Prevalence of U.S. Pregnant Women Meeting 2015 ACOG Physical Activity Guidelines

In December 2015, the American College of Obstetrics and Gynecology (ACOG) published updated physical activity (PA) guidelines for pregnant women, recommending women with uncomplicated pregnancies engage in ≥20–30 minutes/day of exercise on most days/week.1 Previous guidelines advocated ≥30 minutes/day of exercise on most days/week2; updated recommendations represent a more obtainable PA target during pregnancy. Although previous estimates indicated that few women in the U.S. accrued sufficient PA during pregnancy,3 it is important to determine how many women meet new recommendations. This paper describes the prevalence of pregnant women meeting the 2015 ACOG PA guidelines.


Introduction
I n December 2015, the American College of Obstetrics and Gynecology (ACOG) published updated physical activity (PA) guidelines for pregnant women, recommending women with uncomplicated pregnancies engage in Z20-30 minutes/day of exercise on most days/week. 1 Previous guidelines advocated Z30 minutes/day of exercise on most days/week 2 ; updated recommendations represent a more obtainable PA target during pregnancy. Although previous estimates indicated that few women in the U.S. accrued sufficient PA during pregnancy, 3 it is important to determine how many women meet new recommendations. This paper describes the prevalence of pregnant women meeting the 2015 ACOG PA guidelines.

Study Design
Data were from a population-based survey assessing the U.S. population's health, the National Health and Nutrition Examination Survey (NHANES) (collected 2007-2014 4 ; analyzed February 2016). PA was self-reported during interviews with 247 pregnant women aged 20-44 years, using a questionnaire. 5,6 Minutes/week women spent in moderate and vigorous leisure-time PA (LTPA) and in active transport (walking/cycling) during a typical week were derived. The number of days women engaged in weekly PA overall and by trimester of pregnancy (reported in 2007-2012 only; n=131) was calculated. Guidelines were operationalized as Z100 or Z150 minutes/week LTPA (i.e., Z20 or Z30 minutes on Z5 days/week), with and without the requirement of "on most (5) days/week." Whether including weekly active transport influenced the prevalence of women meeting PA guidelines was also explored. All estimates were weighted to reflect the U.S. population. NHANES participants gave informed written consent; the University of North Carolina IRB approved this study.

Results
Pregnant women were aged 28.8 (SD=6.0) years on average and had a mean BMI of 29.6 (SD=8.0); 65% women had some/college education, and 51% were of non-white ethnicity. Sixty percent of women reported engaging in no LTPA; those who did (n=148) were active for a median 150 (interquartile range [ (Table 1), and did not differ by trimester among the subsample. There was little difference in prevalence of women meeting guidelines when Z5 days was specified (12.7%-13.3%). Ignoring "most days," including women with any Z100 minutes/week or Z150 minutes/week of LTPA resulted in prevalences of 28.9% and 23.4%, respectively. Inclusion of active transport was associated with higher prevalence of meeting guidelines.

Conclusions
The updated ACOG guidelines recognize the benefits of PA during pregnancy, 1 providing women with a more manageable target of Z20 minutes of exercise on most days/week. Yet, most U.S. pregnant women reported LTPA below this target, in part explaining why the few women meet guidelines, regardless of trimester. Interestingly, using the thresholds of Z100 versus Z150 minutes/week made little difference to the proportion of women meeting guidelines, but removing the need to engage in PA on Z5 days/week resulted in approximately double the number of women meeting guidelines. In current ACOG guidelines, active transport does not contribute to "exercise," yet makes a meaningful contribution to women's overall PA, mainly through walking. 7 Consequently, including active transport in women's weekly PA had a substantial impact on the proportion of women classified as meeting recommendations.
Although new ACOG guidelines were largely based on research using self-report measures, self-reported PA is often higher than accelerometry. 8 Findings here may therefore represent an overestimation of women meeting PA guidelines. As NHANES ceased to oversample pregnant women during the study period, this study combined data from 2007 to 2014, preventing analysis of trends. It was also unable to identify women for whom PA was contraindicated.
Nevertheless, practitioners face a considerable challenge in ensuring that pregnant women free of complications meet PA guidelines. However, practitioners are well placed to highlight the benefits of PA; to assess PA readiness (using resources like the PA Readiness Medical Examination, 9 a guideline for health screening prior to exercise participation); and advise on how to exercise safely during pregnancy. In light of these findings, emphasizing the need to be physically active across the week and the various types of activity (e.g. active transport) that contribute toward daily PA (where not contraindicated) may also be helpful, 10 as PA does not have to be limited to planned exercise. Finally, given the current extent of low PA during pregnancy, multilevel approaches (e.g., intervening at the individual, interpersonal, and community levels simultaneously) will likely best support pregnant women and encourage them to achieve PA recommendations. KH was supported by the Wellcome Trust (107337/Z/15/Z). KRE received support from NIH R21 HL115385. The views expressed herein are those of the authors and do not necessarily represent those of the funding bodies. The authors thank Fang Wen from the University of North Carolina-Chapel Hill for her help with data management.
No financial disclosures were reported by the authors of this paper. Note: LTPA defined as a moderate or vigorous intensity for Z10 minutes; Active transport defined as walking or cycling for Z10 minutes. a Calculated by multiplying the lower 20-minute threshold by 5, where 5 is deemed to be "most" days. b No significant difference in women meeting PA guidelines by trimester (T1: n¼39; T2: n¼46; T3: n¼46, χ 2 test) for lower and higher physical activity thresholds, regardless of inclusion of "any" physical activity or active transport. c Calculated by multiplying the higher 30-minute threshold by 5, where 5 is deemed to be "most" days. ACOG, American College of Obstetrics and Gynecology; LTPA, leisure-time physical activity; NHANES, National Health and Nutrition Examination Survey.