Data extraction and analysis
The following details of each study were extracted and described in the summary table (table S2): first author, country, setting, (number of) participants, (duration of the) intervention, control condition, maternal mental health outcome and retention and compliance rates. The retention rate is calculated as the percentage of women who remained till the latest follow-up and the compliance rate as the percentage of women who attended all sessions of all women allocated to the intervention group. Birth, neonatal and infant outcomes are described in another table (table S3).
The collaborative care criteria (CCC) and the collaborative care score (CCS) of each study are summarized in table 1. The CCC are defined as follows19:
  1. A multi-professional approach to patientcare: Care provided by a midwife or gynaecologist and at least one other health care professional (e.g., psychiatrist, psychologist, social worker, psychiatric nurse)
  2. Structured management plan: Evidence based management plan according to the NICE or Marcé guideline or national guideline derived from these20,21
  3. Scheduled patient follow-ups: One or more telephone or in-person follow-up appointments are scheduled during or after treatment to provide specific interventions, facilitate treatment adherence, or monitor symptoms or adverse effects (e.g., calls between sessions, evaluation of treatment goals, follow-up or booster sessions). Monitoring symptoms for research purposes was insufficient to meet this criterion. Also, active outreach for women who missed sessions and providing telephone sessions for women who missed a session was insufficient
  4. Enhanced interprofessional communication: Team meetings, case-conferences, individual consultation/supervision, shared medical records, patient-specific written or verbal feedback between caregivers. Communication to check whether all involved therapists work according to the same instructions was not scored
We contacted authors for additional information on CCC, when certain information was missing or unclear (n=13, 3 replies). The CCS is the total number of criteria met by an intervention. In table 2 we described the relation between the CCS and the effect of the intervention on maternal mental health. The effect of the intervention was cited as positive (+) when maternal mental health was significantly better in (a part of) the intervention group compared to the control group at> 1 follow-up moment. The score was +/- when there was not a significant difference between both groups and negative (-) when the maternal mental health was significantly worse in the intervention group compared to the control group.