Overweight and obesity is a major public health problem among women in reproductive age. Excessive gestational weight gain (EGWG) among this group is becoming a worldwide epidemic over recent decades. EGWG is associated with adverse outcomes including increased risk of developing gestational diabetes mellitus (GDM), cesarean section, hypertensive disorders of pregnancy (HDP), elevated infant birth weight and adiposity, and increased risk of metabolic syndrome and childhood obesity in offspring. Therefore, interventions are needed to help overweight and obese pregnant women to control GWG.

Lifestyle intervention has been proved effective on weight management during pregnancy. However, the effects of interventions on controlling overweight and obese women's GWG are inconsistent. Traditional face-to-face counseling are less cost effective. Effective intervention models based on Mobile health that can be scaled up are scarce. Thus, this randomized controlled trial aims to identify: firstly, whether the mobile health lifestyle interventions will be effective on improving gestational weight gain and preventing GDM among overweight or obese pregnant women; secondly, whether the intervention will be beneficial for improving pregnancy outcomes, delivery outcomes, neonatal outcomes, metabolic indicators, body composition indicators, etc. among overweight or obese pregnant women.

The interventions are composed of health education (online and offline health education on recommended gestational weight gain, prenatal dietary guidance and physical activity recommendation), diet behavior modification (8 core dietary goal setting and monitoring weekly), active physical activity (150 min per week of moderate-to vigorous-intensity physical activity including aerobic exercise (brisk walking) and resistance exercise; goal of 6000 steps/day), regular face to face or telephone sessions, lifestyle (diet and physical activity behavior) and weight monitoring via Huawei Wristband or WeChat Public Account. Tailoring of the intervention will be guided by the transtheoretical model. A total of 200 overweight or obese singleton pregnant women of 8-14 weeks of gestation will be recruited and they will be randomly allocated at a 1:1 ratio to either the intervention or control group, stratified by the categorical variables of age, BMI and parity. Participants in the control group will be provided usual prenatal care.

Women in both study arms will attend three research appointments at 8-14 weeks (baseline),24-28 weeks (midterm) and 32-36 weeks (terminal) of gestation for data collection via questionnaires, physical measurements, and clinical laboratory examination. Information on demography, socioeconomic status, medical and family history, obstetric history, current pregnancy information, smoking, consumption of alcohol, attitude and knowledge about GWG, diet and exercise habits, sleep situation, quality of life, mental health (depression, anxiety), social support, self-efficacy, etc. will be collected with questionnaires and interviews by research stuff. Physical measurements including weight, height, blood pressure, and body composition using bioelectrical impedance (BIA) will be obtained using standardized methods. Laboratory tests performed in conjunction with antenatal visits include a 75 g 2-hour oral glucose tolerance test (OGTT). Data on mode of delivery, gestational age at birth, birth weight, Apgar scores, perinatal complications, etc. will be obtained from patient records. In addition, blood and urine samples will be drawn at three appointments and a sample of cord blood will be collected at birth. Maternal postpartum weight (42 days,6 months,1 year after delivery) will be obtained through routine physical examination or telephone follow-up. Offspring physical growth indicators, such as height, weight, head circumference, etc., will be collected from routine physical examination in 42 days, 6 months and 12 months of age.