Examination of risk factors for high Edinburgh Postnatal Depression Scale scores: a retrospective study at a single university hospital in Japan

doi:10.21203/rs.3.rs-3204237/v1

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Examination of risk factors for high Edinburgh Postnatal Depression Scale scores: a retrospective study at a single university hospital in Japan

https://doi.org/10.21203/rs.3.rs-3204237/v1

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published 04 Mar, 2024

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Background: Perinatal mental health, such as postpartum depression, is an important issue that can threaten the lives of women and children. It is essential to understand the risk factors in advance and intervene before they can lead to postnatal depression. The risk factors of postpartum depression are reported to vary considerably in Japan. This study aimed to evaluate the risk factors for women with high Edinburgh Postnatal Depression Scale (EPDS) scores and to find women who may need our intervention to prevent postpartum depression.

Methods: This was a retrospective observational study conducted at a single center. At the one-month check-up after birth, the EPDS test was performed in 1625 women who gave birth at our hospital from 2008 to 2016. We evaluated maternal, birth, neonatal and social factors and the breastfeeding status from medical records. Thereafter, we examined the factors that contributed to a high EPDS score.

Results: There were 284 women in the high-score group with an EPDS of ≥ 9, and 1341 women in the low-score group with an EPDS score ≤ of 8. Maternal mental disorders and neonatal transport were significantly associated with high EPDS scores. Conversely, exclusive breastfeeding was significantly associated with the low-score EPDS group.

Conclusions: The principal factor for high EPDS scores was a mental disease. Based on this result, we suggest that early intervention in women at high risk for postpartum depression could prevent serious consequences such as abuse and suicide.

breast feeding

Edinburgh Postnatal Depression Scale

maternal health

maternal mental disorders

neonatal transport

perinatal mental health

postpartum depression

Perinatal mental health, such as postpartum depression, is an important issue that can threaten the lives of women and children. In Japan, maternal suicide occurs more than twice as often as maternal death due to perinatal complications. Nearly half of the women who committed suicide experienced postpartum depression and other mental disorders [1]. Postpartum depression adversely affects "bonding," i.e., a mother's emotional attachment to a child [2], [3]. Women with postpartum depression are more likely to abuse their newborns through actions, such as neglect [4]. Postpartum depression, bonding disorders, and abuse negatively impact the development of the affected children [5], [6], and the adverse effects may be transmitted across generations [7], [8].

The incidence of postpartum depression is ~ 13% -19% [9], and its prevalence in Japan is 17% [10]. A rapid decrease in estrogen and dysregulation of cortisol have been reported to be associated with postpartum depression, but the exact cause remains unknown [11], [12], [13], [14]. There are various reports on the risk factors for postpartum depression. Half of the women with postpartum depression are believed to have symptoms during pregnancy [15], and depression during pregnancy is the most important risk factor for postpartum depression [16], [17]. In addition, other risk factors for postpartum depression include being a single mother, young women, grand multipara, low income, low education levels, a history of mental disorders, stressful life events (such as bereavement of a loved one, divorce, and unemployment), and lack of social support [9], [17], [18], [19]. Japanese studies have also reported risk factors such as anxiety and depression during pregnancy, negative feelings toward the pregnancy, lack of social support, primipara, maternal complications, history of mental disorders, and a lack of family cohesion [20], [21], [22]. It is important to assess these risk factors and implement appropriate interventions to prevent disastrous consequences, such as suicide and abuse.

The Edinburgh Postnatal Depression Scale (EPDS) is a questionnaire developed by Cox in the United Kingdom to screen for postpartum depression [23]. The EPDS is a 10-item self-report scale that is highly sensitive and specific in detecting postpartum depression [24]. The EPDS is designed to be unaffected by changing physical symptoms during the puerperium and therefore does not include physical symptoms items. Each of the ten questions has a 4-level answer applying 0 to 3 points; the overall score ranges from 0 to 30 points. The EPDS is currently translated and used mainly in Europe and the United States. In 1996, Okano et al. evaluated the reliability of the Japanese version of the EPDS. When the cut-off score was set at 8/9, the sensitivity was 0.75 and the specificity was 0.95, indicating higher values than the other score [25].

The study aimed to evaluate the risk factors for women with high EPDS scores, regarding the potential for postpartum depression.

