Postpartum stress in the first 6 months after delivery: a longitudinal study in Nantong, China

Abstract

Objectives

The objective is to to explore the longitudinal change trajectories of postpartum stress and its related factors.

Design

A longitudinal study with follow-ups from 42 days to 6 months after delivery.

Settings and participants

A total of 406 postpartum women were recruited at baseline (42 days after delivery) from 6 hospitals in Nantong, Jiangsu Province, China, and followed up at 3 and 6 months. After the follow-ups, 358 postpartum women were retained for further analysis.

Methods

Postpartum stress was evaluated using the Maternal Postpartum Stress Scale (MPSS) at baseline (42 days) and 3 and 6 months after delivery. MPSS has three dimensions, such as: personal needs and fatigue, infant nurturing and body changes and sexuality. Postpartum depression and anxiety were measured using the Edinburgh Postnatal Depression Scale and the short-form Depression, Anxiety and Stress Scale, respectively. The MPSS scores were normalised using a rank-based inverse normal transformation.

Results

Postpartum stress decreased significantly after 3 months, and postpartum stress reduced further after 6 months. Additionally, the scores for all three dimensions reduced after 6 months, while infant nurturing reduced after both 3 and 6 months. Older age (β=0.028, p=0.049), higher education level (β=0.153, p=0.005) and higher body mass index (BMI) (β=0.027, p=0.008) of the postpartum women were significantly associated with higher postpartum stress levels in corresponding dimensions at 42 days. Older age was also associated with higher postpartum stress at 3 (β=0.030, p=0.033) and 6 months (β=0.050, p<0.001) in the dimension of personal needs and fatigue. Postpartum stress levels were significantly higher in women with depression or anxiety symptoms.

Conclusions

Postpartum stress continuously declined from 42 days to 6 months after delivery. Postpartum women with older age, higher education levels, higher BMI and anxiety or depression symptoms should be the target population for early intervention.

STRENGTHS AND LIMITATIONS OF THIS STUDY.

• In addition to postpartum stress, depression and anxiety were measured in our study. The changing trends of postpartum stress levels were evaluated by stratifying postpartum women with depression or anxiety symptoms.

• We had recruited only one unmarried woman in our study that was excluded due to insufficient sample size for stratified analysis (unmarried vs married). Future studies including unmarried women, whose stress may be even higher, are warranted.

• Postpartum women in our study were selected using a non-randomised sampling strategy, so there is a risk of sampling bias. A random sampling method is warranted in further studies.

• The follow-up questionnaires were administered by telephone, which is different from the pen-and-paper/online administration method.

Introduction

The process of becoming parents is a significant milestone for numerous individuals, encompassing not only happiness and enthusiasm but also the potential for substantial stress and an increased vulnerability to experiencing postpartum depression.^{1 2} The postpartum period is a time of rapid transformation. Studies found that there are different types and magnitudes of stressors during the postpartum period for women, such as drastic changes in their daily routine, adjusting to their new role as a mother, developing a bond with their child and adjusting to the temporary changes in their relationship with their partners.³ Due to new challenges and physiological and psychosocial changes following childbirth, the postpartum period is a period of increased vulnerability to the onset or relapse of psychological distress.^{4 5} Although increases in stress levels to some degree are normative during the postpartum period,⁶ excessive stress can pose a serious threat to maternal, infant, emotional, behavioural and family well-being, as well as cause cognitive problems.^7–10 Therefore, identifying and treating these common conditions are crucial for the mother and her infant. In addition, researchers have emphasised the need for in-depth exploration of stress as a separate psychological construct, highlighting that maternal stress carries unique implications that are distinct from those associated with depression and anxiety.^{1 11}

Prenatal maternal stress and postpartum stress refer to stress that a mother experiences during pregnancy¹² and after delivery, respectively. Postpartum stress could significantly negatively impact women’s health status and affect infant growth, nutrition, bonding, temperament and mental well-being.^{13 14} Prenatal stress has been linked to the initiation of various physical and mental health issues in women, including inadequate nutrition, heightened risk of cardiovascular diseases, elevated anxiety levels and postpartum depression.¹⁵ Postpartum stress may lead to postpartum depression and postpartum weight retention due to abnormal eating behaviours.¹⁶ Studies have confirmed that depression is associated with an elevated risk of cardiovascular disease,^{17 18} while postpartum weight retention is associated with later adverse cardiovascular health.¹⁹

