In order to increase the clarity for the SPPM in this paper, especially in the context of the stress-APO relationship related to African American women, the discussion will fall under the three main sections: Stress Onset, Stress Reactions and Stress Outcomes. Please note the following: 1).  In an earlier version of the SPPM the SRC was referred to as the FRCS. 2) Because an attempt is being made to explain the stress-APO relationship in the experiential context of pregnant African American women, for the sake of brevity the nomenclature of Black women, African American women, or simply, women, will be used interchangeably throughout the paper.

Stress Onset                                                                                                                                                                                                   This phase is the most important section of the SPPM, simply because it is where a series of subjective processes begin.  This being the case, six crucial areas are involved including: exogenous (outside)[#3a, #5a] and endogenous (inside)[#3b, #5b] factors; external [#4a] and internal[#4b] stressors; the Sociopsychophysiological Resource Center, or simply the SRC as it will subsequently be called; and stress levels[#7]. Again, as the arrows indicate, the SPPM is a multicausal, bi-directional and interactive model, where the basic and fundamental assumption is that the wider society [#1 – in this case the American society] encompasses and, therefore, is likely to have an impact on the individual [#2 - which in this case refers to the African American female] in a dynamic and interactive manner. For African American females[#2], this later point is very important, given the dominant and institutionally racist nature²⁸ [Livingston, 1987]of the wider U.S. society [#1]. It is reasoned in this paper that a contributing factor to the stress-APO relationship for African American females is their perception of and negative experiences with the daily realities of both positive[#5a] (e.g., social support) and negative exogenous factors[#3a] (e.g., racism and poverty).

           Whatever the precursor and actual sources of stress, it is important to note that exogenous factors [#3a and #5a] and endogenous factors [#3b and 5b] all interact and combine in contributing to the effectiveness of African American women’s SRCs [#6].  As seen in Figure 1, the SRC is at the “core” of the SPPM and it is defined as “The mind body enduring capacity that individuals have that filters, mediates, neutralizes, and subsequently serves to stabilize all entering noxious and other stimuli or stressors.” ⁴¹ 

           As illustrated in the model seen in Figure 1, the strength of African American women’s SRCs is a direct result of the input and possession of a collection of  “resource” conditions. Because these collective resource conditions comprise a variety of social factors (e.g., having social support and being empowered by others), psychological (e.g., attitudes and self-concept) and biological (e.g., physical health and the immune system) resource conditions; the composite label sociopsychophysiological was given to designate the contributions of these resources. Additionally, because of the “protective” cluster that all these resource conditions represent, collectively they constitute both a structural and functional resource center, especially for stress-prone individuals, such as at-risk, pregnant African American women. It is very evident from the SPPM that if the SRC is strong (i.e., its contributing resources are at their highest possible level), women are, then, more likely to exhibit better coping (i.e., active) skills, which in turn increases the likelihood that, over time, they will in turn experience lower levels of stress[#7].

             A woman’s perception of outside stressors or demands[#4a] is influenced by a host of possible exogenous factors, the latter of which can be either negative[#3a] or positive[#5a].  Essentially, the negative exogenous factors (e.g., racism) contribute to the possibility that women will either perceive their daily realities (e.g., discriminatory practices) as threatening. In some cases, these exogenous factors could be perceived as stressors themselves. In contrast, positive exogenous factors (e.g., such as having a supportive relationship) could be perceived as a resource to moderate any perceived stressful conditions. As seen in Figure 1, this would occur by women experiencing less threat when the supportive relationships [#5a] they perceive as having are greater than the perceived stressful experiences[#4a – e.g., denial of a job, denial of a bank loan, inability to leave low-income, crime-infested neighborhood] brought on by exogenous factors (e.g., an institutionally racist society[#3a]). Based on the transactional manner in which stress is defined in this paper, such a resource could lower the posed threat, especially if it (i.e., the resource) is greater than the perceived demands of the external stressors (if any). While the ultimate precipitating stressors may be external [#4a – e.g., undesirable life events], as well as internal [#4b - e.g., endogenous or physiological trauma, pain] for African American women, this paper focuses more on exogenous negative factors (e.g., racism, poverty, low socioeconomic status, life events) that contribute to external stressors [4a] because of the former’s salient and more enduring characteristics.

