Development of a theory and definition of postpartum fatigue
Based on Pugh and Milligan’s (1993) classic framework and a review of previous studies related to postpartum fatigue, we developed a theory of postpartum fatigue in Korean women, illustrated in Figure 1. In this study, the definition of fatigue is ‘an overwhelming sustained sense of exhaustion and decreased capacity for physical and mental work’, according to the work of Pugh and Milligan (1993), which is also the definition of the North American Nursing Diagnosis Association (NANDA) (Carpenito-Moyet 2006, p. 155). This definition of fatigue represents an unpleasant sensation in contrast to the satisfied feeling of having done a job well or feeling good after exercise (Carpenito-Moyet 2006, p. 156).
In the theoretical framework of this study, social support and infant temperament are exogenous variables, and postpartum fatigue, postpartum depression, childcare stress, sleep quality, breastfeeding difficulty and Sanhujori satisfaction are endogenous variables.
Relationships among the research variables
When reviewing previous studies, we found a controversy about the relationship between fatigue and depression. Although there is an opinion that postpartum fatigue is a predicting factor for postpartum depression (Beck 2001, 2008, Corwin & Arbour 2007, Runquist 2007), depression is also explained as one of the important psychological factors that cause fatigue in the framework for the study of childbearing fatigue (Pugh & Milligan 1993), the unpleasant symptom theory (Lenz et al. 1997), and many empirical studies related to postpartum fatigue (Milligan 1989, Gardner 1991, Wambach 1998, Rychnovsky 2007). Therefore we set up a path in which postpartum depression directly affects postpartum fatigue.
Sleep quality or problem is an important variable that is most frequently reported in studies on fatigue. Unsatisfactory sleep or segmented sleep can cause fatigue by interfering with the deep-sleep rapid eye movement stage, and has been significantly related to postpartum fatigue in various studies (Hantos 1993, Webster 1994, Wambach 1998, Lee & Zaffke 1999, Hunter et al. 2009, Rychnovsky & Hunter 2009). Therefore we set up a path in which sleep quality directly affects postpartum fatigue.
Feeding difficulties are one of the main concerns for first-time mothers (Wambach 1998, Haku 2007), and previous studies have shown a significant relationship between a feeding problem and postpartum fatigue (Milligan 1989, Hantos 1993, Pugh & Milligan 1995, Wambach 1998, Fisher et al. 2004). Therefore, we set up a path in which unsatisfactory feeding directly affects postpartum fatigue. Also, unsatisfactory feeding may increase a mother’s stress and anxiety (Fisher et al. 2004, Haku 2007) and the chance of waking more frequently during the night, which may lead to segmented or unsatisfactory sleep (Alley & Rogers 1986, Rychnovsky 2007, Hunter et al. 2009). Therefore we set up a path in which unsatisfactory feeding directly affects childcare stress and sleep quality, and indirectly affects postpartum fatigue through these variables.
Reports on the relationship between childcare stress and postpartum fatigue are limited. Although it is explained that the process of acquiring the maternal role causes tension and stress (Mercer & Walker 2006, Fontenot 2007), and stress during transition to motherhood may be related to postpartum fatigue (Milligan 1989, Wambach 1998), the relationship between childcare stress and postpartum fatigue has rarely been supported by empirical data. Considering that various researchers explain childcare stress as a significant predicting factor of postpartum depression rather than postpartum fatigue (Barnet et al. 1996, Beck 2001, Honey et al. 2003, Park et al. 2004, Leung et al. 2005), childcare stress was proposed as indirectly affecting postpartum fatigue through postpartum depression in this study.
Infant temperament is also considered a predicting factor of postpartum fatigue, such that mothers of fussier infants are more likely to experience fatigue (Milligan 1989, Hantos 1993, Wambach 1998). Therefore we set up a path in which difficult infant temperament directly affects postpartum fatigue. Also, fussy infant temperament has an impact on mothers’ childcare stress (Fisher et al. 2004), feeding difficulty (Fisher et al. 2004), inferior quality of sleep (Dennis & Ross 2005) and postpartum depression (Beck 2001, Honey et al. 2003, Fisher et al. 2004, Dennis & Ross 2005). Consequently, the quality of Sanhujori deteriorates because it is difficult to take sufficient rest (Yoo 1993, 1997, 1998). Therefore we set up paths in which infant temperament directly affects childcare stress, postpartum depression, unsatisfactory feeding, sleep quality and Sanhujori satisfaction, and indirectly affects postpartum fatigue through these variables.
Social support is also important in the study of postpartum fatigue. Postpartum fatigue has been shown to increase with an absence or only a small number of helpers (Gardner & Campbell 1991), and social support had been found to reduce postpartum fatigue along with sleep and rest (Webster 1994). Therefore we set up a path in which social support directly affects postpartum fatigue. Also Milligan (1989) reported that social support buffered breastfeeding difficulties at 6 weeks after delivery, and other studies have shown that support from significant others reduces breastfeeding difficulties (Freed & Fraley 1993, Freed et al. 1993, Haku 2007). Furthermore, social support has also been widely recognized as an influencing factor in depression (Barnet et al. 1996, Beck 2001, Honey et al. 2003, Park et al. 2004, Gao et al. 2009) and childcare stress (Hung & Chung 2001, Warren 2004, Hung 2005), and has also been reported to be associated with improved quality and satisfaction of Sanhujori in Korea (Yoo 1993, 1997, 1998). Therefore we set up paths in which social support directly affects unsatisfactory feeding, postpartum depression, childcare stress and Sanhujori satisfaction.
Lastly, Sanhujori, the traditional Korean postpartum care, is influential in affecting sleep quality, psychological and physical recovery, and general health of the parturient woman (Yoo 1993, 1997, 1998, Kim & Yoo 1998, Yoo et al. 1998, Chong & Yoo 1999, Ahn 2005). Therefore we set up paths in which Sanhujori satisfaction directly affects sleep quality, postpartum depression and postpartum fatigue.