Posttraumatic Stress Disorder after Pregnancy, Labor, and Delivery ABSTRACT

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1 JOURNAL OF WOMEN S HEALTH Volume 13, Number 3, 2004 Mary Ann Liebert, Inc. Posttraumatic Stress Disorder after Pregnancy, Labor, and Delivery MARSHA M. COHEN, M.D., 1,2 DONNA ANSARA, M.Sc., 1,2 BERIT SCHEI, M.D., Ph.D., 3 NOREEN STUCKLESS, Ph.D., 1,4 and DONNA E. STEWART, M.D. 5 ABSTRACT Objectives: Other studies of posttraumatic stress disorder (PTSD) after birth did not include questions about prior traumatic life events. This study sought to determine if a difficult birth was associated with symptoms of PTSD as well as considering sociodemographics, history of violence, depression, social support, and traumatic life events. Methods: New mothers were recruited on the postpartum ward of six Toronto-area hospitals (n 5 253) and were interviewed by telephone 8 10 weeks postpartum (n 5 200). We dichotomized the postpartum stress (PTS) into high PTS (answered yes to 3 or more items) or low PTS (answered yes to 0 2 items). We calculated the odds ratios between difficult birth, other factors, and the binary PTS variable. Results: Results of multivariable logistic regression revealed that no factor suggestive of a difficult birth was significantly related to high PTS scores, except having two or more maternal complications (odds ratio [OR] 5 4.0, 95% confidence interval [CI] ). Other independent predictors of high PTS scores were depression during pregnancy (OR , 95% CI ), having two or more traumatic life events (OR 5 3.2, 95% CI ), being Canadian born (OR 5 3.2, 95% CI ), and having higher household income (lowest income group, OR 5 0.1, 95% CI ), intermediate income group OR 5 0.4, 95% CI ). Conclusions: In this study, postpartum stress symptoms appeared to be related more to stressful life events and depression than to pregnancy, labor, and delivery. INTRODUCTION THE FOURTH EDITION OF Diagnostic and Statistical Manual of Mental Disorders 1 (DSM-IV) defines posttraumatic stress disorder (PTSD) as a reaction to an event, either personally experienced or witnessed, that involves actual or threatened death or serious injury or a threat to the physical integrity of self or others. As well, the response to the traumatic event must involve intense fear, 1 Centre for Research in Women s Health, Toronto, Canada. 2 Department of Health Policy, Management & Evaluation and The Clinical Epidemiology & Health Care Research Program, University of Toronto, Toronto, Canada. 3 Department of Community Medicine and General Practice, Norwegian University of Science and Technology, Trondheim, Norway. 4 Society, Women and Health Program, Sunnybrook and Women s College Health Sciences Centre, the Centre for Addiction and Mental Health, and Department of Psychiatry, University of Toronto, Toronto, Canada. 5 University Health Network, Women s Health Program, and Women s Health, University of Toronto, Toronto, Canada. This work was supported by the Atkinson Foundation and the Centre for Research in Women s Health. 315

2 316 helplessness, or horror. The three principal symptoms of PTSD are (1) reexperiencing the traumatic event (criterion B, e.g., nightmares, flashbacks, intrusive and recurrent thoughts of the event), (2) persistent avoidance of stimuli associated with the trauma and numbing of general responsiveness (criterion C), and (3) increased arousal (criterion D, e.g., difficulty sleeping, irritability, hypervigilance, difficulty concentrating). In contrast to earlier versions of the DSM that require exposure to a traumatic event that is generally outside the range of usual human experience, the DSM-IV allows a broader range of experiences provided they precipitate acute feelings of fear, helplessness, or horror. Several authors have proposed that a posttraumatic stress (PTS)-like disorder may occur after a distressing pregnancy, labor, or delivery. 