Study Protocol effectiveness of a nutritional intervention based on encouraging the consumption of unprocessed and minimally processed foods and the practice of physical activities for appropriate weight gain in overweight, adult, pregnant women: a randomized controlled trial

This is a two-armed parallel randomized controlled trial that will be conducted among overweight, pregnant women receiving prenatal care in seven Primary Health Units of Ribeirão Preto, SP, Brazil: Waldemar Barnsley Pessoa (Parque Ribeirão), Dr. Marco Antônio Sahão (Vila Virgínia), Dr. Sérgio Botelho da Costa Moraes (Jardim Presidente Dutra), Adalberto Texeira Andrade (Vila Recreio), Carlos Chagas (Vila Abranches), Rubens Issa Halak (Jardim Juliana) and Dr. Ítalo Baruffi (Castelo Branco). The Primary Health Units were selected according to the high demand for prenatal care and the minimum infrastructure necessary to conduct the study.

The study has been approved by the Research Ethics Committee of the School Health Centre of the Ribeirão Preto Medical School, University of São Paulo. Ribeirão Preto, SP, Brazil, (69,997,717.6.0000.5414, and 97,288,818.0.0000.5414).

The pregnant women that agree to participate in the study by signing the consent form will be randomly allocated to the intervention or control groups. The women allocated to the intervention group, in addition to the usual prenatal care at the Health Units, will be invited to participate in three individualized nutritional counselling sessions. Each session will last approximately 30 min. The counselling sessions will be held on days of return for medical consultations during the prenatal period, facilitating adherence and minimizing losses.

In the first meeting of the intervention all the pregnant women will be informed about the goals of the nutritional strategy (appropriate weight gain, daily consumption of fresh or minimally processed foods and regular practice of 150 min of physical activities per week), adopting the recommendations of the Institute of Medicine [23], Food Guide for the Brazilian Population [24] and American College of Obstetricians and Gynecologists [25] as the theoretical reference. It should be emphasized that pregnant women that present obstetric contraindications for the practice of physical activities will be instructed to follow the instructions of their physicians.

For the nutritional intervention strategy, educational material will be used consisting of three folders, one for each meeting, with key messages and illustrative images related to the goals set. All topics of the intervention will be addressed in the three meetings, although different approaches will be employed, appropriate for the gestational evolution. The development and validation of the educational material have been conducted prior to the implementation of the study.

Three folders were developed by the research team containing about six key messages and photos, encouraging appropriate weight gain, the consumption of fresh or minimally processed foods and the practice of physical activities. Intervention scripts were also developed as support material for the nutritionists responsible for conducting the intervention. For the semantic validation of the material, focus groups were conducted with pregnant women users of Primary Health Units, as well as nutritionists with professional experience in nutritional counselling.

The validation of the educational material consisted of the evaluation, adjustment and confirmation of the understanding of the instrument’s messages and images [26, 27]. The focus groups for the validation of the folders investigated whether there was relevance between the text and the illustrations; whether the language was understandable, accessible, clear and appropriate; whether the educational goals could be achieved with the messages and images; the practical feasibility of the proposed messages; whether the content was motivating and stimulated reflection; and whether the pregnant women identified with the messages and images. The focus groups for the scripts verified whether there was relevance between the message of the folder and the way it should be presented, whether the language was understandable, accessible, clear and appropriate; whether the educational objectives were achieved with the form of guidance: whether the proposed guidance was appropriate; and whether the content was motivating and stimulated reflection.

The original study protocol predicted that nutritional counselling sessions would take place at predetermined gestation periods: with the first meeting being conducted up to the 19th gestational week (GW), the second meeting between the 20th and 26th GW, and the third meeting between the 27th and the 33rd GW. However, due to the high rate of absenteeism observed in the prenatal consultations of the women included in the study, it was decided to make the intervention period more flexible, maintaining the three sessions between the first and second study evaluations.

The women allocated to the control group will receive only the usual prenatal care from the Health Units. After the birth, the participants in both groups will receive standardized nutritional counselling to assist them in recovering their pre-gestational weight.

The primary outcome of the study is adequacy of weight gain. Weight measurements will be performed by trained nutritionists in the first and second study evaluations using a portable digital scale (Tanita®, model HS 302).

