Preterm Birth Causes, Consequences, and Prevention (2007) / Chapter Skim
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SECTION II Causes of Preterm Birth: 3 Behavioral and Psychosocial Contributors to Preterm Birth
SECTION II Causes of Preterm Birth: 3 Behavioral and Psychosocial Contributors to Preterm Birth
Pages 87-123
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From page 89... ...
Rather, they must be studied as the distinct theoretical risk factors that they are. Evidence indicates that some psychosocial factors in the etiology of preterm birth include major life events, chronic and catastrophic stress, maternal anxiety, personal racism, and lack of support.
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From page 90... ...
The section on psychosocial factors includes findings on stress (life events and chronic and catastrophic stress) , emotional responses and affective states (anxiety and depression)
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From page 91... ...
Smoking is strongly related to placental abruption, reduced birth weight, and infant mortality (Cnattingius, 2004) ; but the relationship of cigarette smoking to preterm birth is rather modest and not entirely consistent.
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From page 92... ...
. There is consistent support of an adverse effect for heavier users of alcohol; for example, women who have more than one drink per day, on average, have an increased risk of preterm birth (Albertsen et al., 2003; Kesmodel et al., 2000; Larroque, 1992; Lundsberg et al., 1997; Parazzini et al., 2003)
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From page 93... ...
In the Preterm Prediction Study, a low prepregnancy body mass index (BMI) was strongly associated with an increased risk of preterm birth, with the RRs being greater than 2.5 (Goldenberg et al., 1998)
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From page 94... ...
. What is less certain is the extent to which the association reflects a causal effect of the weight gain on the risk of preterm birth compared with the extent to which the low weight gain and preterm birth are manifestations of some shared etiology.
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From page 95... ...
found an effect of supplementation on birth weight, such that mothers with a lower body mass index (BMI) who received supplementation had babies with greater birth weight than women with low BMI who did not receive supplementation.
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From page 96... ...
. In an observational study conducted in the Faroe Islands, the levels of fatty acids in blood were examined as predictors of gestational age and birth weight (Grandjean et al., 2001)
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From page 97... ...
found no association overall; but RRs for preterm birth on the order of 1.3 were found for women who work more than 42 hours per week, women who stand for more than 6 hours per day, and women with low levels of job satisfaction. However, a study of Thai women found that increased risks of small-for-gestational-age births but not preterm births
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From page 98... ...
Given these and other findings, the continued study of employmentrelated physical activity and psychosocial stress offers an opportunity to study potential modifiable causes of preterm birth, but the consideration of paid employment in the aggregate in relation to preterm birth is unlikely to be helpful in identifying modifiable causes or improving the understanding of the causes of preterm birth more generally. The impact of employment is highly dependent on the socioeconomic conditions in the geographic location of the study, the implications of employment for economic resources and medical care access, and the particular character of the work.
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From page 99... ...
, but more recent studies have continued to report not just an absence of increased risk associated with sexual activity but a notably diminished risk of preterm birth (Sayle et al., 2003)
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From page 100... ...
PSYCHOSOCIAL FACTORS AND PRETERM BIRTH In 1985 the Institute of Medicine (IOM) issued a report on low birth weight that concluded that stress was one promising avenue for future research (IOM, 1985)
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From page 101... ...
Fourth, most researchers now analyze data with attention to separating preterm labor and delivery from infant birth weight rather than studying only one of these outcomes without controlling for the other or lumping together several outcomes into what was sometimes termed "complications." Finally, studies have involved greater control for potential confounders of the stress-preterm birth relationship. Thus, the methodological problems that have plagued past research on stress and preterm delivery (Hoffman and Hatch, 1996; Lobel, 1994)
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From page 102... ...
. Altogether these research developments strengthen the theoretical premises that causal pathways link maternal and fetal environmental stress exposures and maternal emotional states through biological mediators to preterm delivery or low birth weight and, furthermore, to developmental outcomes across the life span.
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From page 103... ...
The IOM committee review of electronic databases yielded more than two dozen newly published reports on stress and its effects on preterm birth or birth weight. Databases containing data on low birth weight are viewed as potentially different, in terms of the mechanisms underlying the causes of
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From page 104... ...
All four investigations on low birth weight that measured stress also found significant associations.2 In sum, the overall pattern of findings since they were last reviewed suggests that more rigorous approaches are yielding more definitive results regarding the effects of stress on preterm delivery and gestational age, although the exact nature and strength of these effects are not yet clear. This led the committee to turn to examining the specific forms of stress involved, especially in more definitive studies, to obtain clues on the patterns of exposures.
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From page 105... ...
, which had a case-control design, indicated that three or more life events in pregnancy were significantly associated (OR = 3.1) with very low birth weight (all cases were also preterm births; see also Sable and Wilkenson [2000]
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From page 106... ...
The severity of homelessness is a fairly objective measure of chronic stress or strain and not merely a measure of perceived stress or distress; but it may have been confounded nonetheless by inadequate nutrition or general health neglect, as the authors point out, which could account in part for these effects. Nonetheless, these are unique findings on the possible role of chronic stress in preterm birth and low birth weight.