2 6 This hypothesis suggests that a difficult or traumatic birth may act as a significant stressor in a fashion similar to known stressors, such as violence or war, and living through this experience might trigger the symptoms of PTS (i.e., reexperiencing the traumatic event, increased arousal, and avoidance of stimuli associated with the event). Other study findings have supported this hypothesis. A large Swedish study investigating PTSD after childbirth (between 1 and 13 months) found that 1.7% of 1650 study women met the criteria of a PTSD profile. 6 Similarly, a study from Australia showed that of 499 participants interviewed 4 6 weeks after birth, 5.6% met the DSM- IV criteria for PTSD. 7 A study of 264 women in the U.K. found that 3% of respondents endorsed questionnaire items suggestive of PTSD 6 weeks postpartum, 8 and another study of 289 women from the U.K. found that 2.8% of women fulfilled the criteria for PTSD at 6 weeks postpartum. 9 Finally, a prospective study of 103 U.S. women reported that 1.9% met the DSM-IV criteria for PTSD 4 weeks after childbirth. 10 These studies suggest that about 2% 6% of women will experience a PTSD reaction at some point in the early period after childbirth. Previous studies have examined potential factors that may explain or be associated with PTSD after childbirth. These include sociodemographic factors 4,6,8 (e.g., age, education), pregnancy, labor and delivery-related factors, 4,9,10 obstetrical interventions, 7 coping or expectations of labor and birth, 4,8,10 and prior psychiatric history 6,8,9 (e.g., depression during pregnancy). One study 10 found that antecedent factors, including a history of sexual assault and social support, were predictive of PTSD. A recent review of PTSD found that prior trauma was a significant factor in predicting PTSD. 11 To our knowledge, however, none of the previous studies of PTSD after childbirth have examined such issues as traumatic life events and interpersonal violence. To shed more light on whether a difficult birth is associated with symptoms of PTSD, we conducted a study to determine the proportion of women who exhibited the symptoms of PTS 2 months after birth and the factors associated with elevated symptoms of PTSD. Participants MATERIALS AND METHODS After receiving ethics approval from the university and participating hospitals, a pilot study aimed at recruiting 240 women was carried out at six hospitals in the Toronto area (three teaching and three community hospitals). Recruitment took place between January 1999 and September Women were eligible for the study if they were 18 years of age or older, spoke and understood English, delivered a full-term singleton infant, and consented to participate. We excluded women who did not understand English, did not give consent (for language or other reasons), could not be easily contacted for the postpartum interview (e.g., no telephone), or were giving up the child for adoption. As well, women who had delivered premature or multiple infants, infants with major congenital anomalies or needing neonatal intensive care, stillbirths or early neonatal deaths were excluded as we thought that the mothers experience with these infants would be highly stressful because of the circumstances related to the infant rather than to the experience of childbirth per se. Data collection COHEN ET AL. On the day after delivery, eligible women were approached on the postpartum ward of the hospital and were invited to participate in the study. Two female research assistants identified eligible women (with the assistance of the postpartum ward staff), and as many women as possible were approached. Our ability to recruit varied by length of hospital postpartum stay, the presence of visitors, and other factors.