This is a retrospective observational study conducted at a single center. We evaluated the data of women who gave birth at our hospital between 2008 and 2016 and who underwent EPDS at the one-month check-up after birth. In principle, all women completed the EPDS questionnaire unless they did not speak Japanese, were undergoing psychiatric treatment due to poor mental status, or were transferred. The EPDS scores at the one-month check-up after birth, maternal factors, birth factors, neonatal factors, breastfeeding status, and social factors were extracted from the medical records. Maternal factors included age at birth, parity, fetus number, pregnancy complication (e.g., hypertensive disorder of pregnancy, gestational diabetes mellitus), underlying maternal disease (e.g., autoimmune disease, heart disease), mental disorder, and maternal transport (i.e., the woman was transferred to our hospital from another hospital due to complications). Birth factors included gestational age at birth and birthing method. Neonatal factors included birth weight, Z-score of the birth weight, hospitalization at the neonatal intensive care unit (NICU), and neonatal transport (i.e., the newborn was transported from our hospital to another hospital due to complications). Social factors included the presence of the partner, welfare, and late visit (i.e., the first visit was after 22 gestational weeks).

Women were assigned to a high-score group with an EPDS of ≥ 9 and a low-score group with an EPDS of ≤ 8. The following items were compared between the groups: age at birth, number of young pregnant women (age at birth ≤ 19 years), advanced maternal age (age at birth ≥ 40 years), primipara, multiple pregnancy, pregnancy complications, underlying maternal disease, mental disorder, maternal transport, gestational age at birth, number of preterm birth, urgent caesarean section, birth weight, Z-score of birth weight, low birth weight (< 2500 g), light for date (birth weight < 10th percentile), hospitalization at the NICU, neonatal transport, exclusive breastfeeding, bottle-feeding, no partner, welfare, and late visit. Multivariate analysis was performed using items with P < 0.2 in the univariate analysis, and risk factors that resulted in high EPDS scores were extracted.

As a sub-analysis, women were divided into two groups according to the presence of mental disorders, and the backgrounds between the two groups were compared. Risk factors for high EPDS scores in both groups were determined by univariate and multivariate analysis, respectively. In addition, for the group with mental disorders, we investigated whether any factors resulted in a high EPDS score among the differences in disease classification by International Classification of Diseases (ICD)-10, medication, and disease condition. Disease classification by ICD-10 was as follows: F10 -F19, Mental and behavioural disorders due to psychoactive substance use; F20 -F29, Schizophrenia, schizotypal and delusional disorders; F30 -F39, Mood [affective] disorders; F40 -F48, Neurotic, stress-related and somatoform disorders; F50 -F59, Behavioural syndromes associated with physiological disturbances and physical factors; F60 -F69, Disorders of adult personality and behavior; F70 -F79, Mental retardation; F80 -F89, Disorders of psychological development; F90 -F98; Behavioural and emotional disorders with onset usually occurring in childhood and adolescence; F99 -F99, Unspecified mental disorder. Medications included the variables “none”, “single-agent”, “polypharmacy”, or “interruption during pregnancy”. Disease conditions included history only, onset during pregnancy, and postpartum exacerbations.

Statistical analyses were performed as follows. Student’s t-test and chi-square test were used for univariate analysis. For multivariate analysis, binomial logistic regression analysis was performed using SPSS version 23 (IBM, Armonk, NY, USA). Differences were considered statistically significant at P < 0.05.

This study was approved by our ethics review board (29–196). All data were anonymized and participants were allowed to refuse participation by opting out.

From 2008 to 2016, the total number of births at our hospital was 1861. The EPDS questionnaire was administered to 1625 women, and the implementation rate was 87%. The characteristics of the women are presented in Table 1. Since our hospital is a university hospital with various medical departments, the proportion of pregnancy complications and underlying maternal disease was high. In addition, we have a psychiatric department, so the pregnancy rate with mental disorders was high (5.2%)

