Protocol for a quasi-experimental study of the effectiveness and cost-effectiveness of mother and baby units compared with general psychiatric inpatient wards and crisis resolution team services (The ESMI study) in the provision of care for women in the postpartum period

Introduction Research into what constitutes the best and most effective care for women with an acute severe postpartum mental disorder is lacking. The effectiveness and cost-effectiveness of psychiatric mother and baby units (MBUs) has not been investigated systematically and there has been no direct comparison of the outcomes of mothers and infants admitted to these units, compared with those accessing generic acute psychiatric wards or crisis resolution teams (CRTs). Our primary hypothesis is that women with an acute psychiatric disorder, in the first year after giving birth, admitted to MBUs are significantly less likely to be readmitted to acute care (an MBU, CRTs or generic acute ward) in the year following discharge than women admitted to generic acute wards or cared for by CRTs. Methods and analysis Quasi-experimental study of women accessing different types of acute psychiatric services in the first year after childbirth. Analysis of the primary outcome will be compared across the three service types, at 1-year postdischarge. Cost-effectiveness will be compared across the three service types, at 1-month and 1-year postdischarge; explored in terms of quality-adjusted life years. Secondary outcomes include unmet needs, service satisfaction, maternal adjustment, quality of mother–infant interaction. Outcomes will be analysed using propensity scoring to account for systematic differences between MBU and non-MBU participants. Analyses will take place separately within strata, defined by the propensity score, and estimates pooled to produce an average treatment effect with weights to account for cohort attrition. Ethics and dissemination The study has National Health Service (NHS) Ethics Approval and NHS Trust Research and Development approvals. The study has produced protocols on safeguarding maternal/child welfare. With input from our lived experience group, we have developed a dissemination strategy for academics/policy-makers/public.

2014), so these are important to acknowledge. This study will open the door for further longitudinal analysis. I have only one suggestion, which pertains to addressing selection bias. The most unwell and "hard to reach" women and infants may not be well represented. This arises as a consequence of competence to consent being determined at discharge, the large number of self-reported questionaires, propensity score matching, dropout and listwise deletion for those with insufficient data for imputation. Is it possible to include a parameter to assess if participants of the study are representative of the base population?

GENERAL COMMENTS
"A quasi-experimental study of the Effectiveness and costeffectiveness of Mother and Baby Units compared with general psychiatric Inpatient wards and crisis resolution team services (The ESMI study)" The protocol is scientifically credible and is presented in an appropriate context ; the design is ethically and procedurally sound. The protocol reports an ongoing study.
The primary aim is to investigate the effectiveness and costeffectiveness of psychiatric Mother and Baby Units (MBUs). The primary hypothesis is that women with an acute psychiatric disorder, in the first year after giving birth, admitted to MBUs are significantly less likely to be readmitted to acute care (an MBU, Crisis Resolution Teams CRTs or generic acute ward) in the year following discharge than women admitted to generic acute wards or cared for by CRTs.
The protocol study is well structured and written. This is an essential study for perinatal mental health and MBUs.
Minor remark: In title, the authors should mention the post-partum period.

Reviewer one
We thank reviewer one for the positive comments and for the detailed review of the paper. We have now included a reference to the two papers provided by the reviewer within the Introduction, page 4, paragraph 4: "Severe postpartum psychiatric disorders are among the most challenging to treat as they are rapid in onset, can deteriorate quickly and are a leading cause of maternal death from suicide 1. These disorders may also be associated with deficits in caring for the new-born baby and disruptions in the mother-baby relationship 1-3. Over the longer-term, the children of mothers admitted to inpatient psychiatric services may develop a range of health, developmental and mental health concerns 4. A recent examination of the costs of perinatal mental health problems indicates that the greatest costs relate adverse child outcomes 5." Reviewer one also raised an important point regarding the possibility of including a parameter to assess if study participants are representative of the base population. This issue is something that the study team have sought to address from the outset of the study. We attempted to obtain Section 251 approval to gather some key demographic and clinical data on the overall base population, in order to use as a comparison with our sample, but unfortunately our application was not approved. The team have carefully considered alternative options to gathering this information and believe it may be possible to capture such data on the MBU base population, from national audit data. Unfortunately, we are not aware of any such audit data for the other acute care services. The team will seek to request the MBU audit data from the relevant organisations. We have now made reference to this point in the manuscript, on page 8, paragraph three: "In order to assess the representativeness of our study sample, we sought to obtain Section 251 approval to collect a minimum dataset -on readmissions, number of inpatient and CRT days, HONOS, Mental Health Act status and age and ethnicity -from clinical records of all women admitted to each type of service for acute perinatal psychiatric disorders. Unfortunately, our Section 251 application was not approved. It may, however, be possible for us to capture some of this data on the overall MBU population, from national audit data; we are not aware of any such audit data for the other acute care services"

Reviewer two
We thank reviewer two for the positive comments. We have addressed their point about the revision to the protocol title, and we now include a mention of the post-partum period. The title has now been changed as follows: "A quasi-experimental study of the Effectiveness and cost-effectivenesS of Mother and Baby Units compared with general psychiatric Inpatient wards and crisis resolution team services (The ESMI study) in the provision of care for women in the post-partum period"