Psychosocial stress has been identified as a potential risk factor for preterm birth. However, an association has not been found consistently, and a consensus on the extent to which stress and preterm birth are linked is still lacking. A literature search was performed with a combination of keywords and MeSH terms to detect studies of psychosocial stress and preterm birth. Studies were included in the review if psychosocial stress was measured with a standardized, validated instrument and if the outcomes included either preterm birth or low birthweight. Within the 138 studies that met inclusion criteria, 85 different instruments were used. Measures that had been designed specifically for pregnancy were used infrequently, although scales were sometimes modified for the pregnant population. The many different measures that have been used may be a factor that accounts for the inconsistent associations that have been observed.
Healthy People 2010 set a goal of reducing preterm births in the United States from the 1998 baseline of 11.6% to 7.6%. However, the number of preterm births has been increasing steadily. In 2006, 12.8% of all births, or approximately one-half of 1 million newborn infants, were delivered at <37 weeks of gestation. There are multiple known risk factors that are associated with preterm birth, although 50% of the women who deliver prematurely have no clearly delineated risk factor. Although socioeconomic status and psychosocial stress both have been associated with preterm birth, the specific biologic mechanisms that links these factors to preterm birth and to disparities in preterm birth remain unclear. Moreover, the associations themselves have not been demonstrated consistently.
Investigators, as far back at the 1940s, who have explored the association of psychosocial stress with perinatal outcomes, have used numerous measures to quantify the presence of stress. Initial studies defined stress in terms of major life events, such as the death of a loved one or a large-scale environmental disaster. However, assessing life events may not ascertain the stress that pregnant women are most exposed to, given the low number of major acute life events that typically occur in pregnant women and the additional contribution that may exist from chronic stress. Indeed, in some studies, stressors more reflective of life-course stress have been shown to have a greater association with pregnancy outcomes. Furthermore, a woman’s experience in dealing with the aftermath of life stressors may be more relevant in the determination of her health status than any 1 particular stressful event. As a result, investigators have diversified their definition and measurement of psychosocial stress to include perceived stress, anxiety, depression, racism, lack of social support, coping mechanisms, job strain, acculturation stress, and domestic violence. Newer concepts include those that apply directly to pregnancy states, such as pregnancy-related anxiety and pregnancy intendedness.
As measures of stress have evolved, so have definitions of relevant pregnancy outcomes. Two literature reviews that were published in the 1990s noted that most of the studies that have been concerned with stress and pregnancy outcomes have consolidated a diverse spectrum of pregnancy and intrapartum events into 1 outcome variable: “complications in pregnancy.” Additionally, early efforts at estimating maturity used low birthweight or a birthweight of <2500 g as a proxy measure for preterm birth, given that gestational age often was measured inaccurately, particularly in the pre-ultrasound era. Although low birthweight is associated with significant morbidity and mortality rates, it has been identified as an imprecise gauge of prematurity because it encompasses both growth-restricted and premature infants.
Despite many years of research, a clear consensus on the contribution of psychosocial stress to preterm birth is still lacking. One potential cause for the inconsistent association that has been observed between stress and preterm birth is the extensive variability in the measures that are used for both psychosocial stress and pregnancy outcomes. The purpose of this study was to characterize the spectrum of psychosocial stress scales that are used in the existing preterm birth literature.
Materials and methods
Search strategy
A literature search was performed with MEDLINE, PsycINFO, EMBASE, and HAPI databases with a combination of keywords and MeSH terms that included psychosocial stress , maternal stress , chronic stress , life events , self-reported stress , anxiety , depression , domestic violence , social support , preterm birth , premature birth , and low birthweight . The literature search was performed by 1 researcher; however, if any questions arose regarding findings in individual articles, a second researcher reviewed the article, and the 2 researchers reached an agreement. Only articles published after 1970 were included in this assessment, given that studies conducted before that time are generally considered to be less rigorous in design. The most recent article included in this analysis is from January 2010. The references of retrieved articles were reviewed for additional publications that were not captured in the original search; these articles were then retrieved as well. This process was continued iteratively until no additional publications that met criteria for inclusion were found.