According to a recent study, postpartum stress can persist long after delivery, as long as 12 months in one-quarter of women.²⁰ The first 6 months after delivery is a sensitive period for mother–infant bonding,^{21 22} which can be affected by postpartum stress.²³ Therefore, it is particularly important to study and detect the continuity of stress in women during this period. However, existing studies have primarily explored postpartum stress at a single time point.^{24 25} In addition, there are limited studies evaluating the change trends, which do not depend as much on the time of exposure as on the severity and duration of postpartum stress.²⁶ Moreover, postpartum stress is difficult to quantify, and data for the most effective postpartum stress instrument are limited. This lack of evidence on the accuracy of postpartum stress instruments makes it challenging to understand and mitigate information bias related to postpartum stress.²⁷

Many studies have investigated the change trends of perinatal depression and anxiety symptoms in women after delivery. In a Canadian perinatal cohort study, anxiety and depression symptoms were found to be heterogeneous; this finding highlighted the importance of conducting multiple mental health assessments during the perinatal period. Chronically elevated depressive symptoms during the peripartum period have been found to be associated with higher levels of postpartum stress.²⁸ Postpartum women undergo intense and potentially rapid emotional fluctuations in this period.^{29 30} During this period, mothers encounter various physiological and psychological hurdles, including disrupted sleep patterns, recalibration of the parental dynamic and the demand for swift adjustment to novel routines and acquisition of additional skills.³¹ These aforementioned challenges have the potential to trigger or exacerbate maternal stress, particularly among women experiencing limited social support, diminished self-esteem or dissatisfaction within the parenting relationship.³² Maternal stress hinders daily functioning and heightens the risk of postpartum depression in mothers, as well as adversely affects infant behavioural and emotional development.^{28 33}

Most prior studies on postpartum stress are cross-sectional and measure postpartum stress at a single time point. Studies measuring postpartum stress at multiple time points throughout the postpartum period are scarce. Therefore, it is difficult to provide sufficient evidence for accurately describing the change trends of stress during the postpartum period.^{34 35} Longitudinal studies of developmental trajectories could help researchers identify the onset, duration and severity of symptoms of stress for specific trajectories.

Although there are many studies on postpartum stress, the findings are inconsistent. This may be because different postpartum stress measures were used. Some studies found that postpartum stress levels in mothers increased over time. For instance, a large Irish population cohort study with a 1-year follow-up showed that the postpartum stress level was the highest at 6 months after delivery.³⁶ Another cohort study found an increase in stress from 1 to 6 months post partum.³⁷ In contrast, some studies reported decreased stress levels in mothers over time. For instance, an Australian cohort study showed a decline in stress levels from childbirth to 6 months postpartum.³⁸ In addition, a Hong Kong-based study demonstrated significantly decreased maternal stress from 6 weeks to 6 months after delivery.³⁹ However, other studies did not identify any change in postpartum stress during the postpartum period. For instance, a Korean study showed that maternal stress remained unchanged from 6 weeks to 3 months postpartum.⁴⁰ This may be because postpartum stress measurement tools used in the studies were generic and not postpartum specific. Therefore, a postpartum-specific tool that can measure postpartum stress over a longer period (up to 1 year) and evaluate the change trends is warranted.

Nakić Radoš et al recently developed the Maternal Postpartum Stress Scale (MPSS),⁴¹ which is a reliable and valid 22-item scale for measuring postpartum stress based on self-reported data. This scale measures three dimensions of postpartum stress: personal needs and fatigue (nine items), infant nurturing (seven items), and body changes and sexuality (six items). Cronbach’s alpha coefficient (α) of internal consistency of the MPSS was 0.880. However, no studies in the literature have prospectively used this scale to measure postpartum stress.

Considering these gaps in the literature, the primary objective of this study was to assess the change trends of postpartum stress at three time points (baseline (42 days), 3 months and 6 months) using MPSS. The change trends of postpartum stress were evaluated by stratifying women with depression or anxiety symptoms, as well as other relevant variables. In addition, this study aimed to explore possible stressors at baseline that may be associated with postpartum stress at different follow-up time points.