Table 1

Characteristics of the women
		Average / N	SD / %
Maternal	Age at birth (years)	33.1	± 5.1
	Young pregnant women (≤ 19 years)	22	1.4
	Advanced maternal age (≥ 40 years)	137	8.4
	Primipara (no.)	849	52.2
	Multiple pregnancy (no.)	25	1.5
	Pregnancy complication (no.)	914	56.3
	Underlying maternal disease (no.)	744	45.8
	Mental disorder (no.)	85	5.2
	Maternal transport (no.)	296	18.2
Birth	Gestational age at birth (weeks)	38.0	± 1.9
	Preterm birth (no.)	318	19.6
	Cesarean section (no.)	849	52.3
	Urgent cesarean section (no.)	395	24.3
Neonate	Birth weight (g)	2,826	± 510
	Z-score of birth weight	0.41	± 1.2
	Low birth weight (< 2500 g) (no.)	391	24.1
	Light for date (no.)	117	7.2
	Hospitalization at NICU (no.)	901	55.5
	Neonatal transport (no.)	12	0.7
Lactation	Exclusive breastfeeding (no.)	660	40.6
	Bottle-feeding (no.)	149	9.2
Social	No partner (no.)	31	1.9
	Welfare (no.)	4	0.2
	Late visit (no.)	17	1.0
SD: standard deviation; Maternal transport: woman was transferred to our hospital from another hospital due to complications; Light for date: birth weight was below the 10th percentile; NICU: neonatal intensive care unit; Neonatal transport: newborn was transported from our hospital to another hospital due to complications; Late visit: first visit was after 22 weeks

The median EPDS score was 4 (range: 0–28) point. The high-score group with an EPDS of ≥ 9 comprised 284 women, and the low score group with an EPDS of ≤ 8 comprised 1341 women. Table 2 summarizes the characteristics of both groups. Maternal age at birth, gestational age of birth, and birth weight did not differ between the two groups. The Z-score of birth weight was slightly lower in the high-score group. The rate of primipara, underlying maternal disease, mental disorder, maternal transport, preterm birth, light for date, neonatal transport, bottle-feeding, and late visit were higher in the high-score group than in the low-score group. Only the rate of exclusive breastfeeding was significantly higher in the low-score group. An item with P < 0.2 (welfare) was added to the above items with significant differences in univariate analysis, and binomial logistic regression analysis was performed. Items significantly associated with a high EPDS score of ≥ 9 were considered to indicate maternal mental disorder (P = 0.00; odds ratio [OR] 4.92; 95% confidence interval [CI] 2.98–8.11) and neonatal transport (P = 0.03, OR 4.03, 95% CI 1.16-14.0). Conversely, exclusive breastfeeding was significantly associated with a low EPDS score of ≤ 8 (P = 0.01, OR 0.65, 95% CI 0.48–0.88). (Table 3)

Table 2

Univariate analysis of the factors contributing to a high EPDS score
		High-score group EPDS ≥ 9 (N = 284)		Low-score group EPDS ≤ 8 (N = 1341)
		Average/N	SD/%	Average/N	SD/%	P-value*
Maternal	Age at birth (year)	33.0	± 5.4	33.1	± 5.1	0.688
	Young pregnant women (≤ 19 years)	5	1.8	18	1.3	0.588
	Advanced maternal age (≥ 40 years)	30	10.6	119	8.9	0.370
	Primipara (no.)	167	58.8	692	50.9	0.015
	Multiple pregnancy (no.)	4	1.4	21	1.6	0.845
	Pregnancy complication (no.)	151	53.2	763	56.9	0.250
	Underlying maternal disease (no.)	153	53.9	591	44.1	0.003
	Mental disorder (no.)	46	16.2	39	2.9	0.000
	Maternal transport (no.)	40	14.1	256	19.1	0.047
Birth	Gestational age at birth (weeks)	38.1	1.9	38.0	1.9	0.141
	Preterm birth (no.)	43	15.1	275	20.5	0.038
	Urgent cesarean section (no.)	67	23.6	328	24.5	0.757
Neonate	Birth weight (g)	2,809	± 530	2,826	510	0.540
	Z-score of birth weight	0.26	± 1.3	0.44	± 1.1	0.022
	Low birth weight (< 2500 g) (no.)	71	25.0	320	23.9	0.684
	Light for date (no.)	29	10.2	88	6.6	0.031
	Hospitalization at NICU (no.)	162	57.0	739	55.1	0.551
	Neonatal transport (no.)	5	1.8	7	0.5	0.027
Lactation	Exclusive breastfeeding (no.)	81	28.5	579	43.2	0.000
	Bottle-feeding (no.)	51	18.0	98	7.3	0.000
Social	No partner (no.)	8	2.8	23	1.7	0.218
	Welfare (no.)	2	0.7	2	0.1	0.086
	Late visit (no.)	7	2.5	10	0.7	0.010
EPDS: Edinburgh Postnatal Depression Scale; SD: standard deviation; Maternal transport: woman was transferred to our hospital from another hospital due to complications; Light for date: birth weight was below the 10th percentile; NICU: neonatal intensive care unit; Neonatal transport: the newborn was transported from our hospital to another hospital due to complications; Late visit: the first visit was after 22 weeks; no.:number
* statistically significant (P < 0.05); Bold: statistically significant

