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). Other studies over the years have focused on the role of general distress. Determination of whether either depression or anxiety is a risk factor for preterm delivery has, however, been difficult for many reasons. Among these is the fact that the two emotional states are often comorbid, although they are distinguishable clinically. However, the questionnaire measures used in obstetric research to assess anxiety and depression are not well suited to their differentiation. Thus, many studies have investigated general distress by using the General Health Questionnaire (Hedegaard et al., 1993, 1996; Perkin et al., 1993) or the Hopkins Symptom Checklist (Paarlberg et al., 1996). General emotional distress may not be as clear-cut a risk factor as the potentially separable effects of either anxiety or depression.

Recent studies suggest that anxiety may be a potentially important risk factor for preterm delivery. The IOM committee found 12 studies in total that tested the emotional components of stress as predictors of preterm birth. Eleven studies had prospective designs; of these, nine tested the association of anxiety with gestational age or preterm birth. Two found no significant effects for state anxiety (Lobel et al., 2000; Peacock et al., 1995); one study found that general anxiety was associated with intrauterine growth restriction (but not with preterm birth), but only in white patients (Goldenberg et al., 1996a); and one study found that general anxiety was associated with preterm labor in women who had a history of preterm labor (Dayan et al., 2002).

Four more investigations were very consistent in finding that anxiety concerning the pregnancy itself was associated with gestational age or preterm birth. For example, Rini et al. (1999) reported that prenatal anxiety (a combination of state anxiety and pregnancy anxiety), assessed by interviews with women at 28 to 30 weeks of gestation, was associated with gestational age in 230 Hispanic and white women when other sociodemographic, medical, and behavioral risk factors were controlled for (estimated OR for preterm birth = 1.59). In a larger prospective study, Dole et al. (2003) replicated these findings; pregnancy-related anxiety at 24 to 29 weeks of gestation predicted preterm birth in a sample of 1,962 women (RR = 2.1) when the data were adjusted for alcohol and tobacco use. This effect was robust for women with spontaneous pre-term 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.

Mancuso and colleagues (2004) also replicated these findings with a sample of 282 women assessed twice during their pregnancies (Behavior in Pregnancy Study [BIPS]). Pregnancy-specific anxiety at 28 to 30 weeks of gestation (but not at 18 to 24 weeks of gestation) significantly predicted gestational age. In addition, Mancuso et al. (2004) reported that cortico-tropin-releasing hormone levels mediated the effects of pregnancy anxiety on gestational age (see also Hobel et al. [1999]). Further multivariate analyses of this sample reported by Roesch et al. (2004) sought to determine which of three stress indicators (state anxiety, pregnancy anxiety, and perceived stress) was most predictive of gestational age in the women participating in BIPS.

They determined that pregnancy anxiety was the only significant predictor of gestational age when all three indicators were included in the model. Other studies of perceived stress that used the standard scale in BIPS (PSS) have had mixed results for this component (Lobel et al., 1992, 2000; Sable and Wilkenson, 2000; Zambrana et al., 1999).

When considered together, these results are quite consistent in pointing to anxiety as a possible risk factor. Although results of studies on general anxiety are somewhat mixed, studies on anxiety regarding the pregnancy itself are more consistent in predicting gestational age at birth or preterm birth. The most vulnerable times in pregnancy for emotions to have effects on physiology are not yet clear, but some research points to weeks 24 and 30 of gestation (Rini et al., 1999). The possibility of the confounding of anxiety over existing medical risk conditions was considered and controlled to some extent in some of these investigations, suggesting that anxiety over existing medical risk conditions does not fully account for the effects. That is, high-risk pregnancies may elicit anxiety, but this does not appear to account for these findings; in short, anxiety resulting from knowledge of one's medical risk conditions is not implicated as a risk factor per se. Followup research on anxiety and its timing and mechanisms of effects on pre-term labor and delivery is recommended.

Depression

Ten studies on depression and preterm birth or low birth weight were reviewed. All studies had prospective designs. Of these, four reported nonsignificant effects (Dole et al., 2003; Goldenberg et al., 1996a; Lobel et al., 2000; Misra et al., 2001; Peacock et al., 1995). Three found that prenatal depression in the mother affected fetal growth (Hoffman and Hatch, 2000) and birth weight percentiles (Paarlberg et al., 1999). Two studies reported associations of depression and preterm delivery (Dayan et al., 2002; Jesse et al., 2003; Orr et al., 2002). One found significant effects only among women who were underweight (BMI < 19) before the pregnancy (Dayan et al., 2002). Another was a large study of African American women only (Orr et al., 2002) reporting adjusted OR of 1.96 for spontaneous preterm birth among women in the top 10 percent on a standard depression measure.

Overall, recent prospective studies on depression do not suggest a strong pattern for depression as a general risk for preterm delivery consistent with the results of earlier studies (Copper et al., 1996; Perkin et al., 1993) with some exceptions. For example, depression in African American women seems to be an area worthy of further investigation. 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. Pathways from emotion to low birth weight through health behaviors such as diet and nutrition, substance use, sleep, and inactivity are important to elucidate. Women who are depressed or anxious during pregnancy are unlikely to take care of themselves as adequately as those who are not. Anxiety may be linked to different behavioral implications than depression. Studies of these states also must address their frequent confounding as well. This is a potential topic for follow-up research.

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