Design and sampling
This randomized controlled trial study with parallel groups was conducted on pregnant women referred to Urmia health centers in 2018–2019. The study was last 12 months for execution, from April 2018 to May 2019. This trial was registered in Iranian registry of clinical trials (IRCT) in 05/06/2020 with IRCT20151004024340N15 identifying number. Also this study was verified by the Urmia ethics committee with IR.UMSU.REC.1397.162 code.
Sample size and sampling method
The sample size was calculated according to the Michele Bisson  study, because of the similarity in the targeted primary and secondary outcomes, where the moderate and vigorous physical activity (MVPA) index was 11.7 ± 9.5 min/day in their control group and 25.4 ± 20.4 min/day in their treatment group after the intervention. With the 90% of study power (Z1−β = 1.28), and the two-sided alpha level at 0.05 (Z1−α/2 = 1.96), and a 10% chance of dropout, the sample size was determined 45 subjects for each group. Therefore, ninety subjects were included in the study. The flow diagram of participants has shown in Fig. 1.
Inclusion criteria in the study were: the tendency to participate in the study, having an ability for reading and writing, be under 20 weeks of gestational age, lack of chronic diseases (i.e., diabetes, hypertension, kidney disease), lack of any medical limitation for improving physical activity by mother, no mental illness and no history of hospitalization (based on the participant’s self-report), lack of cerclage and prenatal care, having a smartphone, access to the internet, and residence in Urmia. The exclusion criteria were: having any problems or special diseases in the current pregnancy such as preeclampsia, diabetes, anemia, high-risk pregnancy and cerclage surgery, frequent bleeding during the intervention, premature contractions, reduction of fetal movements, amniotic fluid leakage, diet for a specific disease, and migration from Urmia.
We used stratified sampling method for including subjects from different socioeconomic strata of Urmia. There were three levels of health centers; 1, 2, and 3 according to their social and economic status. Then, two centers from each category were chosen randomly by lottery (drawing). Also participants for each group were randomly assigned with one to one allocation ratio with the block randomization method. First, the blocks were created with the combination of AAABBB by computer and all the possible statuses were identified and an exclusive code was assigned for each. Next, considering the sample size (N = 90) and block sizes (S = 6), 15 blocks were chosen by a simple randomization method by the researcher. Selected subjects were allocated to control or intervention group consecutively by the study manager. All these stages were done under the provision of a consultant epidemiologist and using Random Allocation Software version 1.0.0.
Data collection tools
In this study, demographic, Pregnancy Physical Activity Questionnaire (PPAQ) questionnaires was used and completed. Height measured with a Stadiometer and weight by a Seca scale. Demographic information questionnaire had questions such as age, weight, height, education level, employment status, economic status, BMI, pregnancy age, number of fetuses, number of pregnancies, history of the underlying disease, history of infertility, cerclage, ectopic pregnancy, and specific disease in the current pregnancy.
Standard PPAQ, which is related to physical activity in pregnancy, includes two parts: Part I consisted of information about individual characteristics and Part II includes 32 questions on physical activities. The questionnaire of pregnancy physical activity consists of 4 groups of questions related to activities: at home (16 questions), community (3 questions), and activity in the workplace (5 questions), and sports and entertainment (8 questions). Within the manual of PPAQ the categorization and classification of daily physical activities based on the intensity and duration of them has been explained well. Based on that manual sum of the values of multiplied intensity and duration for some activities within the questionnaire can predict the amount of MET/Min for each category of activities as sedentary, light, moderate and sever that has pointed in detail in the data analysis section.
After selection of subjects in the first meeting, the researcher introduced herself to mothers and explained the study purpose. Informed written consent was then obtained. Later the questionnaires related to personal information and physical activity were filled in. Body mass index (BMI) was calculated and assessed. The mother’s weight was checked with minimum clothing and without shoes, using a digital scale with a precision of 100 g. People’s height was measured using a wall gauge with an accuracy of 1 cm while standing barefoot by the wall, as the shoulders were in a normal position. BMI was calculated by dividing weight by height squared.
Based on weight status (i.e., normal, overweight, and obese) and through the permuted block randomization, all the pregnant women were randomly assigned to the control and treatment group by Random Allocation Software version 1.0.0. Both groups received individual diets according to BMI, by a nutritionist, who also provided the necessary explanations. All educational content in the format of text, audio, and video files was delivered and provided through of what’s app as social media platform. All intervention and control subjects received their specific educational contents according to the prepared study protocol for each group.
The control group subjects were quiet match and nearly similar in properties with the intervention one. They received a routine pregnancy care that was provided by health care centers and were followed alongside with the intervention group in the same time period. Subjects joined a virtual group in a social network (What’s app) that was accessible through both mobile, laptop or PC devices for all subjects from each centers in control group. They received prepared individually diets and materials about that how to track its effect on their weight gain during pregnancy. In parallel, the treatment group also joined a virtual training group in a social network (What’s app), that was similarly accessible through mobile, laptop or PC devices for all subjects from each centers in intervention group. Just the difference that was for this group, they received special and prepared educational content as written, audio or video materials to improve their physical activity along with an individually designed diet during 16 sessions in 8 weeks. The content delivered to the virtual group twice a week and in a specified time period. Each session was about 90 min that all educational programs were delivered by an educated and specialized midwife. During different session subjects regarding the advantages of executing appropriate exercises and physical activities during pregnancy, introducing suitable exercises for pregnant women and the manner of their execution was educated. Also in some sessions topics about the necessary precautions and probably health risks with some activities was discussed. Reminder massages was sent twice a week regarding the importance of doing proposed exercises and activities truly, the importance of good adhering to the diet, and announcement about the time of next session and its content. All women’s questions were answered both within the group and in private chat based on the type of question. The respondent rate for both groups was %87.8 in average. Mothers’ weights were recorded after a face-to-face meeting in the fourth week. All delivered massages deposited in virtual group by the end of intervention. Our primary outcome was measuring the amount of changes in the mean daily total physical activity level, while secondary outcomes were measuring the level of changes in other subgroups of daily physical activity alongside with the level of weight gain during pregnancy.
At the end of the intervention, pregnant mothers in both groups filled the PPAQ questionnaires for the second time. The data acquired in this phase were compared with the first one.
Quantitative data were reported as mean ± standard deviation and qualitative data were expressed in the form of frequencies and percentages. Activity intensity was measured based on the amount of Metabolic Equivalent of Task (MET). To calculate the total MET/Min of activities, the MET level regarding the intensity of activities was multiplied by the amount of time spent per day. The level of daily activity determined based on the amount of MET/Min obtained for activities and their average per day. The categorization for the level of physical activity was done according to the PPAQ specific manual. An activity with MET/Min less than 1.5 was considered as inactivity or sedentary, with MET/Min 1.5–3 as light activity, with MET/Min 3–6 as moderate activity, and with MET/Min more than 6 as a sever activity. An independent t-test was used to compare the data about the groups for comparing them at start and at the end of intervention. A paired t-test was used for comparing changes within groups and comparing before and after data. Also, the chi-square test was used to compare data regard the qualitative variables between the two groups at start of the study. To control the possible influence of confounding factors and better determination of treatment effect, multivariate analysis was done. The significance level for all statistical tests was considered less than 0.05. We used per protocol analysis for comparing the extracted results between study groups. All analyses were performed using SPSS-21 software.