Pregnancy carries a positive meaning as a normal developmental process that requires a woman’s physiological and psychological adaptation. Pregnant women are, nonetheless, vulnerable to a variety of mental health problems may have fears of giving birth or harbor feelings of inadequacy concerning their role as a mother, as well as experiencing mixed feelings and negative thoughts about pregnancy [1-3]. Among these considerations, depression is common among pregnant women, with 25.6% of expectant mothers worldwide experiencing the disease, and contributing to the emergence of a major public health problem [4-6]. In South Korea (hereafter Korea), the rate of depression experienced during pregnancy in 2008 was 26.5% [7], which increased to 41.0% in 2018 [8]—an increase of more than 15% over 10 years. In addition, the incidence of depression during pregnancy—including incidences of mild depression—was reported being as high as 35.9%, with reports suggesting that many Korean women experience moderate depression during pregnancy [9]. In light of these facts, identifying factors associated with depression as it appears during pregnancy is required.

Depression during pregnancy has been identified as a risk factor along with other major health problems that cause problems in fetal development, including premature births, a low birth weight, and the risk of adverse postnatal and cognitive-emotional function development in children [10-13]. In addition, depression may also manifest in children after childbirth [14]. Criticism of the family, or the transmission of depression to the husband [15,16], is known to have a negative impact on familial and social relationships.

Various individual factors have been reported as influencing the likelihood of depression during pregnancy, including a higher age, lower education level, no occupation, lower household income, and lower socioeconomic status [14,17-19]. Pregnancy-related characteristics, including the experience of a miscarriage and history of prepregnancy depression, have also been reported as factors that lead to an increased likelihood of prenatal depression [10,20]. It has also been reported that sleep disturbances, a health behavioral factor, affect prenatal depression [21]. In addition, some studies revealed that poor health status and higher perceived stress levels were associated with higher depression during pregnancy [9,19,22]. As hormonal changes lead to changes in oral conditions in pregnancy, oral health status has also been reported as related to depression [23].

However, in previous studies on factors related to depression in pregnant women, various factors were reported individually [14,17-20], and health behavior factors, were commonly omitted [21]. There are insufficient studies to comprehensively examine the effects of socioeconomic factors, health behaviors, health status, and psychological factors on depression. Therefore, this study aimed to examine the socioeconomic status, health behaviors, health status, and psychological factors of pregnant women in Korea, using nationally representative data, with the purpose of providing practical evidence-based data that can contribute to the prevention and control of depression during pregnancy.

The level of depression of this study is lower than a previous study in Korean pregnant women, which used the Edinburgh Postnatal Depression Scale (EPDS) [18]. Although it is difficult to directly compare prenatal depression levels using different scales, the study of 200 pregnant women in Korea identified 33.5% as having significant depressed mood (EPDS score of ≥10) [18]. This may be due to differences in participant characteristics such as monthly income. In this study, 53.8% had a monthly household income of 4 million KRW or more, which is higher than the previous Korean study (42.5%) [18]. Using the same instrument, however, the depression level (2.35 points) in this study was also lower than in a study conducted in the United States (7.0 points) [26]. Also, using the same cutoff of 10 points and higher, the study on pregnant women in the United States [26] reported a higher proportion (24.9%) of prenatal depression. This difference may be related to this study’s participants being recruited from the community via the probability-proportional phylogenetic extraction method. Furthermore, the United States study reported between 24.9% and 33.2% of participants having concurrent psychological problems such as sleep disorders, anxiety disorders, and post-traumatic stress. This study aligns with prior studies that reported a relatively low level of depression among Korean pregnant women, suggesting that pregnancy itself is perceived as part of a happy life cycle [27], and the fact that pregnant Korean women receive a lot of respect and love from people around them, thus they may perceive pregnancy as a positive process [28]. Nevertheless, depression in pregnant women can cause various health problems, and the proper assessment and management of depression can lead to healthier pregnancy outcomes.

This study identified household monthly income and education level as the sociodemographic characteristics that were associated with depression in pregnant Korean women. This is in line with a study [29] that reported low monthly income being indicative of a high risk of depression throughout pregnancy; another study [30] showed that depression during pregnancy was more frequent in women with a low education level, and that the odds ratio of depression during pregnancy increased among those who are either unemployed or are housewives. Therefore, it is necessary to assess and manage the risk of depression for pregnant women, particularly if they have such vulnerable characteristics. For pregnant women with a low level of education, policy support including health care and service improvement is necessary to avoid prenatal depression.