             Exogenous Factors, External Stressors and the SRC.  As is illustrated in the model, if African American women are predisposed to experience a host of negative (i.e., adverse), exogenous factors ([#3a], e.g., like poverty, racism, undesirable life events), these factors could contribute to related stressors or demands[#4a], where in the absence of more positive (i.e., moderating) exogenous factors[#5a] could lead to perceived threat in their SRCs[#6]. It is important to note that given the dynamic nature of the SPPM, an initially predisposing negative, exogenous condition[#3a](e.g., racism, low socioeconomic status –Williams; ⁴⁷  Clark et al; ⁴⁸ Rich-Edwards et al.¹⁰) may itself be perceived as a stressor[#4a] (e.g., discrimination, as seen in denial of certain needs involving housing, hospitalization and work). For example, it was said, “A woman’s perception that she resides in a ‘bad’ [“posed threat”] neighborhood may be a chronic stressor that disproportionately affects the reproductive outcome of African Americans.”⁴⁹ Women’s perception of negative exogenous factors[#3a] as stressors[#4a] is at the core of the transactional definition of stress used in this paper. Therefore, what makes women perceive negative exogenous factors[#3a – e.g., racism] as external stressors[#4a – e.g., discriminatory practices] is related to their “collective” experiences (i.e., associated with their SRCs), hence the seemingly uniformity in their perceptions, stress reactions and, ultimately, stress outcomes (e.g., APOs).

               Another example of a possible negative exogenous condition has to do with the disproportionately large percentage of African Americans who live in impoverished urban communities infiltrated with violence and illicit drug traffic.⁵⁰ Again, depending on the capabilities of the women’s SRCs (as well as various other factors, e.g., the availability of mitigating, positive exogenous factors) they may or may not perceive these factors as negative external stressors[#4a]. Only recently have researchers started to suspect that such a residential pattern of “difficult” living contributes to the unexplained three-fold greater incidence of very-low-birthweight (VLBW; < 1,500 gm) infants among African Americans compared with Whites.^51,52  

             It is the cumulative life course (i.e., long-term) exposure to adverse socioeconomic conditions[#3a] that may have the largest impact on health[#9]. Additionally, low socioeconomic pregnant women experience more stressful life events[#4a] during their pregnancy^46,53  (i.e., versus the less obvious and more difficult to measure internal stressors – [#4b]). Furthermore, chronic stressors are embedded within and accrue from the environment of low socioeconomic women[#3a]. Therefore, the threat caused by financial insecurity[#3a] can lead to (i.e., be perceived as) various related external stressors[#4a], such as poor and crowded housing conditions, domestic violence and stressful working conditions.⁵⁴  

            Reports also indicate that a high frequency of stressors (e.g., undesirable life events or stressful life events - SLEs conditions) during pregnancy are associated with an increased risk of low birthweight, preterm delivery and spontaneous abortion.⁵⁵ This being the case, experiencing these SLEs[#3a] may lead to acute stressors[#4a] that can contribute to the elevated VLBW rate among African American women.⁴⁹

            There are increasing reports concerning the relationship between violence, fear and APOs. It must be stated, however, that while there may be an inverse relationship between socioeconomic status and violence, women of all socioeconomic classes are abused. Again, as the SPPM indicates, the negative exogenous factor of low socioeconomic status[#3a] is associated with violence as an external stressor[#4a] and, depending on a variety of conditions (e.g., the resiliency of  women’s SRC), threat, fear and, ultimately, different levels of stress[#7] are likely to be perceived or experienced by women. These stressful experiences are more problematic for African American women, especially if they are chronic (e.g., discrimination, violence) versus acute in nature.  Whereas many studies have estimated on a more general basis that 4-8 percent of pregnant women are physically abused, ⁵⁶ other studies that have assessed violence in late pregnancy reported higher prevalence estimates of 16 percent and 20 percent.⁵⁷ Additionally, other studies have reported that battered women had large and statistically significant increases in the risk of APOs (i.e., low birthweight ⁵⁷ and preterm birth⁵⁸).