Methods

Study design

A longitudinal study was conducted that followed-up participants from 42 days to 6 months after delivery.

Patient and public involvement

Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

Recruitment of postpartum women at baseline (42 days after delivery)

Using the convenience sampling method, postpartum women who underwent physical examination 42 days after delivery at six hospitals (The Affiliated Hospital of Nantong University, The First People’s Hospital of Nantong, The Second People’s Hospital of Nantong, The Third People’s Hospital of Nantong, The Affiliated Maternity and Child Health Care Hospital of Nantong University, and The Sixth People’s Hospital of Nantong) in Nantong, Jiangsu Province, China, from August 2022 to November 2022 were selected. The inclusion criteria were as follows: (a) maternal age ≥18 years; (b) no malformations or serious complications in the newborn; (c) willingness to cooperate with the survey, ability to communicate effectively and ability to understand the content of the questionnaire and complete it independently and (d) voluntary participation. Women who met the inclusion criteria were administered paper questionnaires in the postpartum clinic at 42 days after delivery. The exclusion criteria were as follows: (a) unmarried mothers; (b) preterm births or twins; (c) comorbid psychosomatic diseases, such as chronic urticaria, neurodermatitis, hyperthyroidism, migraine, muscle pain, rheumatoid arthritis, sleep disorders and malignant tumours; (d) mental illnesses (other than depression and anxiety), severe organic diseases such as heart, liver, and kidney diseases, and severe complications during pregnancy; (e) low intelligence and inability to understand the contents of the questionnaire and (f) poor compliance and unwilling to cooperate in the study.

Follow-up 3 and 6 months

Based on the first questionnaire, the researchers established the frequency of calls made to the participants. The participants were informed that they would receive telephone calls to determine the symptoms of postpartum stress at different follow-up time points (3 and 6 months postpartum). If the participant disconnected the call, the participation was nullified. In case of no response, the researchers would call the participant again the following day. Those who did not respond the following day as well were considered to have abandoned the participation.

During the call, which lasted for approximately 5–15 min, postpartum stress was assessed using MPSS. If the participant responded positively to the MPSS, they were asked to provide further details of how these situations arose to closely monitor the mothers’ mental health and provide help if necessary. To ensure the survey quality, the options for each item were carefully checked over the telephone call, and it was ensured that all questions were answered before submission. No incentive was provided for participation.

Measures

Baseline questionnaire

The demographic sheet was designed by our research team. The baseline questionnaire included (a) basic information, such as age (years), body mass index (BMI, kg/m²; overweight 24.0–27.9, obesity ≥28.0), maternal and paternal education (primary school, junior high school, senior high school, secondary specialised school, junior college, undergraduate, postgraduate and higher), and years of marriage; (b) perinatal condition, such as mode of delivery (vaginal, vaginal (lateral episiotomy), and caesarean section), abortion history (yes/no), parity (primipara/multipara), pregnancy complications (yes/no), assisted reproduction (yes/no) and infant caretaker (only maternal/involves others); and (c) basic information of newborns, such as birth weight and mode of feeding (breast feeding, mixed-feeding and formula milk). Postpartum stress was measured using MPSS, which is a reliable and valid instrument for measuring self-reported postpartum stress among postpartum women. Other mental health symptoms including depression and anxiety were measured using the Edinburgh Postnatal Depression Scale (EPDS) and the short-form Depression, Anxiety and Stress Scale (DASS-21), respectively.

Measurement of postpartum stress

The MPSS is a 22-item scale that measures three dimensions of postpartum stress.⁴¹ The Personal needs and fatigue dimension includes nine items: adjustment to frequent wake-ups, baby’s irregular patterns of daily sleep, my fatigue and exhaustion, the amount of household chores, lack of help with the baby and household chores, lack of time for socialising with friends, lack of time for myself, impossibility to complain to someone, and loneliness at home with the baby. The infant nurturing dimension includes seven items: choosing the appropriate way of feeding the baby (breast feeding/formula), baby’s irregular feeding pattern, insufficient milk supply when breast feeding, baby’s development, baby’s health problems, recognising the baby’s needs, and impossibility to soothe a crying or upset baby. The body changes and sexuality dimension includes six items: being uncertain when to resume intercourse after childbirth, insufficient frequency of sexual intercourse, insufficient enjoyment in sexual intercourse, the thought that my partner finds me unattractive, the impossibility to return to prepregnancy weight and physical appearance after childbirth. Each item was scored on a 5-point Likert scale, with 0 indicating ‘not at all’ and 4 indicating ‘completely’. A higher MPSS total score suggested a higher level of postpartum stress.⁴¹ Cronbach’s α of the Chinese version of the MPSS, which we verified for internal consistency, was 0.940, while Cronbach’s α coefficients of the above three dimensions were 0.903, 0.911 and 0.882, respectively.⁴² The MPSS was measured at three postpartum time points: 42 days, 3 months and 6 months.

