Abstract / Summary
Abstract Background. Reported adherence to physical activity (PA) guidelines in pregnancy varies widely, partly because studies differ in whether activity accumulated in non-leisure domains is counted when defining adherence. This decision is rarely reported explicitly, yet it determines who is classified as active. This study quantified adherence and classification agreement under two domain-inclusion criteria and examined their association with the rate of gestational weight gain (GWG). Methods. A cross-sectional survey was conducted among 335 pregnant women in three provinces of China (Guangdong, Zhejiang, Shaanxi). PA was assessed with the Pregnancy Physical Activity Questionnaire (PPAQ). Two adherence criteria were applied, both defined as at least 7.5 MET-hours per week of moderate-intensity activity: all-domain adherence (summed across the household/caregiving, occupational, transport and sports/exercise domains) and exercise/leisure-time (LTPA) adherence (sports/exercise domain only). The outcome was the rate of GWG (kg/week). Prevalence was compared using McNemar’s test and agreement with Cohen’s kappa. Hierarchical linear regression examined the association of each PA measure with GWG rate, with models repeated using GWG amount (kg) as the outcome. Results. All-domain adherence was 79.1% (95% CI 74.4–83.1) versus 29.0% (95% CI 24.4–34.0) under the LTPA criterion (difference 50.1 percentage points; p < 0.001); classification agreement was only 48.7% (κ = 0.175), and 170 of the 265 all-domain adherents (64.2%) reached the threshold entirely through non-leisure activity. Non-leisure domains accounted for 96.9% of total activity, whereas sports/exercise contributed only 3.1%. Neither criterion was associated with the rate of GWG (adjusted β = −0.001, p = 0.983 for all-domain; adjusted β = −0.024, p = 0.537 for LTPA); continuous, domain-specific and sedentary measures were likewise not associated, and results were unchanged with GWG amount as the outcome. Parity was the only consistent correlate (adjusted β = 0.093 kg/week, p = 0.046). Conclusions. The domain-inclusion criterion substantially affects prevalence estimates of guideline adherence during pregnancy but did not alter the (null) association with GWG. Studies using domain-structured questionnaires should state and, where possible, compare domain-inclusion criteria; objective measurement may be needed to clarify the PA–GWG relationship.