Participant recruitment

The study population consisted of all pregnant women of 14–32 weeks’ gestation referred to selected hospitals. It was performed in two educational and therapeutic centers affiliated with the Babol University of Medical Sciences in Iran between November 2020 and January 2022.

The sample consisted of women meeting the eligibility criteria to enter the study during the trial. A total of 96 individuals who obtained the necessary scores based on the relevant questionnaires were enrolled through the convenience sampling method. Afterward, an independent midwife outside the research team randomly assigned samples into two intervention groups [SIT and VSIT], using the blocking method and computer-generated randomization [23, 24]. Randomization was based on a 1: 1 ratio of four blocks [balanced block randomization] using a computer random number generator [www.random.org]. After the creation of two groups of 4 blocks with 96 participants, 24 random blocks were created using the company computer. The allocation order was kept confidential and was not available to any participant or researcher. A midwife in the selected hospital who was unaware of the treatment allocation and was not involved in the recruitment of the women assessed the consequences. Similarly, the statistical analyzer was not informed about the coding of the semi-attendance intervention and virtual intervention groups.

Inclusion criteria included the willingness to participate in the study, 14–32 weeks of gestation, obtaining a score higher than 0.5 based on the BSI-18 questionnaire, not attending similar classes, no severe psychiatric disorders [such as bipolar] based on self-report, the educational level of at least the third year of middle school, age over 16, and access to the Internet and WhatsApp messenger. Exclusion criteria included inactive and irregular attendance, unwillingness to continue attending meetings, a pregnancy accompanied by high-risk situations [such as bleeding, miscarriage, preterm delivery] and migration.