3 PTSD AFTER BIRTH 317 Women were asked if they would participate in a study about women s health after pregnancy. They were told that the study would include sensitive items but were not specifically told the study research questions. The study protocol was explained to them, and a consent form and information sheet were provided. A brief in-hospital interview was undertaken at this time to collect sociodemographic information (e.g., education, employment, family income). Women were asked if they would consent to a telephone interview at 8 10 weeks postpartum and a clinical chart review. Each woman was contacted by telephone to set up a convenient time during which the interview could take place in private. Up to eight telephone calls were tried before a woman was considered a nonrespondent. For those who were still interested, a telephone interview of minutes was undertaken in which questions about PTS were included. In addition, women were asked a number of questions related to their personal history of depression, the pregnancy, their experience of labor and delivery, social support after the birth, traumatic life events, a history of violence, and depression during the pregnancy. Measures Posttraumatic stress (PTS). We used the Davidson Trauma Scale (DTS), 12 a 17-item questionnaire measuring each of the 17 DSM-IV symptoms. The DTS measures the severity and frequency of PTSD symptoms in the preceding week on a 5-point scale (0 4). In the present study, respondents first indicated whether or not they had experienced each of the 17 symptoms during the last 7 days, then rated the severity of the symptoms to which they responded yes (no 5 0, not at all distressing 5 1, mildly distressing 5 2, distressing 5 3, very distressing 5 4). Eight of the 17 items refer specifically to the birth experience (e.g., Have you felt as if the pregnancy, labor, and birth were recurring?, Have you had bad dreams about this?), whereas the remaining 9 items are generic (e.g., Have you had difficulty enjoying things? Have you had difficulty concentrating?) A validation study using 353 women and men with different trauma experiences (i.e., rape, combat, natural disaster, mixed trauma survivors) revealed that the DTS has good test-retest reliability (r ) and internal consistency (r ). 12 Concurrent validity was obtained against the Structured Clinical Interview for DSM-III-R (SCID), with a diagnostic accuracy of 83% at DTS score of 40. The sensitivity was 0.69, specificity 0.95, positive predictive value 0.92, negative predictive value 0.79, and efficiency In this study, we defined possible PTSD when respondents had to answer distressing or very distressing to at least one symptom of intrusive reexperiencing, at least three symptoms of avoidance and numbing, and at least two symptoms of hyperarousal. History of depression and panic attacks. The following three variables were evaluated: (1) depression prior to pregnancy, (2) depression during pregnancy, and (3) panic attacks during pregnancy. These potential risk factors were measured as binary variables. Respondents were asked whether or not they had been depressed or had panic attacks during these time frames. Postpartum depression. The study used the Edinburgh Postnatal Depression Scale (EPDS). 13 The 10-item EPDS instrument has been widely used in the study of postpartum depression in various settings and among different populations History of violence. For sexual abuse as an adult, we used the sexual violence question from the revised Conflict Tactics Scales (CTS2) 17 and added two additional questions: As an adult, did someone make you touch them sexually, or did they touch you sexually when you did not want this? and As an adult, has someone forced you to have sex when you did not want to? Any positive reply to these questions was considered as sexual abuse. For sexual abuse as a child, we asked: As a child before you were 14, did anyone physically abuse you? and Did you have any unwanted sexual experiences before the age of 14? A positive reply to either question indicated sexual abuse. For physical abuse as an adult, we used the revised CTS2 17 or the Abuse Assessment Screen. 18 One additional question was added: Were you seriously physically attacked or assaulted? We considered a positive response to any question to be indicative of physical abuse. For emotional abuse, women were asked questions from the Canadian Violence Against Women Survey 19 or a modified version of a psy-