Study selection criteria
Abstracts of articles that were obtained from the search were assessed for suitability based on 2 criteria: (1) the study measured the exposure variable of psychosocial stress with a scaled instrument, and (2) the outcome variable included preterm birth or low birthweight.
Studies were excluded if authors did not distinguish preterm birth or low birthweight from a larger category of adverse pregnancy outcomes when conducting their analyses. Studies that evaluated the effect of psychosocial interventions on preterm birth or low birthweight delivery also did not meet criteria for inclusion. Additionally, if multiple articles were published from the same study, only 1 article was included to avoid over-counting the same instrument. Finally, only articles that were published in English were reviewed.
Scale selection criteria
Many authors developed their own questions to assess psychosocial stress. However, only scales that had been validated previously and were referenced explicitly were included. Finally, if the scale validation studies were not written in English or were unavailable through a literature or internet search, the instrument could not be assessed in terms of its psychometric properties and therefore was excluded from this study.
Data extraction
The data that were extracted from each article consisted of the study design; the names of the psychosocial instruments that were used; the number of times, the gestational ages when, and the method (self or via interviewer) by which the instruments were administered; the outcomes that were assessed; the presence of attempts to control for confounding, and the magnitude of association between psychosocial stress and a preterm or low birthweight delivery.
Analysis
A descriptive analysis of the included studies was conducted. To organize the data, we categorized the instruments into 4 domains of stress (ie, external stressors, perceived stress, enhancers of stress, and buffers of stress) based on a construct that had been published in the literature. Examples of external stressors are objective life events or daily hassles, perceived stress that reflects subjective stress levels and perceptions of racial or gender discrimination, enhancers of stress encompass anxiety or depression, and buffers of stress that cover a variety of social support systems and coping mechanisms. Within each domain of stress, subcategories of instruments that measure the same aspect of psychosocial stress were formed. Instruments that did not fit into any of the 4 domains were placed into an “other” category. The psychometric properties of each instrument and its frequency of use in the literature were also reported.
This study was exempt from institutional review board approval.
Results
Description of studies
The literature search yielded 200 articles for abstract review. Of those, 136 articles met inclusion criteria for analysis. Many studies were excluded because of the lack of a validated instrument to measure the exposure (n = 38), with the next most common reason being the use of a composite outcome of “complications of pregnancy” (n = 22). Four articles were judged to have duplicative information. Of note, both of the articles by Omer et al each included 2 separate studies that accounted for a total of 138 studies from 136 articles.
Table 1 outlines characteristics of the included studies. Most were prospective cohort studies, and the studies were split between those in which participants self-administered the instrument and those in which the participants were interviewed. Most of the questionnaires were administered 1 time. The studies were split evenly in terms of outcome measured. Nearly 90% of the analyses controlled for confounding factors.
| Variable | Percentage |
|---|---|
| Study design | |
| Cohort | |
| Prospective cohort | 73.9 |
| Retrospective cohort | 2.2 |
| Case control | 15.9 |
| Cross sectional | 8.0 |
| Method of data collection | |
| Interview | 52.2 |
| Self-report | 38.4 |
| Interview and self-report | 7.2 |
| Unknown | 2.2 |
| No. of times of survey administration | |
| 1 | |
| First trimester | 1.4 |
| Second trimester | 18.8 |
| Third trimester | 8.0 |
| Labor and delivery | 2.2 |
| Postpartum period | 23.9 |
| Unknown | 15.9 |
| 2 | 14.5 |
| 3 | 8.7 |
| 4 | 5.8 |
| 6 | 0.7 |
| Main outcome measured | |
| Preterm birth or gestational age | 29.7 |
| Low birthweight or birthweight | 30.4 |
| Both gestational age and birthweight | 39.9 |
| Controlled for potential confounding variables | |
| Yes | 86.2 |
| No | 13.8 |
Description of psychosocial stress scales
A total of 85 instruments were used in the reviewed studies. The breakdown by domain is as follows: external stressors (n = 18), perceived stress (n = 13), enhancers of stress (n = 22), buffers of stress (n = 22), and other (n = 10). For each psychosocial stress instrument, a description of the scale, its psychometric properties, and the number of studies in which it appears are presented in Tables 2-6 .