Measurement of other mental health symptoms

Edinburgh Postnatal Depression Scale

The EPDS-10 is a screening instrument developed by Cox et al,⁴³ commonly used to identify depression in pregnant women.⁴⁴ This validated questionnaire shows a sensitivity of 70%–87% and a specificity of 94%–97% among gravidas, with a cut-off score of ≥10.⁴⁵ Using the EPDS, which includes 10 items, the participants rated how they felt during the last 7 days. Response categories were scored 0–3 for each item, with 3 indicating a higher severity of the symptoms. The total score ranges from 0 to 30.

Depression, Anxiety and Stress Scale-21

DASS-21 is a 21-item scale that measures three dimensions (7 items each): anxiety, depression and stress. It is used to measure an individual’s negative mood and the severity of symptoms in the previous week.⁴⁶ Four grades ranging from 0 to 3 were used: ‘completely inconsistent’, ‘partially consistent’, ‘mostly consistent’ and ‘completely consistent’. Higher scores indicated more intense negative emotions. Based on the score, each dimension was categorised into asymptomatic, mild, moderate, severe and extremely severe. In this study, however, we used only the anxiety dimension. Cronbach’s α for the anxiety dimension⁴⁷ was 0.879. The recommended cut-off score for the anxiety scale was 7, and those with scores >7 were defined as having anxiety.

Statistical analyses

A two-sided χ² test and one-factor analysis of variance (ANOVA) were used to assess the differences in each demographic characteristics group. The MPSS scores were normalised using a rank-based inverse normal transformation. One-way repeated measures ANOVA was used to evaluate the differences in the MPSS scores at each follow-up time point. Multiple linear regression analysis was used to examine postpartum stress-related factors. All statistical analyses were performed using SPSS V.25.0 (IBM). Figures were drawn using R V.3.6.2. The statistical significance level was set at p<0.05.

Results

Basic information on the follow-up process

A total of 406 postpartum women who completed face-to-face questionnaires were recruited at the baseline. At 3 months after delivery, 32 postpartum women were lost to follow-up, resulting in the retention of 374 participants and a follow-up rate of 92.12%. At 6 months after delivery, 16 postpartum women were further lost to follow-up, resulting in the retention of 358 participants and an overall follow-up rate of 88.18%, which eventually constituted the final sample used in subsequent analyses (figure 1).

Figure 1.

Study design of the longitudinal study.

Characteristics of the participants

The characteristics of the 358 postpartum women are summarised in online supplemental table 1. The characteristics between the 358 postpartum women and the 48 women lost to follow-up were compared. However, no statistically significant difference was observed between them. Thus, the data from the 358 postpartum women are well representative of the overall sample of 406 women.

Item-analysis of the MPSS at different follow-up time points

The mean of each item of the MPSS among all 358 participants at different time points (42 days, 3 months and 6 months after delivery) are presented in figure 2. At baseline, the average mean of each item ranged from 0.28 to 1.23, with item 1 (choosing the appropriate way of feeding the baby) as the highest and item 11 (the amount of household chores) as the lowest. At the 3-month follow-up, the average mean of each item ranged from 0.32 to 1.20, with item 18 (lack of time for socialising with friends) as the highest, and item 11 (the amount of household chores) as the lowest. At the 6-month follow-up, the average mean of each item ranged from 0.09 to 1.39, with item 18 (lack of time for socialising with friends) as the highest, and item 3 (insufficient milk supply when breast feeding) as the lowest.

Figure 2.

Means of scores of each item of the MPSS at different follow-up time points. MPSS, Maternal Postpartum Stress Scale.

