Corticotrophin-releasing hormone and CRH-binding protein. Differences between patients at risk for preterm birth and hypertension

Neonatal Hair Cortisol and Birth Outcomes: An Empirical Study and Meta-Analysis

OBJECTIVE

Prenatal stress physiology is often posited as a predictor of birth outcomes, including gestational age at birth and birthweight. However, research has predominantly relied on indicators in the maternal system, with few studies examining hormones of the fetal system. The current study focuses on fetal cortisol in the third trimester, as measured in neonatal hair, as a biological factor that might be associated with birth outcomes (gestational age at birth and birthweight). We report findings from two studies: a longitudinal cohort (Study 1), and a meta-analysis of the existing literature (Study 2).

METHODSSTUDY

Hair was collected for cortisol analysis from 168 neonates (55.95% female) shortly after birth. Gestational age at birth and birthweight were abstracted from medical records.

METHODSSTUDY

An exhaustive search of four databases was conducted, yielding 155 total studies for screening. Papers reporting neonatal hair cortisol (collection <2 weeks postpartum) and birth outcomes among human neonates were retained for analysis, including Study 1 results ( k = 9).

RESULTSSTUDY

Higher neonatal hair cortisol was related to longer gestation ( r = 0.28, p < .001) and higher birthweight, r = 0.16, p = .040. Sex did not moderate either association.

RESULTSSTUDY

Across the nine studies, higher neonatal hair cortisol predicted both longer gestation ( r = 0.35, p < .001, 95% confidence interval = 0.24-0.45) and higher birthweight ( r = 0.18, p = .001, 95% confidence interval = 0.07-0.28). Neonatal sex did not moderate these associations.

CONCLUSIONS

Fetal cortisol exposure in the third trimester plays a role in normative maturation of the fetus, and findings reveal that higher cortisol is associated with positive birth outcomes.

Diverse presentations of Cushing's syndrome during pregnancy - A case series

BACKGROUND

Cushing's syndrome (CS) encompasses various causes of hypercortisolism including adrenocorticotropic hormone (ACTH) secreting pituitary adenoma with or without bilateral adrenal hyperplasia, an adrenal adenoma or carcinoma, ectopic ACTH or corticotrophin-releasing hormone (CRH) secretion by a neoplasm or exogenous corticosteroid therapy. The diagnosis of CS in pregnancy presents a challenge due to overlapping clinical features of pregnancy (weight gain, striae, acne). If untreated, CS in pregnancy is associated with increased risk of maternal and fetal complications.

AIMS

With fewer than 250 cases currently published, we aim to review the clinical presentations, diagnostic methods, management, and outcomes of patients with CS in pregnancy to help optimise our clinical practice.

MATERIALS AND METHODS

This is a single-centre, retrospective review of woman with documented hypercortisolism receiving antenatal care at a tertiary maternity hospital in Perth between 2006 to 2022. Data were collated from electronic and chart reviews. OMNI calculator was used for birthweight calculations. Local ethics and patient consent were obtained.

RESULTS

Five women and seven pregnancies were identified. Four women had a pituitary source of ACTH-dependent CS as confirmed by brain magnetic resonance imaging. One woman had an ectopic source of ACTH. Two women were diagnosed during pregnancy. All pregnancies occurring prior to treatment of the Cushing's disease were complicated by secondary hypertension and diabetes.

CONCLUSION

CS represents a rare and difficult to diagnose condition in pregnancy. When untreated, maternal and fetal outcomes are compromised. Close monitoring of the associated complications with involvement of a multidisciplinary team are recommended.

The association between maternal prenatal hair cortisol concentration and preterm birth: A systematic review and meta-analysis

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.

CONCLUSION

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.

A framework for testing pathways from prenatal stress-responsive hormones to cardiovascular disease risk

Cardiovascular disease (CVD) is a leading cause of death globally, with the prevalence projected to keep rising. Risk factors for adult CVD emerge at least as early as the prenatal period. Alterations in stress-responsive hormones in the prenatal period are hypothesized to contribute to CVD in adulthood, but little is known about relations between prenatal stress-responsive hormones and early precursors of CVD, such as cardiometabolic risk and health behaviors. The current review presents a theoretical model of the relation between prenatal stress-responsive hormones and adult CVD through cardiometabolic risk markers (e.g., rapid catch-up growth, high BMI/adiposity, high blood pressure, and altered blood glucose, lipids, and metabolic hormones) and health behaviors (e.g., substance use, poor sleep, poor diet and eating behaviors, and low physical activity levels). Emerging evidence in human and non-human animal literatures suggest that altered stress-responsive hormones during gestation predict higher cardiometabolic risk and poorer health behaviors in offspring. This review additionally highlights limitations of the current literature (e.g., lack of racial/ethnic diversity, lack of examination of sex differences), and discusses future directions for this promising area of research.

Preterm Birth and Corticotrophin-Releasing Hormone as a Placental Clock

Preterm birth worldwide remains a significant cause of neonatal morbidity and mortality, yet the exact mechanisms of preterm parturition remain unclear. Preterm birth is not a single condition, but rather a syndrome with a multifactorial etiology. This multifactorial nature explains why individual predictive measures for preterm birth have had limited sensitivity and specificity. One proposed pathway for preterm birth is via placentally synthesized corticotrophin-releasing hormone (CRH). CRH is a peptide hormone that increases exponentially in pregnancy and has been implicated in preterm birth because of its endocrine, autocrine, and paracrine roles. CRH has actions that increase placental production of estriol and of the transcription factor nuclear factor-κB, that likely play a key role in activating the myometrium. CRH has been proposed as part of a placental clock, with early activation of placental production resulting in preterm birth. This article will review the current understanding of preterm birth, CRH as an initiator of human parturition, and the evidence regarding the use of CRH in the prediction of preterm birth.

Pregnancy anxiety, placental corticotropin-releasing hormone and length of gestation

OBJECTIVE

High pregnancy anxiety is a consistent predictor of earlier labor and delivery. Placental corticotropin-releasing hormone (pCRH) predicts earlier delivery consistently and it has been identified as a biological mediator of the association between pregnancy anxiety and gestational length. However, studies have not examined whether changes in pregnancy anxiety are associated with earlier birth as mediated by changes in pCRH during pregnancy. Accordingly, this study tests whether linear changes in pregnancy anxiety are associated with length of gestation indirectly through nonlinear increases in pCRH over pregnancy.

METHODS

A sample of pregnant women (n=233) completed prenatal assessments in early pregnancy, second trimester, and third trimester that included a 4-item assessment of pregnancy anxiety and collection of blood samples assayed for pCRH using radioimmunoassay. Length of gestation was abstracted from medical records after birth.

RESULTS

Increases in pregnancy anxiety from early pregnancy to third trimester predicted shorted length of gestation, as did nonlinear increases in pCRH over pregnancy. However, there was no evidence of an indirect effect of changes in pregnancy anxiety on length of gestation via changes in pCRH.

CONCLUSIONS

These results indicate that linear changes in pregnancy anxiety and nonlinear changes in pCRH during pregnancy are independent risk factors for shortened gestational length. This study adds to a small but growing body of work on biopsychological processes in pregnancy and length of gestation. Modeling changes in psychological and biological processes during pregnancy could provide more insight into understanding risk for adverse pregnancy outcomes.

Revisiting the placental clock: Early corticotrophin-releasing hormone rise in recurrent preterm birth

Objective

To determine if maternal plasma CRH and preterm birth history were associated with recurrent preterm birth risk in a high-risk cohort.