| Name and description of scale | Psychometric properties | Studies, n | Associated with decrease in gestational age or preterm birth | Not associated with decrease in gestational age or preterm birth | Associated with decrease in birthweight or low birthweight | Not associated with decrease in birthweight or low birthweight |
|---|---|---|---|---|---|---|
| Daily chronic stressors | ||||||
|
| 5 | Modified version a , | Health subscale ( P = .03) ; inner concerns subscale ( P = .03) ; financial responsibility subscale ( P = .02) | References a , | |
| Everyday Problems Checklist (EPCL; Vingerhoets, 1994 ): 114 items about daily stressors that include family life, living and working conditions, physical appearance, transactions, and business in the past 2 months; scores include (1) frequency, (2) mean severity score, (3) product of 2 scores (total score) |
| 2 | 109-item version ( P < .01) | Reference | ||
| Major life events | ||||||
| Life Experiences Survey (LES; Sarason et al, 1978 ): 57-item checklist of life events in past year; events rated as positive or negative and perceived impact of event; score summed as positive change, negative change, and total change |
| 6 | White women with high stress, RR, 1.8 (95% CI, 1.2–2.8) ; white women with few positive life events ( P < .01) ; modified 39-item, RR, 1.6 (95% CI, 1.1–2.3) | Modified 39-item ; references | Reference | |
| Social Readjustment Rating Scale (SRRS; Holmes and Rahe, 1967 ): the SRRS is an adaptation of the Schedule of Recent Events with associated magnitude weightings for intensity and length of time necessary to accommodate the life event for each of 43 life events; scores include item frequency and life-change score (sum of item frequency times item weighting). | In adult convenience sample: high correlations for magnitude of event weightings among each subgroup (0.820–0.975), and coefficient of concordance for all individuals (0.477; P < .0005); test-retest reliability over 2 wk to 5 mo (0.78–0.83); validity demonstrated by ability to predict health change with higher life-change score | 7 | 27-item version: white women with high number of life events in first and second trimesters ( P = .04) ; for events in previous 2.5 y through pregnancy ( P < .01) | For events in previous 6 mo ; for events in previous 2 y through pregnancy | 11-item version: white women with high cumulative stress ( P < .01) ; modified version ( P < .05) ; money-related stressors ( P < .001) | For events in previous 6 mo |
| Interview for Recent Life Events (IRLE; Paykel, 1969 ): modified from Holmes and Rahe’s SRRS, IRLE has 64 events organized into 10 categories of work, education, finance, health, bereavement, migration, cohabitation, legal, family and social relationships and marriage; for each event, respondent reports month of occurrence, independence of event from psychiatric illness, and objective negative impact. |
| 3 | References | References | ||
| Life Events Inventory (LEI; Cochrane, 1973 ): modified from Holmes and Rahe’s SRRS, 35-item check list with additional 16 items for those who were ever married and 4 items for those who were never married. |
| 1 | Reference | Reference | ||
| Modified Life Events Inventory (Newton, 1979 ): modified from Cochrane’s LEI, 59-item checklist of events validated in pregnant women. | In pregnant women: 2 groups of pregnant women at different hospitals scored each item according to the amount of “worry, disruption, or upheaval” on scale of 1-100; scores >60 were considered major life events; women in both groups produced an identical list of 28 major life events. | 6 | More major life events ( P < .02) ; more objective life events ( P = .001) | Case control study ; prospective cohort study ; 2 items regarding physical violence ; 27-item version | More objective life events ( P = .004) | 2 items regarding physical violence |
| Life Events Checklist (Johnson, 1980 ): 46-item checklist of life events related to child and adolescent life stress within past year; positive and negative life-change scores derived from sum of positive or negative impact of event ratings. |
| 2 | References | |||
| Psychiatric Epidemiology Research Interview Life Events Scale (Dohrenwend, 1978 ): 102 events related to school, work, love and marriage, children, family, residence, crime and legal matters, finances, social activities, and health. | In adults living in New York City: the severity of 101 events was rated in relation to marriage; the severity of 60 events were “consensual” or agreed on, 22 were “status dependent,” and 19 were “noisy” or indeterminate. | 3 | Stressful life events during pregnancy ( P = .001) | References | ||