The change trends of postpartum stress at different follow-up time points

As shown in figure 3A, compared with postpartum stress at baseline, postpartum stress decreased significantly at 3 months after delivery (p=0.004) and reduced further at 6 months after delivery (p<0.001). A similar change trend was also found in the dimension of infant nurturing (figure 3B). For both personal needs and fatigue and body changes and sexuality dimensions, there were no significant changes at 3 months (p>0.05) compared with that at baseline (figure 3C,D). However, at 6 months, postpartum stress decreased significantly in these two dimensions (p<0.001 and p<0.001, respectively) (figure 3C,D).

Figure 3.

The change trend of postpartum stress at different follow-up time points. (A) Total scores of MPSS; (B) scores of infant nurturing; (C) scores of personal needs and fatigue; (D) scores of body changes and sexuality. Data are shown in median (IQR). MPSS, Maternal Postpartum Stress Scale.

Baseline variables associated with postpartum stress at different follow-up time points

As shown in online supplemental table 2, at baseline, the older age of the postpartum women (β=0.028, p=0.049), higher maternal (β=0.153, p=0.005) and paternal education levels (β=0.120, p=0.027) and higher BMI (β=0.027, p=0.008) were significantly associated with higher postpartum stress levels in the dimensions of personal needs and fatigue, infant nurturing, and body changes and sexuality, respectively. At the 3- month follow-up, the older age and higher education level of the postpartum women were significantly associated with higher postpartum stress levels in the dimensions of personal needs and fatigue (β=0.030, p=0.033) and infant nurturing (β=0.115, p=0.027), respectively. At the 6-month follow-up, the older age (β=0.035, p=0.014) and higher education level (β=0.135, p=0.013) of the postpartum women were significantly associated with higher levels of the total postpartum stress, as indicated by the high MPSS scores. In addition, older age (β=0.050, p<0.001) and higher educational level (β=0.123, p=0.020) were significantly associated with higher levels of postpartum stress in the dimension of personal needs and fatigue. Furthermore, the higher the BMI, the higher the postpartum stress in the dimension of body changes and sexuality (β=0.039, p<0.001).

Stratified analysis of the change trends in postpartum stress at different follow-up time points

The age, education level and BMI of the postpartum women were significantly associated with a change in postpartum stress at different time points after delivery. The change trends were evaluated by stratifying these variables. The postpartum stress levels of women who were older (≥30 years), have higher education levels (bachelor’s degree or higher) and were overweight/obese were significantly higher at every follow-up time point (figure 4A). Similar trends were also observed in the three dimensions of the MPSS (figure 4B–D).

Figure 4.

Stratified analysis of the change trends in postpartum stress at different follow-up time points. Data are shown in mean±SD. (A) Total scores of MPSS in different age, education level and BMI groups; (B) scores of the dimension of infant nurturing in different age, education level and BMI groups; (C) scores of the dimension of personal needs and fatigue in different age, education level and BMI groups; (D) scores of the dimension of body changes and sexuality in different age, education level and BMI groups. BMI, body mass index; MPSS, Maternal Postpartum Stress Scale.

Postpartum stress has been found to directly correlate with minor postpartum psychiatric illnesses, including postpartum depression and anxiety.⁴⁸ The change trends of postpartum stress were evaluated by stratifying women with depression or anxiety symptoms. As shown in figure 5, postpartum stress in women with depression or anxiety symptoms was significantly higher than in those without these symptoms at each time point. However, at 3 and 6 months after delivery, postpartum stress decreased in all four groups, and it was reduced by a greater extent in women with depression or anxiety symptoms (figure 5A). Similar trends were observed in all three dimensions (figure 5B–D).

Figure 5.

The change trends of postpartum stress by stratifying women with depression or anxiety symptoms. Data are shown in mean±SD. (A) Total scores of MPSS; (B) scores of infant nurturing; (C) scores of personal needs and fatigue; (D) scores of body changes and sexuality. MPSS, Maternal Postpartum Stress Scale.

Discussion

The WHO identifies maternal mental health as a major public health concern due to its established association with poor maternal and child health.^49–51 Given the high prevalence of maternal mental health problems during pregnancy and postpartum, it is important to consider the protective factors mitigating risks associated with these problems. The American College of Obstetricians and Gynecologists recommends incorporating maternal mental health screening at least once during the perinatal period and conducting appropriate follow-ups for women in need.⁵² This longitudinal study aimed to examine maternal postpartum stress starting from 42 days to 6 months after delivery. We found that postpartum stress decreased significantly at 3 months after delivery and decreased further at 6 months.