4 318 COHEN ET AL. chological mistreatment measure. 20 Respondents had to endorse three or more items for emotional abuse. Traumatic life events. To assess traumatic life events, a subset of 12 questions used in the National Comorbidity Survey (NCS) 21 were used (5 questions about sexual abuse were excluded). The 7 questions asked about direct experience in a war; life-threatening accident; involvement in a fire, flood, or natural disaster; witnessing someone badly injured or killed; being threatened by a weapon, held captive, or kidnapped; suffering a great shock because one of the events happened to someone close to you; having any experiences that most other people never go through. 21,22 We grouped responses into two categories (two or more events, one or no events). TABLE 1. Difficult birth. We included a number of variables to examine pregnancy, labor, and delivery. These included having an unplanned pregnancy, having any perineal trauma, having an episiotomy, having a long labor (12 or more hours), having labor induced, having an assisted or cesarean birth, experiencing a severe level of pain during labor and birth, and two or more complications of labor and delivery (e.g., heavy bleeding after birth, uterine infection, urinary tract infection, retained placenta). Statistical analyses Descriptive statistics were calculated for all variables. For each item on the DTS, we determined the mean and median number of positive responses. We also determined the mean and NUMBER OF WOMEN ANSWERING YES AND MEAN SCORES a FOR PTS EVENTS IN THE PREVIOUS 7 DAYS No. of women Mean Median 25th 75th Maximum Item answering yes score score percentile score Pregnancy, labor, and delivery-related items 1. Have you had painful images, memories, or 24/ thoughts of the pregnancy or labor and birth? 2. Have you had bad dreams about this? 1/ Have you felt as if the pregnancy, labor, and 6/ birth were recurring? 4. Have you been upset by something that 15/ reminded you of your pregnancy, labor, or birth? 5. Have you been avoiding thoughts or feelings 5/ about this? 6. Have you been avoiding doing things or going 8/ into situations that remind you about your pregnancy, labor, or birth? 7. Have you found yourself unable to recall 18/ important parts of the event? 17. Have you been physically upset by reminders of 4/ your pregnancy, labor, or birth? General items 8. Have you had difficulty enjoying things? 14/ Have you felt distant or cut off from other 45/ people? 10. Have you been unable to have sad or loving 6/ feelings? 11. Have you found it hard to imagine having a long 10/ life fulfilling your goals? 12. Have you had trouble falling or staying asleep? 30/ Have you had difficulty concentrating? 49/ Have you been very irritable or had outburts of 70/ anger? 15. Have you felt on edge, been easily distracted, or 54/ had to stay on guard? 16. Have you been jumpy or easily startled? 27/ All items 0/ a Each item was coded as: 0 5 no, 1 5 not at all distressing, 2 5 mildly distressing; 3 5 distressing, 4 5 very distressing.

5 PTSD AFTER BIRTH 319 TABLE 2. median of the severity ratings (0 4) for each item (Table 1). We next determined the proportion of women who scored 3 or 4 (distressing or very distressing) on subscales of the DTS (intrusiveness, avoidance, and hyperarousal) as well as the number of women scoring 3 or 4 on the stressor-related items (i.e., pregnancy, labor, or delivery) and the general items (not specifying the event) (Table 2). We also determined the proportion of women meeting the study criteria for possible PTSD. Because few women were expected to meet the criteria for full PTSD, we examined the scores on the DTS in different ways. Although women may not meet the criteria for PTSD, it is likely that endorsing more items on the DTS would indicate more postpartum stress. First, we subclassified the items as relating specifically to the traumatic event (i.e., pregnancy, labor, and delivery) or general items (not specifying the event). Although we considered using scores on the DTS as a continuous (linear) variable in the analysis, we were unable to do so because scores on the DTS were highly positively skewed (most women answered no to most questions). Therefore, rather than the actual score, we used frequencies of yes or no responses for individual items. Next, we dichotomized the outcome variable into a new variable, high PTS (answered yes to 3 or more items) or low PTS (answered yes to 0 2 items). This cutoff was based on the 75 percentile of response scores. For the next step, we calculated the unadjusted relationship between the difficult birth variables and the binary PTS variable using chi-square or Fisher s exact tests. We also used chi-square or Fisher s exact test to assess the relationships between the other variables of interest (e.g., sociodemographic factors, depression, violence, traumatic life events, social support) and PTS (high/low). Variables were screened for inclusion in a logistic regression analysis if they were associated with PTS at p, 0.05 in the bivariate analysis. Variables that met this criterion were forced into a multivariable logistic regression model to determine the adjusted associations between these covariates and PTS. To obtain the final parameter estimates, a final logistic regression model was run that contained only those variables that were