Exercise, Inflammation, and Spontaneous Preterm Labor
Objective: Current research suggests that maternal systemic inflammation leads to the induction of preterm labor (PTL). Many environmental factors influence the activity of the innate and adaptive immune systems and thus, the amount of systemic inflammation that an individual experiences. Although the relationship between exercise patterns and systemic inflammation has been studied effectively in the general population, exercise studies in the context of pregnancy have been inconclusive and limited by poor study design. These few studies have failed to consider a variety of pro- and anti-inflammatory cytokines as markers of inflammation, and have not considered the intensity of exercise in relation to cytokine expression. Categorization of exercise intensity in general population studies has demonstrated that exercise cannot be treated as one all-encompassing variable because the physiological effects of exercise at different intensities are inherently distinct. Thus, our study aimed to effectively investigate antenatal exercise patterns in relationship to systemic inflammation and PTL by considering exercise intensity in relation to a variety of pro- and anti-inflammatory cytokines.
Methods: All data used for this study was collected through the Ontario Birth Study (OBS): a platform for research on pregnancy complications, and maternal and infant health. Out of 1375 pregnant participants, 40 experienced SPTB (delivery at <37 weeks) and 28 of these subjects completed the questionnaires containing exercise information and gave blood samples during the relevant periods (gestational age (GA) 16.2 and 27.1 weeks). Utilizing a case-control study design, this group was compared to 52 healthy pregnant controls that delivered at term (>37 weeks) and also provided blood samples at 16.2 and 27.1 weeks. Subjects were matched on age (<3 years difference) and parity (via dichotomization as nulliparous or multiparous). Luminex bead-based assays were used to simultaneously measure the concentration of 19 cytokines in maternal blood samples. Physical activity was assessed using the validated International Physical Activity Questionnaire (IPAQ).
Results: We found that PTL women tended to do less walking at 16.1 weeks GA than those who gave birth at term (p=0.055). Based on preliminary analyses, there is no significant relationship between cytokine concentration at 16.2 or 27.1 weeks GA and PTL or patterns of physical activity.
Conclusion: These results suggest that the contribution of physical activity, assessed cumulatively or based on intensity, is insignificant to total systemic inflammation. These results also suggest that systemic inflammation during pregnancy is not a reliable predictor of PTL.
1. Systemic inflammatory profiles of asymptomatic pregnant women could be predictive of spontaneous preterm birth.
2. Low intensity physical activity protects pregnant women from spontaneous preterm birth by inducing anti-inflammatory immune responses.
•To determine whether systemic inflammatory profiles of women who gave birth preterm (28-36 weeks of gestation) are different from women who delivered at term (≥37 weeks of gestation), and if so, whether these differences are gestational age-dependent
The Ontario Birth Study began at Mount Sinai Hospital in 2013 and is an open, longitudinal cohort study designed to serve as a platform for research on maternal and infant health.
Figure 1) Assessment of exercise intensities in asymptomatic pregnant women at 16 and 27 weeks of gestation. Total MET-minutes of walking (A), moderate-intensity (B), and vigorous (C) physical activity, as well as cumulative (D) physical activity per week are shown. Women who delivered spontaneously preterm reported less walking at 16 and 27 weeks GA than women who subsequently delivered at term (p<0.01). Combination of all three categories of physical activity at 27 weeks GA showed that cumulatively, sPTL women exercised less than TL controls (p<0.01). Data presented as mean ± SEM.
Figure 2) Categorization of activity levels indicating whether women are inactive or sufficiently active. The activity levels of sPTL and TL women were not different at either time point. Data presented as percentage of participants in each group (sPTL/TL).
Figure 3) Categorization of physical activity level in relation to peripheral blood sample cytokine concentration. At 27 weeks GA, women who were sufficiently active had significantly higher concentrations of IL-17 (A), IFNγ(B), and IL-4 (C) than those who were inactive (p<0.05). Data presented as mean ± SEM.
SUMMARY OF RESULTS