Study design

Secondary analysis of pregnant women with a prior preterm birth ≤35 weeks receiving 17-alpha hydroxyprogesterone caproate for the prevention of recurrent spontaneous preterm birth. All women with a 24-week blood sample were included. Maternal plasma CRH level at 24- and 32-weeks’ gestation was measured using both enzyme-linked immunosorbent assay (ELISA) and extracted radioimmunoassay (RIA) technologies. The primary outcome was spontaneous preterm birth <37 weeks. The association of CRH, prior preterm birth history, and the two combined was assessed in relation to recurrent preterm birth risk.

Results

Recurrent preterm birth in this cohort of 169 women was 24.9%. Comparing women who subsequently delivered <37 versus ≥37 weeks, mean levels of CRH measured by RIA were significantly different at 24 weeks (111.1±87.5 vs. 66.1±45.4 pg/mL, P = .002) and 32 weeks (440.9±275.6 vs. 280.2±214.5 pg/mL, P = .003). The area under the receiver operating curve (AUC) at 24 and 32 weeks for (1) CRH level was 0.68 (95% CI 0.59–0.78) and 0.70 (95% CI 0.59–0.81), (2) prior preterm birth history was 0.75 (95% CI 0.67–0.83) and 0.78 (95% CI 0.69–0.87), and (3) combined was 0.81 (95% CI 0.73–0.88, P = .001) and 0.81 (95% CI 0.72–0.90, P = .01) respectively for delivery <37 weeks. CRH measured by ELISA failed to correlate with gestational age or other clinical parameters.

Conclusion

In women with a prior preterm birth, CRH levels were higher and had an earlier rise in women who experienced recurrent preterm birth. Second trimester CRH may be useful in identifying a sub-group of women with preterm birth due to early activation of the placenta-fetal adrenal axis. Assay methodology is a variable that contributes to difficulties in reproducibility of CRH levels in the obstetric literature.

Associations Between Placental Corticotropin-Releasing Hormone, Maternal Cortisol, and Birth Outcomes, Based on Placental Histopathology

Preterm birth remains the leading cause of neonatal morbidity and mortality, with complex biochemical pathways requiring continued understanding and assessment. The objective of this study is to assess the associations between maternal cortisol and placental corticotropin-releasing hormone (placental CRH) concentrations with birth outcomes when stratified by placental histopathology. We conducted an analysis of 112 singleton pregnancies who received betamethasone between 23 and 34 weeks' gestation. Maternal blood and saliva were collected prior to betamethasone administration and samples assayed for plasma cortisol (pCort), salivary cortisol (sCort), and placental CRH levels. Placental findings were characterized as inflammatory, maternal vascular underperfusion (MVU), or no pathology, and compared for the outcomes of placental CRH, pCort, and sCort levels, gestational age at birth (GAB), and birthweight percentiles (BWP). Thirty-six subjects were characterized as inflammatory, 38 as MVU, and 38 without placental abnormalities. Histopathology groups differed significantly on placental CRH levels, GAB, and BWP. Post hoc tests suggested that the MVU group had higher placental CRH than the inflammatory or no pathology groups, and despite delivering earlier than the other two groups, the inflammatory group had infants with significantly higher BWP. No differences existed between groups in terms of mean plasma or sCort levels. Higher placental CRH and pCort levels were associated with earlier GAB in the overall sample, but when split by group, these associations remained significant only among the MVU group. Higher placental CRH was also associated with lower BWP in the overall sample but did not remain significant when split by group. Higher sCort was associated with lower BWP only in the MVU group. There is differentiation of placental CRH, cortisol, and birth outcomes when evaluated by placental histopathology. This highlights the importance of evaluating birth outcomes within the context of placental histopathology.

Placental CpG methylation of HPA-axis genes is associated with cognitive impairment at age 10 among children born extremely preterm

A major component of the neuroendocrine system is the hypothalamus-pituitary adrenal (HPA) axis. HPA axis genes are also known to play a role in placental physiology. Thus, disruptions in the signaling of HPA axis-associated genes may adversely impact the placenta as well as fetal development, with adverse consequences for health and development of the child. In support of this, recent studies have shown that placental epigenetic methylation of HPA axis genes has an impact on infant behavior. In this study, we evaluated CpG methylation of 14 placental HPA axis-associated genes from a subcohort (n=228) of the Extremely Low Gestational Age Newborns (ELGAN) cohort in relation to cognitive function in mid-childhood (e.g. 10 yrs). Multivariable logistic regression revealed that placental CpG methylation of 10 HPA-axis associated genes were significantly associated with cognition at age 10. Specifically, placental CpG methylation levels of the glucocorticoid receptor gene, Nuclear Receptor Subfamily Group 3 C Member 1 (NR3C1 ) and Brain-derived Neurotropic Factor (BDNF ) were significantly associated with increased odds in developing moderate/severe adverse cognitive impairment at age 10. Methyl-CpG Binding Protein 2 (MECP2) was the major transcriptional regulator of the ten identified HPA genes. The data suggest that placental CpG methylation is associated with cognitive outcomes in mid-childhood.

Area racism and birth outcomes among Blacks in the United States

There is increasing evidence that racism is a cause of poor health outcomes in the United States, including adverse birth outcomes among Blacks. However, research on the health consequences of racism has faced measurement challenges due to the more subtle nature of contemporary racism, which is not necessarily amenable to assessment through traditionally used survey methods. In this study, we circumvent some of these limitations by examining a previously developed Internet query-based proxy of area racism (Stephens-Davidowitz, 2014) in relation to preterm birth and low birthweight among Blacks. Area racism was measured in 196 designated market areas as the proportion of total Google searches conducted between 2004 and 2007 containing the "n-word." This measure was linked to county-level birth data among Blacks between 2005 and 2008, which were compiled by the National Center for Health Statistics; preterm birth and low birthweight were defined as <37 weeks gestation and <2500 g, respectively. After adjustment for maternal age, Census region, and county-level measures of urbanicity, percent of the Black population, education, and poverty, we found that each standard deviation increase in area racism was associated with relative increases of 5% in the prevalence of preterm birth and 5% in the prevalence of low birthweight among Blacks. Our study provides evidence for the utility of an Internet query-based measure as a proxy for racism at the area-level in epidemiologic studies, and is also suggestive of the role of racism in contributing to poor birth outcomes among Blacks.

Measurement of Perceived Stress Among Pregnant Women: A Comparison of Two Different Instruments

Assess the amount of agreement between the classification of stress from the Perceived Stress Scale (PSS) and the Assessment of Stress portion of the Prenatal Psychosocial Profile (PPP) among pregnant women. A secondary data analysis on a cross-sectional study of 301 pregnant women from the New Orleans and Baton Rouge areas who were exposed to Hurricane Katrina was conducted. Women with complete data (219) were analyzed. Women scoring in the third tertile of each instrument were compared. The kappa statistic was used to assess agreement between instruments. Additional comparisons were made with three instruments that measure other important psychosocial constructs that could be related to stress: the Edinburgh Depression Scale (EDS) and the Assessments of Support (partner and other support) and Self-Esteem from the PPP. No significant difference was found between the two tests. The PSS and the PPP were both statistically significantly correlated to each other (ρ = 0.71, p < 0.01). Thirty-five women were classified discordantly resulting in a Kappa Coefficient of 0.61 (95% CI 0.50-0.72, p < 0.01). No significant differences were found between these two instruments in correlation with the EDS (PPP, r = 0.76; PSS, r = 0.72; p < 0.01 for each), partner support (PPP, r = -0.47; PSS r = -0.46; p < 0.01 for each), other support (PPP, r = -0.31; PSS r = -0.32; p < 0.01 for each) and self-esteem (PPP, r = -0.41; PSS, r = -0.52; p < 0.01 for each), respectively. Given the similarities between the PSS and PPP, researchers are encouraged to choose and administer one instrument to participants, or to use the instruments in combination as an external reliability check.