significant (at p, 0.1) in the multivariable model. RESULTS Two hundred fifty-three women were recruited from six hospitals. Of those who were approached for participation (n 5 332), 76% consented (n 5 253). Participation rates varied across the six hospitals, ranging from 60.2% to 87%. Of the 253 women, 53 were lost to follow-up at 8 weeks (20.8%), leaving 200 women in the study. Two women did not complete all the items on the DTS, and, thus, this study reports on 198 women. Those lost to follow-up were different from the interviewed women in that they had less education, had lower income, and were more likely to be born outside of Canada. With respect to scores on the DTS, most women said yes to at least one item (71.7 %) and 33% said yes to three or more items. The median number of symptoms reported was 2 (25 75 percentile, 0 3). The mean and median scores for the severity ratings (0 5 no to 4 5 very distressing) for the scale were 0.24 and 0.12, respectively (25 75 percentile, ) (Table 1). PROPORTION OF WOMEN IN SUBSETS OF PTSD SYMPTOMS No. (%) of women indicating distressing or very distressing On 1 item On 3 or more items Item n (%) n (%) Overall (n 5 17 items) 50 (25.2) 12 (6.1) Intrusiveness (n 5 5 items) 13 (6.6) 1 (0.5) Avoidance (n 5 7 items) 12 (6.1) 2 (1.0) Hyperarousal (n 5 5 items) 40 (20.2) 6 (3.0) Pregnancy-related items (n 5 8 items) 15 (7.6) 1 (0.5) General items (n 5 9 items) 43 (21.7) 11 (5.6) Meeting criteria for PTSD 0

6 320 COHEN ET AL. These data show that for individual items, the mean scores of the severity rating tended to be low because most people indicated no for the items. The mean scores appeared to be higher for the general items compared with the pregnancyrelated items. The item endorsed most was Have you been very irritable or had outbursts of anger? (35.5%), and the item least endorsed was Have you had bad dreams about your pregnancy, labor, or birth? (0.5%). Examining the proportion of women who reported that a symptom was distressing or very distressing (score 3 4), 50 women (25.2%) found at least one item on the scale was distressing, and 12 women (6.1%) indicated at least three or more items were distressing (Table 2). More respondents found symptoms of hyperarousal as being distressing (20.2% saying yes to at least one item, and 3.0% saying yes to three or more items). More women reported that the general symptoms were distressing than reported the TABLE 3. pregnancy-related symptoms were distressing (21.7% vs. 7.6%). Overall, there were 3 women (1.5%) who responded yes to at least one symptom of intrusive reexperiencing, at least three symptoms of avoidance and numbness, and at least two symptoms of hyperarousal. None of the 3 women found all of these symptoms to be distressing or very distressing, however. Thus, there were no women who met our predefined study criteria for possible PTSD. Results of the chi-square tests assessing the association between high PTS (i.e., indicating yes to three or more symptoms on the DTS) and factors suggestive of a difficult birth are shown in Table 3. The only obstetrical factor suggestive of a difficult birth that was significantly associated with high PTS scores was having two or more maternal complications after labor and delivery (chi-square (1, n 5 198) , p ). The relationships between the other factors (sociodemographic, depression, traumatic life ASSOCIATION BETWEEN HIGH OR LOW PTS AND FACTORS SUGGESTIVE OF A TRAUMATIC BIRTH No. of High PTS a Low PTS Item women (%) (%) p value b Perineal trauma Yes (1st 4th degree) No Episiotomy Yes No Length of labor 121 hours ,12 hours Induction of labor Yes No Mode of birth Spontaneous Forceps/vacuum assisted Cesarean section Level of pain None/very little/mild Moderate/severe/very severe Maternal complications Yes (21) No (0 1) Pregnancy planned Yes No Any 4 of the above c Yes No a Response was yes to three or more items (of 17) on the Davidson Trauma Scale. b Chi-square statistic or Fisher s exact test. c Forceps-assisted delivery or cesarean section considered as one item vs. spontaneous vaginal delivery.

7 PTSD AFTER BIRTH 321 TABLE 4. ASSOCIATION BETWEEN HIGH AND LOW PTS AND SOCIODEMOGRAPHIC FACTORS, PSYCHOSOCIAL FACTORS, AND INTERPERSONAL VIOLENCE No. of Low PTS High PTS a Item women (%) (%) p value b Age of respondent (years) Income (Canadian $),$32, $32,000 $80, $80, Born in Canada Yes No Employed prior to pregnancy Yes No First birth Yes No Depression prior to this pregnancy Yes No Depression during this pregnancy Yes , No Panic attacks during this pregnancy Yes No Traumatic life events Social support Low High EPDS score , Childhood sexual abuse Yes No Adult sexual abuse Yes No Childhood physical abuse Yes No Adult physical abuse Yes No Childhood emotional abuse Yes No Adult emotional abuse Yes No a Response was yes to three or more items (of 17) on the Davidson Trauma Scale. b Chi-square statistic or Fisher s exact test.

