Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Food Science and Human Nutrition

First Advisor

Christina G. Campbell


Obesity and incidence of chronic disease continue to rise in the United States. The current medical paradigm focuses on treatment of chronic disease. A shift from the management of disease to prevention of obesity and its associated co-morbidities including diabetes mellitus and cardiovascular disease is necessary to protect the health of future generations. Pregnancy is a "teachable moment" offering a time when many women are motivated to make healthier lifestyle choices to optimize the health of their unborn child. This critical stage of the life cycle offers a unique opportunity to influence the health of future generations by modifying the lifestyle of the expectant mother.

An abundance of evidence exists to associate excessive gestational weight gain (GWG) with adverse maternal and infant outcomes. Prenatal physical activity (PA) has been recommended to curtail the increasing rates of excessive weight gain during pregnancy yet few pregnant women meet current PA guidelines. Furthermore, the ability to accurately assess PA during pregnancy is convoluted by many factors, most notably the uncomfortable waist-worn placement of many commonly used activity monitors. Therefore, to make considerable strides in improving the health of future generations, it is imperative that strategies are developed to increase and accurately evaluate prenatal PA and explore its potential relationship with improved maternal and infant outcomes.

In order to provide possible answers to these issues, the Blossom Project at Iowa State University conducted two studies. The first study evaluated the validity of the SenseWear® Mini armband (SWA) to estimate energy expenditure (EE) in pregnant women. Multiple activities of daily living ranging in intensity from sedentary to moderate walking on a treadmill were performed while EE was measured by the SWA and indirect calorimetry. The results of the study showed significant overestimation by the SWA compared to indirect calorimetry (0.57 ±0.06 kcal*min-1) but average individual correlation coefficients revealed good overall agreement between methods (mean r = 0.93). Due to the convenient location worn on the upper-arm, the SWA is a plausible method to estimate EE and PA during pregnancy. Future studies should develop pregnancy-specific algorithms to further improve estimation of EE in this population.

The second study was a pilot randomized-controlled trial entitled "The Blossom Project Online". The study had two aims: 1) To evaluate the efficacy of a behaviorally-based website (based on Social Cognitive Theory; SCT) to increase intentional PA in sedentary pregnant women; and 2) To explore the impact of the PA intervention in pregnancy on maternal and infant outcomes. Fifty-one participants were enrolled while 50 were randomized to either usual care (UC) or a behaviorally-based intervention (BI-group) and received access to the study website with a username and password. Forty-five women completed the study (n=21 UC; n=24 BI-group). Participants receiving usual care could only view general diet and PA recommendations during pregnancy while intervention participants had access to all of the website features including the diet and PA recommendations, exercise goal-setting modules, problem-solving modules, a journal, a calendar to track all of their exercise through delivery, and a community forum to interact with other participants in the intervention group. Intervention participants were encouraged to work up to at least 150 minutes of moderate-vigorous PA (MVPA) per week (in at least 10-minute bouts) by week 19 of pregnancy and sustain at least this amount until delivery. All women were categorized into tertiles of website engagement to evaluate the efficacy of the website to increase PA. Additional outcomes of interest included adherence to PA guidelines, weekly MVPA, GWG, maternal weight-retention at 1-month postpartum and infant body composition at 1-month postpartum.

Results of the behaviorally-based randomized controlled trial indicated a significant increase from baseline of 95 (67-130) minutes per week in weekly intentional PA according to the website among the BI-group (P < 0.0001). Weekly PA reported by the BI-group on the website was 124 ± 44 minutes. On average 31.8% of women met the goal each week of > 150 minutes of PA. Objective MVPA assessment by the SWA confirmed significantly more MVPA sustained in 20- and 30-minute bouts among BI-group compared to UC at weeks 24-26 of pregnancy (P = 0.005 and P = 0.0008, respectively), and this MVPA in BI-group was significantly greater than baseline assessment (20-min: 61.3 ± 21.9 min; 30-min: 39.6 ± 14.8 min, both P <0.05). Those participants engaging in a greater amount of website activity completed more sustained MVPA than their not-engaged counterparts (118 ± 102 vs 57 ± 63 minutes per week, P < 0.05).

However, the significant increase in MVPA among the BI-group did not prevent excessive GWG. Excessive total GWG occurred in 62.2% of all participants, and in 42.1%, 82.4%, and 66.7% of normal weight, overweight, and obese women, respectively, with no differences in GWG, adherence to GWG recommendations, or weight retention between groups. Interestingly, energy intake significantly increased in the BI-group between baseline and weeks 24-26 of pregnancy (336 ± 127 kcals, P = 0.04) and was significantly greater than energy intake by UC (2503 ± 703 vs 1894 ± 594, P = 0.005). No differences were seen between groups in infant birth outcomes or weight, length, and body composition at 1-month of age. However, while group randomization assignment was not a significant predictor of infant body composition at 1-month of age, when combined with MVPA sustained for at least 30-minutes and diet quality at 24-26 weeks of pregnancy, 22% of the total variation in infant body composition was explained.

In conclusion, the SWA correlates well with indirect calorimetry to provide estimates of EE and PA during pregnancy. Further refinement of the algorithms may improve the validity of the monitor while currently available algorithms allow for PA to be assessed objectively during pregnancy with minimal user burden. Additionally, an interactive website based on SCT was successful in preventing the typical decline in PA during pregnancy and simultaneously increased PA in previously sedentary women. The intervention also inadvertently increased energy intake among the BI-group. Thus, given the energy intake of the BI-group, the amount of MVPA performed was not sufficient to prevent excess GWG or improve maternal weight retention. Given the benefits associated with prenatal PA, previously sedentary women without contraindications to exercise should be encouraged to increase prenatal PA and may need additional dietary counseling to prevent excessive GWG.

Copyright Owner

Katie Marie Smith



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File Size

175 pages