Treatment with serotonin reuptake inhibitors during pregnancy is associated with elevated corticotropin-releasing hormone levels

Treatment with serotonin reuptake inhibitors (SSRI) has been associated with an increased risk of preterm birth, but causality remains unclear. While placental CRH production is correlated with gestational length and preterm birth, it has been difficult to establish if psychological stress or mental health problems are associated with increased CRH levels. This study compared second trimester CRH serum concentrations in pregnant women on SSRI treatment (n=207) with untreated depressed women (n=56) and controls (n=609). A secondary aim was to investigate the combined effect of SSRI treatment and CRH levels on gestational length and risk for preterm birth. Women on SSRI treatment had significantly higher second trimester CRH levels than controls, and untreated depressed women. CRH levels and SSRI treatment were independently associated with shorter gestational length. The combined effect of SSRI treatment and high CRH levels yielded the highest risk estimate for preterm birth. SSRI treatment during pregnancy is associated with increased CRH levels. However, the elevated risk for preterm birth in SSRI users appear not to be mediated by increased placental CRH production, instead CRH appear as an independent risk factor for shorter gestational length and preterm birth.

Alcohol use disorders in pregnancy

Alcohol use disorders (AUDs) are less prevalent in pregnant women than in nonpregnant women, but these disorders can create a host of clinical challenges when encountered. Unfortunately, little evidence is available to guide clinical decision making in this population. Drinking alcohol during pregnancy can have negative consequences on both fetus and mother, but it remains controversial as to the volume of alcohol consumption that correlates with these consequences. Likewise, little evidence is available to support the use of particular pharmacologic interventions for AUDs during pregnancy or to guide the management of alcohol detoxification in pregnant women. The use of benzodiazepines (the mainstay of most alcohol detoxification protocols) in pregnant women is controversial. Nevertheless, despite the lack of robust data to guide management of AUDs in pregnancy, clinicians need to make management decisions when confronted with these challenging situations. In that context, this article reviews the epidemiology of AUDs in pregnancy and the pharmacologic management of both AUDs and alcohol withdrawal in pregnant women, with the goal of informing clinicians about what is known about managing these co-occurring conditions.

Prenatal air pollution exposure and ultrasound measures of fetal growth in Los Angeles, California

BACKGROUND

Few previous studies examined the impact of prenatal air pollution exposures on fetal development based on ultrasound measures during pregnancy.

METHODS

In a prospective birth cohort of more than 500 women followed during 1993-1996 in Los Angeles, California, we examined how air pollution impacts fetal growth during pregnancy. Exposure to traffic related air pollution was estimated using CALINE4 air dispersion modeling for nitrogen oxides (NOx) and a land use regression (LUR) model for nitrogen monoxide (NO), nitrogen dioxide (NO2) and NOx. Exposures to carbon monoxide (CO), NO2, ozone (O3) and particles <10μm in aerodynamic diameter (PM10) were estimated using government monitoring data. We employed a linear mixed effects model to estimate changes in fetal size at approximately 19, 29 and 37 weeks gestation based on ultrasound.

RESULTS

Exposure to traffic-derived air pollution during 29 to 37 weeks was negatively associated with biparietal diameter at 37 weeks gestation. For each interquartile range (IQR) increase in LUR-based estimates of NO, NO2 and NOx, or freeway CALINE4 NOx we estimated a reduction in biparietal diameter of 0.2-0.3mm. For women residing within 5km of a monitoring station, we estimated biparietal diameter reductions of 0.9-1.0mm per IQR increase in CO and NO2. Effect estimates were robust to adjustment for a number of potential confounders. We did not observe consistent patterns for other growth endpoints we examined.

CONCLUSIONS

Prenatal exposure to traffic-derived pollution was negatively associated with fetal head size measured as biparietal diameter in late pregnancy.

New insights into the role of perinatal HPA-axis dysregulation in postpartum depression

Postpartum depression affects 10-20% of women following birth and exerts persisting adverse consequences on both mother and child. An incomplete understanding of its etiology constitutes a barrier to early identification and treatment. It is likely that prenatal hormone trajectories represent both markers of risk and also causal factors in the development of postpartum depression. During pregnancy the maternal hypothalamic-pituitary-adrenal axis undergoes dramatic alterations, due in large part, to the introduction of the placenta, a transient endocrine organ of fetal origin. We suggest that prenatal placental and hypothalamic-pituitary-adrenal axis dysregulation is predictive of risk for postpartum depression. In this model the positive feedback loop involving the systems regulating the products of the HPA axis results in higher prenatal levels of cortisol and placental corticotropin-releasing hormone. Greater elevations in placental corticotropin-releasing hormone are related to a disturbance in the sensitivity of the anterior pituitary to cortisol and also perhaps to decreased central corticotropin-releasing hormone secretion. Secondary or tertiary adrenal insufficiencies of a more extreme nature, which emerge during the prenatal period, may be predictive of an extended or more pronounced postpartum hypothalamic-pituitary-adrenal refractory period, which in turn represents a risk factor for development of postpartum depression. In addition to reviewing the relevant existing literature, new data are presented in support of this model which link elevated placental corticotropin-releasing hormone with low levels of ACTH at 3-months postpartum. Future research will further elucidate the role of hypothalamic-pituitary-adrenal axis dysregulation in postpartum depression and also whether prenatal placental and hypothalamic-pituitary-adrenal profiles might prove useful in the early identification of mothers at risk for postpartum mood dysregulation.

Changes in the maternal hypothalamic-pituitary-adrenal axis in pregnancy and postpartum: influences on maternal and fetal outcomes

Overexposure of the developing fetus to glucocorticoids is hypothesised to be one of the key mechanisms linking early life development with later life disease. The maternal hypothalamic-pituitary-adrenal (HPA) axis undergoes dramatic changes during pregnancy and postpartum. Although cortisol levels rise threefold by the third trimester, the fetus is partially protected from high cortisol by activity of the enzyme 11β-hydroxysteroid dehydrogenase type 2 (HSD11B2). Maternal HPA axis activity and activity of HSD11B2 may be modified by maternal stress and disease allowing greater transfer of glucocorticoids from mother to fetus. Here we review emerging data from human studies linking dysregulation of the maternal HPA axis to outcomes in both the mother and her offspring. For the offspring, greater glucocorticoid exposure is associated with lower birth weight and shorter gestation at delivery. In addition, evidence supports longer term consequences for the offspring including re-setting of the HPA axis and susceptibility to neurodevelopmental problems and cardiometabolic disease. For the mother, the changes in the HPA axis, particularly in the postpartum period, may increase vulnerability to mood disturbances. Further understanding of the changes in the HPA axis during pregnancy and the impact of these changes may ultimately allow early identification of those most at risk of future disease.

Fetal DNA Methylation Associates with Early Spontaneous Preterm Birth and Gestational Age

Spontaneous preterm birth (PTB, <37 weeks gestation) is a major public health concern, and children born preterm have a higher risk of morbidity and mortality throughout their lives. Recent studies suggest that fetal DNA methylation of several genes varies across a range of gestational ages (GA), but it is not yet clear if fetal epigenetic changes associate with PTB. The objective of this study is to interrogate methylation patterns across the genome in fetal leukocyte DNA from African Americans with early PTB (24^1/7–34^0/7 weeks; N = 22) or term births (39^0/7–40^6/7weeks; N = 28) and to evaluate the association of each CpG site with PTB and GA. DNA methylation was assessed across the genome with the HumanMethylation450 BeadChip. For each individual sample and CpG site, the proportion of DNA methylation was estimated. The associations between methylation and PTB or GA were evaluated by fitting a separate linear model for each CpG site, adjusting for relevant covariates. Overall, 29 CpG sites associated with PTB (FDR<.05; 5.7×10⁻¹⁰<p<2.9×10⁻⁶) independent of GA. Also, 9637 sites associated with GA (FDR<.05; 9.5×10⁻¹⁶<p<1.0×10⁻³), with 61.8% decreasing in methylation with shorter GA. GA-associated CpG sites were depleted in the CpG islands of their respective genes (p<2.2×10⁻¹⁶). Gene set enrichment analysis (GSEA) supported enrichment of GA-associated CpG sites in genes that play a role in embryonic development as well as the extracellular matrix. Additionally, this study replicated the association of several CpG sites associated with gestational age in other studies (CRHBP, PIK3CD and AVP). Dramatic differences in fetal DNA methylation are evident in fetuses born preterm versus at term, and the patterns established at birth may provide insight into the long-term consequences associated with PTB.

