Methods: The study is a randomized controlled experimental study. Groups were determined by stratified randomization according to the BMI of the pregnant women. In the study, individual identification form, Healthy Living Behaviors in Pregnancy Scale (HLBPS), and maternal questionnaire were used. The initiative program was carried out via WhatsApp messages on a smartphone. Messages regarding routine prenatal care were sent to the intervention group three times a week, and to the control group once a month, about appropriate weight gain, nutrition, and physical activity via WhatsApp.

Results: The mean gestational weight gain was 13.1±4.3 in the intervention group and 14.6±4.2 in the control group, and no significant difference was found between the groups. According to the IOM guideline, there was a significant difference between the groups in terms of appropriate GWG , while no significant difference was found between excessive GWG.HLBPS scale total score, nutrition and physical activity post-test mean scores increased significantly in the intervention group compared to the control group. In the intervention group, the group/time interaction in the scale total score, nutrition and physical activity scores of the pregnant women who gained appropriate weight according to the IOM guideline was significant, and the intervention was effective.Significant differences were found between the groups in the pretest-posttest score differences in the HLBPS total score, nutrition and physical activity sub-dimensions of the pregnant women.

Conclusion: Healthy nutrition and physical activity short message intervention with a smart phone increased the appropriate gestational weight gain rates of pregnants in the intervention group according to the IOM guideline, and the intervention was effective. However, there was no difference between the groups in terms of excessive gestational weight gain. It is recommended to conduct studies with a high level of evidence, including internet and social media applications, with larger samples.

Most of the descriptive characteristics of the intervention and control group pregnant women who participated in the study were homogenously distributed (p>0.05). A significant difference was found only between gestational week and place of residence (p<0.05).The mean total GWG of all pregnant women participating in the study was 13.9±4.3/kg. The mean difference between the intervention (13.1±4.3/kg) and control group (14.6±4.2/kg) pregnant women was 1.5 kg, but no significant difference was found between the groups (p>0.05). The rate of GWG within the limits of IOM guideline recommendations in the intervention group pregnant women (48.9%) was significantly higher than in the control group (22.2%) (p<0.05). Excessive GWG was found to be higher in the control group (68.9%) than in the intervention group (48.9%), but no significant difference was found (p>0.05).In the pre-intervention, pre-test data, pregnancy responsibility, nutrition and physical activity and HLBPS total scores were higher in the intervention group than in the control group (p<0.05). While no significant difference was found between the groups in the post-test scores of the pregnancy responsibility sub-dimension of the intervention/control group pregnant women (p>0.05), a statistically significant difference was found in both intervention (p<0.001) and control groups (p<0.001) in the in-group pre-post comparison. While there was a significant increase in the intra-group nutrition, physical activity sub-dimension and HLBPS total score of the intervention group pregnant women (p<0.001), no significant increase was observed in the control group (p>0.05). In the post-test comparison between groups, nutrition, physical activity sub-dimension score and HLBPS total score increased significantly in the intervention group compared to the control group (p<0.001). While the nutrition sub-dimension score of the intervention group was effective in appropriate GWG, it was not effective in the control group. Physical activity sub-dimension and HLBPS total score were effective in appropriate GWG in both intervention and control groups.

Inclusion Criteria:

Between the ages of 18-45,

• Using Whatsapp,
• Having a smart phone and using the internet,
• At least primary school graduate/literate,
• Does not have any chronic and psychological disorders,
• Having spontaneous pregnancy,
• Volunteer to participate in the research,
• Pregnancy below the 16th week of participation in the study,
• Not having any physical disability,
• Pregnant women with low pregnancies with low BMI and not morbidly obese were included in the study.

Exclusion Criteria:

Dropping out of research participation and initiative program,

• Low,
• Giving birth before 37 weeks,
• Having multiple pregnancy,
• Those who did not have a spontaneous pregnancy were not included in the study.

It is a study conducted with pregnant women.

The individuals included in the study were first stratified according to their BMI classes (normal, preobese, obese). Then, the BMI classes were included in the experimental and control groups in a balanced way by block randomisation method. Within each stratum, randomisation lists were generated with the help of "The random sorting randomization algorithm" (Maximum Allowable Deviation = 10%) PASS 11.0 software (NCSS LLC, Kaysville, UT). In total, participants were randomly assigned to experimental and control groups of 51 participants each.The study was completed with 96 pregnant women