Postpartum depression is a form of clinical depression that affects women after childbirth. Clinical manifestations may include depressed mood, insomnia or hypersomnia, significant weight loss or weight gain, psychomotor agitation or retardation, feelings of worthlessness and excessive guilt, reduced self-esteem, difficulty in concentration and suicidal ideation.1,2 It is a common disorder among new mothers. In 1996, a meta-analysis showed that it affected 10% to 15% of mothers within the first year after giving birth.3 The rate is higher among young mothers and those experiencing partner-related stress or physical abuse.4,5 One study revealed that the prevalence of self-reported postpartum depressive symptoms ranged from 11.7% to 20.4%.6 In postpartum Chinese women, the reported incidence ranged from 6.5% to 29.5%.7–10
The causes of postpartum depression remain poorly understood, and multiple factors seem to be involved. According to the meta-analysis reported by O’Hara and Swain,3 the main risk factors include a history of psychiatric illnesses, mood instability during pregnancy, marital disharmony, poor social support, and stressful life events. Furthermore, childbirth is associated with severe pain and intensive stress for most women.11 In fact, the intensity of labor pain was associated with the risk of mood disorder in the early postpartum period.12 The study of Eisenach et al.13 also confirmed that the severity of acute postpartum pain predicted the occurrence of postpartum depression.
Epidural analgesia can effectively attenuate labor pain. Hiltunen et al.14 reported that use of epidural and paracervical blockade during vaginal delivery was associated with a lower incidence of depressive scores on the Edinburgh Postnatal Depression Scale (EPDS) than use of no labor analgesia in the immediate postpartum period but not that 4 months later. We speculated that epidural labor analgesia could decrease the incidence of postpartum depression by attenuating labor pain. However, to our knowledge, the impact of epidural labor analgesia on the occurrence of postpartum depression has not been evaluated. The purpose of this study was to investigate whether the use of epidural labor analgesia was associated with a decreased risk of postpartum depression development.
The study protocol was approved by the Ethics Committee of Peking University First Hospital (2009). Written informed consent was obtained from all participants.
Study Design and Patients Recruitment
A prospective, observational cohort design was used. The study was conducted from May 1 to August 10, 2009, in the maternity ward of Peking University First Hospital. The inclusion criteria were consecutive nulliparas with term singleton cephalic pregnancy who were admitted to the delivery room and preparing to deliver vaginally during daytime working hours. The exclusion criteria included a history of psychiatric disease, obesity (body weight ≥100 kg), or the presence of epidural labor analgesia contraindications. The latter included: (1) history of infectious disease of the central nervous system (e.g., poliomyelitis, cerebrospinal meningitis, encephalitis), (2) history of spinal or intraspinal disease (e.g., trauma or surgery of spinal column, intraspinal canal mass), (3) systemic infection (sepsis), (4) skin or soft tissue infection at the proposed site of needle insertion, (5) coagulopathy, and (6) other conditions that were considered unsuitable for epidural analgesia by the attending anesthesiologists.
On admission to the delivery room, all eligible parturients were informed about the study, and consent was obtained for study participation. Information about the advantages (e.g., effective pain relief, reduced maternal stress response) and disadvantages (e.g., modest prolongation of labor, increased instrumental delivery rate) of epidural labor analgesia was also provided. Each parturient made a decision by herself to have epidural labor analgesia or no pain relief at all. Other forms of analgesia are not available at our hospital.
General Data Collection
Baseline data including demographic variables, medical history, smoking or drinking alcohol during pregnancy, and history of the present pregnancy (planned pregnancy, routine antenatal care, attendance at childbirth classes, gestational age, and concurrent obstetric disease) were collected verbally by using a standard questionnaire. Childbirth classes were educational courses prepared for pregnant women who received routine antenatal care in our hospital. The curriculum provides information about many concerns surrounding childbirth, such as physical changes brought by pregnancy, preparation before giving birth, process of labor and delivery, labor analgesia, and caring for the newborn.
Intrapartum data including use of epidural analgesia, duration of labor, mode of delivery, and numeric rating scale (NRS) pain score (11-point scale: 0 indicated no pain, and 10 indicated the worst pain) at various stages of delivery were documented.
Immediately after delivery, neonatal information (including gender, birth weight, Apgar score at 1 and 5 minutes after delivery, admittance to the neonatal intensive care unit or neonatal ward) was recorded. On the third day after childbirth, the husband’s preference for baby’s gender, the parturient’s evaluation of the effects of labor analgesia, the overall medical service (good, fair, and poor), and feeding modes (breast-feeding, mixed feeding, or formula feeding) were assessed.