Maternal mental disorders in pregnancy and the puerperium and risks to infant health

Prenatal and postnatal period presents the highest prevalence of mental disorders in women’s lives and depression is the most frequent one, affecting approximately one in every five mothers. The aggravating factor here is that during this period psychiatric symptoms affect not only women’s health and well-being but may also interfere in the infant’s intra and extra-uterine development. Although the causes of the relationship between maternal mental disorders and possible risks to a child’s health and development remain unknown, it is suspected that these risks may be related to the use of psychotropic drugs during pregnancy, to substance abuse and the mother’s lifestyle. Moreover, after delivery, maternal mental disorders may also impair the ties of affection (bonding) with the newborn and the maternal capacity of caring in the post-partum period thus increasing the risk for infant infection and malnutrition, impaired child growth that is expressed in low weight and height for age, and even behavioral problems and vulnerability to presenting mental disorders in adulthood. Generally speaking, research on this theme can be divided into the type of mental disorder analyzed: studies that research minor mental disorders during pregnancy such as depression and anxiety find an association between these maternal disorders and obstetric complications such as prematurity and low birth weight, whereas studies that evaluate severe maternal mental disorders such as schizophrenia and bipolar disorder have found not only an association with general obstetric complications as well as with congenital malformations and perinatal mortality. Therefore, the success of infant growth care programs also depends on the mother’s mental well being. Such findings have led to the need for new public policies in the field of maternal-infant care geared toward the population of mothers. However, more research is necessary so as to confirm the association between all factors with greater scientific rigor.

Cumulative stress and maternal prenatal corticotropin-releasing hormone in an urban U.S. cohort

BACKGROUND

To date, there have been conflicting reports of the association of psychosocial stressors with prenatal corticotropin-releasing hormone (CRH) levels.

METHODS

We examined whether racial discrimination, community violence, interpersonal violence (IPV), negative life events, considered independently, and as a composite measure of cumulative stress, were associated with prenatal CRH levels in the Asthma Coalition on Community, Environment, and Social Stress (ACCESS) project, a multiethnic pre-birth cohort in urban Boston. Blood was collected between 20 and 37 weeks gestation (Mean=28.1, SD=4.6 weeks gestation). During pregnancy, women were administered the Conflict Tactics Scale survey to assess IPV, the Crisis in Family Systems-Revised survey to assess negative life events, the My Exposure to Violence survey to assess community violence, and the Experiences of Discrimination survey. A cumulative stress measure was derived from these instruments to characterize exposure to high levels of multiple stressors.

RESULTS

None of the individual stressors or cumulative stress was associated with CRH in combined analyses including Whites (n=20), Blacks (n=46), and Hispanics (n=110). In separate analyses of Blacks and Hispanics, racial discrimination, community violence, and cumulative stress were associated with CRH in Blacks, but were not associated with CRH in Hispanics.

CONCLUSIONS

Though these results require replication, they suggest that the effects of stress on prenatal CRH levels may be mediated by factors that differ between racial/ethnic groups. Further studies in larger samples are warranted to clarify whether associations of chronic stressors and prenatal CRH levels differ by race/ethnicity and to better understand underlying mechanisms.

A standardized template for clinical studies in preterm birth

BACKGROUND

Preterm birth is a major societal and economic problem accounting for 80 to 90% of neonatal morbidity and mortality worldwide. It is recognized as a complex multifactorial condition comprising several distinct clinical phenotypes with different underlying etiologies. As animal models are expensive and fail to mimic the biology of spontaneous preterm birth in humans, understanding the pathophysiology requires detailed clinical studies. Meta-analyses and clinical translation of data, however, are limited by heterogeneity of study design and size, publication and reporting biases, definition of patient groups, and a lack of standard universal definitions. This article provides a harmonized open-source template for designing clinical studies addressing preterm birth.

METHODS

Recommendations are made for clinical definitions, choice and assignment to preterm birth phenotypes, selection of enriched populations and control pregnancies, and potential confounding factors. In addition, recommendations are made for study design, sample size and power calculations, the minimal data sets needed for any study of preterm birth, and the optimal data set of an ideal study.

RESULTS

Recommended patient phenotypes are infection, uterine overdistension, hemorrhage, stress (either maternal or fetal), and idiopathic. Confounding factors include medical conditions, obesity, antenatal glucocorticoids, multifetal pregnancies, and fetal sex. Guidelines regarding study design, sample size, and clinical data acquisition are provided to serve as a universal template for preterm birth studies.

CONCLUSIONS

Adoption of a harmonized template will allow generation of protocols and studies with a basic degree of compatibility and will allow data to be compared, and samples and data sets to be combined for meaningful meta-analyses.

Ecological momentary assessment of maternal cortisol profiles over a multiple-day period predicts the length of human gestation

OBJECTIVE

Biobehavioral models of prenatal stress highlight the importance of the stress-related hormone cortisol. However, the association between maternal cortisol levels and the length of human gestation requires further investigation because most previous studies have relied on one-time cortisol measures assessed at varying gestational ages. This study assessed whether ecological momentary assessment (EMA) of cortisol sampling improves the ability to predict the length of human gestation. In addition, associations between EMA-based measures of psychological state (negative affect) with cortisol levels during pregnancy were assessed.

METHODS

For a 4-day period, 25 healthy pregnant women (mean gestational age at assessment = 23.4 [standard deviation = 9.1] weeks) collected seven salivary samples per day for the assessment of cortisol and provided a rating of negative affect every waking hour using an electronic diary.

RESULTS

Higher salivary cortisol concentrations at awakening and throughout the day (p = .001), as well as a flatter cortisol response to awakening (p = .005), were associated with shorter length of gestation. Women who delivered an infant at 36 weeks of gestations had 13% higher salivary cortisol levels at awakening than women who delivered an infant at 41 weeks of gestation. The EMA-based measure of negative affect was associated with higher cortisol throughout the day (p = .006) but not to gestational length (p = .641). The one-time measure of cortisol was not associated with length of gestation, and traditional retrospective recall measures of negative affect were not associated with cortisol.

CONCLUSIONS

Our findings support the ecological validity of repeated ambulatory assessments of cortisol in pregnancy and their ability to improve the prediction of adverse birth outcomes.

Critical windows of fetal lead exposure: adverse impacts on length of gestation and risk of premature delivery

OBJECTIVE

Research on the role of environmental lead exposure in the complex etiology of premature birth has yielded inconsistent results. We assessed the trimester-specific effect of prenatal lead exposure on gestational age and risk of premature delivery.

METHODS

We used linear and logistic regression to identify critical windows of susceptibility to lead exposure on gestational length.

RESULTS

In single-trimester models, decreases in gestational length were most strongly associated with first and second trimester blood lead. In adjusted logistic regression models, a one-standard deviation increase in second trimester blood lead was associated with an odds ratio of prematurity of 1.75 (95% CI: 1.02, 3.02).

CONCLUSIONS

Maternal whole blood lead levels measured during first and second trimesters yielded the most prominent inverse association with length of gestation and increased the risk of prematurity.