           It is stated that health and mortality are affected by the quality of one's environment.⁵⁹ The environment may be defined as the social and economic characteristics of an individual.⁶⁰ Alexander and Korenbrot⁶¹ suggested that the challenges of overcoming high-risk socioeconomic related factors associated with low-income populations might be potentially stressful for the at-risk residents of these communities. In support of this argument, Williams⁶² argued that socioeconomic status (SES) accounts for much of the racial differences in health and that the rate of poverty is three times higher for Blacks than for Whites.

            Collins and David⁵¹ noted that extreme poverty[#3a], which is more common among African Americans, may produce such a powerful negative force that isolated changes in the classical risk factors do not dramatically reduce the high percent of low birthweight infants. Also, this negative force may not be fully captured or described by the usual measures of socioeconomic status. This suggestion may indicate that African American women may have different risk profiles, such as perceived exposure to racial discrimination, more stress and less wealth which, in turn, may have an impact on their reproductive health[#9].  

           As a result of the persistence of racial disparities in health outcomes, it has been argued that research efforts must begin to measure racism as a stressor^{7, 48}  and, therefore, as a potential condition to explain racial disparities in APO. Therefore, stress measures that do not include racism[#3a] cannot adequately measure stress[#7] among African American women.

            Positive exogenous factors exist if they basically fulfill certain criteria: a) are initiated and reside external to women and b) they serve as resources to moderate against the effects of external stressors, c) reduce perceived threats, and d) ultimately strengthen, rather than weaken, African America women’s SRCs. Because they are exogenous to women, and in some cases are more measurable and manageable, these positive exogenous factors (versus positive endogenous factors -#5b) are emphasized in this paper. As mentioned before, one of the most salient and important of these positive exogenous moderating factors is perceived social support.

            In a cross-sectional investigation of a sample of 72 pregnant women, ⁶³ it was reported that high levels of maternal psychological stress and low levels of social support were significantly associated with depressed lymphocyte activity (thus addressing stress and immunity in human pregnancy). Additionally, stressful events[#5a], their related stressors[#4a] and lack of social support[#5a] during pregnancy have been associated,  in some studies, with increased risk of preterm delivery[#9].⁶⁴  Furthermore, intimate social support is reported to be associated with improved pregnancy outcomes.⁶⁵  

             Endogenous Factors, Internal Stressors and the SRC.  Although these negative (i.e., adverse) and positive (i.e., moderating) factors are basically internal because of African American women’s skills, personality, dispositions and/or developmental experiences, based on the dynamic interplay of the important segments of the SPPM, as seen in Figure 1, they are likely to influence, or are affected by, exogenous factors[#3a and #5a] and external stressors[#4a]. It is also evident by examining the SPPM that the endogenous factors are also related to a possible variety of internal stressors[#4b]. However, again because of their relative importance and greater visibility, internal stressors[#4b] are de-emphasized versus external stressors[#4a] in this paper.

            The SRC plays a very important mediating role in African American women experiencing internal eliciting stressors[#4b - e.g., infection, trauma]. Depending on the individual make-up and constitution of women, these stressors can result from negative endogamous factors, for example, poor physical health, inadequate nutrition, inadequate sleep[ #3a]. Again, focusing on the dynamic nature of the SPPM and how stress is defined in the model, negative endogenous factors are only risk factors that can contribute to internal stressors, depending on the “disposition” of the women involved.  Additionally, and as seen in Figure 1 (note the bi-directional arrows), based on the perceived experiences women have with exogenous factors[#3a and #5a] and external stressors[#4a], these factors can indirectly affect their internal stressors[#4b] through the functioning of their SRCs, and vice versa. Also, endogenous factors can directly impact their internal stressors, or there may be an indirect pathway through their SRCs, again as illustrated by the arrows shown in the SPPM.

            It has been stated in the past, ²⁸ that from an early developmental level, various stresses[#7] in Blacks begin their insidious influence even in utero [i.e., negative endogenous condition -#3b] in mothers who must cope with the vicissitudes of poverty[#3a] and related potential stressors, both external[#4a](e.g., literally surviving on a daily basis in a crime-infested housing project, inadequate prenatal care, all of which are negative exogenous factors[#3a] that can, depending on the individual[#2] make-up of women lead to related external stressors[#4a]). In a related manner, a host of possible negative endogenous factors[#3a] (e.g., poor/inadequate nutrition, inadequate sleep, poor health) can lead to internal stressors[#4b] as well. As seen from the SPPM in Figure 1, it is evident that such stressors, and subsequent stress, have the very real potential of negatively contributing to the strength of African women’s SRCs and, eventually, to the their APO experiences[#9] alluded to so far in the paper.