| Life Events and Difficulties Schedule (Brown, 1978 ): semistructured interview about the severity of events and difficulties in the areas of health, role changes, leisure, employment, housing, money, crises, forecasts, marriage, interactions with parents, and resources in the last 12 months. | In female psychiatric and healthy women: interrater reliability (>0.90); validity: patients and their relatives had 81% agreement about the occurrence and onset of the same stressful event; patients reported more life events than healthy women; in terms of recall, there was little fall-off of events reported throughout year. | 2 | P < .001 | 21-item version | ||
| Life Events Questionnaire (LEQ; Norbeck, 1984 ): 82-item checklist of events designed for female adults of childbearing age; life events pertain to health, work, school, residence, love and marriage, family and close friends, parenting, personal and social, financial, and crime and legal matters; scores include negative events, positive events, and total events scores. |
| 2 | References | Reference | ||
| Prenatal Social Environment Inventory Scale (PSEI; Orr, 1992 ): 41-item checklist of chronic life stressors and major stressful events that pregnant women have experienced in the past 12 mo. | In pregnant women: internal consistency (0.80); test-retest reliability over 30 d (0.73); validity: PSEI significantly and positively correlates with the Center for Epidemiologic Studies Depression scale ( P = .001) | 4 | 6-item anxiety subscale, medium anxiety (RR, 1.5; 95% CI, 1.1–2.1) and high anxiety (RR, 2.1; 95% CI,1.5–3.0) ; 6-item anxiety subscale, African American women with high anxiety (RR, 2.0; 95% CI, 1.3–3.2) and white women with high anxiety (RR, 1.6; 95% CI, 1.1–2.3) ; 6-item anxiety subscale, score of 5 of 6 (OR, 1.70; 95% CI, 1.01–2.87) and score of 6 of 6 (OR, 2.73; 95% CI, 1.03–7.27) | African American women with high stressors ( P = .05) | ||
| Family Inventory of Life Events (FILE; McCubbin, 1982 ): 71 items that measure stressful events for the family in previous 12 mo; 17-item subscale for intra-family strain and 54 items for strains in marriage, pregnancy, work, finances, health, legal matters, home transitions, and losses. |
| 1 | Reference | |||
| Trauma History Questionnaire (THQ: Green, 1995 ): 24 items about lifetime history of exposure to traumatic events in the areas of crime, disaster, and unwanted physical/sexual violence. | In psychiatric outpatients with severe mental illness: test-retest reliability over 2 wks (0.76); criterion-related validity demonstrated by significant positive correlations with symptoms of posttraumatic stress. | 1 | Reference | |||
| Violence and abuse | ||||||
| Abuse assessment screen (AAS; Parker, 1991 ): 5 items identify victims of domestic violence and measures the frequency, severity, and sites of injury because of abuse. |
| 19 | Modified version, RR, 1.7 (95% CI, 1.1–2.6) ; teenagers: OR 3.5 (95% CI, 1.1–10.8) ; OR, 2.8 (95% CI, 1.3–5.9; P = .01) ; RR, 2.5 (95% CI, 1.4–4.1) ; OR, 1.6 (95% CI, 1.1–2.3) ; OR, 3.1 (95% CI, 2.0–4.9) | References ; 3-item version |
| References |
| Conflict Tactics Scale (CTS; Straus, 1979 ): 19 items that measure method of dealing with conflict within families; 3 subscales of reasoning, verbal aggression, and violence. |
| 5 | 10-item version ; reference | Modified version, OR, 10.2 (95% CI, 1.4–73.9; P = .015) | 10-item version ; reference ; violence subscale | |
| Index of Spouse Abuse (ISA; Hudson, 1981 ): 30 items that measure severity of physical (ISA-P) and nonphysical abuse (ISA-NP) by partner. | In college/graduate students: internal consistency reliability (ISA-P = 0.90; ISA-NP = 0.91); construct validity: ISA discriminated between clinically abused and nonabused groups better than other clinical scales not related to abuse (ISA-P = 0.73; ISA-NP = 0.80). | 1 | Reference | |||
| HITS scale (Sherin, 1998 ): 4 items ask whether respondent has been physically Hurt, Insulted, Threatened, or Screamed at. |
| 1 | Verbal abuse ( P = .002) |
a In study by Wadhwa et al, the scores from the Daily Hassles Scale, Cohen’s Perceived Stress Scale, and Hopkins Symptom Checklist were combined to create a composite measure of “perceived stress” for analysis.