The change trends of the dimension of infant nurturing were consistent with the total MPSS score, which was lower at 3 months than at 42 days and decreased further at 6 months after delivery. This may be because the physical and mental demands of parenting change as the child develops.⁵³ Chinese primiparous women have relatively good parenting competence at 3 months postpartum.⁵⁴ Later into the postpartum period, the women were able to better choose appropriate and regular feeding patterns, recognise their baby’s needs, and soothe their crying or upset baby. Hence, postpartum stress associated with infant nurturing was reduced, and it only increased if the baby developed any health issues.^55–57 Studies also found that maternal postpartum mental health may benefit from positive father engagement in infant care,^{58 59} and higher father engagement may mitigate maternal stress associated with infant sleep disturbances.⁶⁰ Most Chinese fathers do not observe gender role boundaries in child rearing and are reported to be actively involved in childcare activities, such as feeding and bathing.⁶¹

In the personal needs and fatigue dimension, there were no significant changes at 3 months compared with baseline; however, postpartum stress decreased significantly after 6 months. Taylor and Johnson⁶² found that perinatal fatigue reached the lowest level at 6 months after delivery, in line with our study. In another study, the lowest fatigue score was also observed at 6 months in the ‘perinatal fatigue persistently low’ group.⁶³ This may be because the number of night wakings gradually stabilises at 6 months, thus gradually increasing the sleep duration at night.⁶⁴ This allows the mother to get better rest, reducing fatigue.

Personal needs were also associated with stress.^65–67 Fulfilment of personal needs helps reduce postpartum stress.⁶⁸ In China, postpartum women usually return to work approximately 6 months after giving birth. Returning to work increases socialisation and reduces the burden of performing some of the household chores. Reportedly, maternal employment reduces postpartum depression symptoms.⁶⁹

In the body changes and sexuality dimension, there were no significant changes in postpartum stress at 3 months compared with baseline; however, postpartum stress decreased significantly after 6 months. In the MPSS, sexuality stress refers to the uncertainty of when to resume intercourse after childbirth, insufficient frequency of sexual intercourse, and insufficient enjoyment of sexual intercourse. The period starting from birth to 3 months after delivery is considered to be quite critical where couples are at a heightened risk for sexual dysfunction across this transition.⁷⁰ A postpartum sexual health study reported that 85% of women experienced moderate or greater sexual problems in the first 3 months after childbirth,⁷¹ dropping to approximately 60% at 6 months, and over 90% of women resumed sex within 6 months after delivery.^{72 73} In addition, a recent study found distinct trajectories for different groups of postpartum parents, with approximately half of birthing parents reporting few changes in their sexual function postpartum, and one-third reporting moderate sexual dysfunction in the first 3 months postpartum; however, significant improvements were observed by 1 year.⁷¹ This may be because postpartum sexuality is changed by the mental, physical and social/relationship effects of a variety of hormones.⁷⁴ Therefore, maternal stress due to sexuality remains high during the first 3 months but gradually improves. These may be the possible explanations that sexuality stress decreased from 3 to 6 months.

Furthermore, we found that older age was associated with higher postpartum stress at 42 days, 3 months and 6 months. Some studies found that older primiparae were consistently fatigued during postpartum. Older women tend to sleep less and feel overwhelmed by their daily lives. They had significantly lower maternal confidence and satisfaction compared with their younger counterparts at 1 month postpartum.⁷⁵ In addition, older postpartum women adapt to the maternal role more slowly than their younger counterparts. However, qualitative research found that because older primiparous mothers have established careers, they tend to have more emotional and social strengths. Their anxieties mainly stem from knowing the greater physical risks associated with giving birth at an older age, which may affect their physical strength and the baby’s health, and due to a lack of support after discharge.⁷⁶ Increased maternal age reportedly contributes to decreased maternal–fetal attachment/bonding.¹⁴ Matsumoto et al⁷⁷ examined 675 postpartum Japanese women for 3 months after childbirth and found that women aged ≥35 years had an increased risk for emotional problems than those aged 30–34 years.