            The stress-related scenarios mentioned above are more realistic, especially for African American women who are at risk, example, pregnant and susceptible to initial stressors related to the traditional negative exogenous factors of racism and poverty. One of the main reasons for placing greater emphasis on the negative exogenous factors[#3a] and external stressors[#4a], versus the internal stressors[#4b] (and later to be discussed negative endogenous factors), is because the exogenous factors are more identifiable. Also, because of the dynamic and interactive nature of the SPPM, the exogenous factors (both negative and positive) can have a dominant influence (i.e., directly or indirectly) on women’s SRCs, as well as their endogenous factors (see arrows in Figure 1). However, because these negative exogenous factors are more difficult to control and, therefore, less likely to modify, it is argued in the latter section of the paper that intervention efforts will be more successful if directed at the more controllable endogamous (both positive and negative) factors. In a related manner, it will also be discussed that intervention efforts to reduce stress are more likely to succeed if directed at positive exogenous factors (e.g., social support) as well.

            Factors that are potential buffers, or moderators, in the stress-APO relationship are positive endogamous factors[#5b], such as having strong personality characteristics like a “hardy personality.”⁶⁶ These factors are also likely to reduce the effects of stressors, both external[#4a] and to a lesser extent internal stressors[#4b] by moderating their effects. Again, because of the dynamic nature of the SPPM, as seen in Figure 1, the moderating effect may be either in an indirect manner, where these endogamous positive factors[#5b] can increase the personal resiliency of women’s SRCs, thereby reducing the perceived threat of external stressors[#4a]. Alternatively, they can act directly through a pathway to internal stressors, thereby reducing the latter’s potential negative effect. Contributing factors to personal resiliency include self-esteem, optimism, and mastery beliefs of being in control of life’s activities.³

           Various other positive endogamous factors can be mentioned that further underscore the dynamics of the SPPM, especially as it allows for the interaction between the African American women[#2] and their environment[#1]. Also, the transactional view of stress is more vividly seen when there are reports suggesting an association between  (negative – e.g., low socioeconomic class) exogenous and (negative – e.g., low self-efficacy) endogamous factors.  One particular psychosocial factor that differentiates between class groups is self-efficacy, i.e., the sense of control over one’s environment and fate. Accordingly, Lachman and Weaver⁶⁷ examined two aspects of control – mastery and perceived constraint. It was seen that lower-class individuals had a more limited sense of mastery and higher perceived constraints. Mastery represents the empowering side of control in which the individual has a sense that they are capable of achieving anything they want. Perceived constraints are disempowering in that the feeling of control over one’s future is limited.

           According to Henry, ⁶⁸ empowered individuals are more likely to take proactive steps in terms of personal health, while disempowered individuals are more likely to take a fatalistic approach.  It was found that high-class individuals held a greater sense of possibilities and that this provided an empowering perception.⁶⁸ Also, this was associated with the individual being more likely to embrace change (e.g., in the form of exogenous and/or external stressors) and to see change as an opportunity for growth.  Conversely, lower-class individuals were found to be more likely to exhibit preferences for stability in their lives. Another manifestation of weaker self-confidence, which is very relevant to the stress-APO relationship for African American women implied in the SPPM, is the preference amongst lower-class groups to avoid stressful, challenging tasks in their lives.⁶⁹ Such activities run counter to the assumption is that, in some cases, stressful circumstances must and should be addressed, rather than avoided.

