Influence of Diet and Lifestyle on the Development of Gestational Diabetes Mellitus and on Perinatal Results

GDM is a multifactorial disease, so there is controversy regarding the mechanisms involved in its pathogenesis. We speculate whether lifestyle and eating habits influenced the appearance and pathogenesis of GDM. To explore this issue, the aim of the present study was to analyze maternal diet and lifestyle characteristics in early pregnancy and their influence on the development of GDM. The study included 103 pregnant women who completed a questionnaire on nutritional knowledge, lifestyle and eating habits. Perinatal and biochemical outcomes as well as pregestational lifestyle and eating habits were compared between normoglycemic women and those who developed GDM. The results obtained showed that women who developed GDM had erroneous knowledge regarding nutrition. Consumption of white bread (p = 0.018), added sugars (p = 0.037), legumes (p = 0.025), fish (p = 0.014), butter (p = 0.010) and the performance of less physical activity (p = 0.024) correlated with glucose intolerance in pregnant women. In conclusion, we found a relationship between dietary and lifestyle habits at the beginning of pregnancy and the later diagnosis of GDM.


Introduction
Gestational diabetes mellitus (GDM) is defined as any degree of hyperglycemia that is first recognized during pregnancy [1][2][3]. However, the International Association of Diabetes and Pregnancy Study Groups (IADPSG), World Health Organization (WHO) and the International Federation of Gynecology and Obstetrics (FIGO) have differentiated two categories of hyperglycemia in pregnancy: GDM diagnosed for the first time in pregnancy and overt diabetes, the latter referring to pregestational diabetes or diabetes diagnosed at the first prenatal visit and meeting the criteria for diabetes outside of pregnancy [2,4]. The worldwide prevalence of GDM is 16.5% [1], and according to the International Diabetes Federation (IDF), most cases of hyperglycemia in pregnancy (75%-90%) are GDM. The prevalence varies depending on the criteria used for diagnosis, for which there has been a lack of consensus. Currently, the ADA, the WHO, the FIGO and the Endocrine Society recommend the diagnosis of GDM using the IADPSG criteria [1], which were developed based on the results of the HAPO study [5]. However, the surprisingly high rate of this condition (nearly 30% of all pregnant women) when these criteria are applied in some countries [6] with previously lower prevalence makes one consider whether overdiagnosis stigmatizes women with otherwise problem-free pregnancies. Accordingly, many countries have not accepted these criteria, and some organizations, such as ADA, have reconsidered the continued use of IADPSG in favor of the previous criteria [6,7]. Despite increasing rates of diagnosis and intensive surveillance, hyperglycemia during pregnancy is still associated with short-and long-term health complications for the mother, fetus and newborn. Women with GDM have a higher risk of hypertensive disorders (with preeclampsia being the highest risk) [8,9], vaginal and urinary infections [10], premature birth [5], hydramnios [11] and surgical delivery, in addition to increased risk of developing DM2 and cardiovascular diseases in the long term [1]. Regarding complications in the fetus and/or newborn, macrosomia [2,5] and perinatal hypoglycemia should be highlighted, as they can damage the vital organs of the newborn, such as the brain, and in the long term, cause an increase in the probability of the mother developing DM2 and CVD [1]. It seems that our focus should shift from overdiagnosis to prevention of hyperglycemia in pregnancy, regardless of the cutoffs that can be used as criteria for definitions. Current evidence, as demonstrated in this meta-analysis [12], focuses on whether diet (as a treatment) decreases the complications derived from GDM, but does not show the influence of diet as a method of preventing GDM.
GDM is a disease of multifactorial etiology, so there is controversy regarding the mechanisms involved in its pathogenesis. We speculate whether lifestyle and dietary habits influence the onset and pathogenesis of GDM. One of the environmental factors that most influence GDM is maternal nutrition, given the nutritional dependence of the fetus on the mother, whereby poor or inadequate nutrition of the mother negatively affects fetal development and growth [10]. Certain bacteria that constitute our microbiota are related to insulin resistance [13,14]. This may explain some dietary risk factors for GDM [15,16]. In addition, a deficit of selenium and zinc [17] and an imbalance of B vitamins [18][19][20] can influence the development of GDM. Low vitamin C levels were also associated with an increased risk of GDM [21], as well as vitamin D deficiency [22,23].
Currently, diet and lifestyle are used as tools in the initial treatment of GDM, but are not considered as possible risk factors that influence its development. This approach deserves careful consideration. It is known that the adoption of a healthy dietary pattern has positive effects on the prevention and treatment of diabetes, but few studies have analyzed the impact of the interaction between diet and the etiology, pathogenesis and prognosis of GDM. To shed light on this issue, the objective of the present study was to evaluate the influence of maternal diet and lifestyle in early pregnancy on the further development of GDM and on perinatal outcomes, especially those related to GDM-related complications.