Higher maternal and paternal education level was associated with higher postpartum stress at 42 days compared with those with lower educational level, and higher education level of maternal was also associated with higher postpartum stress at 3 months.

This may be because women with higher educational levels better understand infant nurturing and tend to worry more regarding the baby’s health and development, such as scientifically proven best feeding options for the infant in terms of nutrition and health. Previous studies demonstrated a positive correlation between education level and the risk of postpartum stress and depression,^{78 79} in line with our study. So the association between education and postpartum stress may due to the association with infant nurturing. It may be that more educated parents know more but also have higher fears and concerns about infant care, development and nurturing.

In our study, higher BMI was associated with higher postpartum stress at 42 days and 6 months. Reportedly, BMI was significantly associated with postpartum stress.⁸⁰ Higher weight retention is associated with stress in women after childbirth.⁸¹ Higher serum morning cortisol in late pregnancy among women with obesity is also associated with greater weight retention after pregnancy.⁸² A study found that a higher BMI is associated with low participation in healthy behaviours, which, in turn, is associated with adverse outcomes during postpartum.⁸⁰ In a qualitative interview study, postpartum women perceived that the medical staff were unconcerned regarding weight and displayed a lack of support; postpartum weight loss support was scarce or absent, resulting in postnatal BMI retention and increased postpartum stress.⁸³ Therefore, postpartum women with older age, higher education level, and higher BMI may experience higher stress during the postpartum period, and more attention should be paid to this group.

Depression or anxiety could have some effects on postpartum stress. A previous longitudinal study revealed that antenatal depression and anxiety directly impact postpartum parenting stress.⁸⁴ Prenatal anxiety could also independently predict postpartum stress.⁸⁵ This indicates that ongoing maternal mental illness during pregnancy and postpartum may be an important predictor of postpartum stress. Here, the postpartum stress levels of women with depression and anxiety symptoms were significantly higher than in those without these symptoms at each follow-up time point. In addition, although postpartum stress decreased at 3 and 6 months after delivery for all three groups, the decrease was significant in women with depression and anxiety symptoms. This trend was observed in all three dimensions. Although these results cannot indicate causation, they add to the literature by demonstrating factors that influence postpartum stress. These findings also highlight the need for an integrated approach to develop effective postpartum services and care to support women after childbirth. Motherhood can be a complicated period for mothers with low confidence, depression and stress, although it improves over time for most mothers. Therefore, further studies are needed to identify parents who are struggling and train health professionals to support those entering motherhood/parenthood. Early intervention in postpartum women with depression or anxiety was effective in reducing postpartum stress.⁶

This study has some limitations. First, the follow-up questionnaires were administered by telephone, which is different from the pen-and-paper/online administration method. Second, the postpartum women in our study were selected using a non-randomised sampling strategy, so there is a risk of sampling bias. A random sampling method is warranted in further studies. Third, mothers who delivered preterm babies or twins were excluded from the sample. Therefore, the findings of this study might not be representative of the entire population of postpartum women. Fourth, although both married and unmarried women were included at the site for recruitment; however, only one unmarried woman was recruited in our study, which was excluded in further analysis, mainly due to insufficient sample size for stratified analysis (unmarried vs married). Future studies including unmarried women, whose stress may be even higher, are warranted. Fifth, data on whether the women were on maternity leave or were working during the study period could not be obtained. Lastly, while postpartum stress and depression were measured using specific scales, MPSS and EPDS, postpartum anxiety was measured only by the anxiety dimension of the DASS-21.

Conclusions

Postpartum women with depression and anxiety symptoms, older age, higher education level and higher BMI may be associated with higher stress. However, postpartum stress decreased continuously from 42 days (baseline) to 6 months after delivery, especially for the dimension of infant nurturing. Nonetheless, corresponding nursing management should target postpartum women early in the postpartum period. Conducting these assessments and implementing interventions at different time points after delivery may help reduce the carryover of difficulties or spillover across other domains of functioning.

Data availability statement

Data are available on reasonable request.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).

Ethics approval

The study was approved by the ethics committee of the Affiliated Hospital of Nantong University (approval number: 2022-K50-01). The study was anonymous, confidential and voluntary. All participants signed the written informed consent forms before participating in the study and were informed that they could withdraw from the study at any time.