Table 3

Multivariate analysis of the factors that resulted in a high EPDS score.
		P-value*	Odds Ratio	95% Confidence Interval
Maternal	Primipara	0.24	1.18	0.90–1.56
	Underlying maternal disease	0.94	0.99	0.73–1.33
	Mental disorder	0.00	4.92	2.98–8.11
	Maternal transport	0.49	0.86	0.56–1.32
Birth	Preterm birth	0.07	0.68	0.45–1.04
	Light for date	0.06	1.58	0.99–2.54
Neonate	Neonatal transport	0.03	4.03	1.16 -14.0
Lactation	Exclusive breastfeeding	0.01	0.65	0.48–0.88
	Bottle-feeding	0.06	1.50	0.98–2.31
Social	Welfare	0.18	3.94	0.51–29.3
	Late visit	0.08	2.54	0.90–7.17
EPDS: Edinburgh Postnatal Depression Scale; Maternal transport: the patient was transferred to our hospital from another hospital due to complications; Light for date: birth weight was below the 10th percentile; Neonatal transport: newborn was transported from our hospital to another hospital due to complications; Late visit: first visit was after 22 weeks
* statistically significant (P < 0.05); Bold: statistically significant.

Since maternal mental disorders were the greatest risk factor for high EPDS score, the women were grouped depending on the presence/absence of mental disorders, and a sub-group analysis was performed. The group with mental disorders had a median EPDS of 10 in 85 women, and the group without mental disorders (i.e., 1540 women) had a median of 5. The group with mental disorders was characterized by more primipara, bottle-feeding, no partner, fewer pregnancy complications, maternal transport, preterm birth, urgent caesarean section, and exclusive breastfeeding (Table 4). This did not indicate that women with mental disorders had a lower risk of pregnancy complications, maternal transport, preterm birth, and urgent caesarean section, but rather was based on the institutional protocol at our hospital for women with high-risk pregnancies.

Table 4

Characteristics of the women with mental disorders.
		With mental disorder (N = 85)		Without mental disorder (N = 1540)
		Average/N	SD/%	Average/N	SD/%	P-value*
	EPDS score (median)	10		5		0.000
Maternal	Age at birth (years)	32.2	5.5	33.1	5.1	0.103
	Young pregnant women (≤ 19)(no.)	2	2.4	21	1.4	0.452
	Advanced maternal age (≥ 40) (no.)	7	8.2	142	9.2	0.759
	Primipara (no.)	59	69.4	790	51.3	0.001
	Multiple pregnancy (no.)	3	3.5	22	1.4	0.126
	Pregnancy complication (no.)	32	37.6	882	57.3	0.000
	Maternal transport (no.)	5	5.9	291	18.9	0.002
Birth	Gestational age of birth (weeks)	38.7	1.8	38.0	1.9	0.332
	Preterm birth (no.)	8	9.4	310	20.1	0.015
	Urgent cesarean section (no.)	11	12.9	384	24.9	0.012
Neonate	Birth weight (g)	2,887	485.9	2,822	511.2	0.256
	Z-score of the birth weight	0.24	1.3	0.42	1.2	0.161
	Low birth weight (< 2500 g) (no.)	22	25.9	369	24.0	0.687
	Light for date (no.)	8	9.4	109	7.1	0.418
	Hospitalization to NICU (no.)	50	58.8	851	55.3	0.520
	Neonatal transport (no.)	0	0.0	12	0.8	0.414
Lactation	Exclusive breastfeeding (no.)	16	18.8	644	41.8	0.000
	Bottle-feeding (no.)	37	43.5	112	7.3	0.000
Social	No partner (no.)	5	5.9	26	1.7	0.006
	Welfare (no.)	0	0	4	0.3	0.638
	Late visit (no.)	1	1.2	16	1.0	0.903
EPDS: Edinburgh Postnatal Depression Scale; SD: standard deviation; Maternal transport: patient was transferred to our hospital from another hospital due to complications; Light for date: birth weight was below the 10th percentile; NICU: neonatal intensive care unit; Neonatal transport: newborn was transported from our hospital to another hospital due to complications; Late visit: first visit was after 22 weeks; no.:number
* statistically significant (P < 0.05); Bold: statistically significant