Materials and Methods
This study was designed as a prospective cohort study, and it was carried out at the La Paz University Hospital and approved by the hospital's bioethics committee.

Study Population
The target population of the study comprised 104 pregnant women, who, having given informed consent, completed a questionnaire on nutritional knowledge, lifestyle and dietary habits, and who underwent pregnancy monitoring, including biochemical, obstetrics and perinatal assessments. The inclusion criteria were: 1. Maternal age greater than 16 years. 2. Signing of the informed consent. 3. Knowledge and understanding of the language. 4. Gestational age less than 16 weeks. The exclusion criteria were: 1. Non-acceptance of informed consent. 2. Repeated vomiting after OGTT and impossibility of performing diagnostic tests. 3. Known fetal anomaly. 4. Pre-gestational diabetes.

Diagnosis of Gestational Diabetes
The diagnosis of GDM was carried out according to the two-step strategy and to the recommendations of the Spanish Group of Diabetes and Pregnancy [6].

Patient Recruitment
The recruitment of pregnant women took place in the antenatal clinic of the health centers dependent on La Paz University Hospital, Madrid. A total of 104 pregnant women were recruited, from whom data was obtained on their lifestyle and dietary habits and on whom pregnancy follow-up was carried out.

Questionnaire
A specific questionnaire was developed to assess the knowledge of pregnant women about nutritional needs during pregnancy, as well as their lifestyle and dietary habits (see Supplementary Materials File S1 In the fifth block of the questionnaire (eating habits), there was a table of foods that specified both the weekly frequency and the daily rations of the food groups (See Appendix A Table A1).

Biochemical Analysis and Clinical Parameters Assessed
Maternal parameters were assessed in the second trimester of pregnancy, including the results of screening and diagnostic tests for GDM (fasting glycemia, O'Sullivan test glycemia at one hour, glycemia determined at one hour, two hours and three hours after the glucose overload of 100 g), basal insulin, HbA1c, ferritin, total protein, hemoglobin, total cholesterol and vitamin D.
Among the maternal outcomes of pregnancy, the following parameters were assessed: blood pressure (BP), final weight, total weight gain, gestational age at delivery, route of delivery, intake of supplements, reason for admission and diagnosis at discharge after delivery.
The neonatal results assessed were newborn weight, height, head circumference, weight percentile and Apgar test at one minute and five minutes of life.

Statistical Analysis
Statistical analysis was performed using the Statistical Package for Social Sciences (SPSS) program. A descriptive analysis of all the variables under study was performed with graphical representation in histogram or sector diagram, depending on whether the variable was quantitative or categorical. The normality test of the quantitative variables was also included in order to use parametric or non-parametric tests in future hypothesis tests.
When the number of variables was greater than fifty, the Kolmogorov-Smirnov statistic was applied for the normality test. The level of significance previously established was 95% (p < 0.05).
If a quantitative variable was normally distributed in the groups according to the categorical variable (presence of GDM), means were compared by parametric tests (Student's t test); if it did not have a normal distribution, non-parametric tests (Mann-Whitney's U test) were used. When a variable had a small sample size in both categories, nonparametric tests were used.
For the comparison of the categorical variables, Fisher's exact test or chi-square test were used, and the data were shown as number and percentage.
Correlation between variables was performed using Spearman's correlation analysis, since most of the variables followed a non-normal distribution. The results of the questionnaire were correlated with parameters (HbA1c, O'Sullivan result, basal glycemia, OGTT 100 among others).

Results
A total of 103 pregnant women completed the questionnaire, and dietary and lifestyle data were obtained. Of these, seventy completed pregnancy follow-up at the La Paz University Hospital. Sixty-eight gave birth at the center, and delivery data were also obtained.
Among these women, the development of a total of 10 cases of GDM (10/70; 14.3%) was detected. This corresponds to an incidence of GDM of 14.3%.