Levels of maternal serum corticotropin-releasing hormone (CRH) at midpregnancy in relation to maternal characteristics

BACKGROUND

Corticotropin-releasing hormone (CRH) in maternal blood originates primarily from gestational tissues and elevated levels in midpregnancy have been linked to adverse pregnancy outcomes. Investigators have hypothesized that high levels of maternal stress might lead to elevated CRH levels in pregnancy. Yet a few studies have measured maternal CRH levels among subgroups of women who experience disproportionate socioeconomic disadvantage, such as African-American and Hispanic women, and found that these groups have lower CRH levels in pregnancy. Our goal was to identify maternal characteristics related to CRH levels in midpregnancy and examine which if any of these factors help to explain race differences in CRH levels.

METHODS

The Pregnancy Outcomes and Community Health (POUCH) Study prospectively enrolled women at 15-27 weeks' gestation from 52 clinics in five Michigan communities (1998-2004). Data from the POUCH Study were used to examine maternal demographics, anthropometrics, health behaviors, and psychosocial factors (independent variables) in relation to midpregnancy blood CRH levels modeled as logCRHpg/ml (dependent variable). Analyses were conducted within a sub-cohort from the POUCH Study (671 non-Hispanic Whites, 545 African-Americans) and repeated in the sub-cohort subset with uncomplicated pregnancies (n=746). Blood levels of CRH and independent variables were ascertained at the time of enrollment. All regression models included week of enrollment as a covariate. In addition, final multivariate regression models alternately incorporated different psychosocial measures along with maternal demographics and weight. Psychosocial variables included measures of current depressive symptoms, perceived stress, coping style, hostility, mastery, anomie, and a chronic stressor (history of abuse as a child and adult).

RESULTS

In sub-cohort models, the adjusted mean log CRH level was significantly lower in African-Americans vs. non-Hispanic Whites; the difference was -0.48pg/ml (P<0.01). This difference was reduced by 21% (-0.38pg/ml, P<0.01) after inclusion of other relevant covariates. Adjusted mean log CRH levels were also lower among women with <12 years vs. >or=12 years of education (minimal difference=-0.19pg/ml, P<0.05), and among women with high levels of depressive symptoms who did not use antidepressants vs. women with lower levels of depressive symptoms and no antidepressant use (minimal difference=-0.13pg/ml, P<0.01). Log CRH levels were inversely associated with maternal weight (-0.03pg/ml per 10 pound increase, P<.05) but unrelated to smoking and all other psychosocial measures. Results were similar in the subset of women with uncomplicated pregnancies, except that lower CRH levels were also linked to higher perceived stress.

CONCLUSION

African-American women have lower blood CRH levels at midpregnancy and the race difference in CRH levels is reduced modestly after adjustment for other maternal characteristics. CRH levels were not elevated among women with high levels of perceived stress or more chronic stressors. The inverse association between CRH levels and maternal weight is likely due to a hemodilution effect. Relations among maternal CRH levels and maternal race, educational level, and depressive symptoms are difficult to explain and invite further investigation. Our results highlight a group of covariates that merit consideration in studies that address CRH in the context of pregnancy and/or post-partum complications.

Racial/ethnic disparities in obstetric outcomes and care: prevalence and determinants

Wide disparities in obstetric outcomes exist between women of different race/ethnicities. The prevalence of preterm birth, fetal growth restriction, fetal demise, maternal mortality, and inadequate receipt of prenatal care all vary by maternal race/ethnicity. These disparities have their roots in maternal health behaviors, genetics, the physical and social environments, and access to and quality of health care. Elimination of the health inequities because of sociocultural differences or access to or quality of health care will require a multidisciplinary approach. We aim to describe these obstetric disparities, with an eye toward potential etiologies, thereby improving our ability to target appropriate solutions.

Differing prevalence and diversity of bacterial species in fetal membranes from very preterm and term labor

BACKGROUND

Intrauterine infection may play a role in preterm delivery due to spontaneous preterm labor (PTL) and preterm prolonged rupture of membranes (PPROM). Because bacteria previously associated with preterm delivery are often difficult to culture, a molecular biology approach was used to identify bacterial DNA in placenta and fetal membranes.

METHODOLOGY/PRINCIPAL FINDINGS

We used broad-range 16S rDNA PCR and species-specific, real-time assays to amplify bacterial DNA from fetal membranes and placenta. 74 women were recruited to the following groups: PPROM <32 weeks (n = 26; 11 caesarean); PTL with intact membranes <32 weeks (n = 19; all vaginal birth); indicated preterm delivery <32 weeks (n = 8; all caesarean); term (n = 21; 11 caesarean). 50% (5/10) of term vaginal deliveries were positive for bacterial DNA. However, little spread was observed through tissues and species diversity was restricted. Minimal bacteria were detected in term elective section or indicated preterm deliveries. Bacterial prevalence was significantly increased in samples from PTL with intact membranes [89% (17/19) versus 50% (5/10) in term vaginal delivery p = 0.03] and PPROM (CS) [55% (6/11) versus 0% (0/11) in term elective CS, p = 0.01]. In addition, bacterial spread and diversity was greater in the preterm groups with 68% (13/19) PTL group having 3 or more positive samples and over 60% (12/19) showing two or more bacterial species (versus 20% (2/10) in term vaginal deliveries). Blood monocytes from women with PTL with intact membranes and PPROM who were 16S bacterial positive showed greater level of immune paresis (p = 0.03). A positive PCR result was associated with histological chorioamnionitis in preterm deliveries.

CONCLUSION/SIGNIFICANCE

Bacteria are found in both preterm and term fetal membranes. A greater spread and diversity of bacterial species were found in tissues of women who had very preterm births. It is unclear to what extent the greater bacterial prevalence observed in all vaginal delivery groups reflects bacterial contamination or colonization of membranes during labor. Bacteria positive preterm tissues are associated with histological chorioamnionitis and a pronounced maternal immune paresis.

Stress questionnaires and stress biomarkers during pregnancy

OBJECTIVE

Both self-reported indicators of stress and hormones such as cortisol and corticotrophin-releasing hormone (CRH) have been examined in relation to preterm birth. Although these hormones have been interpreted as biomarkers of stress, it is unclear whether psychosocial measures are empirically associated with biomarkers of stress in pregnant women.

METHODS

We analyzed data from 1,587 North Carolina pregnant women enrolled in the Pregnancy, Infection,and Nutrition study during 2000-2004 who provided at least one saliva sample for cortisol measurement or blood samples for CRH at 14-19 and 24-29 weeks' gestation. Cortisol measures were limited to those taken between 8 and 10 a.m. Perceived stress, state-trait anxiety, coping style, life events, social support, and pregnancy-specific anxiety were measured by questionnaires and interviews. Spearman correlations and multiple regressions were used to describe the relationship among the measures of stress.

RESULTS

No correlations larger than r = 0.15 were seen between reported psychosocial measures and cortisol or CRH. Women with demographic characteristics associated with poor pregnancy outcomes (unmarried, African-American, young, low pre-pregnancy body mass index) reported higher levels of stress but did not consistently have higher levels of stress hormones. Pre-eclampsia was associated with higher CRH, but not with higher cortisol.

CONCLUSIONS

The relationship between measurements of reported stress and biomarkers is not straightforward in large epidemiological studies of pregnancy.

Low levels of corticotropin-releasing hormone during early pregnancy are associated with precocious maturation of the human fetus

Elevation in placental corticotropin-releasing hormone (pCRH) during the last trimester of pregnancy has been associated with an increased risk for preterm delivery. Less is known about the consequences for the human fetus exposed to high levels of pCRH early in pregnancy. pCRH levels were measured in 138 pregnant women at least once at 15, 20 and 25 weeks of gestation. At 25 weeks of gestation, fetal heart rate (FHR) responses to a startling vibroacoustic stimulus (VAS) were recorded as an index of maturity. pCRH levels at 15 weeks of gestation, but at no later point, predicted FHR responses to the VAS. Fetuses exposed to the lowest concentrations of pCRH at 15 weeks of gestation exhibited a distinguishable response to the VAS, whereas fetuses exposed to higher levels of pCRH did not respond. The findings suggest that exposure to low levels of pCRH early in gestation may be optimal and associated with a response pattern indicating greater maturity.

