Methods
weight gain, GDM, gestational diabetes
GDM, COMPLICATIONS, GESTATIONAL DIABETES
This study was conducted between April 2022 and November 2022 at 2 obstetrics and gynecology clinics in Babol City, Iran. The Research Ethics Committee of Babol University of Medical Sciences approved this study (code: IR.MUBABOL.REC.1401.016).Inclusion criteria were a pre-pregnancy BMI of 25 kg/mA sample size of 32 in each group was calculated based on, a 50% reduction in the incidence of gestational diabetes with significance level (alpha) of 0.05 (two-tailed) and 80% statistical power by G-power software [Of the 92 eligible pregnant women referred to the clinics, 28 were excluded according to exclusion criteria. In total, 64 women signed the written informed consent form. The women were randomly assigned to 2 groups: the usual care group and health coaching intervention group (1:1) according to the block of 4 using computer-generated random numbers. However, in a quasi-experimental design, true randomization may not be feasible due to various constraints and ethical considerations, but this study had the rationale for using a quasi-experimental design based on the existing literature, ethical considerations factors. In addition, due to the intervention methods of the 2 groups, blinding was not feasible, and the study was open-label. The dropout of the study was 6.3% (1 subject in the intervention group and 3 subjects in the control group; Fig. 
Consort fellow diagram of the participantsBoth groups received standard prenatal care to ensure the safety of the mother and fetus, including risk assessment, physical examination, patient education, health promotion, and therapeutic intervention by 2 attending obstetricians. In the intervention group, in addition to standard prenatal care, 4 telephone call-based coaching sessions were conducted every 2 weeks (16–22 weeks of pregnancy), and each session lasted 30–45 min by a midwife coach (undergraduate midwife coach); however, it is important to note that standard prenatal care was not provided during the coaching sessions.The health coaching protocol is based on the GROW (Goals, Reality, Options, and Will) coaching model to help pregnant women define their goals. In each session, the participant gave personal feedback on their nutrition and exercise habits during the last 5 days. Briefly, the goals of the coaching sessions include (1) promoting a positive attitude through education and skill development, (2) providing verbal and written access to evidence-based information about lifestyle (how to control weight and how to gain ideal weight during pregnancy and undertake at least 30 min of moderate regular exercise 3 to 4 days a week), (3) minimizing dangerous lifestyles and consume evidence-based healthy diets (such as fruits, high-fiber, whole-grain products, and vegetables), (4) optimizing weight control management, (5) problem-solving methods and activity planning, and (6) promoting active monitoring of weight gain during pregnancy and considering it important in preventing complications, including GWG.All participants with a BMI of 30 kg/mDuring the intervals between coaching sessions, the intervention group received short messages on various topics, such as recording weight changes, encouraging goal achievement, re-emphasizing positive lifestyle changes, and encouraging self-evaluation of the situation. Throughout the study, the participants were encouraged to identify obstacles to achieving their goals and to develop strategies to overcome them, with the help of the coaching program. This approach enabled them to make positive changes in their lifestyle and successfully achieve their weight management goals.The primary outcome was the incidence of GDM for both groups. Diagnosis of GDM was made based on at least 1 abnormal value report of glucose 2 h after 75-g oral glucose tolerance test (OGTT) at 24–28 gestation weeks, and a fasting glucose (0 h) value ≥ 92 mg/dL, 1-hour ≥ 180 mg/dL, or 2-hour ≥ 153 mg/dL (2011) [Baseline socio-demographic and clinical characteristics were collected at enrollment using a checklist. Anthropometric measurements and physical activity levels of all participants were collected at both baseline and after the intervention period using the Pregnancy Physical Activity Questionnaire (PPAQ) and anthropometry measurements. Data on maternal and neonatal outcomes and birth weight were obtained from the medical records of the women. Finally, participants were asked about their experience with phone health coaching during pregnancy.PPAQ is a standard self-reported questionnaire devised by Taber et al. for assessing physical activity of pregnant women [The participant’s weight was measured using a Seka scale (Germany) without shoes and with minimal clothing and an accuracy of 100 g. The measurements were taken at the initial antenatal visit (baseline) and again at 24 to 28 weeks. Height was measured using an inflexible tape measure mounted on the wall with an accuracy of 1 cm. Measurements were taken without shoes in a standing position with their heels attached to the wall and looking forward. The weight gain was changes in weight from baseline to 24–28 weeks gestation and also changes from baseline to birth. The body mass index was calculated using the formula of weight in kilograms divided by the square of the body height in meters, in accordance with the definition of the World Health Organization.