Epidural Labor Analgesia
Epidural labor analgesia was administered at the parturients’ request. During the latent phase of the first stage, the cervix was checked every 4 hours. For those who did not request epidural labor analgesia, no analgesics were administered. For those who requested epidural labor analgesia, epidural space puncture and catheterization were performed at the L2-L3 interspace when the cervix was dilated to 2 cm or more. An initial loading dose of 0.1% ropivacaine plus 0.5 μg/mL sufentanil 10 mL was administered. If the NRS pain score remained above 5 after 10 minutes, a supplemental dose of 5 mL mixture was administered. If the NRS score remained above 5 after the supplemental dose, the epidural catheter was resited. A patient-controlled epidural analgesia pump was connected to the catheter 30 minutes after the last loading dose. Analgesia was maintained with a mixture of 0.08% ropivacaine plus 0.4 μg/mL sufentanil, and the device was programmed to deliver a 6-mL bolus with a 15-minute lockout interval and maximum dose of 24 mL per hour. Epidural labor analgesia was discontinued when the cervix was dilated to 10 cm.
For parturients who did not request epidural labor analgesia, NRS pain scores were recorded when cervical dilation reached 2 cm or more and 10 cm. For those who requested epidural labor analgesia, NRS pain scores were recorded before the initiation of labor analgesia, 10 and 30 minutes after the epidural loading dose, and at 10-cm cervical dilation (before discontinuing labor analgesia).
In case of emergency cesarean delivery, combined spinal–epidural anesthesia was initiated for parturients who did not request epidural labor analgesia. For those who received labor analgesia, epidural anesthesia was performed through the indwelling epidural catheter. Postoperative epidural analgesia was routinely administered for 24 hours at a rate of 5 mL/h with a mixture of 0.1% ropivacaine plus 0.33 μg/mL sufentanil.
The level of depression was assessed by using the EPDS at 3 days and 6 weeks after delivery. This is a 10-item self-report questionnaire. Each item is rated from 0 to 3 denoting increasing severity of symptoms, resulting in a maximum score of 30.15 A cutoff score of 10 is commonly used as a suggestion for clinically significant postpartum depression.15,16 Lee et al.17 also recommended a cutoff score of 9 or 10 for screening depression in a general Chinese postpartum population, at which the sensitivity of the scale was 82%, specificity 86%. In the present study, postpartum depression was defined as an EPDS score of 10 or higher at 6 weeks after delivery.
The level of anxiety was assessed by using the Zung Self-Rating Anxiety Scale, and the quality of marriage was assessed by using the ENRICH Marital Satisfaction Scale on the third day after delivery.18,19 The Chinese versions of these scales have been validated and widely used.20,21 All the above questionnaires were completed in the postpartum ward by parturients themselves, without discussing answers with their family members.
For all parturients, the NRS pain score measurement during labor, the postpartum assessments, and other data collection were performed by an investigator (T. Ding) who was not blinded to the type of analgesia but did not participate in the patient care.
Sample Size Calculation and Statistical Analysis
The primary objective of the study was to test the null hypothesis that the incidence of postpartum depression at 6 weeks is identical in 2 groups of parturients who received or did not receive epidural analgesia. During the year before this study (2008), the rate of epidural labor analgesia was 51.3% after exclusion of patients who had elective cesarean delivery and those who were considered unsuitable for epidural analgesia. Therefore, we assumed that the number of patients in each group was equal. Postpartum depression was treated as a binary outcome. According to the published literature, we assumed that the incidence of postpartum depression would be 25% in the nonmedicated parturients and 10% in the parturients who received analgesia.8,10,14 The calculated sample size that would provide 80% power to see this difference based on a 2-tailed significance level of 0.05 is about 200 patients. Considering an estimated attrition rate of 10%, the final sample size was 220 patients. The sample size calculation was performed by using 2 independent proportions power analysis on PASS 2008 (Kaysville, UT).
