(174) Physical activity and sedentary behavior and spontaneous preterm birth (SPTB): Insights from Fitbit tracker data

Objective: We sought to assess if objectively quantified physical activity amount and intensity differ throughout gestation by history of SPTB and by recurrent PTB in the current pregnancy.

Study Design:

Primary analysis of a prospective observational cohort designed to identify factors associated with recurrent SPTB. Patients with singleton, non-anomalous gestations and ≥1 prior SPTB 16.0-34.9 wks (hx SPTB) and a smaller subset of individuals with ≥1 prior births ≥ 37 wks and no prior PTB (no SPTB hx) were recruited, 9.0-13.9 wks, 2017-2022. Physical activity was quantified using study-provided FitBit activity trackers. Subjects were instructed to maintain their ‘usual activity.’  Those with ≥7 valid monitoring days (FitBit recorded heart rate for ≥80% of the day) were included. Daily steps and activity intensity (sedentary, light, fairly/very active minutes) were compared by hx SPTB. For those with a hx SPTB, steps and activity intensity were also evaluated by recurrent PTB < 35 wks.  Fixed-effects regression was used to account for varying numbers of obs/subject and adjust for confounders.

 

Results:

131 patients met inclusion criteria. 99 (76%) had a hx SPTB < 35 wks; 18/99 (18%) had recurrent PTB < 35 wks (median 31.9 wks). All 32 patients with no hx SPTB delivered at term. The cohort was racially (37% Black) and ethnically (16% Hispanic) diverse. There were 9,401 Fitbit wear days (median 63 days/person). Those with hx PTB were less active and more sedentary than those with no hx SPTB (all p< 0.001), Figure Panel A. Among those with hx PTB, those with recurrent PTB < 35 wks were less active but not more sedentary than those with hx SPTB who delivered ≥ 35 wks, Figure Panel B. In separate adjusted models, median steps/day (β=-0.04, 95% CI -0.007, -0.001, p=0.003) and sedentary minutes (β=0.002, 95% CI 0.0006, p=0.009) were associated with recurrent PTB < 35 wks.

Conclusion:

Patients with hx SPTB < 35 wks are less active and more sedentary than those with only prior term births. Fewer median steps per day and increased sedentary minutes are associated with recurrent PTB.