8 322 events, history of violence) and high PTS are shown in Table 4. The sociodemographic factors that were associated with high PTS were higher income (chi-square (2, n 5 185) , p ) and having been born in Canada (chi-square (1, n 5 198) , p ). Other factors associated with high PTS included having suffered from depression prior to pregnancy (chi-square (1, n 5 197) , p ), depression during pregnancy (chi-square (1, n 5 197) , p, 0.001), panic attacks during pregnancy (chisquare (1, n 5 197) , p ), and having two or more traumatic life events (chi-square (1, n 5 198) , p ). Women who scored highly on the EPDS were also more likely to have high PTS scores (chi-square (2, n 5 197) , p, 0.001). Of the violence-related variables, only adult emotional abuse was significantly related to high PTS (chi-square (1, n 5 197) , p ). Results of the multivariable logistic regression are shown in Table 5. Only characteristics or events that could be used to predict a future occurrence of high PTS were included in the model. Thus, postpartum depression was excluded because it occurred simultaneously with PTS (i.e., in the last 7 days). According to the results of the logistic regression analysis, the significant predictors of high PTS were having had two or more maternal complications, depression during pregnancy, having had two or more traumatic life events, being born in Canada, and higher income. After adjusting for the other covariates, women with two or more maternal complications had 4 times the odds of high PTS compared with women with fewer complications. The strongest predictor of high PTS was prior depressed mood. Women who were depressed during their pregnancy had almost 19 times the odds of high PTS as women who were not depressed. Lower income women had a lower odds of high PTS compared with high income women. Those in the lowest income group had 0.1 times the odds of high PTS scores compared with those in the highest income group, and those in the intermediate income group had 0.4 times the odds. Finally, women with a history of two or more traumatic life events had 3.2 odds of high postpartum stress. DISCUSSION COHEN ET AL. This study of women interviewed at 8 10 weeks postpartum did not find any participants who met the criteria for PTSD. We did not attempt to make a diagnosis of PTSD but attempted to measure the presence of PTSD-like symptoms. If the estimate from Wijma et al. 6 is used (1.7%), we would have expected to find 3 women who met our predefined criteria. Although there were 3 women who nearly met the criteria, they did not find all the items distressing. We concluded, therefore, that our study did not find any women who were probably suffering from PTSD. Thus, our study did not find support for a PTSD syndrome associated with a difficult birth or pregnancy, labor, and delivery using a wellknown PTSD instrument. Our findings are consistent with those of Czarnocka and Slade, who concluded that aspects of labour and childbirth such as duration, the nature of interventions or type of delivery appear unimportant. 8(p49) However, our findings are contrary to those of Creedy et al., 7 who found a significant association between emergency cesarean section, forceps or vacuum delivery, and postdelivery pain with trauma symptoms. Similarly Soderquist et al. 23 found a relationship between emergency cesarean section or an instrumental delivery and symptoms of PTSD. Finally, Soet et al. 10 found that cesarean section and pain in the first stage of TABLE 5. PREDICTORS OF HIGH POSTPARTUM STRESS: RESULTS OF MULTIVARIABLE LOGISTIC REGRESSION (n 5 184) Variable Reference category Odds ratio 95% CI 21 maternal complications 0 1 maternal complications Depression during pregnancy No depression during pregnancy traumatic life events 0 1 traumatic life events Born in Canada Not born in Canada Income (Canadian $),$32,000.$80, $32,000 80,000.$80,

