In this study, we examined long-term maternal mental health outcomes following preterm birth. It is noteworthy that we revealed high and prolonged levels of maternal psychological distress, anxiety and trauma-related stress reactions. The levels remained high and stable after an initially significant decrease. In addition, our study revealed a main effect of time between T0 and T1 on maternal mental health outcomes. The prevalence of PTSR decreased from T0 to T3; PTSD showed a considerable increase from T0 to T1 and then stabilized toward T3. Altogether, 23% of the mothers reported PTSD, though only 8% of the mothers reported depression at T3. Preeclampsia, IVH, mother's age, bleeding in pregnancy, previous psychological treatment and maternal trait anxiety were detected as predictors for mental health outcomes in this study.
One striking result in our study is the significant effect of time between T0 and T1 on maternal psychological distress, anxiety and trauma-related stress reactions. Our findings correspond to some extent with the study of Holditch-Davis et al. on the effect of time on depression  but are contradictory with regard to state anxiety. It is interesting that their study revealed significant decrease in posttraumatic stress scores in the ‘high depressive symptom’ and ‘extreme distress’ classes in their study, which corresponds with our results of significant decreased IES scores from T0 to T1.
We found higher levels of maternal psychological distress, anxiety and trauma-related stress reactions following preterm birth, both short and long term, compared to studies of mothers giving birth at term and mothers giving birth to children with malformations. Our results correspond with the results of another study : the study of Kersting et al. also reported a marked difference between preterm and term outcomes in IES and STAI-X1 . However, our results in IES are lower than their results at 6 months (T2) and 18 months (T3). Another study reported mean sum scores in IES, GHQ Likert and STAI-X1 for mothers giving birth at term that were ordinarily 48%, 38% and 34% lower, respectively, at points of measurement comparative to T0, T1 and T2 in our study . One study of psychological distress in parents of children born with malformation reported 19% lower scores in IES at T0, but equivalent results at T1 and T2 [47, 48]. Our findings are interesting and raise questions about effective treatment programs for maternal mental health problems following preterm birth. Altogether, 18 of 29 mothers included in our study received psychological counselling in the hospital or psychological treatment following discharge from the hospital. Further research on effective treatment programs for this group is necessary.
Interestingly, our study showed a decrease in PTSR, anxiety and depression, but an increase in PTSD from T0 to T3. We revealed 23% higher prevalence of PTSD at T3 in our study, and our results correspond with the findings in the study of Engelhard et al. . Our PTSR/PTSD results also correspond with the Jotzo and Schmitz study, but the latter reported higher levels of traumatic symptoms (77% at T0, and 49% at T2). However, our results were higher than theirs at T3 (12.5%) .
The prevalence of anxiety and depression that we found corresponds with the results of other studies [12, 13, 15] and contrasts with those of studies that have reported higher prevalence of depression at T0 and T1 , and a decrease to zero at T2 .
We found that higher maternal mental health outcomes were associated with ‘acute Caesarean section’, and lower maternal health outcomes were correlated with ‘planned Caesarean section’ and ‘vaginal delivery’. Our results seem to be inconsistent. However, both planned Caesarean section and vaginal delivery may present more control and less distress in labor for the mother, while an acute Caesarean section may be experienced as more distressing with less time to prepare for the critical preterm birth event.
Another striking result in our study was the physical predictors of maternal mental health outcomes. ‘Preeclampsia’ and ‘bleeding in pregnancy’ are perinatal complications that we found to predict posttraumatic stress responses in IES and general psychological distress in GHQ, respectively. One should note that bleeding in pregnancy reduced the GHQ outcome. There is no obvious explanation for this result in our study. Is it possible, however, to provide an existential explanation for why bleeding in pregnancies contribute to lower psychological distress in GHQ? Could it be that bleeding in pregnancy is experienced by the mother as a near-loss event early in pregnancy, leaving her with the frightening impression that her child is at risk? Given such an enduring impression of threat, the mother can be expected to be prepared for incidents such as a preterm birth. It is possible that the preparation of the mother for possible risks explains the low psychological stress outcome. Our detection of preeclampsia as a predictor of posttraumatic stress might correspond with the findings of Blom et al. that certain perinatal complications like preeclampsia, hospitalization, emergency caesarean and foetal distress predicted higher depression outcomes in a normal population sample . Depression is often a co-morbidity of psychological trauma, but posttraumatic stress symptoms were not examined in their study.
In addition, we detected that ‘intraventricular haemorrhage (IVH) grades 1 and 2’ was a predictor of maternal posttraumatic stress responses in IES. Only two children in our sample were struck by IVH grade 3 or 4 following birth. The analysis of the impact of the most severe IVH was limited by our small sample size. Our result, however, corresponds to some extent with those of Singer et al. who found that maternal distress following preterm birth of a very low-birth weight child depended on the medical risk status, age and developmental outcome of the child . Our finding also corresponds with the studies by DeMier et al. that postnatal complications in infants predicted maternal PTSD symptoms [37, 38].
Other predictors of posttraumatic stress responses in IES, general psychological distress in GHQ, and state anxiety in STAI in our study were ‘mother's high age’, ‘previous psychological treatment’ and ‘trait anxiety’, respectively. Our results correspond with one of the predictors of postpartum depression, previous psychiatric disorder , and with the results from postpartum research showing trait anxiety predicts posttraumatic stress and anxiety .
Strength and limitations
The strength of the present study is the longitudinal design. The participants came from well-defined geographic areas and were included consecutively in the study, thus minimizing selection bias. However, the exclusion of severely ill babies with very small chance of survival could affect selection bias. On the other hand, the impact of maternal grieving following the death of a preterm baby would represent a significant difference from our study group, though grieving mothers would have been interesting as a comparison group. The response rate is high both for the case and the psychometric instruments (IES, GHQ and STAI-X1) used in our study. These instruments are commonly used and have been validated in the research literature. We have assessed several important aspects of mental health problems, like psychological distress, anxiety and trauma-related stress, and also assessed tentative clinical diagnosis for the prevalence of mental health problems.
The present study describes a small preterm group of mothers with higher educational attainment, greater age, higher rate of IVF and higher socioeconomic status than would be found in a typical population of mothers who deliver preterm in our country. In our sample, 27.6% had been through IVF treatment to become pregnant. The moderating role of this treatment on the mother's psychometric outcome has not been examined. The homogeneity of the group in terms of socio-demographic background and distress related to it represents a limitation in this study. On the other hand, our results were controlled for high-risk socio-economic background variables as no one in our study group reported any socio-economic problems in the semi-structured interview we used for data collection.
Ethical considerations called for a referral procedure to meet the need for treatment when severe maternal mental health problems in the preterm mothers were detected. It is a limitation that we cannot assess to what extent the psychological treatment influenced our results.