Different secretion patterns of matrix metalloproteinases and IL-8 and effect of corticotropin-releasing hormone in preterm and term cervical fibroblasts

The aims of the present study were to compare the levels of mRNA and protein expression of matrix metalloproteinase (MMP)-1, -3, -8 and -9 in human cervical tissue in preterm and term labor as well as not in labor and to determine if corticotropin-releasing hormone (CRH) has an effect on MMP-1, -3 and interleukin (IL)-8 secretion in both preterm and term cervical fibroblasts. Cervical biopsies were taken from 60 women: 18 at preterm labor, 7 at preterm not in labor, 18 at term labor and 17 at term not in labor. ELISA and Immulite were used for protein and real-time RT–PCR for mRNA analysis. Cervical fibroblast cultures were incubated for 18 h with different CRH concentrations (10⁻¹³–10⁻⁶ M). The mRNA expression of MMP-1, -3 and -9 was higher in laboring groups compared with term not in labor. Protein levels of MMP-8 and -9 were higher in term in labor group compared with non-laboring groups. There were no significant differences in mRNA and protein expression between the preterm and respective term control groups. CRH significantly increased secretion of IL-8 in preterm and term cervical fibroblasts compared with controls. The secretion of IL-8 and MMP-1 was significantly higher and MMP-3 secretion lower in preterm cervical fibroblasts. In conclusion, cervical ripening at preterm seems to be a similar inflammatory process as at term with CRH involved. However, preterm and term cervical fibroblasts might have different phenotypes based on different secretion patterns of IL-8, MMP-1 and MMP-3.

Bioassay research methodology: measuring CRH in pregnancy

BACKGROUND

There are documented associations between elevated maternal corticotropin-releasing hormone (CRH) levels and adverse pregnancy outcomes. However, reports of these findings often lack sufficient detail and rationale regarding the bioassay methodology. This shortcoming can be problematic for researchers who do not possess in-depth laboratory sciences knowledge but who want to include bioassays in their investigations or to evaluate published reports. The quality and reliability of CRH measurement results can be significantly affected by variables encountered during sample collection, processing, storage, and bioassay. Thus, it is important to establish research laboratory protocols that are based on well-informed rationales and to carefully consider and control for relevant variables.

APPROACH

A synthesis of laboratory sciences literature regarding variables affecting CRH measurement in pregnancy is presented. Additionally, consultation with experienced researchers provided an in-depth understanding of CRH measurement. From these sources, a laboratory protocol for clinical research was developed.

RESULTS

Multiple variables that are specific to the reliability of CRH measurement in pregnancy have been identified. These include sample collection methods, sample processing, sample integrity, sample storage, and the actual assay selected.

CONCLUSION

The reliability of CRH measurements can be significantly improved by identifying and controlling for variables encountered during sample collection, processing, storage, and bioassay. Adequate methodological details are difficult to glean solely from the published literature, thus consultation with well-informed researchers is necessary. A protocol for CRH bioassay in clinical research is proposed.

Lipopolysaccharide stimulation of trophoblasts induces corticotropin-releasing hormone expression through MyD88

OBJECTIVE

We hypothesized that intrauterine infection may lead to placental corticotrophin-releasing hormone (CRH) expression via Toll-like receptor signaling.

STUDY DESIGN

To test this hypothesis JEG3 cells were stimulated with lipopolysaccharide (LPS), chlamydial heat shock protein 60, and interleukin (IL)-1. CRH expression was assessed by reverse transcription polymerase chain reaction (RT-PCR). The signaling mechanisms that were involved were examined in transient transfection experiments with beta-galactosidase, CRH-luciferase, cyclic adenosine monophosphate (AMP) response element-luciferase, dominant-negative (DN)-myeloid differentiation primary response gene (MyD88) and DN-toll-IL-1-receptor domain containing adapter inducing interferon (TRIF) vectors. Luciferase activity was determined by luciferase assay. Beta-galactosidase assay was performed to determine transfection efficiency.

RESULTS

LPS, chlamydial heat shock protein 60, and IL-1 stimulation led to CRH expression in the JEG3 cells. LPS-induced CRH expression was not due to the autocrine effect of LPS-induced IL-1 because the supernatant from LPS-conditioned JEG3 cells did not induce CRH expression in the naïve cells. DN-MyD88, but not DN-TRIF, blocked the LPS-induced CRH expression. The cAMP response element did not play a role in LPS-induced CRH expression.

CONCLUSION

Toll-like receptor signaling 4 may induce placental CRH expression through MyD88.

Corticotrophin-releasing hormone in lipopolysaccharide-stimulated term fetal membranes and amniotic fluid from term and preterm birth in African Americans and Caucasians

The objective of this study is to document differences in corticotrophin-releasing hormone (CRH), CRH receptor 1 (CRHR1), and CRH binding protein (CRHBP) gene expression in fetal membranes derived from African Americans and Caucasians in vitro in response to lipopolysaccharide (LPS) stimulation and to assess racial disparity in CRH concentrations in the amniotic fluid (AF) of women with spontaneous preterm birth (PTB). Fetal membranes (African American, n = 8; Caucasian, n = 8) at term, placed in an organ explant system, were stimulated with LPS. Microarray analysis documented differences in the mRNA expression pattern of CRH, CRHBP, and CRHR1 between races. CRH was measured in AF (a case [PTB]-control [term] study) and culture media. Between races, LPS significantly increased CRH and CRHR1 expression in African Americans and CRHBP in Caucasians, with no differences in controls. CRH was detectable only in LPS-stimulated African American membranes. AF CRH concentrations were higher in PTB compared with controls (P < .001), and no difference was noticed between races (P = .1). AF analysis did not document racial disparity in CRH concentrations in PTB. In fetal membranes, African Americans showed a higher expression and production of CRH in response to an in vitro stimulus.

Psychosocial stress and pregnancy outcome

This article is intended to help clinicians better understand the ever-expanding body of research on whether psychosocial stress (both acute and chronic) is linked to 2 major adverse pregnancy outcomes: preterm birth and low birth weight. We summarize the existing literature and then review assessment tools commonly used to diagnose various types of psychosocial stress, with attention to how and when assessments should be made. After discussing the physiologic mechanisms hypothesized to underlie these relationships, we examine the range of existing interventions aimed at reducing psychosocial stress and review their efficacy at improving birth outcomes. Future directions for prevention of adverse pregnancy outcomes are discussed and suggest that an entirely new approach may be necessary.

Monthly number of preterm births and environmental physical activity

Recent studies have reported links between external physical factors and human homeostasis.

OBJECTIVE

to determine whether the monthly values of specific physical environmental factors are associated with the monthly number of preterm births in a major medical center in Israel.

METHODS

The sample included 1006 infants weighing less than 1500g born live to 774 mothers during 96 consecutive months (1995-2002) at a tertiary medical center in Israel. Monthly values of indices of solar, cosmic ray, and geomagnetic activity for the same period were obtained from national data monitoring facilities in the United States of America, Russia, and Finland. The findings were statistically correlated with the monthly number of preterm births.

RESULTS

The number of preterm births correlated with the month of the year (1-12), with a progressive rise in the number of infants born as the year progressed (p = .02). The monthly number of preterm births showed a significant and direct correlation with solar activity indices (r = .32, p = .0016), and a significant and inverse correlation with cosmic ray activity indices (r = -0.3, p = .008). The relation was significant only for singelton births and for the whole group of preterm newborns, but not for multiple pregnancies.