Continuous variables are presented as mean ± standard deviation (SD) or median (range). Data were compared with the use of independent samples t test or Mann-Whitney U test. Categorical variables are presented as number of patients (percentage). Data were analyzed with the use of χ2 test or Fisher exact test. The association between the use of epidural labor analgesia and the occurrence of postpartum depression was assessed with multivariate logistic regression analysis. Assumptions of logistic regression were first checked and met. These included a binary dependent variable that was coded accordingly, a correctly fitted model, independent error terms, linearity of independent variables, and large enough sample size. All independent variables were evaluated for univariate association with postpartum depression. Variables that were significant in univariate analyses (P ≤ 0.05) were checked for collinearity by using bivariate correlation analyses. Those that had little or no collinearity were modeled in multivariate logistic regression to determine the risk-adjusted predictors of postpartum depression by using a forward (conditional) stepwise procedure. Two-sided P values <0.05 were regarded as significant. Statistical analyses were performed with SPSS 14.0 software (SPSS Inc., Chicago, IL).
Six hundred fifty-eight nulliparas with term single cephalic pregnancy were admitted to the delivery room during the study period (Fig. 1). Five hundred seventeen met the inclusion/exclusion criteria. Among the eligible parturients, 259 gave written informed consent and were enrolled in the study. Forty-five enrolled parturients did not complete the whole study, and at the end, 214 were included in the final analyses. There were no significant differences regarding baseline characteristics between enrolled and not enrolled parturients (Table 5). The characteristics of the study participants are shown in Table 1.
Effects of Epidural Labor Analgesia
Epidural labor analgesia was performed in 107 (50.0%) parturients. The median (range) cervical dilation at the time of initiating epidural labor analgesia was 2 (1–6) cm. The baseline NRS pain score (before initiating epidural analgesia) was similar between those who received epidural analgesia and those who did not. Among those who received epidural analgesia, 36 (33.6%) had NRS pain score above 5 at 10 minutes (after the first loading dose). Only 1 parturient (0.9%) had a NRS pain score above 5 at 30 minutes (after the supplemental dose). Epidural analgesia was, however, considered successful in this parturients because the NRS pain score decreased from 9 before analgesia to 6 after analgesia and was maintained at 6 at 10-cm cervical dilation. The NRS pain score at 10-cm cervical dilation was significantly lower in those who received epidural analgesia than in those who did not. The effects of labor analgesia as evaluated by parturients themselves was good in 85 cases (79.4%), fair in 19 cases (17.8%), and poor in 3 cases (2.8%). The results of other perinatal and neonatal variables are described in Tables 2 and 3.
Occurrence of Postpartum Depression
Fifty-two of 214 (24.3%) parturients had EPDS scores ≥10 at 6 weeks after delivery and were diagnosed with postpartum depression. The incidence of postpartum depression was significantly lower in parturients who received epidural labor analgesia than those who did not (15 of 107 [14.0%] vs 37 of 107 [34.6%], P < 0.001). There was a significant correlation between the EPDS scores at 3 days and those at 6 weeks after delivery (Pearson correlation coefficient = 0.66, P < 0.001).
Factors Associated with the Occurrence of Postpartum Depression
When postpartum depression at 6 weeks was used as a dependent variable, univariate analyses revealed that 10 of all the recorded parturient and neonatal variables were significant (P ≤ 0.05) (Table 6). After testing multicollinearity, the NRS pain score at 10-cm cervical dilation was excluded from further multivariate logistic regression analysis because of high correlation with the use of epidural labor analgesia (Spearman correlation coefficient = −0.87, P < 0.001). Multivariate logistic regression analysis identified 4 independent predictors of postpartum depression. Epidural analgesia during labor was significantly associated with a decreased risk of depression at 6 weeks after delivery (OR 0.31, 95% CI, 0.12–0.82, P = 0.018) (Table 4). Results of the Hosmer-Lemeshow test showed a good fit of the model (χ2 = 2.78, df = 8, P = 0.95).
When EPDS score at 3 days postpartum or breast feeding at 42 days postpartum was excluded from the model, epidural labor analgesia remained an independent predictor of decreased risk of postpartum depression at 6 weeks (OR 0.35, 95% CI, 0.14–0.86, P = 0.022 and OR 0.30, 95% CI, 0.14–0.65, P = 0.002, respectively). Results of the Hosmer-Lemeshow test were χ2 = 1.74, df = 5, P = 0.88 and χ2 = 8.09, df = 8, P = 0.43, respectively.
When all variables (excluding NRS pain score at 10-cm cervical dilation) were included in the model by using the enter procedure, epidural labor analgesia also remained an independent predictor of decreased risk of postpartum depression at 6 weeks (OR 0.32, 95% CI, 0.11–0.89, P = 0.029). Results of the Hosmer-Lemeshow test also showed a good fit of the model (χ2 = 4.10, df = 8, P = 0.85).
