Pregnancy affects appraisal of negative life events

Abstract

Objective

It has been demonstrated that physiological responses to stress are diminished late in pregnancy. This study investigates whether emotional responding is diminished as well by measuring affective responses to specific life events during pregnancy.

Methods

A total of 292 pregnant women reported the occurrence of and affective responses to a range of major life events during gestation. Two analyses were conducted (across events and within events) on these responses to determine whether life events occurring in the first trimester were rated as more stressful than those that occurred in the third trimester.

Results

Both within-event and across-events analyses of responses to life events demonstrated that events occurring early in pregnancy were perceived as more stressful than events occurring later in pregnancy.

Conclusion

Responses to stress and affective state are progressively altered in pregnant women, suggesting that timing of stress exposure during gestation may be critical in determining its impact.

Introduction

Prenatal stress is associated with a range of adverse outcomes in humans [1], [2], [3], [4], [5], [6], [7], with the most compelling evidence supporting the link between stress and the adverse birth outcomes of low birth weight and preterm birth [8], [9], [10], [11]. Preterm delivery (gestational length <37 weeks) and low birth weight (birth weight ≤2500 g) account for a sizeable percentage of live births in the US and are the most prevalent causes of perinatal, neonatal and infant morbidity and mortality in nonanomalous infants [12]. Despite advances in prenatal medical care, the incidence of premature births has not decreased in the US in recent years [13].

The relation between stress and the adverse outcomes of low birth weight and shortened gestational length exists both when stress is measured as the occurrence of negative events [14], [15], [16] and when measured in the form of stress appraisals (such as reports of perceived stress or negative emotion [9], [17], [18]). However, these studies reveal mixed results, some indicating that stress is a predictor of adverse birth outcome, and others finding no association (for reviews, see [10], [19], [20]). These discrepancies may exist because the relation is weak and inconsistent or because the construct of stress is not being adequately measured. Animal research suggests that it may be premature to conclude the former, because large causal effects of prenatal stress on adverse outcomes have been repeatedly observed (for a review, see Ref. [21]).

In order to characterize more precisely the effects of stress on birth outcome, it is critical to ascertain the variables that affect the amount of stress a woman experiences during pregnancy and that affect the impact of stress on birth outcomes. An understanding of these variables may help explain inconsistencies among studies examining the effects of stress on birth outcomes. A number of such factors have been identified, and these include race/ethnicity [22], [23], acculturation [24] marital status [25], body mass index [26], obstetric risk [27], smoking [28], social support [29] socioeconomic status [30], [31] and personality traits [18], [32].

One rarely studied factor that may affect stress responses and the impact of stress during pregnancy is the timing of stress during gestation. It is well established that the timing of stress is important because of critical periods of development in the fetus [33], [34]. However, timing of stress could also be important because maternal responses to stressful events may differ depending upon when the events occur during gestation. Physiological responses to stressor challenge decrease as pregnancy advances. Responding of both the hypothalamic–pituitary–adrenal and sympathetic–adrenal–medullary systems are progressively dampened during pregnancy [35], [36], [37], [38], [39]. Such changes in the physiological stress response may be associated with attenuated psychological responding. For example, Glynn et al. [14] found that appraisals of the emotional impact of a major earthquake were related to the time of gestation at which the earthquake occurred. Those who experienced the earthquake early in pregnancy rated it as more stressful than those who experienced it late in pregnancy.

The purpose of the present study was to characterize stress appraisals at different stages of pregnancy by examining affective responses to a diverse set of stressful life events. If dampened physiological reactivity found in other studies is associated with diminished affective responding, then we should find that life events experienced early in pregnancy are appraised as more stressful than those experienced later.