CONCLUSION

Our findings suggest that solar and cosmic ray activity may play a role in the timing of premature labor, however in multiple pregnancies additional factors are dominant.

Corticotropin-releasing hormone, its binding protein and receptors in human cervical tissue at preterm and term labor in comparison to non-pregnant state

BACKGROUND

Preterm birth is still the leading cause of neonatal morbidity and mortality. The level of corticotropin-releasing hormone (CRH) is known to be significantly elevated in the maternal plasma at preterm birth. Although, CRH, CRH-binding protein (CRH-BP), CRH-receptor 1 (CRH-R1) and CRH-R2 have been identified both at mRNA and protein level in human placenta, deciduas, fetal membranes, endometrium and myometrium, no corresponding information is yet available on cervix. Thus, the aim of this study was to compare the levels of the mRNA species coding for CRH, CRH-BP, CRH-R1 and CRH-R2 in human cervical tissue and myometrium at preterm and term labor and not in labor as well as in the non-pregnant state, and to localize the corresponding proteins employing immunohistochemical analysis.

METHODS

Cervical, isthmic and fundal (from non-pregnant subjects only) biopsies were taken from 67 women. Subjects were divided in 5 groups: preterm labor (14), preterm not in labor (7), term labor (18), term not in labor (21) and non-pregnant (7). Real-time RT-PCR was employed for quantification of mRNA levels and the corresponding proteins were localized by immunohistochemical analysis.

RESULTS

The levels of CRH-BP, CRH-R1 and CRH-R2 mRNA in the pregnant tissues were lower than those in non-pregnant subjects. No significant differences were observed between preterm and term groups. CRH-BP and CRH-R2 mRNA and the corresponding proteins were present at lower levels in the laboring cervix than in the non-laboring cervix, irrespective of gestational age. In most of the samples, with the exception of four myometrial biopsies the level of CRH mRNA was below the limit of detection. All of these proteins could be detected and localized in the cervix and the myometrium by immunohistochemical analysis.

CONCLUSION

Expression of CRH-BP, CRH-R1 and CRH-R2 in uterine tissues is down-regulated during pregnancy. The most pronounced down-regulation of CRH-BP and CRH-R2 occurred in laboring cervix, irrespective the length of gestation. The detection of substantial expression of the CRH and its receptor proteins, as well as receptor mRNA in the cervix suggests that the cervix may be a target for CRH action. Further studies are required to elucidate the role of CRH in cervical ripening.

Measuring corticotropin-releasing hormone in pregnant women - comparing blood collection protocols for epidemiological studies

We describe a pilot study to determine the effect of delays in blood sample processing under simulated field conditions on measurement of corticotropin-releasing hormone (CRH) levels in pregnant women. CRH, a peptide secreted by the placenta into the maternal blood, is of interest in epidemiological studies of gestational duration. Many investigators suspected that CRH might break down quickly after collection, and believed the optimal treatment of blood samples for CRH must include immediate processing under chilled conditions and quick freezing of plasma. Epidemiological studies often have logistical constraints that make such rapid processing unfeasible. To examine how delays in the processing of blood samples might affect the level of measured CRH, we collected whole blood samples from 33 pregnant women attending a prenatal clinic in Boston. We compared CRH levels measured following three different processing delays with the levels of samples that were processed immediately after blood collection, the 'gold standard'. The delayed strategies involved placing the freshly collected whole blood in a cooler or refrigerator for up to 22 h prior to processing. Correlation coefficients comparing delayed with gold standard processing exceeded 0.96. These results suggest that CRH may be measured in blood samples that were spun and frozen up to 22 h after blood collection.

Pituitary gland and pregnancy

The hypothalamic-pituitary-adrenal axis is central to mammalian reproductive function, including conception, pregnancy maintenance, parturition, and breastfeeding. Pregnancy is associated with substantial physiologic changes within this endocrine axis to meet the demands of pregnancy, which include support of the fetus (volume support, nutritional and oxygen supply, clearance of fetal waste), protection of the fetus (from starvation, drugs, toxins), preparation of the uterus for labor, and protection of the mother from potential cardiovascular injury at delivery. This article reviews the anatomy, embryology, and physiology of the pituitary. The effect of pregnancy on pituitary structure and function, in health and disease, also is discussed.

Fetal and maternal adrenals in human pregnancy

Human pregnancy is marked by alterations in several endocrine systems--perhaps most notably, the striking increase in steroid hormone production by the adrenals of the fetus and mother. Morphologically and physiologically, the human fetal adrenal glands are remarkable organs. In proportion to the adult organs, the adrenal cortex is the largest organ of the fetus. At term, they produce more steroid and weigh the same as adrenal glands of the adult. Much of the steroid that is released by the fetal and maternal adrenals during pregnancy is the sulfated form of dehydroepiandrosterone (DHEA-S), which is used by the placenta to produce estrogens. Herein, we discuss the physiologic and pathophysiologic hormonal changes of the fetal and maternal adrenals during the course of pregnancy.

Placental corticotropin-releasing hormone (CRH), spontaneous preterm birth, and fetal growth restriction: a prospective investigation

OBJECTIVES

Recent advances in the physiology of human pregnancy have implicated placental corticotropin-releasing hormone (CRH) as one of the primary endocrine mediators of parturition and possibly also of fetal development. The aim of this study was (1) to prospectively assess the relationship of maternal plasma concentrations of CRH in the early third trimester of gestation with two prematurity-related outcomes-spontaneous preterm birth (PTB), and small-for-gestational age birth (SGA), and (2) to determine whether the effects of CRH on each of these outcomes are independent from those of other established obstetric risk factors.

STUDY DESIGN

In a sample of 232 women with a singleton, intrauterine pregnancy, maternal plasma was collected at 33 weeks' gestation and CRH concentrations were determined by radioimmunoassay. Each pregnancy was dated on the basis of last menstrual period and early ultrasonography. Parity, obstetric risk conditions for prematurity, mode of delivery, and birth outcomes were abstracted from the medical record.

RESULTS

After adjusting for the effects of established obstetric risk factors, elevated CRH levels at 33 weeks' gestation were significantly associated with a 3.3-fold increase in the adjusted relative risk (RR) for spontaneous preterm birth and with a 3.6-fold increase in the adjusted relative risk for fetal growth restriction. Women who delivered postterm had significantly lower CRH levels in the early third trimester than those who delivered at term. When outcomes were stratified by gestational length and birth weight, the lowest CRH levels at 33 weeks' gestation were associated with the term non-SGA births, intermediate and approximately equal CRH levels were associated with the preterm non-SGA and term SGA births, and the highest CRH levels were associated with the preterm SGA births.

CONCLUSION

For deliveries occurring after 33 weeks' gestation (the time of CRH sampling in this study), our findings support the notion that in humans placental CRH may play an impending, direct role in not only the physiology of parturition but also in processes related to fetal growth and maturation. Our results also support the notion that the timing of onset of parturition may be determined or influenced by events occurring earlier in gestation rather than those close to the time of actual onset of labor (ie, the notion of a "placental clock").

Plasma corticotropin-releasing hormone and unconjugated estriol in human pregnancy: gestational patterns and ability to predict preterm delivery

OBJECTIVE

The purpose of this study was to compare the patterns and timing of the increases in plasma levels of corticotropin-releasing hormone and unconjugated estriol during human pregnancy.

STUDY DESIGN

Corticotropin-releasing hormone and unconjugated estriol were measured in serial samples that were collected from preterm subjects and from spontaneous term control subjects who were selected randomly from a study cohort of 297 women.