9 PTSD AFTER BIRTH 323 labor predicted trauma symptoms 4 weeks after childbirth. Our study findings suggest that PTSD-like symptoms after pregnancy are more likely to be related to factors other than pregnancy, labor, and birth. A more plausible explanation is that other factors, namely, traumatic life events or a history of depression, are associated with PTSD symptomatology. This hypothesis is supported by the finding that women in the study endorsed more items related to general PTSD symptoms than those symptoms related to recall of pregnancy, labor, and birth. An interesting, unexpected finding was that women were born in Canada and those with higher incomes were more likely to exhibit symptoms of PTSD. We did not explore reasons for this finding, but we might speculate that women from developed countries may be more likely to admit to having such symptoms than women from other cultures. We also found that women who had two or more complications after labor and delivery were more likely to have a high PTS score. Although medical complications have been found to be associated with postpartum depression, 24 we are unaware of any studies linking a history of maternal complications and PTSD symptoms. There were a number of limitations to our study. First, the loss of 20% of the original sample may have affected the findings, as women lost to follow-up were different in background from those who remained. Second, the small sample size may have prohibited us from finding any women with high scores suggesting PTSD. If we use the rule of three to determine the upper 95% confidence limit on our zero finding, the upper confidence limit in our study of 198 women would be 1.5%. 25 This is close to the estimate found by Wijma et al. 6 of 1.7%. If we had a larger number of women in this study, we may have been more likely to have found some women who met the criteria of PTSD. Also, this study excluded women with an ill or stillborn infant, who may have been more likely to experience a difficult delivery and, possibly, PTSD. Thus, the extent of PTSD among postpartum women is likely underestimated in the current study. A further limitation of this study is that we did not assess symptoms of PTSD that may have existed prior to birth, although the number of women was likely to be small. Whereas other studies have used other PTSD instruments, such as the Traumatic Event Scale, 6 the Impact of Event Scale (IES), 4 or the Posttraumatic Stress Symptoms Interview, 7 we used the Davidson Trauma Scale. 12 The use of different scales may account for the differences found between other studies and this one. However, as the DTS compared well against other PTSD instruments, 26,27 this is unlikely the reason for the differences among studies. It is possible that this population of women (relatively high income) were at lower risk for PTSD than other populations of women in other studies, and it is also possible that a different definition of the outcome used might explain the discrepancy across studies. For example, Creedy et al. 7 used trauma symptoms (undefined in the paper) and Soderquist et al. 23 used PTSD symptom profile, whereas we used high PTS. It may also be possible that an 8 10-week time frame is insufficient time for PTSD symptoms to develop, although other studies have assessed PTSD at between 4 and 6 weeks postpartum. 7,8,10 Some women who may have met the DSM criterion of PTSD of having persistent symptoms for at least 1 month (criterion E) may not have been experiencing the full extent of these symptoms at 8 10 weeks postpartum. Another possible explanation for our findings is that the commonly used instruments used to assess PTSD contain a number of questions that postpartum women (distressed or not) are likely to answer. These include asking about trouble sleeping, difficulty concentrating, being very irritable, and feeling cut off from other people. Given the isolation and lack of sleep associated with the postpartum period, it is not surprising that the women in the study answered yes to these items. Perhaps a newly developed, specialized instrument specific to the postpartum period may be necessary. Because it is possible that differences between studies may be the result of the instruments used, it would be important to agree on a standardized instrument for use in the study of trauma symptoms after childbirth. CONCLUSIONS In summary, our study did not find any women who met the criteria of PTSD in a group of postpartum women interviewed 8 10 weeks after delivery. Women who had depression during pregnancy and a high number of lifetime