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From page 107... ...
, and also have the potential to test competing theories about acute versus chronic stress exposures and their effects on preterm birth. Emotional Responses and Affective States Anxiety The early research on psychosocial risk factors for preterm delivery and low birth weight focused on maternal anxiety (Gorsuch and Key, 1974)
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From page 108... ...
when the data were adjusted for alcohol and tobacco use. This effect was robust for women with spontaneous preterm labor rather than the medical induction of labor, with medical comorbidities controlled for, and was a stronger effect than that of the life events noted above.
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From page 109... ...
Effects of depression on birth weight or fetal growth is also inconsistent but there are some indications that depression may be a risk factor for fetal growth or low birth weight. Further research is needed to clarify this topic of research.
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From page 110... ...
In addition, most studies appear to view domestic or personal violence as a chronic stressor and have observed that violence affects birth weight but not preterm birth. Mechanisms Linking Stress and Emotions to Preterm Birth Maternal stress can cause the release of increased levels of catecholamines and cortisol, which could prematurely activate placental corticotropin-releasing hormone, thereby precipitating the biological cascade leading to the onset of preterm labor (see Chapter 6)
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From page 111... ...
Limiting the inquiry to the role of anxiety and its biological consequences may prove more fruitful than earlier and cruder approaches to studying general distress and its influence on preterm delivery. Earlier, such studies served the field well in identifying potentially new risk factors, but more scientific precision on the emotional experience of pregnancy and its consequences is greatly needed now to obtain a further understanding of the association of stress with preterm delivery.
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From page 112... ...
Instead, a newer measure of the extent to which women experienced intrusive thoughts or rumination about their two most severe major life events was associated with lower birth weight when gestational age in linear multiple regression analyses was controlled for. Intrusive thought is a recognized symptom of trauma containing both cognitive and emotional components (and is often symptomatic of posttraumatic stress disorder)
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From page 113... ...
Mothers with infants with very low birth weights were twice as likely to report experiences of racial discrimination during pregnancy as women who delivered infants of normal birth weight. After adjustment for socioeconomic condition, levels of social support, cigarette smoking, alcohol intake, and illegal drug use, the adjusted OR was 3.2.
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From page 114... ...
In general, the emerging literature on racism and preterm delivery suggests that racism may be a potent stressor throughout the lifetimes of African American women that contributes to an explanation of the racial and ethnic disparities in the rates of both preterm birth and low birth weight. However, further study is needed to replicate and extend the existing studies.
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From page 115... ...
and to combine distinct outcomes such as preterm birth and low birth weight into one category of complications (Boyce et al., 1985, 1986; Norbeck and Tilden, 1983)
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From page 116... ...
. Thus, the results of observational studies over two decades do not confirm the hypothesized correlation between social support and preterm delivery, but they do provide fairly consistent evidence for a direct association between prenatal maternal social support and infant birth weight.
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From page 117... ...
. The inability of intervention trials to demonstrate the effects of social support on either preterm birth or low birth weight is puzzling to experts and is in some ways a source of controversy.
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From page 118... ...
(1996) , for example, selected pregnant women for intervention partly on the basis of inadequate social support, and then provided social support to those in the treatment group, which produced a reduction in the numbers of infants born with low birth weights.
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From page 119... ...
In sum, the few available studies on self-esteem, mastery, optimism, and perceived control in women expecting infants do not consistently predict preterm birth. It may be that these factors are more related to fetal growth and low birth weight or that these factors are more relevant to particular subgroups of pregnant women, such as populations of women who are socioeconomically disadvantaged.
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From page 120... ...
On the basis of the findings from these preliminary studies, IOM (1995) indicated that the increased risk of low birth weight because of an unintended pregnancy appeared to be related to preterm delivery rather than intrauterine growth restriction.
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From page 121... ...
Thus, although the research available on the association of the intendedness of pregnancy and preterm delivery is limited, that which is available suggests that women with unintended pregnancies are more likely to deliver preterm, and as a consequence, their infants are at higher risk of being of low birth weight. Understanding the pathways from unintended conception to preterm labor and delivery by the use of multilevel approaches would be useful in elucidating the etiology of preterm birth for at least some subgroups of women.
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From page 122... ...
The emerging literature on racism and preterm delivery suggests that racism, a possible stressor throughout the lifetimes of African American women, contributes to the explanation for racial-ethnic disparities in the rates of both preterm birth and low birth weight. The results of more than two decades of observational studies on naturally occurring social support do not confirm a hypothesized link between maternal social support and preterm delivery; however, the studies do provide fairly consistent evidence for a direct association between social support and infant birth weight.
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From page 123... ...
• A more integrative approach to understanding individual-level factors in prematurity is needed. This will require the use of both a longitudinal integration linking a woman's life history to her vulnerability to preterm delivery and a contextual integration linking a woman's individual biology, psychosocial processes, and behaviors to the multilevel, multiple determinants of preterm birth (Misra et al., 2003)
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