Abstract：
BACKGROUND: The risk of preterm birth (PTB) increases when experiencing stress during pregnancy. Chronic stress has been associated with a dysregulation of the hypothalamic-pituitary-adrenal axis, for which hair cortisol concentration (HCC) is a promising biomarker. However, previous studies on the association between HCC and PTB yielded inconsistent results. This systematic review and meta-analysis synthesized previous studies on the association between maternal HCC before and during pregnancy and spontaneous PTB.
METHODS: Data was extracted from N = 11 studies with k = 19 effect sizes retrieved from PubMed, Embase, Web of Science, CINAHL and citation searching by hand in June 2023 and updated in October 2023. Standardized mean differences were calculated, and a random-effects three-level meta-analysis was conducted. Effect heterogeneity was assessed using Q and I2.
RESULTS: HCC during pregnancy was higher among PTB than term groups, but effects were not statistically significant (z = 0.11, 95% CI: - 0.28, 0.51, p = .54) and total heterogeneity was high (Q16 = 60.01, p < .001, I2Total = 92.30%). After leaving out two possible outlier studies in sensitivity analyses, HCC was lower among preterm compared to term delivering groups, although not statistically significant (z = - 0.06, 95% CI: - 0.20, 0.08, p = .39) but with a substantially reduced total heterogeneity (Q12 = 16.45, p = .17, I2Total = 42.15%). No moderators affected the estimates significantly, but an effect of trimester and gestational age at delivery is likely.
CONCLUSIONS: There is currently no evidence of prenatal HCC differences between PTB and term groups as effects were small, imprecise, and not significant. Low statistical power and methodological weaknesses of the small-scale studies challenge possible biological inferences from the small effects, but further research on HCC during pregnancy is highly encouraged.
METHODS: Data was extracted from N = 11 studies with k = 19 effect sizes retrieved from PubMed, Embase, Web of Science, CINAHL and citation searching by hand in June 2023 and updated in October 2023. Standardized mean differences were calculated, and a random-effects three-level meta-analysis was conducted. Effect heterogeneity was assessed using Q and I2.
RESULTS: HCC during pregnancy was higher among PTB than term groups, but effects were not statistically significant (z = 0.11, 95% CI: - 0.28, 0.51, p = .54) and total heterogeneity was high (Q16 = 60.01, p < .001, I2Total = 92.30%). After leaving out two possible outlier studies in sensitivity analyses, HCC was lower among preterm compared to term delivering groups, although not statistically significant (z = - 0.06, 95% CI: - 0.20, 0.08, p = .39) but with a substantially reduced total heterogeneity (Q12 = 16.45, p = .17, I2Total = 42.15%). No moderators affected the estimates significantly, but an effect of trimester and gestational age at delivery is likely.
CONCLUSIONS: There is currently no evidence of prenatal HCC differences between PTB and term groups as effects were small, imprecise, and not significant. Low statistical power and methodological weaknesses of the small-scale studies challenge possible biological inferences from the small effects, but further research on HCC during pregnancy is highly encouraged.
摘要：
背景：当怀孕期间经历压力时，早产（PTB）的风险增加。慢性应激与下丘脑-垂体-肾上腺轴的失调有关，头发皮质醇浓度（HCC）是一个有前途的生物标志物。然而,以往关于HCC与PTB相关性的研究结果不一致.这项系统评价和荟萃分析综合了先前关于怀孕前和怀孕期间母体HCC与自发性PTB之间关联的研究。
方法：数据来自从PubMed检索到的N=11项具有k=19效应大小的研究，Embase,WebofScience,CINAHL和引文搜索于2023年6月进行，并于2023年10月进行了更新。计算了标准化的平均差异，并进行了随机效应三水平荟萃分析。使用Q和I2评估效应异质性。
结果：PTB组妊娠期间HCC高于足月，但效果无统计学意义(z=0.11,95%CI:-0.28,0.51,p=.54),总异质性高(Q16=60.01,p<.001,I2总计=92.30%)。在敏感性分析中遗漏了两个可能的离群值研究之后，与足月分娩组相比，早产组HCC较低，虽然没有统计学意义（z=-0.06，95％CI：-0.20，0.08，p=.39），但总异质性大大降低（Q12=16.45，p=.17，I2总计=42.15％）。没有主持人对估计有重大影响，但在分娩时妊娠和胎龄的影响是可能的。
结论：目前尚无PTB和足月组之间的产前HCC差异的证据，因为影响很小，不精确,并不重要。小规模研究的低统计能力和方法学弱点挑战了可能的生物学推论，但在怀孕期间肝癌的进一步研究是高度鼓励。
方法：数据来自从PubMed检索到的N=11项具有k=19效应大小的研究，Embase,WebofScience,CINAHL和引文搜索于2023年6月进行，并于2023年10月进行了更新。计算了标准化的平均差异，并进行了随机效应三水平荟萃分析。使用Q和I2评估效应异质性。
结果：PTB组妊娠期间HCC高于足月，但效果无统计学意义(z=0.11,95%CI:-0.28,0.51,p=.54),总异质性高(Q16=60.01,p<.001,I2总计=92.30%)。在敏感性分析中遗漏了两个可能的离群值研究之后，与足月分娩组相比，早产组HCC较低，虽然没有统计学意义（z=-0.06，95％CI：-0.20，0.08，p=.39），但总异质性大大降低（Q12=16.45，p=.17，I2总计=42.15％）。没有主持人对估计有重大影响，但在分娩时妊娠和胎龄的影响是可能的。
结论：目前尚无PTB和足月组之间的产前HCC差异的证据，因为影响很小，不精确,并不重要。小规模研究的低统计能力和方法学弱点挑战了可能的生物学推论，但在怀孕期间肝癌的进一步研究是高度鼓励。
