Adverse life events and chronic psychological distress before and during pregnancy have frequently been associated with preterm birth but the biological underpinnings remain unclear. We investigated the association between corticosteroid levels in pre-pregnancy and first-trimester hair and the risk of preterm birth. We followed N = 1,807 pregnant women from a prospective pre-birth cohort study in Lima, Perú. Hair samples were taken at the end of the first pregnancy trimester. The two most proximal 3 cm segments to the scalp (representing pre-pregnancy and first-trimester) were analyzed to obtain hair cortisol and cortisone concentrations (HCC and HCNC). Preterm birth was defined as birth < 37 completed gestational weeks. We constructed four generalized propensity scores for pre-pregnancy and first-trimester HCC and HCNC to create corresponding inverse probability weights before fitting marginal structural models for estimating the effect of HCC and HCNC on preterm birth risk. Pre-pregnancy Log HCC was not independently associated with preterm birth risk (RR = 0.97; 95%CI: 0.79, 1.19), nor was pre-pregnancy Log HCNC (RR = 0.84; 95%CI: 0.58, 1.20). In the first trimester, a one SD increase in Log HCC was associated with a 37% increased risk of preterm birth (95%CI: 1.11, 1.69), whereas Log HCNC was not significantly associated with preterm birth risk (RR = 1.20; 95%CI: 0.87, 1.65). Our findings show that chronic corticosteroid levels in early pregnancy are causally linked to preterm birth risk in pregnant Peruvian women. This finding contributes to understanding the biological underpinnings of preterm birth better to enhance its prevention.

怀孕前和怀孕期间的不良生活事件和慢性心理困扰通常与早产有关，但生物学基础仍不清楚。我们调查了孕前和孕早期头发中皮质类固醇水平与早产风险之间的关联。我们跟踪了来自秘鲁利马一项前瞻性产前队列研究的 N = 1,807 名孕妇。在妊娠早期结束时采集头发样本。分析头皮最近端的两个 3 cm 节段 （代表孕前和孕早期） 以获得头发皮质醇和可的松浓度 （HCC 和 HCNC）。早产定义为出生 < 完成孕周。我们构建了孕前和孕早期 HCC 和 HCNC 的四个广义倾向评分，以创建相应的逆概率权重，然后拟合边缘结构模型来估计 HCC 和 HCNC 对早产风险的影响。孕前 Log HCC 与早产风险不独立相关 （RR = 0.97;95%CI： 0.79， 1.19），孕前 Log HCNC 也不独立相关 （RR = 0.84;95%CI： 0.58， 1.20）。在妊娠早期，Log HCC 每增加 1 个 SD 与早产风险增加 37% 相关 （95%CI： 1.11， 1.69），而 Log HCNC 与早产风险无显著相关性 （RR = 1.20;95%CI： 0.87， 1.65）。我们的研究结果表明，妊娠早期的慢性皮质类固醇水平与秘鲁孕妇的早产风险有因果关系。这一发现有助于更好地了解早产的生物学基础，以加强其预防。