Medical and Obstetric History
Of the pregnant women, 24.3%; (25/103) had a chronic disease, with the most prevalent being asthma (3.9%) and hypothyroidism 5.8% . . . , and 22.2% (22/103) reported having allergies. Regarding diabetes, 32.4% (33/103) stated that they had first-degree relatives with diabetes, and 70% (7/10) of the pregnant women who developed GDM had firstdegree relatives with diabetes. Furthermore, 8.2% had had gestational diabetes in previous pregnancies. Of these, 55.6% required insulin for glycemic control and 44.4% did not, and 60% of them affirmed that they controlled their pre-and postprandial blood glucose levels.
The average weight of previous children was 3310.0 ± 720.8 (2000-6000) g. Regarding previous births, 86.8% of pregnant women had had a vaginal birth in the previous pregnancy and 13.5% had had a previous cesarean section.

Anthropometrics and Body Perception
Pre-pregnancy weight was 63.1 ± 11.0 (42-112) kg, and pre-pregnancy BMI was 23.7 ± 3.9 (15.4-37.2). Regarding their body perception, 82.3% of pregnant women with a BMI of normal weight reported seeing themselves as normal weight, highlighting that only 12.5% of pregnant women with a BMI of obesity considered themselves to be obese.
The results of the comparison of some data (anthropometric, demographic, obstetric history, relatives with Diabetes mellitus) between the two groups (women with GDM and normoglycemic women) are shown in (See Appendix A Tables A2 and A3).

Dietary Habits and Lifestyle
Of the pregnant women, 59.2% reported having a greater appetite since they became pregnant, and 41.2% referred to having cravings. Regarding the number of daily meals, the largest proportion, 39.2% of the pregnant women, ate five meals a day, with only 12.4% having a second dinner. In the food table, the weekly frequency and the daily ration of consumption of each food were specified. (See Appendix A Table A1). Concerning physical activity and exercise, 38.2% of the respondents performed physical activity prior to pregnancy, and 31.4% of the women reported being physically active during pregnancy. Thus, physical activity decreased by 7% during pregnancy. In addition, 81% of the women took supplements during pregnancy, while only 49.0% took them in the months before pregnancy.

Consumption of Tobacco, Alcohol, Caffeine and Processed Foods
Of the pregnant women, 20.4% were smokers in the pre-gestational stage, with a consumption of 5.2 ± 4.2 (0-12) of cigarettes per day, and 78.5% of them quit tobacco at the time of pregnancy. Only 1% of the women reported alcohol consumption during pregnancy, while 55.3% consumed caffeine during pregnancy, with a weekly frequency of 5.7 ± 2.3 cups (1-7) per day. Finally, 72.1% of the pregnant women consumed processed foods during pregnancy, with a weekly frequency of consumption being 4.5 ± 2.2 (1-7) days/week.

Biochemical Results
The biochemical evaluation results are shown in (See Appendix A Table A4).

Perinatal Results
The perinatal results evaluated are shown in the Appendix A section (See Appendix A Table A5). Regarding the route of delivery, of the 103 women recruited, 46.6% of deliveries were spontaneous vaginal deliveries, 3.9% were spontaneous abortions, and 20.3% were cesarean sections. Maternal biochemical parameters were studied in the second trimester of pregnancy. A comparison of means was made between the biochemical parameters of the pregnant women who developed GDM and the normoglycemic women (See Table 1). There were no statistically significant differences in the biochemical parameters between the two groups except for the GDM diagnostic tests (basal O'Sullivan, glucose overload of 100 g).

Obstetric and Perinatal Results
Only two cases of pregnancy-induced hypertension (2/68; 2.9%) were detected out of 68 deliveries that took place in the hospital. Further, a total of eight cases of anemia (8/68; 11.8%) were detected. Concerning the perinatal assessment results (final maternal weight, gestational age at delivery, newborn weight and height, head circumference, Apgar test at one minute and at five minutes, percentile weight and total weight gain), no significant differences were obtained between the group of women who developed GDM and those with normoglycemia, with the exception that the gestational age at delivery was lower in pregnant women who developed GDM (See Table 2). In addition, when performing the Spearman's correlation, there was a negative correlation between gestational age at delivery, fasting glycemia and results from the glucose overloads of 100 g (See Table 3), so it could be said that the higher glucose intolerance the lowered gestational age at delivery.