RESULTS

Gestational increases in log corticotropin-releasing hormone and log unconjugated estriol concentrations were best described by linear and cubic polynomial functions, respectively. Plasma unconjugated estriol levels were similar in preterm and term singleton pregnancies at equivalent gestation, whereas corticotropin-releasing hormone was elevated earlier in premature subjects. Mean corticotropin-releasing hormone levels relative to term control subjects (n = 40 women) were shifted forward 16.5 +/- 8.1 days (P =.027, singleton preterm, spontaneous labor; n = 16) and 33.0 +/- 7.9 days (P <.001, singleton preterm, obstetric intervention; n = 10). The corresponding shifts in unconjugated estriol values were -3.8 +/- 2.0 days and -2.7 +/- 5.6 days (both not significant). The prematurity of delivery showed a significant regression on shifts in corticotropin-releasing hormone (P =.004 and P <.001) but not in unconjugated estriol for the 2 groups. The ability to predict prematurity was not significantly improved by regression on corticotropin-releasing hormone and unconjugated estriol shift values together.

CONCLUSION

The patterns and timing of gestational changes in corticotropin-releasing hormone and unconjugated estriol differ in humans. The usefulness of corticotropin-releasing hormone as a biochemical preterm marker in singleton pregnancies is not enhanced by the additional measurement of plasma unconjugated estriol.

Distribution and origin of corticotropin-releasing factor-immunoreactive axons in the female rat lumbosacral spinal cord

Corticotropin-releasing factor (CRF) is a neuropeptide traditionally known for its hormonal role in the hypothalamic/pituitary/adrenal stress axis. However, CRF has been reported in axons in sites that may be considered outside of the direct stress axis, e.g., in axons in the lumbosacral spinal cord associated with the micturition response. Whether any of these CRF-immunoreactive axons interacts with uterine-related preganglionic autonomic neurons or projection neurons in the lumbosacral spinal cord is unknown. Thus, immunohistochemistry and retrograde tracing were employed to determine the presence, distribution, and origin of CRF-immunoreactive axons in the L6/S1 spinal cord of the female rat and to ascertain whether these axons are associated with uterine-related neurons. CRF-immunoreactive axons were present in the dorsal horn, medial and lateral collateral pathways, dorsal intermediate gray, laminae VlI and X, and sacral parasympathetic nucleus of the spinal cord. Nitric oxide-synthesizing, i.e., NADPH-d-positive neurons and pseudorabies virus labeled uterine-related neurons were in the sacral parasympathetic nucleus and were closely apposed by CRF-immunoreactive axons. Injection of retrograde tracers (fluorogold or fast blue) into the L6/S1 spinal cord labeled neurons in the hypothalamic paraventricular nucleus and pontine Barrington's nucleus, and some of these neurons were immunoreactive for CRF. This study demonstrates that CRF-immunoreactive axons are present in the L6/S1 spinal cord of the female rat in areas associated with sensory and autonomic processing. Some of these axons originate from the paraventricular nucleus and Barrington's nucleus and are adjacent to uterine-related neurons. These results indicate that CRF may influence neural activity related to the female reproductive system.

The utility of plasma CRH as a predictor of preterm delivery

It has been suggested that CRH is a placental clock that controls the duration of pregnancy and that the timing of the rise in CRH may permit prediction of the onset of labor. We have performed a prospective longitudinal study, in 297 women, to examine the utility of a single second-trimester plasma CRH measurement to predict preterm delivery. Venous blood samples were taken at 4-weekly intervals, beginning at 16-20 wk gestation, until delivery for CRH and its binding protein. A time point at which a single plasma CRH test might give optimal data to predict preterm delivery was determined. Thirty-one subjects delivered prematurely (10.4%). Sampling for plasma CRH at 26 wk gestation seemed the optimal time point to maximize sensitivity and specificity of the test. The mean (+/- SD) plasma CRH in women at this gestation who eventually delivered after spontaneous labor within 1 wk of their due date (39-41 wk, n = 127) was 34.7 +/- 27.0 pM. A plasma CRH of more than 90 pM at 26 wk gestation had a sensitivity of 45% and a specificity of 94% for prediction of preterm delivery. The positive predictive value was 46.7%. Calculation of free CRH did not improve these figures. In conclusion, a single measurement of plasma CRH, toward the end of the second trimester, may identify a group at risk for preterm delivery, but over 50% of such deliveries will be unpredicted. These data do not support the routine clinical use of plasma CRH as a predictor of preterm labor.

Placental corticotrophin-releasing hormone, local effects and fetomaternal endocrinology

The human placenta produces corticotrophin-releasing hormone (CRH) in exponentially increasing amounts during pregnancy with peak levels during labour. CRH in human pregnancy appears to be involved in many aspects of pregnancy including placental bloodflow, placental prostaglandin production, myornetrial function, fetal pituitary and adrenal function and the maternal stress axis. Since fetal cortisol levels are associated with pulmonary development and maturity, placental CRH may have an indirect role in fetal development.Although the precise role of placental CRH in the regulation of gestational length and timing of parturition is unclear it appears to be involved in a placental clock. While glucocorticoids inhibit hypothalamic CRH production they stimulate CRH gene expression in the placenta.This difference may allow the fetal and maternal stress axes to influence this placental clock.Maternal CRH levels are elevated in many pathological conditions of pregnancy where fetal well-being is compromised, and in these situations it may act to maintain a stable intrauterine environment. Therefore, CRH appears to link placental function, maternal well-being, fetal well-being and fetal development to the duration of gestation and the timing of parturition.

Biological mechanisms that might underlie iron's effects on fetal growth and preterm birth

A negative association between anemia and duration of gestation and low birth weight has been reported in the majority of studies, although a causal link remains to be proven. This paper explores potential biological mechanisms that might explain how anemia, iron deficiency or both could cause low birth weight and preterm delivery. The risk factors for preterm delivery and intrauterine growth retardation are quite similar, although relatively little is understood about the influence of maternal nutritional status on risk of preterm delivery. Several potential biological mechanisms were identified through which anemia or iron deficiency could affect pregnancy outcome. Anemia (by causing hypoxia) and iron deficiency (by increasing serum norepinephrine concentrations) can induce maternal and fetal stress, which stimulates the synthesis of corticotropin-releasing hormone (CRH). Elevated CRH concentrations are a major risk factor for preterm labor, pregnancy-induced hypertension and eclampsia, and premature rupture of the membranes. CRH also increases fetal cortisol production, and cortisol may inhibit longitudinal growth of the fetus. An alternative mechanism could be that iron deficiency increases oxidative damage to erythrocytes and the fetoplacental unit. Iron deficiency may also increase the risk of maternal infections, which can stimulate the production of CRH and are a major risk factor for preterm delivery. It would be useful to explore these potential biological mechanisms in randomized, controlled iron supplementation trials in anemic and iron-deficient pregnant women.

Salivary cortisol levels and anxiety are not increased in women destined to develop preeclampsia

OBJECTIVE

To compare salivary cortisol levels and maternal anxiety (general and pregnancy-specific) in the early and late second trimester of pregnancy between women who developed preeclampsia (PE) and women who remained normotensive.

DESIGN

Nested case-referent study. In a prospectively studied cohort of 250 pregnant women, nine women developed PE in late pregnancy. These nine patients were matched and compared with nine controls. Diurnal cortisol levels were obtained by collecting saliva samples at 17-18 and 27-28 weeks gestation. Salivary cortisol levels were determined by radioimmunoassay. Maternal anxiety was determined by Spielberger's State-Trait Anxiety Inventory (STAI) and a pregnancy-specific stress questionnaire.

RESULTS

For both patients and controls, a similar pattern of salivary cortisol excretion was observed. Salivary cortisol levels and anxiety scores (general and pregnancy-specific) did not differ significantly between patients and controls.

CONCLUSIONS

Our findings do not lend support to a role for maternal anxiety or second trimester increases in circulating stress hormones in the pathogenesis of PE.