10 324 traumatic events were more likely to have a higher number of PTSD symptoms. As well, women were more likely to endorse general PTSD symptoms rather than those related to pregnancy, labor, or birth. Our study suggests that PTSD symptoms might be associated with other stressful life events and not the pregnancy, labor, and delivery per se. Given the small size of our study, more research is needed to confirm or refute our findings. However, it is essential that future studies include questions about past life events and prior PTSD symptoms to ensure that any PTSD symptoms after birth are related to pregnancy, labor, and delivery and not to other life events. REFERENCES COHEN ET AL. 1. American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 4th ed. Washington, DC: American Psychiatric Association, Ballard CG, Stanely AK, Brockington IF. Post-traumatic stress disorder (PTSD) after childbirth. Br J Psychiatry 1995;166: Fones C. Posttraumatic stress disorder occurring after painful childbirth. J Nerv Ment Dis 1996;84: Lyons S. A prospective study of posttraumatic stress symptoms 1 month following childbirth in a group of 42 first-time mothers. J Reprod Infant Psychol 1998; 16: Reynolds JL. Post-traumatic stress disorder after childbirth: The phenomenon of traumatic birth. Can Med Assoc J 1997;156: Wijma K, Soderquist J, Wijma B. Posttraumatic stress disorder after childbirth: A cross-sectional study. J Anxiety Disord 1997;11: Creedy DK, Shochet IM, Horsfall J. Childbirth and the development of acute trauma symptoms: Incidence and contributing factors. Birth 2000;27: Czarnocka J, Slade P. Prevalence and predictors or post-traumatic stress symptoms following childbirth. Br J Clin Psychol 2000;39: Ayers S, Pickering AD. Do women get posttraumatic stress disorder as a result of childbirth? A prospective study of incidence. Birth 2001;28: Soet JE, Brack GA, Dilorio C. Prevalence and predictors of women s experiences of psychological trauma during childbirth. Birth 2003;30: Ozer EJ, Best SR, Lipsey TL, Weiss, DS. Predictors of posttraumatic stress disorder and symptoms in adults: A meta-analysis. Psychol Bull 2003;129: Davidson JRT, Book SW, Colket JT, Tupler LA. Assessment of a new self-rating scale for posttraumatic stress disorder. Psychol Med 1997;27: Cox JL, Holden JM, Sagovsky R. Detection of postnatal depression: Development of the 10-item Edinburgh Postnatal Depression Scale. Br J Psychiatry 1987;150: Zelkowitz P, Milet TH. Screening for post-partum depression in a community sample. Can J Psychiatry 1995;40: Schaper AM, Rooney BL, Kay NR, Silva PD. Use of the Edinburgh Postnatal Depression Scale to identify postpartum depression in a clinical setting. J Reprod Med 994;39: Warner R, Appleby L, Whitton A, Fragaher B. Demographic and obstetric risk factors for postnatal psychiatric morbidity. Br J Psychiatry 1996;168: Straus MA, Hamby SL, Boney-McCoy S, Sugarman DB. The revised Conflict Tactics Scales (CTS2): Development and preliminary psychometric data. J Fam Issues1996;17: McFarlane J, Parker B, Soeken K, Bullock L. Assessing for abuse during pregnancy: Severity and frequency of injuries and associated entry into prenatal care. JAMA 1992;267: Johnson H. Dangerous domains: Violence against women in Canada. Toronto: Nelson Canada, 1996: Tolman RM. The development of a measure of psychological maltreatment of women by their male partners. Violence Vict 1989;4: Bromet E, Sonnega A, Kessler RC. Risk factors for DSM-III R posttraumatic stress disorder: Findings from the National Comorbidity Survey. Am J Epidemiol 1998;147: Kessler RC, Sonnega A, Bromet E, Hughes M, Nelson CB. Posttraumatic stress disorder in the National Comorbidity Study. Arch Gen Psychiatry 1995;52: Soderquist J, Wijma K, Wijma B. Traumatic stress after childbirth: The role of obstetric variables. J Psychosom Obstet Gynaecol 2002;23: Burger J, Horwitz SM, Forsyth BWC, Leventhal JM, Leaf PJ. Psychological sequelae of medical complications during pregnancy. Pediatrics 1993;91: Hanley JA, Lippman-Hand A. If nothing goes wrong, is everything all right? JAMA 1983;249: Zlotnick, C, Davidson J, Shea MT, Pearlstein T. Validation of the Davidson Trauma Scale in a sample of survivors of childhood sexual abuse. J Nerv Ment Dis 1996;184: Davidson JRT, Tharwani HM, Connor KM. Davidson Trauma Scale (DTS): Normative scores in the general population and effect sizes in placebo-controlled SSRI trials. Depression Anxiety 2002;15:75 8. Address reprint requests to: Dr. Marsha Cohen The Centre for Research in Women s Health 7th Floor, 790 Bay Street Toronto Canada, M5G 1N8 mmcohen@istar.ca