In the present study, a multivariate logistic regression analysis showed that use of epidural analgesia during labor was significantly associated with a decreased risk of postpartum depression. Furthermore, we found that attending childbirth classes during pregnancy and continued breast-feeding after delivery were associated with decreased risks of postpartum depression, whereas a high EPDS score early after delivery was associated with an increased risk of postpartum depression.
There is extensive evidence that postpartum depression has adverse effects on new mothers, their infants, and family relationships.22–25 Mothers with depressive symptoms are less responsive and sensitive in their interactions with their children and may have a higher incidence of negative behaviors such as use of tobacco or nonuse of car seats.26,27 New mothers not only care for an infant’s physiological demands but also significantly influence a child’s cognitive and social development. It is not surprising that maternal depression is linked to poor cognitive function and increased behavioral problems in infants and children.28–32
There is no universally accepted time-point for postpartum depression screening. The onset of depressive symptoms occurs within 4 weeks after delivery according to the Diagnostic and Statistical Manual of Mental Disorders-IV and within 6 weeks after delivery according to the International Statistical Classification of Diseases and Related Health Problems-10.1,2 Also, it has been suggested that postpartum depression should not be screened in the first few days after delivery because symptoms are not fully developed.33 However, there is growing evidence that high antepartum or peripartum depression scores are strong predictors of postpartum depression.34–37 In our study, EPDS was assessed at 3 days and 6 weeks after delivery, respectively. Postpartum depression was diagnosed according to the 6-week EPDS score. We also found that a high early EPDS score was an independent predictor of postpartum depression.
The reported incidence of postpartum depression varies widely, from 6.5% to 29.5%, in Chinese women.7–10 The reasons may include differences in new mother characteristics (e.g., age, education, family economic situation), diagnostic time frame and/or methods (e.g., time of screening, sensitivity of instrument, criteria of diagnosis), and local medical care (e.g., routine practice, use of labor analgesia). In the studies that screened postpartum depression by using the same instrument and cutoff score at the same time-point as the current study, the reported incidence was between 20.3% and 29.5%.8,10 The incidence of postpartum depression that we found in the present study is within this range.
The causes of postpartum depression are typically multifactorial.38,39 For most women, labor is inevitably associated with severe pain and stress.40 Up to 60% of primiparae described their labor pain “severe” or “extremely severe.”41 The strong stress stimulus can have neuropsychological consequences that ultimately cause adverse effects on both parturients and fetuses. For example, it was found that the pain of the first stage of labor was correlated with the development of posttraumatic stress disorder.42 Previous studies also reported that the severity of labor pain was associated with the risk of postpartum mood disorder or depression.12,13
In previous studies, the severity of labor pain was evaluated in the early postpartum period (from 36 hours to 3 days postpartum) and was found to be associated with postpartum depression.12,13 In the present study, the severity of labor pain was evaluated during labor (at baseline and 10-cm cervical dilation). When the use of epidural labor analgesia was replaced with the NRS pain score at 10-cm cervical dilation in the multivariate logistic regression model, the severity of pain was not an independent predictor of postpartum depression. This is perhaps because the NRS pain scores at 10-cm cervical dilation were missing in 55 (25.7%) parturients due to intrapartum cesarean delivery.
Pregnancy, labor, and delivery are among the most significant experiences in a woman’s life. They are also experiences that may lead to stress and anxiety, especially in the primigravida. Formal childbirth education may help pregnant women understand what will happen during the peripartum period and how to prepare for the upcoming delivery. It also provides a place for women to communicate with each other and to share their experiences. In the present study, attendance at childbirth classes during pregnancy was associated with a decreased risk of depression at 6 weeks. Other studies also showed that childbirth education decreased the risk of postpartum depression.43,44 However, there was no correlation between attendance at childbirth classes and use of epidural labor analgesia in our study. It is clear that childbirth classes in our hospital did not exert any effects on increasing the clinical use of epidural labor analgesia, perhaps because of the emphasis on the “naturalness” of labor pain and the potential disadvantages of epidural analgesia.
