*2.1. Subjects*

The participants were pregnan<sup>t</sup> women who were enrolled in the DASDIA (DASh diet for pregnan<sup>t</sup> women with DIAbetes) randomized controlled clinical trial carried out at the Maternity School of the Federal University of Rio de Janeiro, Rio de Janeiro, Brazil, with the aim of evaluating the effect of the DASH diet on perinatal outcomes in pregnan<sup>t</sup> women with pregestational DM (2016–2020, Brazilian Clinical Trials Registry RBR-4tbgv6). Eighty-seven pregnan<sup>t</sup> women participated in the DASDIA trial, of whom 70 were included

in the present study because valid data were available for performing the nutrigenetic analyses.

The participants were pregnan<sup>t</sup> women with pregestational DM; 18 years or older; less than 28 weeks pregnan<sup>t</sup> at the time of inclusion in the study; single fetus; no alcohol, tobacco, or drug use; no sexually transmitted disease (e.g., syphilis, genital herpes, HPV); no psychiatric diseases (e.g., anxiety, depression, eating disorders); and no DM complications (e.g., diabetic nephropathy or retinopathy). Pregnant women with treated and controlled hypothyroidism (TSH 0.1–2.5 mUI/L in the first trimester or 0.3–3.0 mUI/L in the second trimester, using levothyroxine) or chronic hypertension (systolic blood pressure <160 mmHg and diastolic blood pressure <110, using methyldopa, without SHG) were included. The eligible participants were randomly assigned to one of two parallel study groups, traditional diet or DASH diet, using a computer-generated list of random numbers prepared by the head investigator (even numbers to DASH diet group and odd numbers to traditional diet group). The participants were blinded to allocation.

The research was approved by the Ethics Committee of the Maternity School of Federal University of Rio de Janeiro (CAAE–46913115.0.0000.5275; July/2015).

### *2.2. Pregestational Diabetes Diagnosis and Treatment*

Women with type 1 or 2 DM were included in this study, with a pre-pregnancy diagnosis or diagnosed during pregnancy, after presenting with a fasting glucose level ≥126 mg/dL [20]. Women with gestational DM were excluded from the study. Following the institutional protocol, all participants were treated with insulin therapy, which was prescribed by physicians according to individual needs.

### *2.3. Diet Groups and Nutritional Guidance*

The participants were randomly assigned to one of two groups of nutritional guidance, a traditional diet or the DASH diet. Women in both groups received individual nutritional guidance from a registered dietitian from the date of inclusion in the study until the last prenatal appointment in six scheduled visits. The time of intervention was defined as the time between inclusion in the study and childbirth.

Both traditional and DASH diets were designed to contain 45–55% carbohydrates, 15–20% protein, and 25–30% total fat. However, the DASH diet was richer in fruits, vegetables, whole grains, and low-fat dairy products and included a serving of nuts per day. The original North American version of the DASH diet was translated and adapted for the DASDIA trial, considering the characteristics of Brazilian pregnan<sup>t</sup> women with DM, as detailed elsewhere [28]. The traditional diet was a healthy diet currently prescribed for all pregnan<sup>t</sup> women with DM-attending prenatal care at the maternity hospital.

The main differences in the composition of the traditional and DASH diets based on the 2100 kcal meal plan are provided in Table 1.


**Table 1.** Daily composition of the diets used in the study.

\* Expressed as percentual of daily energy intake (% E). Data are presented for a daily energy intake of 2100 kcal, as an example.

The daily energy intake was calculated individually in order to formulate recommendations according to age, physical activity, pre-pregnancy BMI, and recommended GWG for

each woman in both groups. All participants received a meal plan with a list of equivalents based on the traditional or DASH diet, which was explained in detail and revised at each appointment with the registered dietitian, with reinforcement of the nutritional orientations for both diets until the last visit [28].

Adherence to the diets was assessed using a 24-h dietary recall and by applying a tool with four evaluation items, which was scored from 0 to 4 points according to (1) quantity of food consumed—portions; (2) food groups consumed—variety; (3) consumed meals— number and time; and (4) gestational weight gain—adequate when no more than 20% less or above the recommended amount [29]. The adherence score was stratified into low-to-moderate adherence (<2 points) and high adherence ( ≥2 points). For the present analyses, we considered the adherence score obtained at the visit closest to childbirth to reflect the longest possible time of exposure to the intervention.

To improve adherence, participants in the traditional diet group received a bottle of extra virgin olive oil (500 mL) at the first visit, a can of powdered semi-skimmed milk (300 mg), and a pack of oats (250 mg) at each subsequent visit, while the participants in the DASH diet group received a bottle of extra virgin olive oil (500 mL) at the first visit, a can of powdered skimmed milk (280 mg), and a pack of nuts (150 mg) and seeds (200 mg) at each subsequent visit.