| Name and description of scale | Psychometric properties | Studies, n | Associated with decrease in gestational age or preterm birth | Not associated with decrease in gestational age or preterm birth | Associated with decrease in birthweight or low birthweight | Not associated with decrease in birthweight or low birthweight |
|---|---|---|---|---|---|---|
| Subjective stressors | ||||||
|
| 18 | 5-item version ( P < .03) a ; 8-item version ( P < .05) ; 12-item version (OR, 2.8; 95% CI, 1.3–5.9; P < .01) ; 4-item version for Aboriginal Canadian women (OR, 7.6; 95% CI, 1.1–50.9) ; P = .04 ; 4-item version (OR, 1.5; 95% CI, 1.1–1.9) ; 10-item version ( P < .0004) ; 8-item version ( P < .05) |
| 5-item version ( P < .01) a |
|
| Impact of Event Scale (IES; Horowitz, 1979 ): 15 items that measure psychologic impact of a variety of traumas in the past 7 days; 2 subscales of intrusion and avoidance. |
| 1 | 5-item version of intrusion subscale | 5-item version of intrusion subscale ( P < .01) | ||
| Subjective Stress Scale (Schar, 1973 ): 4 statements regarding perceived stress with daily activities. |
| 2 | Reference | In women with body mass index <22 kg/m 2 ( P = .009) | Reference | |
| Work strain | ||||||
| Job Content Questionnaire (JCQ; Karasek et al, 1985 ): 49 items that measure job characteristics with subscales of decision latitude, psychologic demands, social support, physical demands, and job insecurity; job strain , defined as high psychologic demands and low decision latitude, leads to psychologic strain. | In multiple international study populations: internal consistency (0.58–0.86); predictive validity: multiple studies show that JCQ scores predict chronic disease states, such as cardiovascular disease, mental strain, and occupation injury. | 11 |
| 12-item version (OR, 1.8; 95% CI, 1.0–3.3) ; high-strain job associated with birthweight difference of 190 g (95% CI, 48–333 g) ; P < .01) | References | |
|
| 4 |
| References | ||
| Effort-Reward Imbalance Questionnaire (ERI-Q; Siegrist et al, 1996 ): 23 items determine chronic stress resulting from imbalance between high effort and low rewards with the use of subscales to measure effort, reward, and over-commitment. |
| 1 | Reference | |||
| Racial discrimination | ||||||
|
| 5 | In African American women (RR, 1.8; 95% CI, 1.1–2.9) ; ≥3 experiences of discrimination (OR, 3.1; 95% CI, 1.3–7.2) | References | ≥3 experiences of discrimination (OR, 2.6; 95% CI, 1.2–5.3) ; P < .01) | Reference |
|
| 1 | Reference | |||
|
| 1 | Discrimination because of age ( P = .04) and physical disability ( P < .001) | |||
| Perceptions of Racism Scale (PRS; Green, 1995 ): 20 items that measure perception of racism in terms of feelings of racism, experience of racist actions, and racist thoughts in African American women. |
| 1 | Reference | Reference | ||
| Other scales | ||||||
| Prenatal Distress Questionnaire (PDQ; Yali and Lobel, 1999 ): 12 items assess the worries and concerns that a woman has about different aspects of pregnancy that include physical and emotional symptoms, relationships, body image, and mothering ability. |
| 3 | P < .008 | References | Reference | |
| Maternal Adjustment and Maternal Attitudes (MAMA; Kumar et al, 1984 ): 60 items with 5 subscales that measure mother’s perceptions of her body, somatic symptoms, marital relationship, attitudes to sex, and attitudes to the pregnancy and the baby in the past month. |
| 1 | Reference | |||
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| 1 | Reference |
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