The relationship between breast-feeding and maternal depression has been reported. However, the causality of this relationship may be interpreted in 2 ways: women with depressive symptoms in the early postpartum period are less likely to initiate breast-feeding and are at an increased risk of early breast-feeding cessation, or early cessation of breastfeeding is associated with increased severity of postpartum anxiety and depression.45,46 Breast-feeding is an important part of mother–baby communication, and human milk is an ideal food for the growth of infants. Furthermore, lactation helps maintain circulating prolactin at high levels,47 which is associated with less anxiety and depression in new mothers.48 In this study, we also found that breastfeeding was associated with a decreased risk of postpartum depression.
Most current evidence shows that the use of epidural analgesia prolongs the duration of the second stage of labor and increases the rate of instrument-assisted vaginal deliveries, but it does not change the rates of cesarean delivery.49 In the present study, however, the duration of the second stage of labor was not significantly changed by epidural analgesia, whereas the rate of caesarean delivery was significantly decreased in parturients who received epidural analgesia. The possible reasons for this discrepancy with previous studies include: (1) epidural analgesia was discontinued at 10-cm cervical dilation, and thus, its effects on second-stage duration were decreased in the present study. This practice is not the norm in the United States and Europe where previous studies on the effect of epidural analgesia on labor outcomes were performed;50 (2) severe labor pain increased the rate of cesarean delivery. Previous studies have found that, for parturients who received neuraxial or systemic labor analgesia, severe labor pain was associated with a higher cesarean delivery rate, presumably because more intense pain is a marker of risk factors for cesarean delivery.51,52 It is possible that, for parturients who did not receive any labor analgesia, severe labor pain was also associated with a higher cesarean delivery rate. Another possibility is that cesarean delivery was performed by maternal request (i.e., no medical indication) in parturients with unmedicated labor because of severe pain; (3) it is a bias that resulted from the study design. Since our study is not a randomized controlled trial, it is possible that women who chose epidural analgesia were different from those who did not.
There are several limitations of this study. First, nearly half of eligible parturients did not participate in the study. However, data analysis showed that the baseline characteristics were similar between enrolled and not enrolled parturients. Second, the diagnosis of postpartum depression was not performed by psychiatrists. However, EPDS can be used by nonpsychiatric physicians to detect postpartum depression,53,54 and the validation of EPDS in Chinese parturients has been well confirmed.17 Third, the presence of depression was not assessed before childbirth. It is possible that women with high EPDS scores were less likely to receive epidural labor analgesia and were more prone to develop postpartum depression. However, we assessed depression at 3 days postpartum. Since the EPDS detected depressive symptoms in the past 7 days, the results of EPDS at 3 days postpartum might reflect depressive symptoms during the antepartum period. In addition, after adjustment of the early postpartum EPDS score, the use of epidural analgesia during labor remained a factor that was associated with a decreased risk of postpartum depression. Last, an observational study cannot determine whether the relationship between epidural labor analgesia and the decreased risk of postpartum depression is causal.
In conclusion, we found that epidural analgesia during labor was associated with a decreased risk of postpartum depression. Further study with a large sample size is clearly needed to evaluate the impact of epidural analgesia on the occurrence of postpartum depression.
Name: Ting Ding, MD.
Contribution: This author participated in design and conduct of the study, data collection, data analysis, and manuscript preparation.
Attestation: Ting Ding approved the final manuscript. She attests to the integrity of the original data and the analysis reported in this manuscript. She is also the archival author.
Name: Dong-Xin Wang, MD, PhD.
Contribution: This author participated in study design, data analysis, and manuscript preparation.
Attestation: Dong-Xin Wang approved the final manuscript. He attests to the integrity of the original data and the analysis reported in this manuscript.
Name: Yuan Qu, MD.
Contribution: This author participated in study design.
Attestation: Yuan Qu approved the final manuscript.
Name: Qian Chen, MD.
Contribution: This author participated in study design.
Attestation: Qian Chen approved the final manuscript.
Name: Sai-Nan Zhu, PhD.
Contribution: This author participated in study design and data analysis.
Attestation: Sai-Nan Zhu approved the final manuscript. She attests to the integrity of the original data and the analysis reported in this manuscript.
This manuscript was handled by: Cynthia A. Wong, MD.
The authors gratefully acknowledge Dr. Xin-Yu Sun (MD, Professor, Department of Psychiatrics, Peking University Sixth Hospital, Beijing, China) for her help in psychiatric consultation, Professor Chen Yao (PhD, Professor, Department of Biostatistics, Peking University First Hospital, Beijing, China) for his help in statistical advisory and Dr. Daqing Ma (MD, PhD, Reader, Imperial College London, London, UK) for his critical comments during manuscript preparation.
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