Women without mental disease were divided into high and low EPDS score groups, and univariate analysis of risk factors was performed (Table 5). There were 238 high-score women with an EPDS of ≥ 9 points and 1302 women in the low-score group with ≤ 8 points. The rates of light for date, neonatal transport, bottle-feeding, and late visit were higher in the high-score group. Only the rate of exclusive breastfeeding was significantly higher in the low-score group. Items with P < 0.2 (primipara, preterm birth, no partner, welfare) were added to the above items with significant differences in univariate analysis, and binomial logistic regression analysis was subsequently performed. Items significantly associated with a high EPDS score of ≥ 9 in patients without mental disorder were neonatal transport (P = 0.02, OR 4.32, 95% CI 1.20-14.75) and late visit (P = 0.03, OR 3.14, 95% CI 1.12–8.85). Conversely, preterm birth (P = 0.02, OR 0.62, 95% CI 0.42–0.92) and exclusive breastfeeding (P = 0.00, OR 0.62, 95% CI 0.45–0.85) was significantly associated with the low-score group with EPDS ≤ 8 (Table 6).

Table 5

Univariate analysis of the factors contributing to a high EPDS score in the women without mental disorder.
		High-score group EPDS ≥ 9 (N = 238)		Low-score group EPDS ≤ 8 (N = 1302)
		N	%	N	%	P-value*
Maternal	Young pregnant women (≤ 19)(no.)	4	1.7	17	1.3	0.646
	Advanced maternal age (≥ 40) (no.)	26	10.9	116	8.9	0.333
	Primipara (no.)	135	56.7	655	50.3	0.069
	Multiple pregnancy (no.)	2	0.8	20	1.5	0.406
	Pregnancy complication (no.)	136	57.1	746	57.3	0.965
	Maternal underlying disease (no.)	107	45.0	552	42.4	0.463
	Maternal transport (no.)	38	16.0	253	19.4	0.209
Birth	Preterm birth (no.)	39	16.4	271	20.8	0.117
	Urgent cesarean section (no.)	61	25.6	323	24.8	0.787
Neonate	Low birth weight (< 2500 g) (no.)	60	25.2	309	23.7	0.623
	Light for date (no.)	24	10.1	85	6.5	0.049
	Hospitalization to NICU (no.)	135	56.7	716	55.0	0.622
	Neonatal transport (no.)	5	2.1	7	0.5	0.012
Lactation	Exclusive breastfeeding (no.)	73	30.7	571	43.9	0.000
	Bottle-feeding (no.)	28	11.8	84	6.5	0.004
Social	No partner (no.)	7	2.9	19	1.5	0.103
	Welfare (no.)	2	0.8	2	0.2	0.056
	Late visit (no/)	7	2.9	9	0.7	0.002
EPDS: Edinburgh Postnatal Depression Scale; Maternal transport: woman was transferred to our hospital from another hospital due to complications; Light for date: the birth weight was below the 10th percentile; NICU: neonatal intensive care unit; Neonatal transport: newborn was transported from our hospital to another hospital due to complications; Late visit: first visit was after 22 weeks; no,: number
* statistically significant (P < 0.05); Bold: statistically significant

Table 6

Univariate analysis of the factors contributing to a high EPDS score in the women with mental disorders.
		High-score group EPDS ≥ 9 (N = 46)		Low-score group EPDS ≤ 8 (N = 39)
		N	%	N	%	P-value*
Maternal	Young pregnant women (≤ 19) (no.)	1	2.2	1	2.6	0.906
	Advanced maternal age (≥ 40) (no.)	4	8.7	3	7.7	0.867
	Primipara (no.)	32	69.6	27	69.2	0.973
	Multiple pregnancy (no.)	2	4.4	1	2.6	0.657
	Pregnancy complication (no.)	15	33.3	17	43.6	0.334
	Maternal transport (no.)	2	4.3	3	7.7	0.530
Birth	Preterm birth (no.)	4	8.7	4	10.3	0.806
	Urgent cesarean section (no.)	6	13.0	5	12.8	0.976
Neonate	Low birth weight (< 2500 g) (no.)	11	23.9	11	28.2	0.653
	Light for date (no.)	5	10.9	3	7.7	0.617
	Hospitalization to NICU (no.)	27	60.0	23	59.0	0.924
	Neonatal transport (no.)	0	0	0	0	-
Lactation	Exclusive breastfeeding (no.)	8	17.4	8	20.5	0.714
	Bottle-feeding (no.)	23	50.0	14	35.9	0.191
Social	No partner (no.)	1	2.2	4	10.3	0.115
	Welfare (no.)	0	0	0	0	-
	Late visit (no.)	0	0	1	2.6	0.275
EPDS: Edinburgh Postnatal Depression Scale; Maternal transport: patient was transferred to our hospital from another hospital due to complications; Light for date: birth weight was below the 10th percentile; NICU: neonatal intensive care unit; Neonatal transport: the newborn was transported from our hospital to another hospital due to complications; Late visit: first visit was after 22 weeks; no.: number
* statistically significant (P < 0.05);

