP). Related to this, the American Heart Association (AHA) recently identified primordial prevention, a population-level approach that targets preventing rather than treating CVD risk factors, as a necessary strategy to reduce the CVD burden. To achieve primordial prevention, the target must be populations at risk for developing CVD risk factors (vs. those with existing risk factors), such as younger women.
Pregnancy is a biologically unique period for young women during which CVD risk factors such as obesity and high blood pressure (BP) can develop or worsen, contributing to future CVD. Pregnant women also spend most of their time in sedentary behavior (SED). SED is any behavior that occurs in a seated/reclining position with low energy expenditure and is now recognized as a behavior that is distinct from inactivity, or a lack of moderate-vigorous physical activity (MVPA). Though MVPA has known benefits, SED is an emerging, independent risk factor for obesity, CVD, and mortality. Importantly, prolonged bouts of SED (accumulated in bouts lasting 30 min or more) in non-pregnant persons are more strongly related to obesity and induce unfavorable hemodynamic responses, such as increased BP. We hypothesize that too much SED across pregnancy is an important contributor to excess gestational weight gain (GWG) and elevated BP, two important CVD risk factors in young women.
Remarkably, a dearth of studies evaluates SED across pregnancy. In cross-sectional studies, pregnant women spend 50-60% of their day in SED and SED is highest in the 3rd trimester. Yet, no study has evaluated if SED increases across pregnancy (repeated measurements) using best practice SED assessment methodology (objective device capable of capturing posture and intensity). Moreover, no study has evaluated whether greater SED is associated with increased GWG and BP in pregnant women, which in turn are known to impact pregnancy health and later maternal CVD risk. Current guidelines only advise MVPA for pregnant women with no recommendations about SED, highlighting the research gaps about SED and its consequences during pregnancy. Moreover, clarifying the role of SED in pregnancy is important because lowering SED might be a feasible strategy for pregnant women, who have low participation in9 and unique barriers to MVPA. Lastly, little is known about correlates and determinants of SED in pregnancy. Such data are critical for identifying women at risk for high SED during pregnancy and for developing effective interventions.
1.4 Significance: Sedentary behavior is a novel risk factor for weight gain, high BP, and CVD, yet patterns, correlates, determinants and consequences of sedentary behavior are poorly understood in pregnant women. Sedentary behavior is the most common behavior in pregnant women, but the dearth of research studies applying state-of-the-art sedentary behavior assessment methods and with repeated measures across pregnancy is a major research gap that we intend to address with this proposal. To the investigators' knowledge, no studies with optimal sedentary behavior measurement, assessing both posture and intensity while awake (i.e., activPAL), have been conducted in pregnant women. Beyond this, few studies have evaluated temporal trends in sedentary time across gestation. There is no research examining bouts of extended, uninterrupted sedentary time which have particularly deleterious effects on BP and are more strongly related to high BMI. Lastly, correlates and determinants of sedentary behavior are poorly understood overall and, in particular, among pregnant women. Before effective interventions can be designed to reduce sedentary behavior in pregnancy, nonmodifiable and modifiable factors associated with sedentary behavior must be better understood. Thus, the objective, longitudinal measurement of sedentary behavior in pregnancy proposed in this application will determine patterns, correlates, determinants, and consequences of sedentary behavior in pregnancy to move toward future goals of 1) clarifying risks and whether sedentary behavior recommendations are appropriate for pregnant women, 2) identifying groups at risk for high sedentary behavior, and 3) informing intervention targets. Further, this research addresses the AHA's mission to reduce the burden of CVD by investigating a novel strategy for primordial prevention of cardiovascular disease in young women.