The measurement made by the nutritionists up to the 13th GW will be considered as the pre-gestational weight. For the women in the 14th GW included in the study, a value of 0.45 kg will be subtracted from the measured weight and for the women in the 15th GW included in the study a value of 0.91 kg will be subtracted from their measured weight. The results of these calculations will be adopted as an estimate of pre-gestational weight. The weight measured in the second study evaluation, preferably between the 34th and 36th GW, will be considered for the calculation of weight gain, rather than the weight measured at the moment of delivery. These procedures will be adopted due to the limitations regarding the use of self-reported pre-gestational weight and due to the high variability of water retention in the late gestation period, as well as the variability of the gestational age at delivery [28].

Weight data will be obtained from all the prenatal consultations. The mean weekly weight gain will be estimated through the difference between the weight measured in the second evaluation and the first weight recorded in the second trimester of pregnancy, divided by the number of days between the evaluation dates, divided by 7. The women with mean weekly weight gain between 0.23 and 0.33 kg in the second and third trimesters of the pregnancy will be considered to present appropriate weight gain. Insufficient weight gain will be considered for those with a mean weekly weight gain of less than 0.22 kg and excessive weight gain for women with weekly weight gain of more than 0.34 kg [23].

Secondary outcomes will be: mean weekly weight gain, changes in food intake, physical activity and the biochemical profile of the pregnant women (fasting glucose, fasting insulin, total cholesterol and fractions, triglycerides and C-reactive protein), complications in the pregnancy (gestational diabetes mellitus, hypertensive disorders and prematurity), birth weight, neonatal adiposity, weight and length/height of children at 6, 12 and 24 months of age.

Dietary intake will be assessed at the first and second study evaluations through two 24-h recalls on non-consecutive days in each assessment. The multiple-pass technique, performed by trained nutritionists, will be employed to obtain the recalls [29]. The Nutrition Data System for Research software, developed by the University of Minnesota in the United States, will be used to estimate the nutrients intake. Estimation of the usual diet will be carried out using the Multiple Source Method (MSM), a statistical modeling technique program developed by the European Prospective Investigation into Cancer and Nutrition (EPIC) [30]. The MSM eliminates the need for a high number of replications of the method [31] and has been found to be adequate for estimating the diet of pregnant women [32]. In addition, in the first and second evaluations of the study, the women will respond to a questionnaire on the frequency of the weekly consumption of foods of interest to assess adherence to the nutritional counselling program. The instrument used was adapted from the Surveillance System for Risk and Protection Factors for Chronic Diseases by Telephone Survey (Sistema de Vigilância de Fatores de Risco e Proteção para Doenças Crônicas por Inquérito Telefônico - VIGITEL) [33].

The practice of walking for leisure, walking for locomotion, and physical exercise will be assessed in the first and second study evaluations using a questionnaire that includes information on performance and duration in the week prior to the interview, according to the questionnaire adapted from the VIGITEL [33].

Blood samples from the pregnant women will be obtained in the first and second study evaluations after 8–12 h of fasting. Blood collection will be performed by a trained professional of the Health Units, by prior appointment. Fasting serum glucose and insulin levels, total cholesterol, LDL, HDL, triglycerides, and C-reactive protein will be measured. Blood glucose and lipid profile will be determined using enzymatic methods, insulin through the immunofluorometric method, and C-reactive protein using the chemiluminescence method.

Blood pressure will be measured in both study evaluations with an automatic digital arm blood pressure monitor (OMRON®, model HBP 1100, Omron Health Care Inc.), using the mean of three measurements in each evaluation. Pre-gestational hypertension will be considered if the woman presents blood pressure values greater than 140/90 mmHg in the first study evaluation, or if they report the use of antihypertensive medication at the time of the first study evaluation. Those without pre-gestational hypertension that present changes in blood pressure or are using hypertensive drugs at the time of the second study evaluation will be classified as having gestational hypertension [34].

Data for fasting glucose and at one and 2 hours after 75 g glucose load at the time of gestational diabetes mellitus (GDM) screening will be obtained from the HygiaWeb System. For the diagnosis of GDM the criteria proposed by the World Health Organization will be adopted, which require alterations in at least one glycemic value at any time during the pregnancy: from 92 to 125 mg/dL fasting, ≥180 mg/dL 1 h after glucose load or from 153 to 200 mg/dL 2 h after glucose load [35].

