The World Federation of Obesity warns that the main health problem of the next decade will be childhood obesity. Furthermore, obesity and its consequences have been reported to originate in intrauterine life. Gestational obesity produces profound effects on fetal genome programming, thereby inducing changes in prenatal metabolism that extend to the postnatal period, which is also associated with increased susceptibility to developing cardiovascular and metabolic diseases in adulthood.

Excessive maternal weight gain early in pregnancy has been repeatedly associated with increased adiposity in childhood and adolescence of its offspring. Obesity is a complex phenomenon influenced by social determinants of health, which include demographic, socioeconomic, behavioral, environmental, and genetic factors. At the primary prevention level, nutrition constitutes a modifiable risk factor during pregnancy. Therefore establishing healthy nutritional behaviors during the first trimester of pregnancy is key to the primary prevention of the intergenerational transmission of obesity.

New ways of approaching the target population are required to maintain nutritional recommendations as a priority in the daily decision-making (top of mind) of pregnant women. For many women, this period is a powerful motivator for self-care.

Interventions based on behavioral theories provide a better understanding of the underlying mechanisms that determine health-related behavior change and have the potential to be more effective in promoting adherence to weight gain control. Social Cognitive Theory (TCS) is an integrated model of behavior change commonly applied in mobile health interventions that address diet, physical activity or weight loss.

Mobile health programs (mHealth) are potentially more effective than face-to-face interventions, especially during a public health emergency like the COVID-19 outbreak. This proposal intends to "deliver" messages with evidence-based information directly to pregnant women, in order to influence their nutritional behavior to avoid excessive gestational weight gain.

The hypothesis of this proposal is that the mHealth intervention called "mami-educ", which consists of sending messages with nutrition counseling during pregnancy through the Telegram platform, is effective in reducing excessive gestational weight gain in pregnant women attending Family Health Care Centers in an urban and predominantly rural area.

Inclusion Criteria:

• Pregnant women who receive care in the 6 CESFAMs of El Bosque and Aconcagua Valley over 18 years of age; pregnant women with gestational age ≤ 12 weeks of gestation (first trimester)
• Pregnant women with a single pregnancy
• Healthy pregnant women
• Chilean or immigrant women who speak Spanish
• The participants must have a mobile device that allows the use of the Telegram application
• Pregnant women who agree to be randomized
• Pregnant women who have voluntarily signed the informed consent to participate in this study

Exclusion Criteria:

• A multiple pregnancy
• Conditions that require a special diet
• Participants with psychiatric illness or other pre-pregnancy pathology
• History of recurrent abortions

Blinding will be done in a single-blind fashion. The care provider will be blinded to the randomization of the subjects to avoid bias in routine care.