BACKGROUND

This study aimed to examine the relationship between maternal chronic stress, measured as allostatic load (AL), and the subsequent risk of spontaneous preterm birth (sPTB).

METHODS

This analysis was based on a prospective, single-center cohort study conducted in China. Eligible women were recruited during their second trimester and followed up until giving birth. AL was estimated at enrollment by using 10 biomarkers that reflect cardiovascular, metabolic, immune, and neuroendocrine dysregulation. High AL group was defined as women with AL score greater than the upper sample quartile. Latent class analysis (LCA) was performed to identify underlying AL patterns among pregnant women. Logistic regressions were employed to test the association between AL and sPTB. Additionally, the dose-response associations between AL score and sPTB were evaluated by using a 3-knot restricted cubic spline (RCS).

RESULTS

637 pregnant women with a mean AL score of 2.6 ± 1.7 (mean ± SD) were included in this study. Among these participants, 175 (27.5%) were classified into the high AL group (AL score ≥ 4). The sPTB rate was 6.6%. After adjusting for sociodemographic and clinical factors, multivariable logistic regression analysis revealed a significant positive association between AL score and sPTB (OR = 1.28, 95% CI: 1.07-1.52, P = 0.007). Similarly, women in the high AL group had significantly higher sPTB risk compared with those in the low AL group (OR = 2.09, 95% CI: 1.08-3.99, P = 0.025). LCA yielded three AL latent classes: (1) low dysregulation class, (2) metabolic-immune dysregulation class, and (3) cardiovascular dysregulation class. When compared with the low dysregulation class, the metabolic-immune dysregulation class was significantly associated with sPTB (OR = 2.60, 95% CI: 1.18-5.49, P = 0.014). RCS showed there was an obvious dose-dependent association between increased AL score and risk of sPTB.

CONCLUSIONS

This study provides evidence that AL during pregnancy is associated with the risk of sPTB, especially the metabolic-immune dysregulation class of AL. Evaluating AL and chronic stress during pregnancy may be potential tools to identify pregnant women at high risk of sPTB. Further work is needed to validate these findings in larger or diverse populations.