The third evaluation of the study will preferably be performed at the time of the Heel Prick Test, between the third to the fifth day of life of the newborn. If this is not possible, the third evaluation will be conducted at the postpartum consultation (maximum 10 days postpartum) or at the first childcare consultation (within 15 days of life). Using a structured questionnaire, the following variables will be obtained: number of prenatal visits to the Health Unit, continuous use of medications during the pregnancy, report of chronic health problems of the puerpera, date and type of delivery, gestational age at delivery, maternal complications (hypertensive disorders and hyperglycaemia), and complications before, during and after the birth concerning the mother and the infant. Anthropometric measurements of the baby at birth will be obtained from the maternity ward discharge form.

The newborn’s body adiposity will be measured in the third evaluation of the newborn using anthropometric measurements according to standardized procedures [35‐38]. The estimation of the newborn’s body adiposity will be performed using two distinct models, one proposed by Catalano et al. [39, 40] and the other proposed by Deierlein et al. [41]. These models were validated against the air displacement plethysmography (PEA POD®) method, with data accuracy estimated at 83 and 81%, respectively.

Figure 1 presents an outline of the sequence of the recruitment, intervention, and evaluation activities of the study participants.

The sample size calculation was based on the primary outcome of the study. A 20% difference in the proportion of adequacy of weight gain between the treatment groups is expected [42]. Considering a minimum significance level of 5% (α = 0.05) and a power of 90% (β = 0.1), with a 20% loss during monitoring, a sample of 300 women will be sufficient.

The eligible pregnant women that agree to participate in the study will be randomly allocated to the treatment groups. Randomization will be performed directly using the Research Electronic Data Capture (REDCap) software [43, 44], with a spreadsheet of numbers randomly generated by Microsoft Office Excel. Stratification between the groups will be performed considering the prenatal care Health Unit, which may differ in relation to the quality of the prenatal care offered and the socioeconomic profile of the users. Given the nature of the intervention, both the study participants and the researchers will be aware of the group allocation.

The pregnant women of both groups will undergo two evaluations in the Health Units during the pregnancy, at the time of the usual prenatal consultation. The first assessment (baseline) will be conducted prior to the 16th gestational week (GW) and the second assessment will preferably take place between the 34th and 36th GW. The third evaluation of the study comprises the analysis of the mother-child binomial. The approach in the third evaluation of the study will preferably be made at the time of the Heel Prick Test, between the third and fifth day of life of the newborn. If this is not possible, the third evaluation will be conducted at the postpartum consultation (maximum 10 days postpartum) or at the first childcare consultation (within 15 days of life). In addition, secondary data on the puerpera and the newborn will be collected from electronic medical records (SisprenatalWeb, Floresce uma Vida and HygiaWeb).

Study data will be collected and managed using the REDCap electronic data capture tools hosted at the Ribeirão Preto Medical School, University of São Paulo [43, 44]. REDCap is a secure, web-based software platform designed to support data capture for research studies, providing 1) an intuitive interface for validated data capture; 2) audit trails for tracking data manipulation and export procedures; 3) automated export procedures for seamless data downloads to common statistical packages; and 4) procedures for data integration and interoperability with external sources.

To ensure the quality of the data collected, the research group will consist of trained nutritionists. A guidance manual has been prepared, prior to data collection, to be used as a protocol for all study procedures. It should be emphasized that the REDCap system [43, 44] has mechanisms called “bounds” that aim to reduce possible errors in the data collection step. In addition, all information collected will be checked by a researcher other than the one that entered the data into the system.

The analyses of this study will follow the intention to treat principles. The homogeneity of the sample at the beginning of the study will be verified using Student’s t-test for independent variables or the Mann-Whitney U test, depending on the data distribution, for the continuous variables; and the X² test for categorical variables. For the continuous variables the delta will be calculated and differences with the baseline will be tested using Student’s t-test for dependent variables or the Wilcoxon test. The impact of the intervention on the proportion of women with appropriate weight gain will be assessed by means of the relative risk and 95%CI adjusted for confounding factors.

The statistical correlation method will be used to investigate the impact of the intervention on neonatal adiposity and birth weight. If there is linearity between the treatment group data and outcomes, linear regression models will be employed, adopting adiposity and birth weight as the dependent variables, adjusted for potential confounders.