Following clinical practice guidelines, subjects in the control group will receive multidisciplinary rehabilitation programmes with coordinated delivery of supervised exercise therapy, cognitive behavioural therapy (education on pain), as well as therapeutic massage to relieve low back pain during pregnancy.

• Subjects in the experimental group will receive the same treatment described for the control group.
• Subjects in the experimental group will receive an additional Virtual Reality Intervention (VRi).

At the end of each session, participants will experience an immersive virtual landscape displayed by Nature Trek VR software (httpp://naturetreksvr.com/). First, participants will be placed in a sit down position and guided for their breathing control during 5 minutes ("meditation Lotus option"). After that, they will be encouraged to freely move around a relaxing virtual environment during 15 minutes taking special attention to soothing sounds of nature. The themes environment will be selected based on the preferences of the participants.

At the beginning of the study, advice is given on general care, in physical activity and issues concerning drug intake. Patients are advised to refrain from any other specific training during the intervention period. Any deviations from the adherence and practice of the VRi are recorded daily, noting any adverse incidents.

FACS. Pain-related fear avoidance (FA), a common problem for patients with painful medical conditions, involves pain-related catastrophizing cognitions, hypervigilance, and avoidance behaviors, which can ultimately lead to decreased functioning, depression, and disability. (FACS) was developed, which incorporates important components of previous FA- related measures, and includes components of the FA model not previously considered in the earlier-developed questionnaires. The FACS has 20 items, each measured on a 6-point Likert scale, for total possible score of 100 and the lowest possible score of 0, requesting the respondent to either: (5) completely agree; (4) mostly agree; (3) slightly agree; (2) slightly disagree; (1) mostly disagree; (0) completely disagree. Higher scores are intended to indicate higher levels of FA.

FACS. Pain-related fear avoidance (FA), a common problem for patients with painful medical conditions, involves pain-related catastrophizing cognitions, hypervigilance, and avoidance behaviors, which can ultimately lead to decreased functioning, depression, and disability. (FACS) was developed, which incorporates important components of previous FA- related measures, and includes components of the FA model not previously considered in the earlier-developed questionnaires. The FACS has 20 items, each measured on a 6-point Likert scale, for total possible score of 100 and the lowest possible score of 0, requesting the respondent to either: (5) completely agree; (4) mostly agree; (3) slightly agree; (2) slightly disagree; (1) mostly disagree; (0) completely disagree. Higher scores are intended to indicate higher levels of FA.

The Visual Analog Scale (VAS) has been used in previous studies investigating changes in pain and, specifically, in all the randomized trials of interventions for back pain in pregnancy included in or published since the Cochrane and systematic reviews. The VAS was used for assessment of pain before and after the intervention. Measurement will be performed with a 10-cm scale marked with 1-cm increments. Pain felt by participants will be recorded. Pain was rated on a scale of 0 a 10, with 10 representing the most excruciating pain. The value indicated on the scale by the participants was used as the score.

The User Satisfaction Evaluation Questionnaire (USEQ) is a questionnaire that is designed to properly evaluate the satisfaction of the user (which constitutes part of usability) in virtual rehabilitation systems. The USEQ questionnaire is composed of the set of questions in the SEQ that evaluate satisfaction. The USEQ has six questions with a five-point Likert Scale. The total score of the USEQ questionnaire ranges from 6 (poor satisfaction) to 30 (excellent satisfaction). To calculate this total score, we consider all of the questions to be positive, except for Q5, which is considered to be a negative question. The numerical value of the positive questions is used to calculate the score (for instance, if the patient selects 4 in Q1, then 4 is added to the total score). The negative question subtracts the numerical value of the response from 6 and then adds this result to the total score (for instance, if the patient selects 2 in Q5, then 4 is added to the total score).