In addition, breakfast frequency, sleep time, and drinking were identified as health behavioral factors affecting depression in pregnant Korean women. In other words, the depression score decreased significantly with regular breakfast consumption (as ‘more than 5 days’ a week) and with adequate sleep; in the case of binge drinking, which albeit only constituted 8.1% of the sample, the depression score increased significantly. A healthy lifestyle is essential before pregnancy [31], and unhealthy behaviors have been reported to threaten maternal and child health and affect pregnant women [32]. In addition to guidelines for depression screening during pregnancy [33], regular assessment of drinking while pregnant should be reinforced.

A plant-based diet rich in vitamins lowers the risk of prenatal depression [34], while exercise has been shown to also have a positive effect on women’s mental health during pregnancy [35]. In order to promote healthy behaviors including better nutrition, more exercise, improved sleep, and less drinking, the commitment and support of healthcare professionals, along with the preparation and education of social and institutional health behavior guidelines, are necessary in Korea.

Moreover, this study identified health status factors affecting depression; i.e., subjective and oral health status of expectant mothers. This is similar to another study of Korean women which also identified subjective health status and subjective oral health status as variables related to depression during pregnancy [23]. Subjective health status refers to the perception that one’s health status has changed while experiencing physical changes due to pregnancy. Thus, to reduce depression during pregnancy, it is important to have a positive attitude toward one’s health status. In addition, despite the importance of self-evaluation of oral health status, the majority of adults lack awareness of its importance and are prone to neglect this aspect of their physical well-being, which, in turn, negatively affects one’s overall health [36]. As such, a system that continuously monitors the health and oral health of pregnant women is necessary in order to promote well-being during pregnancy and should include education concerning general health promotion and emphasis on basic oral health [23]. Such emphasis on subjective health and subjective oral health should be offered to all women from the early stages of pregnancy.

This study identified stress as a psychological factor affecting prenatal depression, which supports a prior study [9]. Pregnant women’s stressors include not only the pregnancy itself, but underlying issues of poverty, unemployment, economic status, and relationship changes as well [37]. Improving women’s mental health during the prenatal period is important for both mother and child outcomes [18]. It is necessary to systematically consider the stress of pregnant women during prenatal care, and more attention should be paid to identifying psychological risk factors in pregnant women [38]. As such, this study provides further evidence to check and manage the physical condition of pregnant women and fetuses at prenatal checkups, as well as to implement a stress assessment and management program in order to respond more flexibly to everyday stressors.

This study did not find that the age of pregnant women nor their unmet healthcare needs affected depression. According to previous studies, the prevalence of depression during pregnancy has been reported as increasing among younger women in the United Kingdom [14]; in contrast, that age has no effect on prenatal depression [9]. While this study supports the latter report, Korea has a national health insurance system and Korean pregnant women show high rates (95.2%) of early prenatal care (e.g., first visit before 8 weeks into pregnancy) and overall prenatal care (nearly 100%) [39], which may differ from the United Kingdom [14]. Furthermore, 91.8% of pregnant Korean women had reported not having any unmet healthcare needs during pregnancy [31], which matches this study’s findings; As such, this may be considered in its non-relationship with depression.

A limitations of this study was that stress was the only psychological parameter measured during pregnancy in the data available from KCHS. Future studies reflecting a wider spectrum of positive and negative psychological factors throughout pregnancy are thus required. In addition, as the KCHS data did not allow classification of the pregnancy into the first, second, or third trimester, it was impossible to ascertain differences in depression according to pregnancy period. Another limitation is that although prenatal depression is related to obstetrical characteristics (e.g. parity, miscarriage experience, complications), this information was limited due to the nature of a secondary analysis study. Nevertheless, this study offers significant information on the degree of influence on prenatal depression, using probability-proportional sampled data.

In conclusion, this study using a nationally representative database found that low income and low education level, skipping breakfast, less than 8 hours of sleeping, binge drinking, higher stress, and lower subjective health status and subjective oral health status were influential on depression in pregnant Korean women. Findings support the need for healthcare policies and implementing clinical screening to alleviate prenatal depression, especially for pregnant women with low socioeconomic status, poor health behavior, poor health status, and high stress.