            Other more physiologic factors can exist that serve as possible examples of negative endogamous factors. A very important factor in elucidating the behavioral and/or biological influences mediating the effects of prenatal stress on gestational outcomes is the role of the corticotropin-releasing hormone, or CRH. Basically, the CRH, as a hypothalamic neuropeptide, plays a central role in regulating the activity of the HPA axis and in the physiological response to stress.³⁹ Recent reports suggest that the effects of psychosocial stressors[#4a] may be mediated by cortisol-induced positive feedback increases in placenta secretion of CRH.^69,70 Additionally, overwhelming evidence indicates that women in preterm labor have significantly elevated levels of CRH compared with gestational age-matched control women, and that these elevations of CRH precede the onset of preterm labor, in some cases by several weeks.^69,11  

            It has been reported⁷¹ that neuroendocrine stress responses, including epinephrine, norepinephrine and cortisol, provoke CRH release from placental tissue in vitro. In a related manner it is said “…that maternal psychological stress may precipitate surges in neuroendocrine stress responses that stimulate placental CRH production, priming the placental-fetal feed-forward loop to hasten delivery from a stressed environment” (Rich-Edwards, ¹⁰ p. 126) Therefore, given the mediating role of CRH, it qualifies as a dynamic example of a negative endogenous factor in the SPPM that could impact the stress-APOs of African American women. It is important to note that because the relationship between endogenous factors[e.g., 3b] and internal stressors[#4b] is usually at the subliminal level and, therefore, beneath women’s perceptual/appraisal mechanisms, affecting relationships (e.g., CRH and internal stressors) are possible beyond any conscious awareness. Again, it is for these reasons why it is more difficult to intervene, especially when the relationships involve endogenous factors and internal stressors.

            It has been reported that chronic stressors[e.g., #4a] associated with low socioeconomic status[#3a] may lead to adverse intrapsychic processes[#3b], which in turn may have an impact on perceived stress.³ The erosion of personal resilience, which is a very important positive endogenous factor[#5b] may be one such condition contributing to these potential, adverse intrapsychicic processes, or endogenous negative factors[#3b]. Essentially, personal resilience [#5b] refers to an individual’s (i.e., African American woman’s) level of optimism, self-esteem and feelings of personal control.⁶⁶ This cluster of personality traits has been reported to be associated with preterm birth (APO) and appears to be mediated by perceived stress.⁷²

            The dynamic interplay between components of the SPPM, especially those components at the stress onset phase of the stress process that contribute to the “strength” of African American women’s SRCs, is best understood in the following quotation:

  “Living in a chronically stressful environment appears to erode personal resilience, which in turn may heighten perceived stress, anxiety, a sense of helplessness, a lack of optimism, and depression, thereby increasing the risk of preterm birth via the release of CRH, changes in sexual practices that lead to genital tract infection/inflammation, or greater use of cigarettes, cocaine, or other drugs of abuse.” (Paarlberg et al., ⁷³ p.572)

 

Reflecting on the above quotation in the context of the SPPM, chronically stressful environment refers to negative exogenous factors[#3a]; personal resiliency can refer both to positive endogenous factors[#5b] and the SRC[#6]. Additionally, anxiety, helplessness, lack of optimism and depression, changes in sexual practices leading to genital tract infection/inflammation; greater use of cigarettes, cocaine or other drugs of abuse, can all refer to endogenous negative factors[#3b].

            Given the importance of the SRC, there are several adverse health behaviors that women can exhibit that would reduce its resiliency. Having a weaker SRC, which could imply low levels of resources (e.g., low self-concept, negative attitude, poor physical health), stress can lead to producing APOs indirectly through the effects of adverse behaviors, such as excess drinking, smoking, and drug use during pregnancy.⁷⁴ As mentioned before, because these behaviors are personal and reflect the conscious actions of women, based on the SPPM they would be classified under negative endogenous factors[#3b]. African American women under stress are more likely to engage in adverse health behaviors, which may have physiological effects on their fetuses. However, many of these negative behaviors, such as smoking, use of alcohol, and other illicit drugs are some of the substances people use to cope with stress.³⁴ Additional unacceptable behaviors that can affect women’s health include dietary actions, e.g., poor nutrition, and eating habits.³¹ Naturally, all of these stress-related conditions are likely to be simultaneously occurring with other risk factors (e.g., lack of utilization of adequate prenatal care), all of which, while associated with APOs, are not directly addressed in this paper.

