We developed the SLIM scale to identify mothers who may need social support at one month postpartum. The scale was feasible for use in a hospital setting in Japan at the first trimester. We identified two risk factors, “Trouble with others” and “Having someone who can consult with in big trouble”, but on the contrary, maternal age, marital status, education level, number of prenatal checkup, were not associated with postpartum social problems.
Because teen pregnancy is considered as a risk factor for child maltreatment [16, 46–48], we divided maternal age into under 20 years old, 20 to 24 years old, and 25 years old and older. Although we found a non-significant association between maternal age and postpartum social problems in this study, we chose it as an index for the SLIM scale because pregnant teenagers may have already received high social support during pregnancy from a municipality, which might prevent postpartum depression and bonding disorders. In addition, as younger mothers are more likely to drop out of this study (drop-out rate in this study under 20 years old, 20 to 24 years old, and 25 years old and older was 28.0%, 23.0% and 22.6%, respectively), our findings on the non-association between young age and mothers who need social support might be underestimated. Further study using a sample with high retention rate, such as that of an anonymous internet survey, is needed.
The findings of the association between each item of the SLIM scale and postpartum social problems were consistent with those of previous studies. Women’s feeling when pregnancy was confirmed has been identified as a risk factor at 3-month neonatal health checkup in Japan [17]. Because in this study we asked women’s feeling during prenatal checkup, it is less likely that the women had forgotten about the first impression about their pregnancy. History of psychiatric disorder is an established risk factor for child maltreatment and postpartum depression [18–23]. We divided this factor into past and current because the suicide risk varies according to the type and duration of psychiatric disorder [23]. Further, the association between maternal developmental disorder traits and child mistreatment was shown in a previous study [24]. Because it was difficult to directly ask woman whether or not she had developmental disorders, we used “Trouble with others” as an index of developmental disorders for self-report questionnaires. As for social factors, a number of previous studies reported that poverty is risk factor for child maltreatment or PPD [25–27, 49]. Similar to poverty, housing instability was reported as a risk factor for intimate partner violence [41]. In addition to physical social environment, social support should be considered, as a lack of such support was also reported as a risk factor for child maltreatment and PPD [16, 28, 29]. Although previous reviews did not conclude if childhood abused history was an associated factor, owing to methodological issues,[30] one of the most robust risk factors for child maltreatment is history of childhood maltreatment. Several reports from Japan showed the association between maternal history of child abuse and their own child maltreatment or their psychiatric disease [31, 32]. As it was difficult to ask maternal history of child abuse in a hospital setting, we used “Satisfaction of relationship with parents” as an index of history of child abuse for self-report questionnaires. In conjunction with childhood maltreatment history, intimate partner violence [33, 34] and unmarried status [16, 35] are also risk factors for child maltreatment, and intimate partner violence was confirmed to be associated with mothers who need social support during the postpartum period.
Parents with intellectual disabilities are at risk of high levels of parenting stress [36] and lower education was related to physical punishment of children in Japan [37]. In this study, however, we found that several factors, such as maternal education and prenatal checkup, were not significantly associated with postpartum social problems. Education until the completion of junior high school is mandatory in Japan, so we rated this index as “junior high school”, “drop out of high school”, and “high school or higher”. This might have led to sampling bias, i.e., mothers with lower education were more likely to drop out. Thus, we did not find an association between maternal education and postpartum social problems. Inadequate prenatal checkups were associated with increased risk of physical child abuse [38, 39], but it was not the case in the current study. When asking the number of prenatal checkups, we used three times or less as inadequateness according to the Japanese guideline for pregnant women with inadequate prenatal checkups [40]. Again, we need to recategorize the frequency of prenatal checkups, such as those who had no prenatal checkups.
The novelty of this study is that we selected and weighted nine risk factors as the SLIM score, which ranges from 0-34 and categorized into three groups (low (SLIM score: 0-4), middle (SLIM score: 5-10), and High (SLIM score: 11-34) to identify mothers who need social support during pregnancy with moderate predictability (AUC=0.63). Our findings suggest that applying the SLIM scale at the first trimester may be useful in detecting women who have postpartum social problems in a hospital setting.
The current study is also helpful when it comes to preventing postpartum social problems by identifying high-risk mothers and to provide social support promptly from the first trimester. Social support programs on parenting includes financial and psychosocial support, and such programs are based on home visits carried out by health professionals, center-based parenting programs and peer-to-peer groups. Nurse-managed home visiting programs in the United States have resulted in improved maternal mental and physical status,[50] while in Europe, community-based postpartum care programs by health-care professionals are provided [51]. In the US, the Nurse-Family Partnership (NFP) is a home visiting program for families that covers the start of the pregnancy period through to when the child is 2 years old years [50]. In Japan, families with newborns are entitled to the “Hello Baby” home visiting program conducted by public health nurses or midwives until the baby is 4 months old [52]. Following that, the families receive infant health checkup at 4 months, 1.5 years, 3 years, and 5 years old at a municipal health center. We propose that public health nurses should focus on mothers with high SLIM score and to provide the necessary support continuously.
Nonetheless, we acknowledge that our study has several limitations. First, we may have selection bias due to social desirability. Because mothers are generally expected to accept their babies, participants may underreport their feelings against babies in the Mother-to-Infant Bonding Scale, especially when surveys were not anonymous. Also, women with PPD are often hesitant to divulge their mood and anxiety symptoms because of the guilt of having such symptoms when motherhood is expected to be a joyful event. Second, there might be measurement errors due to the survey being self-reported. We used “Satisfaction of relationship with parents” as an index of maternal history of childhood abuse. It is known that retrospective reports in adulthood of major adverse childhood experiences might be underestimated when self-reported [53]. Further, such experiences might be underreported due to the unwillingness of individuals to disclose embarrassing events or painful memories. We considered that it may be possible to estimate the history of childhood abuse by asking pregnant women about their relationship with parents, because history of childhood abuse could be regarded as an insufficiency of parent-child relationship. Third, although we collected postpartum data at the one month health checkup of infants, timing and frequency of survey can be controversial. PPD is defined strictly in the psychiatric nomenclature as a major depressive disorder with a specifier of postpartum onset within one month after childbirth [2]. However, depression in women during the postpartum period may start during pregnancy or may have onset beyond the first postpartum month. According to previous data, women generally increase in bonding with their infant six months postpartum [54]. Further study is needed to determine if the SLIM can predict women’s long-term mental problem. Finally, we extracted women with postpartum social problems in this study, but these women may not necessarily maltreat their children. Further development of a more accurate SLIM scale is warranted