Promoting informed decision making about maternal pertussis vaccination among pregnant women

In 2019, maternal pertussis vaccination (MPV) was implemented in the National Immunization Program of the Netherlands to protect infants in their first months of life. The choice about MPV among pregnant women is largely determined by socio-psychological determinants (79%), but emotions are thought to play a role too. Furthermore, many pregnant women in the Netherlands (32.7%) experience decisional uncertainty about MPV.

To promote informed decision making about MPV, we developed two interventions using intervention mapping.
1. A Centering Pregnancy (CP) intervention about MPV. A training was given to midwives about discussing the MPV in Centering Pregnancy (group prenatal care) sessions.
2. An online tailoring (OT) intervention in the form of a decision aid, providing information, the possibility to test knowledge about MPV, practice a conversation about MPV, and weigh the pros and cons of MPV.

Our research questions are:
1. What is the relative effectiveness of OT and CP compared to the control group and of OT+CP compared to OT on informed decision making, decisional conflict and the determinants of uptake in pregnant women?
2. To what extent do participants use the intervention components (program adherence)?
3. How do participants subjectively evaluate the interventions?

The study population consists of pregnant women in the Netherlands. Recruitment will take place via midwifery clinics. There will be four groups in the trial at clinic level: A group receiving the OT intervention, a group receiving the CP intervention, a group receiving both interventions, and a control condition receiving only the regular information. Because not all clinics in the Netherlands offer CP, clinic allocation to the OT+CP and CP conditions will be non-random. Allocation to OT and control conditions will be at random.

Baseline measurements will be done using questionnaires after enrollment in the study (before or at 16 weeks gestational age). Between 16 and 20 weeks gestational age, the intervention groups will receive the CP and OT interventions. At 20 to 22 weeks gestational age, a follow-up questionnaire will be done including measures of informed decision making, decisional certainty, and acceptance and usability of the interventions. Vaccination status will be derived from Praeventis, the National Immunization Register.

A 10% point difference between the experimental groups and control group in MPV uptake is expected.

- Baseline measurement before or at 16 weeks gestational age
- Follow-up measurement at 20 to 22 weeks gestational age
- Vaccination-status will be derived from Praeventis at the end of the trial, when all participants are no longer pregnant.

1. A Centering Pregnancy (CP) intervention in which maternal pertussis vaccination is discussed.
2. An online tailored (OT) decision aid regarding maternal pertussis vaccination.