  Stress Reaction                                                                                                                                                                                                 This second phase[#8] may be experienced, depending on the functional state of African American women’s SRCs[#6], which in turn contributes to their stress levels[#7].  When activated, especially for a protracted period of time, this stage involves a complex series of measurable neuroendocrinologic reactions and changes.  As seen in Figure 1, the host of possible internal stress reactions can be manifested through a variety of changes involving: hormones, organs, and internal body systems.  Some of the typical and measurable stress hormones that are produced are corticosteroids and catecholamines. Corticosteroids are produced by the adrenal cortex and catecholamines are produced by the adrenal medulla.  The adrenal hormones are relatively accurate physiologic barometers of a person’s level of stress.⁴⁰                

            Physiologic responses to (psychosocial) stress have been well documented.^{75, 40} For purposes of this paper, physiologic responses are the very important pathways linking stress and APOs.  While these responses are varied and complex at times, they include, among others, hormonal changes (e.g. progesterone, estrogen, and oxytocin), calcium ions, adrenergic agents and receptors, catecholamines, and blood flow from the uterus to the placenta.⁴⁰ All of these internal changes, at least for acute stress, are protective, functional and adaptive for the body.

            Physiological, behavioral and various molecular mechanisms facilitate the body adapting to stress. Acute stress increases immune function and also enhances the formation of potentially dangerous events. However, failure to shut off the stress response when it is no longer needed results in the suppression of immune function and remodeling of brain cells in the hippocampus. According to McEwen, ^38,76 such an occurrence is captured in the concepts of allostasis and allostatic load. The concept of “allostasis” (active responding of biological mediators that maintain homeostasis) leads to the concept of “allostatic load” (the wear and tear of the body due to overuse of allostasis by repeated stress regulation of the mediators – failure to shut them off when no longer needed). 

            It has been theorized that frequently stressful experiences, whether they are concurrent, feared and/or remembered, increase allostatic load. Therefore, women experiencing negative exogenous factors (e.g., racism, violence), which can lead to external stressors[#4a],  creates an allostatic load that imprints itself upon their HPA axis prior to conception. It is further reasoned, that this alters the endocrine milieu in which the placenta is established, thereby potentially affecting the hormonal interaction between fetus, placenta and mother.¹⁰ Based on the SPPM seen in Figure 1, chronic stress levels[#7], without any ameliorative mediation from the SRC, is likely to contribute to allostatic load[#8], which in turn can lead to a variety of stress-health outcomes[#9] (e.g., APOs for African American women).

            Many systems of the body show allostasis, for example, the autonomic nervous system and hypothalamo-pituitary-adrenal (HPA) axis and they help to re-establish or maintain homeostasis through adaptation. The brain also shows allostasis. This involves activation of nerve cell activity and the release of neurotransmitters.⁷⁶ It is generally accepted that the HPA is a major hormonal pathway mediating the stress response and that subtle changes in any of the axis components can have long-term effects on behavior and development. According to Peter,⁷⁷ when homeostatic mechanisms fail to correct the effects of a disturbance, an alarm reaction begins general activation of the sympathoadrenomedullary system to release catecholamines and recruit additional neurohormonal systems, mainly the HPA axis.

McCubbin et al⁷⁵ reported that large prenatal blood pressure, or neuroendocrine responses to psychologic stress, may impair fetal development, thus promoting low birthweight, shortened gestation, and a reduced fetal weight gain rate. In a related manner, these findings indicate that large blood pressure responses during pregnancy could be a useful prognostic indicator of potential problems with fetal development and birth outcome. Importantly, these findings indicate a link between prenatal maternal stress reactivity and fetal development and birth outcome.⁷⁵

Several other studies^{75, 40}  have suggested that stress-related responses of the neuroendocrine axis and the autonomic nervous system during pregnancy may contribute to APOs.  More specifically, elevated levels of hypothalamic, pituitary, and placental hormones have been implicated in the initiation of preterm labor.⁷⁸ Other studies (e.g., Shepherd et al⁷⁹⁾ have indicated that vasoconstriction and hypoxia, in response to sympathetic-adrenal-pituitary activation, decrease uteroplacental perfusion, and may, therefore, contribute to fetal growth restriction.  Further, endorphinergic responses have been found to alter pain sensitivity, and may, therefore, influence labor and delivery parameters.⁸⁰