Among the women with mental disorders, 46 were in the EPDS high-score group and 39 in the low-score group. There were no differences between the two groups for any of the items, similar to the other examinations (Table 7). There were no differences between the two groups in disease classification according to ICD-10, medication, and disease condition in the women with mental disorders (Table 8).

Table 7

Multivariate analysis of the factors contributing to a high EPDS score in the women without mental disorders
		P-value*	Odds Ratio	95% Confidence Interval
Maternal	Primipara	0.25	1.19	0.89–1.59
Birth	Preterm birth	0.02	0.62	0.42–0.92
Neonate	Light for date	0.06	1.60	0.98–2.62
	Neonatal transport	0.02	4.21	1.20-14.75
Lactation	Exclusive breastfeeding	0.00	0.62	0.45–0.85
	Bottle-feeding	0.13	1.45	0.89–2.35
Social	No partner	0.67	1.24	0.46–3.39
	Welfare	0.20	3.74	0.50-28.22
	Late visit	0.03	3.14	1.12–8.85
Light for date: birth weight was below the 10th percentile; Neonatal transport: newborn was transported from our hospital to another hospital due to complications; Late visit: first visit was after 22 weeks
* statistically significant (P < 0.05); Bold: statistically significant.

Table 8

Univariate analysis of mental disorder characteristics contributing to a high EPDS score in women with mental disorders
		High-score group EPDS ≥ 9 (N = 46)		Low-score group EPDS ≤ 8 (N = 39)
		N	%	N	%	P-value*
Disease classification by the ICD-10**	F10-F19	1	2.2	0	0.0	1.000
	F20-F29	6	13.3	8	20.5	0.557
	F30-F39	21	46.7	13	33.3	0.308
	F40-F49	15	33.3	13	33.3	1.000
	F50-F59	6	13.3	4	10.3	0.923
	F60-F69	5	11.1	1	2.6	0.275
	F70-F79	3	6.7	2	5.1	1.000
	F80-F89	0	0	0	0	-
	F90-F98	1	2.2	0	0.0	1.000
Medication	None	17	37.8	16	41.0	0.936
	Single agent	16	35.6	10	25.6	0.457
	Polypharmacy	12	26.7	13	33.3	0.669
	Interruption during pregnancy	9	20.0	5	12.8	0.557
Disease condition	History only	4	8.9	6	15.4	0.563
	Onset during pregnancy	2	4.4	2	5.1	1.000
	Postpartum exacerbation	4	8.9	1	2.6	0.448
EPDS: Edinburgh Postnatal Depression Scale; ICD: International Classification of Diseases; F10-F19: Mental and behavioural disorders due to psychoactive substance use; F20-F29: Schizophrenia, schizotypal and delusional disorders; F30-F39: Mood (affective) disorders; F40-F48: Neurotic, stress-related and somatoform disorders; F50-F59: Behavioural syndromes associated with physiological disturbances and physical factors; F60-F69: Disorders of adult personality and behaviour; F70-F79: Mental retardation; F80-F89: Disorders of psychological development; F90-F98: Behavioural and emotional disorders with onset usually occurring in childhood and adolescence; F99-F99: Unspecified mental disorder.
* statistically significant (P < 0.05)
** There was duplication.

The main findings were that the main risk factors for high EPDS scores were maternal mental disorders and neonatal transport. In the group without mental disorders, neonatal transport and late visit were risk factors for high EPDS scores. Exclusive breastfeeding was strongly associated with low EPDS scores overall as well as in the group without mental disorders. Risk factors related to high EPDS scores were not extracted in the group with mental disorders.