Relationship between Lifestyle, Dietary Habits and Nutritional Knowledge with the Development of GDM
A summary of food consumption is presented in Table 4, showing weekly frequency of consumption in each study group (pregnant women with GDM and normoglycemic). We found significant differences in the consumption of white bread among pregnant women who develop GDM and controls (See Table 4). Regarding the time of activity during pregnancy (represented in minutes per week), it was lower among those who developed GDM when compared to normoglycemic women, but the differences did not reach statistical significance (See Appendix A Table A6).

Relationship between Lifestyle and Eating Habits and Glucose Intolerance
Then we analyzed the relationship (obtained by means of Spearman's correlation) between certain food groups and physical activity and glucose tolerance tests (see Appendix A  Tables A7-A12), to ascertain whether they could be associated with the degree of glucose intolerance in the women that were diagnosed with GDM.
As shown in the Appendix A section, in the OGTT of 100 g glucose, we found a significant negative correlation between physical activity and glycemia at two hours (See Appendix A Table A5).
A positive correlation was also observed between a higher consumption of white bread (p = 0.018 in OGTT with determination at two hours) and added sugar in beverages and foods with glucose intolerance in OGTT (p = 0.037 with fasting glycemia; p = 0.009 with glycemia at one hour in the OGTT; p = 0.013 with two hours glucose in OGTT; and p = 0.021 with glucose at three hours in the OGTT) (See Appendix A Tables A6 and A7). Likewise, there was a negative correlation between a lower consumption of legumes both in weekly frequency and in daily ration with increased fasting glucose (p = 0.025 and 0.005) (See Appendix A Table A8). We also found a negative correlation between fish consumption (daily ration) and fasting glucose (p = 0.014) (See Appendix A Table A9). By contrast, the consumption of butter, both in weekly frequency and in daily ration, correlated positively with fasting glycemia (p = 0.010, 0.008) (See Appendix A Table A10).

Results of the Nutritional Survey Significant in the Development of GDM
Statistical results indicated a borderline confirmation (p = 0.05) between the presence of allergies and the development of GDM. Pregnant women who developed GDM had a higher percentage of allergies (40%) compared to normoglycemic women (14.3%). Family history of diabetes was more frequent in women who developed GDM versus normoglycemic patients (80% and 40.7% for GDM and normoglycemic women, respectively; p = 0.02).
Regarding the question raised in the questionnaire on the knowledge of pregnant women about whether excessive weight gain during pregnancy can affect the health of the newborn, we found a significant difference between both groups, since 50% of the pregnant women who developed GDM responded that they were not aware of it, compared to 20% of normoglycemic women (p = 0.04).
In terms of the number of meals eaten per day, the study showed that it was significantly lower in the GDM group, as only 40% of pregnant women who developed GDM ate snacks compared to 73.3% of normoglycemic women (p = 0.036).
Regarding the knowledge of the pregnant women on whether it was correct to consume extra virgin olive oil only in moderation to prevent excess fat/cholesterol in the blood (the correct answer was NO), the result obtained was of borderline significance (p = 0.06); 60% of pregnant women who developed GDM believed that they should consume it in moderation, despite its being a healthy fat, compared to 30% of normoglycemic women.
The answer to the question of whether it was correct to consume fruit only in moderation due to its high sugar content (the correct answer being NO) had a borderline significance (p = 0.056); we found that that 60% of the pregnant women who developed GDM believed that they should consume it only in moderation, compared to 25% of normoglycemic women. Finally, 30% of pregnant women who developed GDM (p = 0.011) considered that their diet and lifestyle were correct, compared to 5% of normoglycemic women.