Maternal mental disorder is a well-established risk factor for postpartum depression [17], [19]. In our study, EPDS scores tended to be high regardless of the type of mental illness. In some instances, the EPDS level was high even if the woman only had a past medical history and was not currently being managed with any medication. The history of mental illness was mainly self-reported by the woman, whereas some women did not list their past mental disorders on the questionnaire. It is important to recognise that a history of mental illness is a risk factor for postpartum depression and requires a detailed interview at the first visit. Women with mental disorders are more likely to have difficulty parenting because of their characteristics (e.g., clumsy or strength of commitment). In addition, it is known that the employment rate of women with mental disease is low [25], and many were not accompanied by a partner at our hospital. It is expected that these factors will potentiate difficulties in parenting and the life-long relationship. Women with a medical history of mental disease may face various difficulties, including postpartum depression, and thus require early mental, social, and economic intervention.

According to the Cochrane systematic review by Moore et al. [26], early mother-infant contact effectively establishes mothers' attachment behavior and mother-child interactions. The effect is shown not only during breastfeeding but also in many attachment behaviors, such as kissing after discharge. Neonatal transport deprives women of the opportunity to touch their infants early after birth, which may impede the mothers' attachment. In addition, since neonatal transfer means that the infant presents with complications, it is natural that the mother's anxiety increases.

In this study, many women exclusively breastfed in the low EPDS group. However, the causal relationship is unclear; exclusive breastfeeding may provide mental stability, or mental stability may enable exclusive breastfeeding. Oxytocin is a peptide hormone secreted by the posterior pituitary gland. It is secreted in response to cervical and uterine elongation during labor and nipple stimulation from breastfeeding, causing muscle fibers in the mammary gland to contract and promote lactation [27]. Oxytocin reduces cortisol, which is secreted in response to stress, but in women with postpartum depressive symptoms, the oxytocin levels during pregnancy and lactation are low [28], [29] or poorly regulated [30]. There are numerous reports on the early interruption of breastfeeding and postpartum depression [31], [32], [33], [34], [35], suggesting the involvement of oxytocin. However, the direct relationship between oxytocin and postpartum depression is unknown. The genotype and the reaction of oxytocin with glucocorticoids may be involved in a complicated manner [36], [37], [38], [39]. Breastfeeding may have a positive effect on maternal mental health, but in rare circumstances, considerable stress can be induced by the obsession with exclusive breastfeeding or its failure. Therefore, it is not desirable to force exclusive breastfeeding.

The strengths of this study are that it included a large cohort it examined the details of mothers with mental disease.

This study has two limitations. First, this survey was conducted at a university hospital where many women had high-risk pregnancies, and therefore the results may differ from those of the general population. Second, we were unable to follow up after the one-month postpartum medical examination. The high EPDS scores and postpartum depression were not equal. It is unknown how many of the 284 people with high EPDS scores developed postnatal depression. EPDS is a screening test for perinatal mental health problems. It is important for early detection in the women who are more likely to present with perinatal mental health problems and intervene appropriately before severe symptoms develop.

Since 2017, we have been applying the results of this survey as a reference to create and utilize a risk assessment tool that includes high EPDS scores. Women who are judged to be at high risk of mental health problems are interviewed, and social support is coordinated. In the future, we aim to evaluate the effectiveness of the intervention.

EPDS: Edinburgh Postnatal Depression Scale

NICU: neonatal intensive care unit

ICD: International Classification of Diseases

OR: odds ratio

CI: confidence interval

Ethics approval and consent to participate: This research has been approved by the Ethics Review Committee of the Gifu University Graduate School of Medicine (29-107). All data were anonymized and participants were given the opportunity to refuse participation by opting out.

Consent for publication: Not applicable

Availability of data and materials: Not applicable

Competing interests: The authors declare that they have no competing interests

Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors' contributions: Tomomi Shiga: Conceptualisation; Data curation; Formal analysis; Investigation; Methodology; Roles/Writing - original draft. Tatsuro Furui: Project administration. Ken-ichirou Morishige: Supervision; Validation; All authors have read and approved the final manuscript.

Acknowledgments: We thank to the perinatal mental health care team for collecting the data and midwives in our ward for providing excellent care to perinatal women. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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No competing interests reported.

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Examination of risk factors for high Edinburgh Postnatal Depression Scale scores: a retrospective study at a single university hospital in Japan

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