Discussion
The objective of this study was to evaluate the influence of maternal diet and lifestyle (before and during the first weeks of gestation) on the development of GDM and on GDMassociated obstetrics and perinatal outcomes. The available evidence focuses on nutrition as a key tool in the initial treatment of GDM, but its possible involvement as a risk factor in the pathogenesis of GDM is not well established [24,25]. The present study demonstrates that an increase in the frequency of consumption of white bread is associated with the development of GDM. White bread is a food with a high glycemic index (GI), so blood glucose levels may be affected, as demonstrated in a meta-analysis showing that low GI diets in pregnant women are associated with better postprandial blood glucose results [12]. Furthermore, the ROLO study showed that women at high risk of developing GDM who had previously given birth to a baby weighing more than 4 kg and who received dietary advice on low GI diets had a lower gestational weight gain, in addition to less glucose intolerance, than those who followed the standard of care [26].
It is evident that there is an association between a decrease in physical activity during pregnancy and the development of GDM. Regular low-or moderate-intensity physical activity reduces both fasting and postprandial blood glucose levels [27]. In addition, it reduces the insulin requirement in pregnant women with GDM [28].
A higher consumption of butter and added sugars leads to greater glucose intolerance, as observed in the GDM diagnostic test (OSB, SOG 100 g). Some previous observational studies show that GDM is more prevalent in women who have a higher intake of meat and a lower intake of whole carbohydrates, fruits, vegetables and fish. Furthermore, a high intake of saturated fats can interfere with insulin signaling, and it also induces inflammation and endothelial dysfunction, both pathogenic factors in GDM [29,30].
The dietary recommendations in pregnancy indicate the realization of six meals a day. In our study, we found a correlation between the absence of snacks and the development of GDM. The group of pregnant women who developed GDM had a higher proportion of women who did not eat snacks, which probably meant that the rest of their meals had a higher glycemic load.
The results of the questionnaire showed that the group of pregnant women who developed GDM had erroneous knowledge about nutrition during gestation. The erroneous conviction that fruits should be consumed only in moderation due to their sugar content could trigger consumption reduction habits, which would imply a decrease in the consumption of micronutrients (vitamins and minerals) essential for pregnancy and the prevention of pathologies. In addition, a lack of knowledge about healthy sugars or carbohydrates could increase the consumption of "no added sugar" products, rich in artificial sweeteners. Previous evidence has shown that certain artificial sweeteners can induce metabolic changes that contribute to the pathophysiological mechanisms of GDM and high neonatal birth weight [31].
In addition, the group of pregnant women who developed GDM responded that they were unaware of the importance of healthy weight gain for the health of the newborn. Moreover, they had the mistaken belief that their lifestyle was correct. These erroneous convictions, together with other risk factors, such as the presence of relatives with diabetes, can influence the development of GDM.
Considering fetal programming and its relevance in the future diseases that children of mothers with GDM may develop, it is essential to improve glucose metabolism and promote the maintenance of a healthy weight. In this scenario, emphasis should be placed on a dietary intake of healthy foods.
This pilot study demonstrates the importance of nutritional education before and during pregnancy, and establishes a basis for future studies on the involvement of diet in the pathophysiology of GDM using a larger cohort, in order to obtain firm conclusions.

Conclusions
In summary, the present study provides information on the influence of lifestyle and dietary habits on the development of GDM and on perinatal outcomes.
The perinatal and biochemical results obtained in pregnant women with GDM indicate that the glycemic control of the pregnant women was good, but the small number of cases did not allow us to reach definitive conclusions. The results obtained from the nutritional survey showed erroneous knowledge (consumption of white bread, absence of snacks, etc.) about nutrition in the group of women who developed GDM. These misconceptions may have influenced their lifestyle habits, and along with other risk factors, such as having a history of diabetes, increased the risk of developing GDM. In fact, there was an association between the consumption of white bread, added sugar, legumes, fish and butter and the undertaking of less physical activity and the degree of glucose intolerance in pregnant women diagnosed with GDM.
This study demonstrates the importance of nutritional education before and during pregnancy.
Research in large cohorts should be emphasized to identify modifiable risk factors and reduce the prevalence and complications of GDM.
In conclusion, the results obtained showed that women who developed GDM had erroneous knowledge regarding nutrition. Further studies are needed to confirm whether this may definitively influence the development of GDM and its perinatal outcomes.

Conflicts of Interest:
The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.   Table A7. Correlation between performing physical activity during pregnancy and the 2 h glucose in the SOG 100 g.

ACTIVITY DURING GESTATION RHO SPEARMAN p-Value
OGTT 100 g 2 h −0.426 0.024 Table A8. Association between a consumption of white bread with glucose intolerance.

WHITE BREAD RHO SPEARMAN p-Value
OGTT 2 h 0.450 0.018 Table A9. Association between a high consumption of added sugars with glucose intolerance.  Table A10. Association between a low consumption of legumes and glucose intolerance in the O'Sullivan test (fasting glucose).

LEGUME (RATION) RHO SPEARMAN p-Value
Fasting glycemia −0.337 0.005 Table A11. Association between lower fish consumption and higher glucose intolerance at baseline O'Sullivan.

FISH (RATION) RHO SPEARMAN p-Value
Fasting glycemia −0.294 0.014 Table A12. Association between higher consumption of butter and greater glucose intolerance in baseline O'Sullivan.